Exaggerated natriuretic response to volume expansion in patients with primary biliary cirrhosis

Fluid retention and ascites are rarely seen in patients with primary biliary cirrhosis (PBC). This contrasts with the conspicuous tendency of patients with Laennec's cirrhosis to retain salt and water. In an attempt to clarify this clinical observation, renal handling of sodium was studied during extracellular volume expansion (ECVE) and maximal suppression of antidiuretic hormone in five patients with PBC. These PBC patients were compared with two control populations: five edema-free patients with Laennec's cirrhosis and nine healthy volunteers. The natriuretic and diuretic response to ECVE was significantly greater in the patients with PBC as compared with the two control groups. CH₂O for given rates of urine flow were similar in PBC patients as compared with normal subjects. The data suggest that a supranormal rejection of sodium at the proximal tubule in response to ECVE underlies the exaggerated natriuresis of PBC. The augmented elimination of salt during ECVE in patients with PBC may explain the rarity of ascites and edema in this variety of cirrhosis.