Causes

When your body performs its normal functions, it produces acid. If this acid is not removed or neutralized, your blood will become too acidic. This can lead to electrolyte imbalances in the blood.

Your kidneys help control your body's acid level by removing acid from the blood and sending it into your urine. Acidic substances in the body are counteracted by alkaline substances, primarily bicarbonate.

Proximal renal tubular acidosis (Type II RTA) occurs when bicarbonate is not properly reabsorbed by the the kidney's filtering system, 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• Drugs such as ifosfamide (a chemotherapy drug), outdated tetracycline, aminoglycoside antibiotics, or acetazolamide
• Fanconi syndrome
• Inherited fructose intolerance
• Multiple myeloma
• Primary hyperparathyroidism
• Sjogren syndrome
• Wilson's disease
• Vitamin D deficiency

Symptoms

• Confusion or decreased alertness
• Dehydration
• Fatigue
• Increased breathing rate
• Osteomalacia
• Muscle pain
• Rickets
• Weakness

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

Arterial blood gas and blood chemistries may suggest metabolic acidosis and electrolyte imbalances, most often low levels of potassium or bicarbonate.

Other tests that may be done include:

• Blood pH level
• Urine pH
• Urinalysis may show abnormal levels of phosphate, calcium, glucose, and amino acids

This disease may also change the results of the following tests:

• Acid loading test (pH)
• Blood potassium level
• Urine calcium
• Urine citric acid
• Urine potassium level

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 acid-induced bone disease, such as rickets, 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 blood potassium levels. Thiazide diuretics may indirectly decrease bicarbonate loss but may worsen the low blood 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.

Alternative Names

Renal tubular acidosis - proximal; Type II RTA; RTA - proximal; Renal tubular acidosis type II

References

Seifter JL. Acid-base disorders. In: Goldman L, Schafer AI, eds.Cecil Medicine. 24th ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 120.

Updated: 4/19/2012

Reviewed by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; Herbert Y. Lin, MD, PHD, Nephrologist, Massachusetts General Hospital; Associate Professor of Medicine, Harvard Medical School. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.