Urinary tract infection
Highlights
Urinary Tract Infections (UTIs) in the United States
According to Urologic Diseases in America, a report published in 2007 by the U.S. National Institutes of Health:
- UTIs are the most expensive of all urologic diseases, accounting for about $3.5 billion a year in medical costs, including $96.4 million in prescriptions.
- Over 60% of women will experience a UTI at least once in their lifetime. At least a third of women experience a UTI by the time they are 24 years old.
- Only 20% of UTIs occur in men. However, men are far more likely than women to be hospitalized for an infection.
- Childhood risk for UTIs is 2% for boys and 8% for girls. Vesicouretereal reflux, a condition in which urine backs up into the kidneys, affects about 10% of all children.
Circumcision Prevents UTIs
Baby boys who are uncircumcised are 10 - 12 times more likely than circumcised boys to develop UTIs during their first year of life, indicates the Urologic Diseases in America report.
High Doses of Zinc Increase UTI Risk
- People who take very high daily doses of zinc supplements may face an increased risk for UTIs and other urologic problems, suggests a 2007 study in the Journal of Urology. Patients in the study who took 80 mg/day of zinc were more likely to be hospitalized for urinary complications than those who did not take zinc.
- In general, the upper limit for zinc supplements should not exceed 40 mg/day. Eight mg/day for women and 11 mg/day for men are the recommended average doses. However, very high doses of zinc are sometimes prescribed for certain medical conditions, such as age-related macular degeneration.
Introduction
A urinary tract infection (UTI) is a condition where one or more structures in the urinary tract become infected after bacteria overcome its strong natural defenses. In spite of these defenses, UTIs are the most common of all infections and can occur at any time in the life of an individual. Almost 95% of cases of UTIs are caused by bacteria that typically multiply at the opening of the urethra and travel up to the bladder (known as the ascending route). Much less often, bacteria spread to the kidney from the bloodstream.
Different classifications have been devised to help doctors choose treatments and determine the causes of UTIs.
Primary or Recurrent UTIs. UTIs are classified as primary or recurrent, depending on whether they are the first infection or whether they are repeat events.
Community- or Hospital-Acquired. UTIs are also sometimes grouped according to where they are acquired:
- Community-Acquired Infections. Most UTIs are thought to develop in the community at large. It is unclear how primary community-acquired infections occur or how they are spread. Although most cases have been thought to arise sporadically, a rare outbreak in 1996 - 2000 caused by drug-resistant bacteria suggests epidemic spread of community-acquired infections could be more common than previously thought and may be spread via contaminated food. Most community-acquired infections are not serious and probably develop when the intestines become colonized with bacteria that are also predisposed to infecting the urinary tract.
- Hospital-Acquired Infections. UTIs are also commonly acquired in the hospital, often due to contaminated urinary catheters. Hospital-acquired infections (known as nosocomial infections) tend to be more serious because the bacteria that cause them are often resistant to drug treatment and patients are often in poor general health.
Uncomplicated and Complicated. UTIs are also sometimes further defined as either being uncomplicated or complicated depending on the factors that trigger the infections.
- Uncomplicated infections are only associated with bacterial infection, most often Escherichia coli (E. coli). They affect women much more often than men.
- Complicated infections, which occur nearly as often in men as women, are also caused by bacteria but they occur as a result of some anatomical or structural abnormality. Often they are associated with catheter use in the hospital setting, bladder and kidney dysfunction, or kidney transplant (especially in the first three months after transplant). Recurrences occur in up to 50 - 60% of patients with complicated UTI if the underlying structural or anatomical abnormalities are not corrected.
Classifications Based on Symptoms and Levels of Infection. UTIs can also occur without symptoms and with symptoms but very low bacterial levels.
- When bacteria are present and there are no symptoms it is called asymptomatic UTI or also bacteriuria.
- Some patients can also have symptoms of infection with very low bacterial counts. In such cases, the condition is called acute urethral syndrome.
Uncomplicated Urinary Tract Infections (UTIs)
Cystitis. Cystitis is the most common urinary tract infection and is sometimes referred to as acute uncomplicated UTI. It occurs in the lower urinary tract (the bladder and urethra) and nearly always in women. In most cases, the infection is brief and acute and only the surface of the bladder is infected. Deeper layers of the bladder may be harmed if the infection becomes persistent, or chronic, or if the urinary tract is structurally abnormal.
Pyelonephritis (Kidney Infection). When infection spreads to the upper tract (the ureters and kidneys) it is called pyelonephritis, or more commonly, kidney infection. As many as half of all women with cystitis may have infections of the upper urinary tract at the same time as cystitis.
Click the icon to see an image of the kidney.
Urethritis. When infection is limited only to the urethra, the infection is known as urethritis. This is a common sexually transmitted disease in men.
Complicated Urinary Tract Infections
Complicated UTIs may develop because of any one of a number of physical problems and affect any gender and age group. The common feature in most complicated UTIs is the inability of the urinary tract to clear out bacteria because of a physical condition that causes obstruction to the flow of urine or problems that hinder treatment success.
Recurrent Urinary Tract Infections
Most women who have had an uncomplicated UTI have occasional recurrences. About 25 - 50% of these women can expect another infection within a year of the previous one. Between 3 - 5% of women have ongoing, recurrent urinary tract infections, which follow the resolution of a previous treated or untreated episode.
Recurrence is often categorized as either reinfection or relapse:
- Reinfection. About 80% of recurring UTIs are reinfections. A reinfection occurs several weeks after antibiotic treatment has cleared up the initial episode and can be caused by the same bacterial strain that caused the original episode or a different one. The infecting organism is usually introduced through the rectal region from fecal matter and moves up through the urinary tract.
- Relapse. Relapse is the less common form of recurrent urinary tract infection. It is diagnosed when a UTI recurs within 2 weeks of treatment of the first episode and is due to treatment failure. Relapse usually occurs in kidney infection (pyelonephritis) or is associated with obstructions such as kidney stones, structural abnormalities or, in men, chronic prostatitis.
Asymptomatic Urinary Tract Infection (Asymptomatic Bacteriuria)
When a person has no symptoms of infection but significant numbers of bacteria have colonized the urinary tract, the condition is called asymptomatic UTI (also called asymptomatic bacteriuria). (In general, there must be at least 100,000 bacteria per milliliter of urine.) The condition is harmless in most people and rarely persists, although it does increase the risk for developing symptomatic UTIs.
Screening for asymptomatic bacteriuria is not necessary during most routine medical examinations, with the following exceptions:
- Pregnant women. Pregnant women with asymptomatic bacteriuria have a 30% risk for acute pyelonephritis in their second or third trimester. Therefore, they need screening and treatment for this condition.
- People undergoing urologic surgery (such as prostate surgery in men). The presence of an infection during surgery can lead to serious consequences.
Some groups recommend screening women with diabetes for asymptomatic bacteriuria. However, a 2003 study suggested that treating women who test positive for this condition does not reduce their risk of complications from UTIs. Asymptomatic bacteriuria may be an indicator for serious health problems in the elderly, but screening for the condition is not warranted in this group.
Acute Urethral Syndrome
Some people have symptoms of cystitis but have a bacterial count lower than that ordinarily found in UTI. Such patients are sometimes diagnosed with acute urethral syndrome. This condition is usually caused by E. coli or other bacteria that cause cystitis, but in lower numbers, or by a sexually transmitted disease such as Chlamydia or gonorrhea.
Interstitial Cystitis
Interstitial cystitis (IC) is an inflammation of the bladder wall that occurs almost exclusively in women. The average age of patients with IC is 40 years, but 25% of cases occur in women under age 30. Symptoms are very similar to cystitis, but no bacteria are present. These women often complain of experiencing pain during sex. Pelvic pain, depression, and stress may intensify symptoms. Women with IC also frequently suffer from other conditions, including allergies, urinary incontinence, sinusitis, and irritable bowel syndrome (IBS). Some doctors think that IC may be related to autoimmune diseases such as fibromyalgia and lupus.
IC is difficult to diagnose and treat. Pentosan (Elmiron) is the most frequent drug treatment, but doctors prescribe other medications as well (see Medications section). Some evidence suggests that diet can worsen IC symptoms. For instance, patients should avoid coffee (both caffeinated and decaf), alcohol, cola, vinegar, citrus fruits, tomatoes, chili, strawberries, pineapple, onions, pizza, chocolate, and apples, according to research presented at the 2006 American Urological Association scientific meeting.
The Urinary System and Its Defenses
The Urinary System. The urinary system helps maintain proper water and salt balance throughout the body and also expels urine from the body. It is made up of the following organs and structures:
- The two kidneys, located on each side below the ribs and toward the middle-back, play the major role in this process. They filter waste products, water, and salts from the blood to form urine.
