Impaired liver clearance of bacteria in rats with chronic biliary obstruction

Potential role of bile duct collaterals in the recovery of the biliary obstruction: experimental study in rats using microcholangiography, histology, serology and magnetic resonance imaging

Obstructive cholestasis induced in animals at the level of the lobar and common bile ducts is known to be reversible with time. This study was conducted not only to test the hypothesis that formation of bile duct collaterals is responsible for the recovery of biliary obstruction but also to assess the potential of hepatobiliary agent-enhanced magnetic resonance imaging for visualizing cholestasis. A total of 52 rats were divided into three groups with selective biliary obstruction, total biliary obstruction and sham surgery. We studied the evolution of cholestasis by correlating microcholangiographic, histological findings with the results of liver tests and hepatobiliary agent-enhanced magnetic resonance imaging. Lobar cholestasis undetected by liver tests but seen on magnetic resonance imaging as a difference between ligated and unligated lobes, occurred in 15 out of 20 rats subjected to selective biliary obstruction within 48 hr after ligation, and recovered later on as a result of the development of bile duct collaterals. Five rats failed to show local cholestasis as a result of the existence of interlobar accessory bile channels. All 18 total biliary obstruction-treated rats were cholestatic soon after ligation, as confirmed by high serum bilirubin and alkaline phosphatase levels and as documented by poor liver enhancement on magnetic resonance imaging. Cholestasis recovered within 4 wk with normalization of liver enhancement on magnetic resonance imaging as a result of the formation of bile duct collaterals (as demonstrated by microcholangiographic and histological study). Bile duct collateral formation is responsible for the recovery from obstructive cholestasis in rats. A similar mechanism might be present in conditions of bile duct obstruction without cholestasis. Hepatobiliary agent-enhanced magnetic resonance imaging is more sensitive than blood tests in detecting local cholestasis and can be used to monitor noninvasively the evolution of biliary obstruction.

A contribution to the model of biliary infection in rats

The model of biliary tract infection induced in rats given suspension of E. coli into the bile duct is described. To prevent leakage of microorganisms after the administration, a temporary ligation of the bile duct followed. Contemporary groups of sham-operated and control rats (given saline by intrabiliary injection) were compared to assess the significance of the changes. The effect of biliary infection was concentration dependent. If 0.1 ml of the concentration containing 10(2), 10(3) and 10(6) colony-forming units/ml was injected, the mortality of rats reached 8%, 57% and 65%, respectively within 24 h. Blood and bile cultures from all dead animals grew E. coli. To evaluate the effect of chronic biliary infection, the concentration of 10(2) colony-forming units/ml was used. Serum concentrations of total and conjugated bilirubin, cholesterol and creatinine, activities of S-alanine-aminotransferase, S-aspartate-aminotransferase, alkaline phosphatase, the count of leucocytes in blood, total body weight with weight of the liver were investigated on days 1, 4 and 12 after the treatment. The results showed: an increase in leucocytes (21 +/- 4.2 10(9)/l, p less than 0.02 vs control animals) on day 4, an augmentation of serum cholesterol on day 1, (2.1 +/- 0.9 mmol/l, p less than 0.02 vs control animals), the presence of E. coli in blood on day 1 and its persistence in the bile on days 1, 4 and 12. Except the bile, all of the other symptoms were reversible by day 12.