Proximal RTA

The process by which bicarbonate is reabsorbed in the proximal tubule has already been described. Click here. 

H⁺ ions must be secreted into the lumen of the tubule and failure of this process will lead to RTA.  This can occur as an isolated defect or as part of a generalised disorder of proximal tubular function - Fanconi's syndrome.

The acidosis is maintained by virtue of the fact that NH₄⁺ excretion remains low despite the acidosis.

Citrate excretion is also high - not seen in other acidoses.

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