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Distal renal tubular acidosis

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Definition:

The term "renal" refers to the kidney. The kidney contains over a million functional units called nephrons, which filter your blood and produce urine. Distal renal tubular acidosis is caused by abnormal excretion of acid from the distal tubule of each nephron. As a result, your body is left an acidic state (called acidosis).

Alternative Names:

Renal tubular acidosis - distal; Renal tubular acidosis type I; Type I RTA; RTA - distal; Classical RTA

Causes, incidence, and risk factors:

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. It can also be caused by low bicarbonate levels ( metabolic acidosis ).

Distal renal tubular acidosis (Type I RTA) is a disorder caused by a defect in the secretion of hydrogen ions in the distal renal tubule of each nephron. This reduces the reabsorption of bicarbonate into the bloodstream.

Type I RTA is caused by a variety of conditions including hereditary disorders, autoimmune diseases and certain drugs including amphotericin B, lithium, and analgesics.

Renal tubular acidosis causes disorders related to the loss of bicarbonate and inability to excrete hydrogen. The body attempts to maintain a balance between positively charged and negatively charged molecules. If the excretion of a molecule is abnormal, the excretion of other molecules may become abnormal in an attempt to maintain a balance.

Type I RTA causes retention of acid and is also associated with mild loss of potassium in the urine.

The acidic condition of the body causes calcium to dissolve from the bones. The calcium accumulates in the bloodstream, and excess serum calcium is excreted by the kidneys, causing a loss of total body calcium and resulting in osteomalacia or rickets , impaired growth of children, skeletal deformities, and muscle weakness .

There is an increased incidence of kidney stones and nephrocalcinosis associated with the excessive excretion of calcium and phosphate through the kidneys.

• Review Date: 12/19/2005
• 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.

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