- Urine passes from each kidney to the bladder through thin tubes called ureters.
- Ureters empty into the bladder, which rests on top of the pelvic floor. This is a muscular structure similar to a sling running between the pubic bone in front to the base of the spine.
- The bladder stores the urine, which is then eliminated from the body via another tube called the urethra, which is the lowest part of the urinary tract. (In men it is enclosed in the penis. In women it leads directly out.)
Defense Systems Against Bacteria. Infection does not always occur when bacteria are introduced into the bladder. A number of defense systems protect the urinary tract against infection-causing bacteria:
- Urine itself functions as an antiseptic, washing potentially harmful bacteria out of the body during normal urination. (Urine is normally sterile, that is, free of bacteria, viruses, and fungi.)
- The ureters are structurally designed to prevent urine from backing up into the kidney.
- The prostate gland in men secretes infection-fighting substances.
- The immune system in both sexes continuously fights bacteria and other harmful micro-invaders. In addition, immune system defenses and antibacterial substances in the mucous lining of the bladder eliminate many organisms.
- In normal fertile women, the vagina is colonized by lactobacilli, beneficial microorganisms that maintain a highly acidic environment (low pH). Acid is hostile to other bacteria. Lactobacilli also produce hydrogen peroxide, which helps eliminate bacteria and reduces the ability of E. coli to adhere to vaginal cells. (E. coli is the major bacterial culprit in urinary tract infections.)
- Some interesting research suggests that when bacteria infect the bladder, the cells that line the bladder literally sacrifice themselves and self-destruct (a process called apoptosis). In so doing, they fall away from the lining, carrying the bacteria with them. This eliminates about 90% of the E. coli.
- Some researchers have identified a possible natural antibiotic called human beta-defensin-1 (HBD-1), which fights E. coli within the female urinary and reproductive tracts.
Click the icon to see an image of the prostate gland.
Causes
The bacterial strains that cause UTIs include:
- Escherichia (E.) coli is responsible for 75 - 90% of uncomplicated cystitis cases in younger women and in more than half the cases in older women (over age 50). In most cases of UTI, E. coli, which originates as a harmless microorganism in the intestines, spreads to the vaginal passage, where it invades and colonizes the urinary tract. Some bacteria may be able to invade into deeper tissue in the bladder, where they survive to reinfect the patient after resolution of the previous infection.
- Staphylococcus saprophyticus accounts for 5 - 15% of UTIs, mostly in younger women. Infections caused by this bacterium tend to have a seasonal variation, with a higher incidence in the summer and fall than in the winter and spring.
- Klebsiella, Enterococci bacteria, and Proteus mirabilis account for most of remaining bacterial organisms that cause UTIs. They are generally found in UTIs in older women.
- Rare bacterial causes of UTIs include ureaplasma urealyticum and Mycoplasma hominis, which are generally harmless organisms.
Organisms in Severe or Complicated Infections
- The bacteria that cause kidney infections (pyelonephritis) are generally the same bacteria that cause cystitis. There is some evidence, however, the E. coli strains in pyelonephritis are more virulent (able to spread and cause illness).
- Complicated UTIs that are related to physical or structural conditions are apt to be caused by a wider range of organism. E. coli is still the most common organism, but others have also been detected, including Klebsiella, P. mirabilis, and Citrobacter.
- Fungal organisms, particularly Candida species. (Candida albicans, for example, causes the so-called "yeast infections" that also occur in the mouth, digestive tract, and vagina.)
- Other bacteria associated with complicated or severe infection include Pseudomonas aeruginosa, Enterobacter, and Serratia species, gram-positive organisms (including Enterococcus species), and S. saprophyticus.
Bacterial Strains in Recurrent UTIs
Recurring infections are often caused by different bacteria than those that caused a previous or first infection.
Even if the reinfecting bacterium is still E. coli, it may be a variant of the original infecting E. coli strain. Such strains produce substances, such as one called P fimbriae, which tend to make the bacteria more infectious. Uncommon causes of reinfection include Ureaplasma and Mycoplasma hominis, which are sometimes associated with acute urethral syndrome.
Factors in Overcoming the Bacterial Defense Systems
The bacteria that cause most UTIs are very common. Nearly everyone harbors them. It is not clear how they proliferate and break down the natural defenses of the body. Among the possible ways this occurs are:
Changes in the Acid-Alkaline Balance of the Urinary Tract. Changes in the amount or type of acid within the genital and urinary tracts are major contributors to lowering the resistance to infection. For example, beneficial organisms called lactobacilli increase the acidic environment in the urinary tract. Reductions in their number (which, for example, occurs with estrogen loss after menopause), increases pH and therefore the risk of infection.
Biofilm. One theory, called the biofilm mode of growth, suggests that sometimes bacteria form capsules that adhere to the urinary tract, protecting them from many of the body's normal defenses.
Symptoms
Symptoms of lower urinary tract infections usually begin suddenly and may include one or more of the following signs:
- The urge to urinate frequently, which may recur immediately after the bladder is emptied.
- A painful burning sensation. (If this is the only symptom, then the infection is most likely urethritis.)
- Discomfort or pressure in the lower abdomen. The abdomen can feel bloated.
- Cramping in the pelvic area or back.
- The urine often has a strong smell, looks cloudy, or contains blood. This is a sign of pyuria, or a high white blood cell count in the urine, and is a very reliable indicator of urinary tract infections.
- Occasionally, fever develops.
Symptoms of Severe Infection in the Kidney (Pyelonephritis)
Symptoms of kidney infections tend to affect the whole body and be more severe than those of cystitis. They may include:
- Symptoms of lower UTIs that persist longer than a week. (Sometimes lower UTI symptoms may be the only signs of kidney infection. People at highest risk for such "silent" upper urinary tract infections include patients with diabetes, impaired immune systems, or a history of relapsing or recurring UTIs.)
- An increased need to urinate at night.
- Chills and persistent fever (typically lasting more than 2 days).
- Pain in the flank (pain that runs along the back at about waist level).
- Vomiting and nausea.
Symptoms of UTIs in Infants and Toddlers
UTIs in infants and preschool children tend to be more serious than those that occur in young women, in part because they are more likely to occur in the kidneys and upper urinary tract. (Older children are more likely to have lower urinary tract infections and standard symptoms.) Infants and young children should always be checked for UTIs if the following symptoms are present:
- A persistent high fever of otherwise unknown cause, particularly if it is accompanied by signs of feeding problems and debility, such as listlessness and fatigue. (Studies have reported that up to 5% of infants and toddlers who are brought to the emergency room with fevers have UTIs. Scarring is a risk so very young children with UTIs need to be screened.)
- Painful, frequent, and foul smelling urine. (Parents are generally unable to identify a UTI just by the smell of their child's urine. Medical tests are needed.)
- Cloudy urine. (If the urine is clear, the child most likely has some other ailment, although it is not absolute proof that the child is UTI-free.)
- Abdominal and low back pain may be present.
- Vomiting and abdominal pain (usually in infants).
- Jaundice (yellowing of the skin and the whites of the eyes) in infants, particularly if it develops after 8 days of age.
Symptoms of UTIs in Older Patients
The classic lower UTI symptoms of pain, frequency, or urgency and upper tract symptoms of flank pain, chills, and tenderness may be absent or altered in older patients with UTIs. In one study, only 20% of these patients had new urinary complaints, and many have no symptoms at all.
Symptoms of UTIs that may occur in seniors but not in younger adults may include mental changes or confusion, nausea or vomiting, abdominal pain, or cough and shortness of breath. Concomitant illness may further confuse the picture and make diagnosis difficult.
Risk Factors
After the flu and common cold, urinary tract infections (UTIs) are the most common medical complaint among women in their reproductive years. Women are 30 times more likely to have UTIs than men. At least a third of American women are diagnosed with a UTI by the time they are 24 years old. Every year, 11% of American women have at least one such infection, and up to 60% of all women will develop a UTI at some time in their lives. A third of these women will have a recurrence within a year. Furthermore, each year about 250,000 women develop kidney infections (pyelonephritis) and 100,000 are hospitalized for treatment.
According to a 2007 report from the U.S. National Institutes of Health, urinary tract infections in both women and men are the most expensive of all urologic problems. Nationally, UTIs account for about $3.5 billion a year in medical costs.
Structure of the Female Urinary Tract. In general, the higher risk in women is mostly due to the shortness of the female urethra, which is 1.5 inches compared to 8 inches in men. Bacteria from fecal matter can be easily transferred to the vagina or the urethra.
Sexual Behavior. Frequent or recent sexual activity is the most important risk factor for urinary tract infection in young women. Nearly 80% of all urinary tract infections occur within 24 hours of intercourse. (Sexual activity is less associated with cystitis in women after menopause.)
