Objective To study the protective effect and mechanism of lactulose on the renal function in acute cholelithiasis with obstructive jaundice. Methods Fifty five cases of acute cholelithotic obstruction were randomly assigned into lactulose group (group L, n=28) and control group (group C, n=27), and 50% lactulose (group L)or 10% glucose (group C ) was administered orally for 3 days before the operation , respectively. The systemic and portal blood endotoxin (ET), blood urea nitrogen (BUN) and endogenous creatinine clearance rate (Ccr) were measured periodically. Results (1) In group L, the level of systemic vein ET and BUN were significantly lower than that in group C (P0.05); and the systemic vein ET and Ccr decreased significantly on 9d (P