Proximal renal tubular acidosis

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Kidney anatomy

Kidney - blood and urine flow

The term "renal" refers to the kidney. The kidney contains over a million functional units called nephrons, which filter your blood and produce urine. Normally, a blood buffer called bicarbonate is reabsorbed into the blood in the proximal tubule of each nephron. When it is not reabsorbed properly, your body is left an acidic state (called acidosis).

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

When healthy, your body is very slightly alkaline. Acidic substances in the body, such as carbon dioxide, are buffered (counteracted) by alkaline substances, primarily bicarbonate. Your kidneys regulate your body's pH by controlling acids and bicarbonate buffer.

An acidic state in your body can be caused by high carbon dioxide levels (respiratory acidosis). It can also be caused by low bicarbonate levels (metabolic acidosis).

Proximal renal tubular acidosis (Type II RTA) is a result of poor bicarbonate reabsorption by the proximal tubules. This leads to lower bicarbonate buffer in the blood, causing metabolic acidosis.

Type II RTA is less common than  Type I RTA. It most commonly occurs during infancy, and may go away by itself.

Many different molecular abnormalities can lead to Type II RTA. It can occur in an isolated form or with general problems with the proximal tubule. (See Fanconi's Syndrome.)

People with Type II RTA tend to reabsorb chloride to compensate, and thus have high blood serum chloride levels. They are also low in potassium.

Review Date: 12/09/2005
Reviewed By: Colm C. Magee, MD, MPH, Medical Director, Renal Transplant, Brigham & Women's Hospital, and Assistant Professor, Harvard Medical School, Boston, MA. Review provided by VeriMed Healthcare Network.