UTIs are very rare in celibate women. It is important to stress, however, that UTIs are NOT sexually transmitted infections, although these infections ( Chlamydia trachomatis, gonorrhea, or herpes simplex virus) may increase the risk for UTIs.
In general, however, it is the physical act of intercourse itself that produces conditions that increase susceptibility to the UTI bacteria, with some factors increasing the risk:
- Women having sex for the first time or who have intense and frequent sex after a period of abstinence are at risk for a condition called "honeymoon cystitis."
- A sudden increase in the frequency of sexual intercourse poses a significant risk for UTI, particularly if a diaphragm is used.
- Sexual position (such as the woman on top) can contribute to the risk.
Click the icon to see an image of a diaphragm.
Contraceptives may also contribute to risk in a number of ways:
- The spring-rim of the diaphragm may bruise the area near the bladder neck, making it susceptible to bacteria.
- Unlubricated condoms may injure vaginal tissue and make it vulnerable to infections. (Using a sterile water-based lubricant, such as KY jelly, may help reduce this risk. Petroleum-based lubricants should be avoided because they weaken latex condoms.)
- Some women experience UTI as an allergic reaction to latex in condoms or to oral contraceptives.
- Use of spermicide, such as nonoxynol-9, doubles or triples a women's risk for UTI, regardless of whether it is used with a condom or diaphragm. Spermicides also pose a risk for sexually transmitted infections, and experts warn against their use.
Pregnancy. Although pregnancy does not increase the rates of asymptomatic bacteriuria, it does increase the risk that it will progress to a full-blown infection. About 2 - 11% of pregnant women have asymptomatic bacteriuria and, of those, 13 - 27% will develop a kidney infection late in their term. (However in early pregnancy, frequent urination -- a common symptom of UTI -- is most likely due to pressure on the bladder.)
Although all pregnant women should be tested for UTIs, women at highest risk have the following conditions or situations:
- Diabetes
- Sickle cell trait
- Low-income
- Have had many children
- History of childhood UTIs
- Have undergone a cesarean section with catheterization of the bladder
- Have received epidural anesthesia
Women who have had a UTI before or during pregnancy also have a higher risk of developing recurrent urinary tract infections after delivery. About 25 - 33% of women who experience bacteriuria during pregnancy will have another urinary tract infection, sometimes as many as 10 - 14 years later.
Menopause. The risk for UTIs, both symptomatic and asymptomatic, is highest in women after menopause. Studies indicate that between 20 - 25% of women over 65 years old have UTIs, and 10 - 15% have asymptomatic bacteriuria (compared to 2 - 5% of young women). Sexual activity plays a lesser role in UTIs in older women than in younger women. In general, biologic changes due to menopause put older women at particular risk for primary and recurring UTIs:
- With estrogen loss, the walls of the urinary tract thin, weakening the mucous membrane and reducing its ability to resist bacteria. The bladder may lose elasticity and fail to empty completely.
- Estrogen loss has also been associated with reduction in certain immune factors in the vagina that help block E. coli from adhering to vaginal cells.
- Levels of lactobacilli (protective bacteria) decline after menopause, perhaps also due to drops in estrogen.
Some women carry the blood group P1, which, as they get older, is associated with high levels of specific cells in the vagina and urethra that bind to a specific strain of E. coli that is resistant to normal infection-fighting mechanisms.
Other Risk Factors in Women. Women who have skin allergies to ingredients in soaps, vaginal creams, bubble baths, or other chemicals that are used in the genital area are at high risk for UTIs. In such cases, the allergies may cause small injuries that can introduce bacteria.
Risk Factors of Recurring Infection in Women
Most women who have had one UTI have occasional recurrences. About 25 - 50% of these women can expect another infection within a year of the previous one.
Between 3 - 5% of women, however, have ongoing, recurrent urinary tract infections, which follow the resolution of a previous treated or untreated episode. The major groups of women who are at highest risk for recurrent infections are young highly sexually active women and postmenopausal women. It might be argued that nearly all women who have a urinary tract infection are at risk for another, particularly if they are not treated for the first one.
Lifestyle Factors Increasing the Risk for Recurrence. Why urinary tract infections become chronic and recurring in many women is not entirely clear, but researchers are identifying certain lifestyle factors that may increase the risk in specific women:
- Engaging in sexual intercourse more than four times a month.
- Recent changes in sexual partners.
- Having a mother with a history of UTIs.
- Having a first UTI before age 15.
- Use of spermicides.
- Smoking and taking tub baths may also increase the risk for recurrent urinary tract infections, but they are less significant than other risk factors.
Biologic and Physical Factors. Some women may also have certain biologic or anatomical factors that increase the risk for recurring UTIs:
- Having a shorter than average distance between the urethra and the anus.
- Certain women may carry a compound called sialosyl galactosyl globoside (SGG) on the surface of kidney cells, which is a highly powerful receptor for E. coli bacteria.
- Certain women have a genetic susceptibility to becoming infected in the vaginal area with greater numbers of disease-causing organisms that adhere to the lining.
- Certain women may be deficient in human beta-defensin-1 (HBD-1), believed to be a naturally occurring antibiotic.
Risk Factors for Recurrence in the Aging Woman. In addition to menopause, other very strong risk factors for recurrences in older women include urinary incontinence and previous operations on the genital or urinary tracts. Additional risk factors for UTIs in older women include diabetes, vaginal itching or dryness, having had children, and poor overall health.
Risk Factors in Children
Each year, about 3% of American children develop urinary tract infections. During the first few months of life, UTIs are more common in boys than in girls. Boys who are uncircumcised are about 10 - 12 times more likely than circumcised boys to develop UTIs by the time they are 1 year old. After the age of 2 years, UTIs are far more common in girls. Throughout childhood, the risk of UTIs is about 2% for boys and 8% for girls. As with adults, Escherichia coli (E. coli) is the most common cause of UTIs in children.
Vesicoureteral Reflux (VUR). Vesicoureteral reflux (VUR) affects about 10% of all children. It is the source of urinary tract infections in 30 - 50% of childhood cases. This is a structural defect of the valve-like mechanism between the ureter and bladder that allows urine to flow backward, carrying infection from the bladder up into the kidneys. VUR also puts children at risk for recurrence. Such recurrences nearly always occur within the first 6 months after the first UTI.
Click the icon to see an image of vesicoureteral reflux.
Risk Factors in Men
Men become more susceptible to UTIs after 50 years of age, when they begin to develop prostate problems. Benign prostatic hyperplasia (BPH), enlargement of the prostate gland, can produce obstruction in the urinary tract and increase the risk for infection. In men, recurrent urinary tract infections are also associated with prostatitis, an infection of the prostate gland that is caused by E. coli. Although only about 20% of UTIs occur in men, these infections can cause more serious problems than they do in women. Men with UTIs are far more likely to be hospitalized than women. [See In-Depth Report #71: Benign prostatic hyperplasia.]
Institutionalization
Hospitalizations and Catheters. About 40% of all infections that develop in hospitalized patients are in the urinary tract. The organisms that cause infections in hospitals (called nosocomial infections) are usually different from those that commonly cause UTIs. They are also more likely to be resistant to standard antibiotics. Hospitalized patients at highest risk for such infections are those with in-dwelling urinary catheters, patients undergoing urinary procedures, long-stay elderly men, and patients with severe medical conditions.
About 80% of UTIs in the hospital are due to catheters. Nearly all patients who need urinary catheters develop high levels of bacteria in their urine, and the longer the catheter is in place, the higher the risk for infection. Catheterized patients who develop diarrhea are nine times more likely to develop UTIs than are patients without diarrhea. In most cases of catheter-induced UTIs, the infection produces no symptoms. Because of the risk for wider infection, however, anyone requiring a catheter should be screened for infection. Catheters should be used only when necessary and should be removed as soon as possible.
Nursing Homes. All older adults who are immobilized, catheterized, or dehydrated are at increased risk for UTIs. Nursing home residents, particularly those who are incontinent and demented, are at very high risk. Up to 40% of elderly patients who live in nursing homes will contract a urinary tract infection.
Anatomical Abnormalities in Adults
Some people have structural abnormalities of the urinary tract that cause urine to stagnate or flow backward into the upper urinary tract. Such conditions include:
- A prolapsed bladder (cystocele) can result in incomplete urination so that urine collects, creating a breeding ground for bacteria.
- Tiny pockets called diverticula sometimes develop inside the urethral wall and can collect urine and debris, further increasing the risk for infection.
Click the icon to see an image of a cystocele.
Antibiotics as Risk Factors for UTIs
Antibiotics often eliminate lactobacilli, the protective bacteria, along with harmful bacteria. This causes an overgrowth of E. coli in the vagina. In one study, the risk for UTI increased during the 15 - 28 days that women were taking antibiotics. In fact, some research suggests that taking antibiotics for a urinary tract infection increases the risk for a subsequent infection.
