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Overview of renal tubular acidosis


The lungs and the kidneys are responsible for the maintenance of acid-base balance within the body. Alveolar ventilation removes carbon dioxide, while the kidneys reclaim filtered bicarbonate and excrete hydrogen ions produced by the metabolism of dietary protein. (See "Chapter 11B: Regulation of renal hydrogen excretion".)

The term "renal tubular acidosis" (RTA) refers to a group of disorders in which, despite a relatively well-preserved glomerular filtration rate, metabolic acidosis develops because of defects in the ability of the renal tubules to perform the normal functions required to maintain acid-base balance [1]. All forms of RTA are characterized by a normal anion gap (hyperchloremic) metabolic acidosis. This form of metabolic acidosis usually results from either the net retention of hydrogen chloride or its equivalent (such as ammonium chloride) or the net loss of sodium bicarbonate or its equivalent [2]. The major cause of a normal anion gap acidosis in patients without a significant impairment in renal function is diarrhea. (See "Approach to the adult with metabolic acidosis".)

There are three major subgroups of RTA with different clinical characteristics (table 1):

  • Distal or type 1 RTA
  • Proximal or type 2 RTA
  • Hypoaldosteronism or type 4 RTA

Although initially used to describe a transiently severe form of distal RTA in infants, the term type 3 or mixed RTA is now most often applied to a rare autosomal recessive syndrome (resulting from carbonic anhydrase II deficiency) with features of both distal and proximal RTA [1,3,4]. In addition to RTA, affected patients suffer from osteopetrosis, cerebral calcification, and mental retardation. (See "Etiology and clinical manifestations of renal tubular acidosis in infants and children", section on 'Mixed (type 3) RTA'.)


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Literature review current through: Jun 2014. | This topic last updated: Jan 15, 2013.
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