What is it?
Diseases of the renal tubule are usually hereditary diseases that due to mutation of a gene cause loss of a function of the tubular cells. They may present with deficits in reabsorption or excretion of specific molecules by tubular cells. The defects that most frequently occur are hypokalemia, acidosis, and hypophosphatemia with different symptoms.
Which are the symptoms?
Clinically, symptomatology changes depending on the tubulopathy. Hypokalemia is the typical defect of Bartter's and Gitelmen's disease, and is present in tubular acidosis in which it is associated with reduced bicarbonatemia and nephrocalcinosis/calcinosis. Hypokalemia causes cramps and arrhythmias. Hypophosphoremia appears in patients with renal rickets who have osteopathy with bone deformities. The development of calcinosis is typical of patients with cystinuria, an amino acid that when it is not reabsorbed by the tubule precipitates in the urine to form calculi. Hypertension and hypokalemia are indicative of Liddle’s disease.
- kidney stones
How is it diagnosed?
This group of diseases is manifested by altered plasma concentrations of one or more electrolytes. Urinalysis plays a key role in diagnostic guidance as it identifies the renal cause of plasma electrolyte defects. A renal ultrasound may be useful to rule out acute tubulointerstitial nephritis as the cause of the blood defects. Cystinuria is diagnosed by analyzing the composition of the stone or by assaying cystine in the urine. Identifying the mutation, genetic analysis confirms the diagnosis.
How is it treated?
The treatment varies in relation to the tubulopathy: generally, it consists in replenishment of lost electrolytes and correction of the acidosis or alkalosis. Hypertension is treated with amiloride in Liddle's syndrome, and cystine stones are prevented by urine alkalinization and eventual administration of thiopronine.
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