Medical Conditions that Increase the Risk for UTIs
Diabetes. Diabetes puts women at significantly higher risk for asymptomatic bacteriuria. The longer a woman has diabetes, the higher the risk. (Control of blood sugar has no effect on this condition.) The risk for UTI complications is also higher in people with diabetes. In fact, certain UTI-related abscesses are reported only in patients with diabetes. These patients are also at higher risk for fungal-related UTIs.
Kidney Problems. Nearly any kidney disorder increases the risk for complicated UTIs.
AIDS and Immunosuppressed Patients. Any infection is dangerous in people whose immune systems are damaged, and UTIs are no exception, particularly pyelonephritis.
Sickle-Cell Anemia. Patients with sickle-cell anemia are particularly susceptible to kidney damage from their disease, and UTIs put them at even greater risk.
Kidney Stones. In some cases, kidney stones can cause urinary tract obstruction that leads to infection, particularly pyelonephritis. Symptoms of severe urinary tract infection in people with a history of kidney stones may indicate obstruction, which is a serious condition.
Click the icon to see an image of kidney stones.
Other Risk Factors
Zinc. High doses of zinc supplements may increase the risk for urinary tract infections and other urologic problems, according to a 2007 study. Researchers found that hospitalizations for urinary complications were far more common among patients who took high doses of zinc than those who did not take this mineral supplement. Patients in the study took 80 mg of zinc daily. In general, the recommended daily amount for zinc is 8 mg/day for women and 11 mg/day for men. Higher doses of zinc are sometimes prescribed for people with certain medical conditions, such as age-related macular degeneration (an eye disease). However, no one should take more than 40 mg/day of zinc without talking to a doctor.
Complications
Urinary discomfort and emotional distress are the primary concerns in most women with recurrent UTIs. One study reported significant impairment of a woman's quality of life during symptom periods, which affected social function, vitality, and emotional well-being.
Medical Complications of Urinary Tract Infections in Adults
Nearly all urinary tract infections are mild, treatable, and have no long-term consequences. Serious physical complications can occur in some cases, however, most often in hospitalized patients.
Obstruction and Widespread Infection. Very severe upper urinary tract infections may cause obstruction that results in widespread and even life-threatening infection. Patients who develop UTIs in the hospital are at higher risk for such infections than those outside the hospital. In one particularly dangerous form of kidney infection that obstructs the ureter, mortality rates exceed 40%. This specific condition should be suspected in people with diabetes who have severe UTIs.
Kidney Damage. In high-risk adults, recurrent UTIs may cause scarring in the kidneys, which over time can lead to hypertension and eventual kidney failure. People with UTIs who develop serious kidney disease from UTIs are likely to have other predisposing diseases or structural abnormalities. (Recurrent urinary tract infections, even in the kidney, almost never lead to progressive kidney damage in otherwise healthy women.)
Urge Incontinence. Recurrent UTIs may increase the risk for urge incontinence after menopause. (People with urge incontinence experience leakage and the need to urinate frequently.) [See In-Depth Report #50: Urinary incontinence.]
Kidney Stones. Kidney stones can be caused by urinary tract infections (as well as increase the risk for UTIs in the first place). Those known as struvite stones are almost always caused by urinary tract infections due to bacteria that secrete certain enzymes. These enzymes raise urine concentrations of ammonia, which composes the crystals forming struvite stones. The stone-promoting bacterium is usually Proteus, but others include Pseudomonas, Klebsiella, Providencia, Serratia, and staphylococci.
Complications of Urinary Tract Infections in Pregnancy
Urinary tract infections during pregnancy pose particular risks for both mother and child:
- If asymptomatic bacteriuria is not detected and treated promptly in pregnant women, as many as 25% develop kidney infection (pyelonephritis), which in turn increases the risk for premature birth, infant mortality, and later chronic kidney disease.
- Even if kidney infection does not develop, untreated UTIs occurring in the first and third trimester of pregnancy slightly increase the risk for mental retardation and developmental delay in the infant.
- Certain strains of E. coli can increase the risk for complications during pregnancy, including miscarriage or premature delivery, even if pyelonephritis does not develop.
- Infants of women who harbor Ureaplasma urealyticum also have an increased risk for respiratory infections.
Complications in Children with Urinary Tract Infections
Urinary tract infections are a major cause of hospitalization in children. Untreated, they can be very serious, particularly in children under 4 years old. Fortunately, with prompt treatment, childhood cases of upper urinary tract infections rarely cause any serious consequences.
Spread of Infection. Widespread infection is a major complication of a primary infection. Although laboratory tests in some infants with UTI may suggest the presence of meningitis (inflammation of the spinal column), in most of these UTI cases the outcome is good with treatment, and there appear to be no neurological symptoms afterward.
Kidney Scarring. Kidney scarring is the major concern in children who develop serious or recurrent UTIs. Scarring in young growing kidneys is much more serious than in the mature kidney. Over the years, it increases the risk for hypertension and kidney failure. In one study, evidence of scarring developed in 6% of children who had been hospitalized for a urinary tract infection. Children most at risk for this complication include:
- Children with vesicoureteral reflux (VUR). (Carefully managed vesicoureteral reflux without scarring is not associated with serious complications.)
- Abnormally structured urinary tracts
- Recurrent kidney infections
- A delay in treating an acute UTI
One encouraging study followed children with evidence of kidney scarring for 16 - 26 years. On average, their total kidney function was well preserved, although the scarred kidney had signs of lower function and patients with scarring in both kidneys were at higher risk for future problems. Earlier studies have shown poorer results, which suggests that outcomes are now improving with early detection and better follow-up.
Complications in People with Diabetes
Women with diabetes have more frequent and more severe UTIs than women without the disease. They also are more frequently hospitalized for kidney infections. In fact, the most serious, but rare, complications of urinary tract infections (pyelonephritis, widespread infections, abscesses, inflammation of the bladder wall) occur mostly in patients with diabetes.
Diagnosis
In younger women, UTI symptoms plus positive results on an over-the-counter dipstick test are often enough to make a diagnosis. Symptoms include frequent urination and vaginal burning, without other complications such as fever, chills, and pain in the kidney. In such cases, young women can usually receive treatment by calling a health professional (usually a nurse) who will prescribe antibiotics. A good response to antibiotic therapy usually eliminates the need for further tests.
This course is recommended only for nonpregnant women at low risk for recurrent infection who do not have symptoms suggesting other problems, such as vaginitis. In some centers, women who are treated over the phone have to be younger than 55 years old; other patients need to see a doctor for evaluation. Pregnant women should be screened for E. coli because of the risk of complications, including miscarriage, from certain strains of these bacteria.
Ruling Out Other Conditions with Similar Symptoms
About half of women with symptoms of a UTI actually have some other condition, such as irritation of the urethra, vaginitis, interstitial cystitis, or sexually transmitted diseases (STDs). Some of these problems may also accompany or lead to UTIs.
Vaginitis. Vaginitis is a common vaginal infection that can be caused by a fungus (candidiasis) or bacteria. Occasionally, the infection causes frequent urination, mimicking cystitis. The typical symptoms of vaginitis are itching and an abnormal discharge.
Sexually Transmitted Diseases. Women with painful urination whose urine does not exhibit signs of bacterial growth in culture may have a sexually transmitted disease. The most common culprit is the organism Chlamydia trachomatis. Other STDs that may be responsible include gonorrhea and genital herpes.
Interstitial Cystitis. Interstitial cystitis (IC) is an inflammation of the bladder wall that occurs almost predominantly in women. The average age of patients with IC is 40 years old, but 25% of cases occur in women under age 30. Symptoms are very similar to cystitis, but no bacteria are present. Pain during sex is a very common complaint in these patients, and stress may intensify symptoms.
Bladder Cancer. Bladder cancer is a rare cause of painful urination and is more common in men than in women.
Kidney Stones. The pain of kidney stones along with blood in the urine can resemble the symptoms of pyelonephritis. There are no bacteria present with kidney stones, however.
Thinning Urethral and Vaginal Walls. After menopause, the vaginal and urethral walls become dry and fragile, causing pain and irritation that can mimic a UTI.
Disorders in Children that Mimic UTIs. Problems that might cause painful urination in children include reactions to chemicals in bubble bath, diaper rashes, and infection from the pinworm parasite.
Prostate Conditions in Men. Prostate conditions, including prostatitis (inflammation of the prostate) and benign prostatic hyperplasia, can cause symptoms similar to urinary tract infections.
Click the icon to see an image of benign prostatic hypertrophy.
