Renal tubular function by lithium clearance in liver cirrhosis

Increased tubule sodium reabsorption has been largely suspected in liver cirrhosis (LC), however studies in humans have produced contrasting results. Therefore to ascertain the entity of renal sodium handling in LC this study was devised. A total of 13 patients with child A LC were studied along with 26 age-sex matched healthy controls (HC). Patients and controls were kept on daily Na-intake of 100 mmol for at last 1 week, by measuring glomerular filtration rate (GFR; inulin) and lithium clearance. We have calculated (1) C(Li); (2) the absolute reabsorption of isotonic fluid in the proximal tubule (APR) as GFR - C(LI); (3) the fractional proximal sodium reabsorption (FPRNa) as 1 - (C(Li)/GFR); (4) the absolute distal reabsorption of sodium (ADRNa) as (C(LI) - C(Na)) x P(Na;) and (5) the fractional distal sodium reabsorption (FDRNa) as (C(LI) - C(Na))/C(Li). GFR was significantly lower in LC (P<.001), C(Li) was significantly higher in LC than in HC (P<.001). APRNa and FPRNa were reduced in LC (P<.0001). ADRNa was higher in LC than in HC (P<.001). No difference was found for FDRNa. In conclusion, lithium clearance discloses an increase sodium reabsorption in distal tubule in humans with LC.