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, incidence, and risk factors

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• Drugs such as ifosfamide (a chemotherapy drug), outdated tetracycline, or acetazolamide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

Signs 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.

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 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.

Support Groups

Expectations (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.

Complications

• Electrolyte imbalances, such as hypokalemia
• Osteomalacia
• Rickets

Calling your health care provider

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.

Images

---

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org). URAC's accreditation program is an independent audit to verify that A.D.A.M. follows rigorous standards of quality and accountability. A.D.A.M. is among the first to achieve this important distinction for online health information and services. Learn more about A.D.A.M.'s editorial policy, editorial process, and privacy policy. A.D.A.M. is also a founding member of Hi-Ethics and subscribes to the principles of the Health on the Net Foundation (www.hon.ch.)

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. ©1997-2008 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.