Physical Examination
During an exam, the doctor should examine the pelvic and vaginal area in women. Men require a digital rectal examination to determine if prostate enlargement is present. The doctor will also examine the male genitals for signs of infection. In both men and women, the doctor should also check the abdomen and areas around the kidneys for swelling and tenderness.
Dipstick Tests
Dipstick tests, available over the counter, are quite reliable in making a reasonable diagnosis of UTIs in women with symptoms. Dipstick tests may also be useful for identifying UTIs in children and infants. The test uses a chemical on a stick that when dipped in urine reacts to nitrites, substances produced by many of the bacteria that cause UTIs. A positive test (which indicates that an infection is present) often eliminates the need for urine cultures, a more expensive test used to detect bacteria. A negative dipstick test helps to avoid unnecessary antibiotics, which are contributing to the growing problem of antibiotic resistance. These tests are not entirely accurate, however, and studies report that they may miss up to 25% of actual UTIs. If a woman has persistent UTI symptoms, and the dipstick test is negative, she should check with her doctor to see if more accurate tests are needed.
Urine Samples
A urine sample is needed for most extensive testing. In most cases, the doctor requests a clean-catch sample. There are also other methods for collecting urine, depending on the patient's condition.
Clean-Catch Sample. A clean-catch sample for UTI depends on a sample free of contaminants normally present at the opening of the urethra (white blood cells and bacteria unrelated to UTIs). To obtain an untainted urine sample, doctors usually request a so-called midstream, or clean-catch, urine sample. To provide this, the following steps are taken:
- Patients must first wash their hands thoroughly, then wash the penis or vulva and surrounding area four times, with front-to-back strokes, using a new soapy sponge each time.
- The patient must then begin urinating into the toilet and stop after a few drops.
- The patient then positions the container to catch the middle portion of the stream. Ideally, this urine will contain only the bacteria and other evidence of the urinary tract infection.
- The patient then urinates the remainder into the toilet.
- The patient securely screws the container cap in place without touching the inside of the rim.
The sample is generally given to the doctor or sent to the laboratory for analysis.
Incontinence Pads. Testing and diagnosing UTIs in elderly patients who are incontinent is especially difficult, because of the similarities in symptoms. Researchers have found that pressing a dipstick into an incontinence pad is an effective way to screen for urinary tract infections in incontinent patients.
Collection with a Catheter. Some patients (small children, elderly people, or hospitalized patients) cannot provide a urine sample. In such cases, a catheter may be inserted into the bladder to collect urine. This is the best method for providing a contaminant-free sample.
Urinalysis
A urinalysis involves a physical and chemical examination of urine. In addition, the urine is spun in a centrifuge to allow sediments containing blood cells, bacteria, and other particles to collect. This sediment is then examined under a microscope. A urinalysis offers a number of valuable clues for an accurate diagnosis:
- Color and cloudiness of urine
- Acidity
- White blood cells (leukocytes). A high count of white cells in the urine is referred to as pyuria. (A leukocyte count over 10 per microliter is considered to indicate pyuria.) Pyuria is usually sufficient for a diagnosis of UTI in nonhospitalized patients if other standard symptoms (or just fever in small children) are also present.
Treatment can be started without the need for further tests if the following urinalysis results are present in patients with symptoms and signs of UTIs:
- A high white cell count
- Cloudy urine
Urine Culture
A urine culture uses a urine specimen that is placed on an agar plate, then incubated in the laboratory for 24 - 48 hours. It is then examined for the presence of bacterial growth. Urinary tract infection is nearly always caused by a single species of bacteria, notably E. coli. Cultures have limitations, however. If a mix of different species is found, the test is considered contaminated and is redone. In addition, even if E. coli is identified, researchers are also looking for variants of these bacteria. Certain types may indicate a higher risk for a second infection, while others may even be protective against recurring infections. Furthermore, some organisms, such as Chlamydia, which is a sexually transmitted organism, may not be detected.
A urine culture is usually performed if the dipstick results are positive, but even if the results are negative, a culture may still be helpful under certain circumstances:
- If urinalysis or dipstick is negative but the patient has UTI symptoms, particularly if the patient has recurring infections or is in a high-risk group.
- If the doctor suspects complications.
- In girls less than 2 years of age with a high fever of unknown origin that lasts 2 days or more.
Even if bacteria are present in the culture, a diagnosis of UTI depends on symptoms and gender:
- The presence in a culture of at least 100,000 bacteria per milliliter of urine usually provides conclusive evidence of infection in women with symptoms.
- A count of 100,000 bacteria per milliliter in a woman without symptoms indicates asymptomatic bacteriuria. The decision to treat depends on the woman's risk factors for complications.
- In young women with symptoms of cystitis, a diagnosis of infection can reasonably be made with counts as low as 1,000 bacteria per milliliter.
- Men are considered to have an infection with a count of only 1,000.
Gram Stain
If doctors suspect that bacteria other than E. coli may be present, a Gram stain is used to help predict the species. This is a staining procedure used to make bacteria visible through a microscope. Many bacteria are categorized by the terms Gram-positive and Gram-negative.
- Bacteria that turn pink from staining are called Gram-negative
- Those that turn blue are called Gram-positive
Escherichia coli bacteria are Gram-negative and the most common cause of UTIs. If doctors suspect that bacteria other than E. coli are causing a UTI, a Gram stain is useful for identifying other species.
Imaging Techniques
Because of the expense and the limited accuracy of imaging procedures, these techniques are used only for the following:
- Serious and recurrent cases of pyelonephritis
- When structural abnormalities are suspected
- If infections do not respond to treatment
- If a doctor suspects obstruction or an abscess
- After a first urinary tract infection in children age 2 - 24 months to detect possible obstruction or vesicoureteral reflux. Tests include ultrasound and a voiding cystourethrogram and possibly scans. Some evidence suggests that ultrasound is probably not necessary, but at this time it is recommended by major medical groups.
Ultrasound. Ultrasound is a noninvasive, risk-free imaging test that can be used to screen for hydronephrosis (obstructions of the flow of urine), kidney stones that predispose to infection, and kidney abscesses. In men, ultrasound can detect enlargement or abscesses of the prostate and, when combined with x-rays, is an accurate method for detecting incomplete emptying of the bladder, a common cause of UTI in men over age 50. In children with urinary tract infections, it also can be used to detect vesicoureteral reflux, the defect of the valve-like mechanism between the ureter and bladder. Ultrasounds are not as accurate as voiding cystourethrograms.
Nuclear Scans. Imaging techniques called nuclear scans may be useful in certain complicated cases, such as detecting kidney scarring after pyelonephritis in children. They produce better images and expose the patient to far less radiation than x-rays. One such scan called dimercaptosuccinic acid (DMSA) scintigraphy uses injections of tiny amounts of radioactive tracers. A scanning machine (scintillation or gamma camera) is then used to detect pictures of the tracer in the kidney. This information is recorded on a computer screen or on film.
Magnetic Resonance Imaging (MRI) or Computed Tomography (CT). Magnetic resonance imaging (MRI) and computed tomography (CT) scans are noninvasive advanced imaging techniques that are sometimes used when nuclear scans are inconclusive. A CT scan is useful for ruling out kidney stones or obstructions in women with recurrent UTIs.
X-Rays. Special x-rays can be used to screen for structural abnormalities, urethral narrowing, or incomplete emptying of the bladder, which can cause stagnation of urine and predispose to infection.
- Voiding cystourethrogram is an x-ray of the bladder and urethra. To obtain a cystourethrogram, a dye, called contrast material, is injected through a catheter inserted into the urethra and passed through the bladder.
- An intravenous pyelogram (IVP) is an x-ray of the kidney. For a pyelogram, the contrast matter is injected into a vein and eliminated by the kidneys. In both cases, the dye passes through the urinary tract and reveals any obstructions or abnormalities on x-ray images. Due to the possible risks to the fetus, x-rays are not performed on pregnant women.
Click the icon to see an image of a voiding cystourethrogram.
Click the icon to see an image of an intravenous pyelogram.
Cystoscopy. Cystoscopy is used to detect structural abnormalities, interstitial cystitis, or masses that might not show up on x-rays during an IVP. The patient is given a light anesthetic, and the bladder is filled with water. The procedure uses a cystoscope, a flexible, tube-like instrument that the urologist inserts through the urethra into the bladder.
Click the icon to see an image of cystoscopy.
Other Diagnostic Tests for Kidney Infections and Severe UTIs
No noninvasive test will differentiate between upper and lower urinary tract infections. This is a particular problem because of the high percentage of women whose cystitis symptoms mask infections that also exist in the upper tract.
Antibiotic Trial. The best current test for pyelonephritis is the short-term antibiotic therapy given for cystitis. If the infection returns within 2 weeks after treatment, upper urinary tract infection is usually present.
Blood Cultures. If symptoms are severe, blood cultures will be taken to determine if the infection is in the bloodstream and threatening other parts of the body.
