Paediatrics: Renal tubular disorders

Renal tubular disorders

The renal tubules are responsible for the regulation of fluid, acid–base, and electrolyte balance. Abnormalities of renal function may occur at any point along the length of the renal tubule system and may lead to a distur-bance in the equilibrium of any of the substances handled by it. It is essen-tial to consider these disorders when there are any of the following:

·  Glycosuria, amino-aciduria, or impaired ability to concentrate or acidify urine shown on urinalysis.

·  Stones or nephrocalcinosis: distal tubular acidosis and oxalosis are major causes.

·  Polyhydramnios and failure to thrive in a newborn: e.g. Bartter syndrome associated with hypokalaemic alkalosis.

·  Failure to thrive with rickets: cystinosis is commonest cause of Fanconi syndrome.

·  Major rickets with low plasma phosphate levels: familial hypophosphataemic rickets.

·  Failure to thrive with low urine osmolality: nephrogenic diabetes insipidus.

Renal tubular acidosis

Renal tubular acidosis (RTA) is a state of systemic hyperchloraemia result-ing from impaired urinary acidification. Three types of RTA exist:

·  Proximal type.

·  Distal type.

·  Mineralocorticoid deficiency-associated.