Proximal renal tubular acidosis
Proximal renal tubular acidosis is a disease that occurs when the kidneys don't properly remove acids from the blood into the urine. As a result, too much acid remains in the blood (called acidosis).
Renal tubular acidosis - proximal; Type II RTA; RTA - proximal; Renal tubular acidosis type II
When the body performs its normal functions, it produces acid. If this acid is not removed or neutralized, the blood will become too acidic. This can lead to electrolyte imbalances in the blood. It can also cause problems with normal function of some cells.
The kidneys help control the body's acid level by removing acid from the blood and excreting it into the urine. Acidic substances in the body are neutralized by alkaline substances, mainly bicarbonate.
Proximal renal tubular acidosis (Type II RTA) occurs when bicarbonate is not properly reabsorbed by the kidney's filtering system.
Type II RTA is less common than Type I RTA. Type II most often occurs during infancy and may go away by itself.
Causes of type II RTA include:
- Cystinosis (body is unable to break down the substance cysteine)
- Drugs such as ifosfamide (a chemotherapy drug), certain antibiotics that are no longer used much (tetracycline), or acetazolamide
- Fanconi syndrome
- Inherited fructose intolerance
- Multiple myeloma
- Primary hyperparathyroidism
- Sjogren syndrome
- Wilson disease
- Vitamin D deficiency
Symptoms of distal renal tubular acidosis include any of the following:
- Confusion or decreased alertness
- Increased breathing rate
- Muscle pain
Other symptoms can include:
- Decreased urine output
- Increased heart rate or irregular heartbeat
- Muscle cramps
- Pain in the bones, back, flank, or abdomen
- Skeletal deformities
Exams and Tests
The doctor will perform a physical exam and ask about the symptoms.
Tests that may be ordered include:
Other tests that may be done include:
The goal is to restore normal acid level and electrolyte balance in the body. This will help correct bone disorders and reduce the risk of osteomalacia and osteopenia in adults.
Some adults may need no treatment. All children need alkaline medicine such as potassium citrate and sodium bicarbonate. This is medicine that helps correct the acidic condition of the body. The medicine helps prevent bone disease caused by too much acid, such as rickets, and to allow normal growth.
The underlying cause of proximal renal tubular necrosis should be corrected if it can be found.
Vitamin D and calcium supplements may be needed to help reduce skeletal deformities resulting from osteomalacia or rickets.
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.
Untreated, distal renal tubular acidosis can lead to any of the following conditions:
- Electrolyte imbalances, such as hypokalemia
When to Contact a Medical Professional
Call your health care provider if you have symptoms of proximal renal tubular acidosis.
Get medical help right away if any of the following emergency symptoms develop:
Most of the disorders that cause proximal renal tubular acidosis are not preventable.
DuBose TD Jr. Disorders of acid-base balance. In: Taal MW, Chertow GM, Marsden PA, et al., eds. Brenner and Rector’s The Kidney. 9th ed. Philadelphia, Pa: Elsevier Saunders; 2011:chap 16.
Seifter JL. Acid-base disorders. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, Pa: Elsevier Saunders; 2011:chap 120.
Bakkalogul SA, Schaefer F. Diseases of the kidney and urinary tract in children. In: Taal MW, Chertow GM, Marsden PA, et al., eds. Brenner and Rector's The Kidney. 9th ed. Philadelphia, Pa: Elsevier Saunders; 2011:chap 75.
Reviewed By: Brent Wisse, MD, Associate Professor of Medicine, Division of Metabolism, Endocrinology & Nutrition, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.