Treatment
Although antibiotics should be used as a cure for most urinary tract infections, severe symptoms can persist for several days until treatment effectively eliminates the bacteria. A number of options are available for relieving symptoms until the antibiotics take action.
Important Note. All of the drugs discussed below treat only symptoms and are not cures. They should never be used to replace antibiotics.
Phenazopyridine
Phenazopyridine (Pyridium, Uristat, Barodium, Eridium, AZO Standard) relieves pain and burning caused by the infection. It should not be taken for more than 2 days and should be discontinued when symptoms are relieved.
Side effects include headache and stomach distress. The drug turns urine a red or orange color, which can stain fabric and be difficult to remove. In rare cases, it can cause serious side effects, including shortness of breath, a bluish skin, a sudden reduction in urine output, shortness of breath, and confusion. In such cases, patients should immediately call the doctor.
Antispasm Drugs
Methenamine (Atrosept, Prosed, Urised) or flavoxate (Urispas) reduce bladder spasms, which may occur with some UTIs. These drugs can have severe side effects, however, that the patient should discuss with the doctor.
Medications
Antibiotics are the mainstay treatment for all UTIs. A variety of antibiotics are available, and choices depend on many factors, including whether the infection is complicated or uncomplicated or primary or recurrent. Treatment decisions are also based on the type of patient (man or woman, a pregnant or nonpregnant woman, child, hospitalized or nonhospitalized patient, person with diabetes). Treatment should not necessarily be based on the actual bacteria count. For example, if a woman has symptoms, even if bacterial count is low or normal, infection is probably present and antibiotic treatment should be considered.
Bacterial Resistance to Antibiotics. Antibiotic-resistant strains of E. coli, the most common cause of UTIs, are increasing. The prevalence of such bacteria has dramatically increased worldwide, in large part due to widespread use of antibiotics in humans and animal feed. In a 2003 report, 42% of E. coli were resistant to one or more of the 12 antibiotics that researchers investigated. As more bacteria have become resistant to the standard UTI treatment trimethoprim-sulfamethoxazole (TMP-SMX), more doctors have been prescribing quinolone antibiotics to treat UTIs. A 2006 study found that quinolones have now overtaken TMP-SMX as the most commonly prescribed antibiotic for UTIs. Experts are concerned that resistance may develop to these drugs as well.
Specific Antibiotics Used for Most UTIs
Beta-Lactams
The beta-lactam antibiotics share common chemical features and include penicillins, cephalosporins, and some newer similar drugs. Their primary actions to interfere with bacterial cell walls. Many have been important in the treatment of urinary tract infections.
Penicillins (Amoxicillin). Until recent years, the standard treatment for a UTI was 10 days of amoxicillin, a penicillin antibiotic, but it is now ineffective against E. coli bacteria in up to 25% of cases. A combination of amoxicillin-clavulanate (Augmentin) is sometimes given for drug-resistant infections. Amoxicillin or Augmentin may be useful for UTIs caused by Gram-positive organisms, including Enterococcus species and S. saprophyticus.
Cephalosporins. Antibiotics known as cephalosporins are also alternatives for infections that do not respond to standard treatments or for special populations. They are often classed as:
- First generation, including cephalexin (Keflex), cefadroxil (Duricef, Ultracef), and cephradine (Velosef).
- Second generation, including cefaclor (Ceclor), cefuroxime (Ceftin), cefprozil (Cefzil), and loracarbef (Lorabid).
- Third generation, including cefpodoxime (Vantin), cefdinir (Omnicef) cefditoren (Sprectracef), cefixime (Suprax), and ceftibuten (Cedex). Ceftriaxone (Rocephin) is an injected cephalosporin. These are effective against a wide range of Gram-negative bacteria.
Other Beta-Lactam Drugs. Other beta-lactam antibiotics have been developed. For example, pivmecillinam (a form of mecillinam), is commonly used in Europe for UTIs. It appears to be safe during pregnancy.
Trimethoprim-Sulfamethoxazole (TMP-SMX)
The typical treatment is a 3-day course of the combination drug trimethoprim-sulfamethoxazole, commonly called TMP-SMX (Bactrim, Cotrim, Septra). A 1-day course is somewhat less effective but poses a lower risk for side effects. Longer courses (7 - 10 days) work no better than the 3-day course and have a higher rate of side effects. TMP-SMX should not be used in patients whose infections occurred after dental work or in patients allergic to sulfa drugs. Allergic reactions can be very serious. Trimethoprim (Proloprim, Trimpex) is sometimes used alone in those allergic to sulfa drugs. TMP-SMX can interfere with the effectiveness of oral contraceptives. High rates of bacterial resistance to TMP-SMX exist in many parts of the United States. Still, even when regional rates approach 30%, cure rates with TMP-SMX reach 80 - 85%.
Fluoroquinolones (Quinolones)
Fluoroquinolones (also simply called quinolones) are now becoming as widely used as TMP-SMX. These drugs interfere with the bacteria's genetic material so they cannot reproduce. They are the standard alternatives to TMP-SMX. Examples of quinolones include ofloxacin (Floxacin), ciprofloxacin (Cipro), norfloxacin (Noroxin), levofloxacin (Levaquin), gatifloxacin (Tequin), and sparfloxacin (Zagam). These antibiotics are effective against a wide range of organisms but are expensive and, in general, used in the following circumstances:
- In patients with complicated or catheter-induced UTIs
- In patients who do not respond or who are allergic to TMP-SMX
- In communities where there are high rates of bacteria resistant to TMP-SMX
- In elderly patients. A 2001 study of older women with UTIs (mean age 80), about half of whom were living in nursing homes, found that 96% responded to ciprofloxacin, compared with 87% to TMP-SMX.
Pregnant women should not take fluoroquinolone antibiotics. They also have more adverse effects in children than other antibiotics and should not be the first-line option in most situations.
Antibiotics Used Specifically for UTIs
Nitrofurantoin. Nitrofurantoin (Furadantin, Macrodantin) is a relatively inexpensive antibiotic that is used specifically for urinary tract infections. It is an effective alternative to TMP-SMX or a quinolone. Unlike many of the other drugs, however, it must be given 7 - 10 days, even in cases of simple cystitis. (Shorter course treatments are being investigated.) It is not useful for treating kidney infections. Nitrofurantoin frequently causes stomach upset and interacts with many drugs. Other chronic or serious medical conditions may also affect its use. It should not be used in pregnant women within 1 - 2 weeks of delivery, in nursing mothers, or in those with kidney disease.
Fosfomycin. The antibiotic fosfomycin (Monurol), which comes in an orange-flavored, soluble powder, is proving to be another good alternative. It can be an effective 1-dose treatment for many women, including those who are pregnant. To date, bacterial resistance rates to this antibiotic are very low.
Tetracyclines
Tetracyclines inhibit bacterial growth. They include doxycycline, tetracycline, and minocycline. Long-term treatment with tetracycline or doxycycline may be used for infections that are caused by Mycoplasma or Chlamydia. Tetracyclines have unique side effects among antibiotics, including skin reactions to sunlight, possible burning in the throat, and tooth discoloration.
Aminoglycosides
Aminoglycosides (gentamicin, kanamycin, tobramycin, amikacin) are given by injection for very serious bacterial infections. They can be given only in combination with other antibiotics. Gentamicin is the most commonly used aminoglycoside for serious UTIs. They can have very serious side effects, including damage to hearing, sense of balance, and kidneys.
Treatment for Uncomplicated UTIs
UTIs in low-risk women can often be successfully treated over the phone. In such cases, a health professional provides the patients with 3-day antibiotic regimens without even requiring an office urine test. This course is recommended only for women at low risk for recurrent infection and who do not have symptoms suggesting other problems, such as vaginitis.
Antibiotic Regimen. Oral antibiotic treatment cures 94% of uncomplicated urinary tract infections, although the rate of recurrence remains high. The following antibiotics are commonly used for uncomplicated UTIs:
- The standard regimen has traditionally been a 3-day course of trimethoprim-sulfamethoxazole, commonly called TMP-SMX (Bactrim, Cotrim, Septra). TMP-SMX combines an antibiotic with a sulfa drug. A single dose of TMP-SMX is sometimes prescribed in mild cases, but cure rates are generally lower than with the 3-day regimens.
- Fluoroquinolone antibiotics, also called quinolones, have usually been a second choice. However, in geographic areas that have a high resistance to TMP-SMX, quinolones are now the first-line treatment for UTIs. Ciprofloxacin (Cipro) is the quinolone antibiotic most commonly prescribed. Quinolones are usually given over a 3day period. Pregnant women should not take these drugs.
- Nitrofurantoin (Furadantin, Macrodantin) is a third option. This drug must be given for longer than 3 days.
