Proximal renal tubular acidosis
Definition
Proximal renal tubular acidosis is a condition that occurs when the kidneys don't properly remove acids in the urine, leaving the blood too acidic.
Alternative Names
Renal tubular acidosis - proximal; Type II RTA; RTA - proximal; Renal tubular acidosis type II
Causes
Your kidneys help regulate your body's acid-base balance (pH). Acidic substances in the body are buffered (counteracted) by alkaline substances, primarily bicarbonate.
The kidneys contain more than a million filtering units, called nephrons. Bicarbonate is reabsorbed into the blood in the nearest (proximal) tubule of each nephron. Proximal renal tubular acidosis (Type II RTA) occurs when bicarbonate isn't properly reabsorbed by the proximal tubules, leaving the body in an acidic state (called acidosis).
Type II RTA is less common than Type I RTA. It most often occurs during infancy, and may go away by itself.
Causes of type II RTA include:
- Cystinosis
- Drugs such as ifosfamide (a chemotherapy drug), outdated tetracycline, or acetazolamide
- Fanconi Syndrome
- Inherited fructose intolerance
- Wilson's disease
Symptoms
- Confusion or decreased alertness
- Dehydration
- Fatigue
- Increased breathing rate
- Osteomalacia
- Muscle pain
- Rickets
- Weakness
Other symptoms can include:
- Bloody urine
- Decreased urine output
- Increased heart rate or irregular heartbeat
- Muscle cramps
- Pain in the bones, back, flank, or abdomen
- Skeletal deformities
Exams and Tests
- Arterial blood gas and blood chemistries may indicate metabolic acidosis and electrolyte abnormalities.
- Measurements of the blood pH and urine pH may show a problem. The urine may be alkaline, although this may change as the body becomes more acidic.
- Urinalysis may show abnormal levels of phosphate, calcium, glucose, and amino acids in the urine.
Treatment
The goal is to restore the normal pH (acid-base level) and electrolyte balance to the body. This will indirectly correct bone disorders and reduce the risk of osteomalacia and osteopenia in adults.
Some adults may need no treatment. All children need alkaline medication to prevent bone disease (rickets in particular) and to allow normal growth. The underlying cause should be corrected if it can be found.
Alkaline medications include sodium bicarbonate and potassium citrate. They correct the acidic condition of the body and correct low potassium levels. Thiazide diuretics may indirectly decrease bicarbonate loss but may increase the low potassium levels.
Vitamin D and calcium supplements may be needed to help reduce skeletal deformities resulting from osteomalacia or rickets.
Outlook (Prognosis)
Although the underlying cause of proximal renal tubular acidosis may go away by itself,the effects and complications can be permanent or life-threatening. Treatment is usually successful.
Possible Complications
- Electrolyte imbalances, such as hypokalemia
- Osteomalacia
- Rickets
When to Contact a Medical Professional
Call your health care provider if you have symptoms of proximal renal tubular acidosis.
Get medical help immediately if you develop any of the following emergency symptoms:
- Decreased alertness or orientation
- Decreased consciousness
- Seizures
Prevention
Most of the disorders that cause proximal renal tubular acidosis are not preventable.
Reviewed By: Charles Silberberg, D.O., Private Practice specializing in Nephrology, affiliated with NY Medical College, Division of Nephrology, Valhalla, NY. Review provided by VeriMed Healthcare Network.
