Health Encyclopedia

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Drugs such as ifosfamide (a chemotherapy drug), outdated tetracycline, or acetazolamide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

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:

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.

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:

Prevention

Most of the disorders that cause proximal renal tubular acidosis are not preventable.

Review Date:11/12/2007
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.

ADAM Quality 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 the first of its kind, requiring compliance with 53 standards of quality and accountability, verified by independent audit. 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 process. A.D.A.M. is also a founding member of Hi-Ethics (www.hiethics.com) and subscribes to the principles of the Health on the Net Foundation (www.hon.ch).

The Agency for Health Care Administration (Agency) and this website do not claim the information on, or referred to by, this site is error free. This site may include links to websites of other government agencies or private groups. Our Agency and this website do not control such sites and are not responsible for their content. Reference to or links to any other group, product, service, or information does not mean our Agency or this website approves of that group, product, service, or information.

Additionally, while health information provided through this website may be a valuable resource for the public, it is not designed to offer medical advice. Talk with your doctor about medical care questions you may have.