- Fosfomycin (Monurol) is not as effective as other antibiotics but may be used during pregnancy. Resistance rates to this drug are very low.
- Many other effective antibiotics are available, including amoxicillin (with or without clavulanate) and cephalosporins. Doxycycline is often effective but cannot be given to children or pregnant women.
After a week of antibiotic treatment, most patients are free of infection. If the symptoms do not clear up within the first few days of therapy, doctors generally suggest that women discontinue their antibiotic and provide a urine sample for culturing in order to identify the specific organism causing the condition.
Treatment for Relapsing Infection. A relapsing infection (caused by treatment failure) occurs within 3 weeks in about 10% of women. Relapse is treated similarly to a first infection, but the antibiotics are continued for at least 2 weeks. (Relapsing infections may be due to structural abnormalities, abscesses, or other problems that may require surgery, and such conditions should be ruled out.)
Antibiotic Treatment for Recurrent Infections
Preventive antibiotics may be required for women who experience two or more symptomatic UTIs within 6 months or three or more over the course of a year. A woman's own perception of discomfort can generally guide her decisions on whether to use preventive antibiotics or not. All women should use lifestyle measures to prevent recurrences.
Intermittent Self Treatment. Many, if not most, women with recurrent UTIs can effectively self-treat recurrent UTIs without going to a doctor. In general, this requires the following steps:
- As soon as the patient develops symptoms, she takes the antibiotic. Infections that occur less than twice a year are usually treated as if they were an initial attack, with single-dose or three-day antibiotic regimens.
- At that time, she also performs a clean-catch urine test and sends it to the doctor for culturing to confirm the infection.
A doctor should be consulted under the following circumstances:
- If symptoms have not completely resolved within 48 hours
- If there is a change in symptoms
- If the patient suspects that she is pregnant
- If the patient has more than four infections a year
Women who are not good candidates for self-treatment are those with impaired immune systems, previous kidney infections, structural abnormalities of the urinary tract, or a history of infection with antibiotic-resistant bacteria.
Postcoital Antibiotics. If recurrent infections are clearly related to sexual activity and episodes recur more than two times within a 6-month period, a single preventive dose taken immediately after intercourse is very effective. Antibiotics for such cases include TMP-SMX, nitrofurantoin, cephalexin, or a fluoroquinolone (such as ciprofloxacin). (Fluoroquinolones are not appropriate during pregnancy.)
Continuous Preventive Antibiotics (Prophylaxis). Continuous preventive (prophylactic) antibiotics are an option for some women who do not respond to other measures. With this approach, low-dose antibiotics are taken continuously for 6 months or longer.
Typical prophylactic regimens include one dose of nitrofurantoin (50 mg), 1/2 tablet of TMP-SMX, or cephalexin (250 mg) daily. Taking the antibiotic at bedtime may be most effective. Studies suggest that continuous prophylactic antibiotics reduces recurrences by up to 95% and may prevent kidney infection.
Adverse effects mostly include gastrointestinal problems and yeast infections. (Taking probiotic supplements or eating yogurt may help prevent yeast infections.) Although there is concern that continuous risk increases the risk for bacteria that are resistant to the antibiotics, studies to date have not reported any significant risk even up to 5 years of use.
Antibiotics for Kidney Infections (Pyelonephritis)
Treating Uncomplicated Kidney Infections. Patients with uncomplicated kidney infections (pyelonephritis) may be treated at home with oral antibiotics. Such patients are healthy and nonpregnant. They typically are experiencing fever, chills, and flank pain. However, they are not nauseous or vomiting and show no symptoms or signs of kidney involvement or complicated infection.
The standard treatment for uncomplicated pyelonephritis is a 14-day course of oral antibiotics, usually trimethoprim-sulfamethoxazole (TMP-SMX) or a fluoroquinolone. Sometimes patients with uncomplicated pyelonephritis are first given an antibiotic injection, if indicated.
Oral amoxicillin or amoxicillin-clavulanate (Augmentin) may be prescribed for women with bacteria (Gram-positive organisms, including Enterococcus species and S. saprophyticus) that do not respond to standard regimens.
A urine culture may be obtained within 1 week of completion of therapy and again 4 weeks later.
Treating Moderate-to-Severe Kidney Infections. Patients with moderate-to-severe acute kidney infection and those with severe symptoms or other complications may need to be hospitalized. In such cases, antibiotics (ceftriaxone and gentamicin) are usually given intravenously for 3 - 5 days or until symptoms are relieved and patients have not shown any signs of fever for 24 - 48 hours.
If fever and back pain persist after 72 hours of antibiotic administration, the doctor will usually order imaging tests to see if abscesses, obstructions, or other abnormalities are present.
Treating Chronic Kidney Infections. Patients with chronic pyelonephritis are often treated with long-term antibiotics, even during periods when they have no symptoms.
Treatments for Interstitial Cystitis
The two approved treatments for interstitial cystitis are pentosan polysulfate (Elmiron), and dimethyl sulfoxide (DMSO). Patients generally prefer Elmiron because it can be taken by mouth. A DMSO solution is instilled into the bladder through a catheter. Elmiron is a type of blood thinner that helps to coat the bladder lining and prevent infections. It may take several months before having an effect on symptoms, but the benefits increase the longer the drug is used.
Doctors sometimes also prescribe other types of medications to help interstitial cystitis symptoms. These drugs include antihistamines, such as hydroxyzine (Atarax), and low doses of the tricyclic antidepressant amitriptyline (Elavil). Drugs that reduce bladder spasms (hyoscine, oxybutynin) are also sometimes used. Other treatments are being investigated, including hyperbaric oxygen therapy. This treatment involves having a patient breathe pure oxygen inside a sealed pressurized chamber.
Some doctors think that interstitial cystitis may be related to immune disorders. Researchers are investigating various drugs that block immune and inflammatory responses.
Treatments for Specific Populations
Treating the Pregnant Woman. Pregnant women should be screened for UTIs, since they are at high risk for UTIs and their complications. The antibiotics used during pregnancy are amoxicillin, ampicillin, nitrofurantoin, or an oral cephalosporin. Fosfomycin (Monurol) is not as effective as others but may be used during pregnancy. Pregnant women should not take fluoroquinolones.
Pregnant women with even asymptomatic bacteriuria (evidence of infection but no symptoms) have a 30% risk for acute pyelonephritis in their second or third trimester. They need screening and treatment for this condition. In such cases, they should be treated with a short course of antibiotics (3 - 5 days). For an uncomplicated UTI, pregnant women may need longer-term antibiotics (7 - 10 days).
Treating Women with Diabetes. Women with diabetes have more frequent and more severe UTIs than women without the disease. Many experts recommend that patients with diabetes and UTI, even an uncomplicated infection, be treated with antibiotics for 7 - 14 days. People with diabetes have higher than average rates of asymptomatic bacteriuria, but it is unclear whether they should be screened and treated for this condition. A 2003 study indicated that treating this condition had little value in these women and did not prevent complications.
Treating Urethritis in Men. Urethritis in men has typically been treated with a 7-day regimen of doxycycline. Some research suggests that a single dose of azithromycin may be just as effective while causing fewer side effects. One-dose treatment also improves compliance, so cure rates may even be better than with a long-term regimen. However, once an infection spreads to the prostate gland it is harder to treat, so most doctors still prefer the longer regimen. Patients with urethritis should also be tested for an accompanying sexually transmitted disease such as gonorrhea.
Treating Children with UTIs. Children with UTIs are generally treated with TMP-SMX or cephalexin (Keflex). These drugs are usually taken by mouth in either liquid or pill form. Doctors sometimes give them as a shot or IV. Children usually respond to treatment within a few days. Antibiotic resistance to cephalosporin antibiotics such as cephalexin is increasing, and some doctors prefer to prescribe an aminoglycoside antibiotic. Gentamicin (Garamycin) is the aminoglycoside antibiotic that is most commonly used. It is given intravenously.
Vesicoureteral reflux (VUR) is a concern for children with UTIs. About a third of children with UTIs develop this condition, in which urine backs up into the kidneys. VUR can lead to kidney infection (pyelonephritis), which can cause kidney damage. Either long-term antibiotics or surgery are options to correct vesicoureteral reflux (VUR) and prevent infection. Many experts recommend surgery over antibiotics, especially due to concerns of antibiotic resistance. Antibiotic treatment usually continues for years with the idea that the condition will resolve when the child has grown. However, a 2006 study suggested that long-term antibiotics are not useful for preventing VUR. Furthermore, the study found that mild-to-moderate VUR does not increase the likelihood of UTIs or pyelonephritis.
Children with acute kidney infection are treated with oral cefixime (Suprax) or a short course (2 - 4 days) of an intravenous (IV) antibiotic (typically gentamicin, given in one daily dose). An oral antibiotic then follows the IV.
