Bartter Syndrome

Bartter syndrome is a rare inherited renal tubular salt-wasting disorder. The primary defect impairs sodium chloride reabsorption, predominantly in the thick ascending limb of the loop of Henle. Ongoing renal salt loss contracts circulating volume and activates the renin-angiotensin-aldosterone system. Increased distal sodium delivery and aldosterone activity promote urinary potassium and hydrogen loss, producing the characteristic hypokalemic, hypochloremic metabolic alkalosis with high renin and aldosterone and low-to-normal blood pressure. A normal blood pressure therefore does not rule out clinically important volume depletion. Abnormal chloride sensing at the macula densa also increases renal prostaglandin production. This contributes to renin and aldosterone stimulation and explains why prostaglandin-suppressing nonsteroidal anti-inflammatory drugs may improve symptoms and electrolyte control in selected patients. Impaired thick-ascending-limb function also reduces the kidney's concentrating ability, contributing to polyuria and polydipsia. In some genetic forms, reduced calcium reabsorption produces hypercalciuria and progressive medullary nephrocalcinosis. Most inherited forms are autosomal recessive, while a transient form is X-linked. The exact phenotype varies by the affected transporter or channel. Some forms present antenatally with fetal polyuria, polyhydramnios, and preterm birth; others present later...