Approach to renal tubular disorders.

The renal tubule plays an important role in fluid and electrolyte homeostasis. Renal tubular disorders may affect multiple ( e.g., Fanconi syndrome) or specific (e.g., nephrogenic diabetes insipidus, renal glucosuria) tubular functions. Most conditions are primary and monogenic but occasionally are secondary to other disorders (focal segmental glomerulosclerosis, cystinosis, Lowe syndrome). Tubular dysfunction should be considered in all children with failure to thrive, polyuria, refractory rickets, hypokalemia and metabolic acidosis. Careful clinical and laboratory evaluation is essential for appropriate diagnosis and specific management of these conditions.