Management of Catheter-Induced Urinary Tract Infections
Preventing Catheter-Induced Infections
Catheter-induced urinary tract infections are very common, and preventive measures are extremely important. Catheters should not be used unless absolutely necessary, and they should be removed as soon as possible. Reducing the risk for infections during long-term catheter use, however, remains problematic.
Catheter Coatings. Catheter coatings, such as silver nitrate, antibiotics, and other substances, are being tested and are showing some benefits, but the problem is still not resolved. One promising catheter (LoFric) uses a so-called hydrophilic coating consisting of PVP (polyvinyl pyrrolidone) and salt. It attracts water to the catheter surface, putting up a water barrier to reduce friction. In a 2003 study, it was associated with significantly fewer UTIs.
Intermittent Use of Catheters. If a catheter is required for long periods, it is best to use it intermittently if possible (as opposed to an indwelling catheter). Some doctors recommend replacing it every 2 weeks to reduce the risk of infection and irrigating the bladder with antibiotics between replacements.
Daily Hygiene. A typical catheter is one that has been preconnected and sealed and uses a drainage bag system. To prevent infection, some of the following tips may be helpful:
- Drink plenty of fluids, including 3 glasses of cranberry juice a day.
- The catheter tube should be free of any knots or kinks.
- Clean the catheter and the area around the urethra with soap and water daily and after each bowel movement. (Women should be sure to clean front to back.)
- Wash hands before touching the catheter or surrounding area.
- Never disconnect the catheter from the drainage bag without careful instructions from a health professional on strict methods for preventing infection.
- Keep the drainage bag off the floor.
- Stabilize the bag against the leg using tape or some other system.
Antibiotics for Catheter-Induced Infections
Patients using catheters who develop UTIs with symptoms should be treated for each episode with antibiotics and the catheter should be removed, if possible. A major problem in treating catheter-related UTIs is that the organisms involved are constantly changing. Because there are likely to be multiple species of bacteria, experts generally recommend an antibiotic that is effective against a wide variety of microorganisms. These medications include those in the fluoroquinolone group and drug combinations such as ampicillin plus gentamicin or imipenem plus cilastatin.
Although high bacteria counts in the urine (bacteriuria) occur in most catheterized patients, administering antibiotics to prevent a UTI is rarely recommended. Many catheterized patients do not develop symptomatic urinary tract infections even with high bacteria counts. If bacteriuria occurs without symptoms, antibiotic therapy has little benefit if the catheter is to remain in place for a long period.
Other Treatments
The following are hygiene tips. Although there is no evidence that good hygiene makes a real difference in preventing UTIs, it is always a wise practice.
- Clean the genital and urinary areas from front to back with soap and water after each bowel movement.
- Keep the genital and anal areas clean before and after sex. Urinate before and after intercourse to empty the bladder and cleanse the urethra of bacteria.
- Avoid tight-fitting pants.
- Wear cotton-crotch underwear and panty hose, changing both at least once a day. (Mild detergents are best for washing underwear.)
- Take showers rather than baths.
- Avoid bath oils, feminine hygiene sprays, douches, and powders. As a general rule, do not use any product containing perfumes or other possible allergens near the genital area. Douching in is never recommended. It may destroy the natural antiviral organisms normally present in the vagina, making women more susceptible to human papillomavirus (HPV), a risk factor for cervical cancer.
- Choose sanitary napkins instead of tampons (which some doctors believe encourage infection). Napkins and tampons, in any case, should be changed after each urination.
- Urinate frequently.
Sexual Precautions
The following recommendations may reduce the risks from sexual activity:
- In women using contraceptives, consider alternatives, particularly if exposed to spermicides from condoms or diaphragms. Discuss the best contraceptive choice with a doctor.
- Avoid sex with multiple partners. This can cause many health problems, including sexually transmitted diseases and UTIs.
Estrogen Cream or Estrogen-Releasing Vaginal Devices
Postmenopausal women with recurrent UTIs may consider the use of an estrogen vaginal cream or estrogen-releasing vaginal ring (Estring). Estrogen may resist infection by increasing the number of lactobacilli, the microorganism that fights infection by lowering the vaginal pH levels and preventing E. coli from adhering to vaginal cells. Estrogen creams and estrogen-releasing rings may help reduce the risk of recurring urinary tract infections. Oral hormone replacement therapies that contain estrogen do not seem to provide the same benefit as the topical forms. Estrogen HRT carries many health risks, including an increased risk for breast cancer and heart disease. It is not clear if vaginal forms of estrogen are associated with these risks.
Fluids
Many doctors believe that emptying the bladder frequently will help prevent bladder irritation and therefore recommend drinking plenty of water daily and urinating often.
Cranberries, Blueberries, and Lignonberries
Cranberries, blueberries, and lignonberry, a European relative of the cranberry, are three fruits that may have protective properties. Researchers are finding that red pigments in these closely related fruits called tannins (or proanthocyanadins) prevent E. coli bacteria from adhering to cells in the urinary tract, thereby inhibiting infection. Fructose, which is commonly used to sweeten fruit juices, may also interfere with bacterial adhesion.
Cranberry juice offers well-known protection against urinary tract infections. In one study, only 15% of elderly women who drank cranberry juice daily for 6 months experienced UTIs, compared with 28% of women who did not drink the juice. Its effects were stronger in helping the body rid itself of infections than in preventing them in the first place, but it showed benefits in both situations.
Studies suggest that for protection, it is necessary to drink at least one to two cups of 30% cranberry or lignonberry juice daily, or to take at least 300 - 400 mg in tablet form twice daily.
Probiotics, Lactobacilli, and Fermented Milk Products
Important research has targeted probiotics (essentially friendly organisms), which may protect against infections in the genital and urinary tracts. They may have other health benefits as well. The best-known probiotics are the lactobacilli strains, such as acidophilus, which is found in yogurt and other fermented milk products (kefir). The probiotics bifidobacteria and GG lactobacilli may prove to be even more important. Other probiotics include the lactobacilli rhamnosus, casel, plantarium, bulgaricus, and salivarius, and also Enterococcus faecium and Streptococcus thermophilus.
Lactobacilli have the potential to help protect women from UTIs in a number of ways:
- Maintain a low pH environment
- Hinder E. coli growth
- Produce hydrogen peroxide, which produces an environment hostile for bacteria
In a 2003 study, drinking fermented milk reduced the risk for UTIs. Not all studies show benefits from drinks containing lactobacilli, but more research is warranted.
Herbs and Dietary Supplements
Researchers are studying several different herbal treatments for urinary tract infections. Studies on these herbs have only been conducted on animals and cell samples -- not in humans:
- Forskolin, an extract from the Indian coleus plant, may help flush out bacteria hiding in the lining of the bladder.
- Green tea contains compounds that may help prevent inflammation in bladder cells.
- St. Johns wort, a popular herbal remedy for depression, may help relieve pain associated with interstitial cystitis.
It is important to inform your doctor of any herbs, dietary supplements, or vitamins and minerals that you take or are considering taking. Some of these remedies may actually increase your chance of developing urinary tract infections. For example, high doses of zinc have been associated with increased risk of UTIs.
Generally, manufacturers of herbal remedies and dietary supplements do not need FDA approval to sell their products. Just like a drug, herbs and supplements can affect the body's chemistry, and therefore have the potential to produce side effects that may be harmful. There have been a number of reported cases of serious and even lethal side effects from herbal products. Always check with your doctor before using any herbal remedies or dietary supplements.
Biofeedback
Biofeedback is a technique that provides visual and auditory clues in response to specific exercises. Some research indicates that biofeedback teaches children who are prone to UTIs to relax and control their pelvic muscles, resulting in fewer recurrences of infection.
Resources
- http://kidney.niddk.nih.gov -- National Kidney and Urologic Diseases Clearinghouse
- www.urologyhealth.org -- American Urological Association
- www.acog.org -- American College of Obstetricians and Gynecologists
- www.ichelp.com -- Interstitial Cystitis Association
References
Bishop BL, Duncan MJ, Song J, Li G, Zaas D, Abraham SN. Cyclic AMP-regulated exocytosis of Escherichia coli from infected bladder epithelial cells. Nat Med. 2007 May;13(5):625-30. Epub 2007 Apr 8.
Johnson AR, Munoz A, Gottlieb JL, Jarrard DF. High dose zinc increases hospital admissions due to genitourinary complications. J Urol. 2007 Feb;177(2):639-43.
Litwin MS, Saigal CS, editors. Urologic Diseases in America. US Department of Health and Human Services, Public Health Service, National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases. Washington, DC: US Government Printing Office, 2007; NIH Publication No. 075512.
Reviewed By: Harvey Simon, MD, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital.
