Renal distal tubular handling of sodium in central fluid volume homoeostasis in preascitic cirrhosis

Background/Aims-Patients with preascitic liver cirrhosis have an increased central plasma volume, and, for any given plasma aldosterone concentration, they excrete less sodium than healthy controls. A detailed study of the distribution of sodium reabsorption along the segments of the renal tubule, especially the distal one, is still lacking in preascitic cirrhosis. Methods-Twelve patients with Child-Pugh class A cirrhosis and nine control subjects (both groups on a normosodic diet) were submitted to the following investigations: (a) plasma levels of active renin and aldosterone; (b) four hour renal clearance of lithium (an index of fluid delivery to the loop of Nenle), creatinine, sodium, and potassium; (c) dopaminergic activity, as measured by incremental aldosterone response to intravenous metoclopramide. Results-Metoclopramide induced higher incremental aldosterone responses, indicating increased dopaminergic activity in patients than controls, which is evidence of an increased central plasma volume (+30 min: 160.2 (68.8) v 83.6 (35.2) pg/ml, p<0.01; +60 min: 140.5 (80.3) v 36.8 (36.1) pg/ml, p<0.01), Patients had increased distal fractional sodium reabsorption compared with controls (26.9 (6.7)% v 12.5 (3.4)% of the filtered sodium load, p<0.05). In the patient group there was an inverse correlation between: (a) absolute distal sodium reabsorption and active renin (r-0.59, p<0.05); (b) fractional distal sodium reabsorption and sodium excretion (r-0.66, p<0.03). Conclusions-These data suggest that in preascitic cirrhosis the distal fractional tubular reabsorption of sodium is increased and critical in regulating both central fluid volume and sodium excretion.