Multivariate analysis of clinical and operative findings associated with bilary sepsis.

A cluster analysis of 17 preoperative and 10 operative variables has been undertaken from a prospective study of 181 patients undergoing operations on the biliary tract in order to identify those with organisms in the bile who would therefore benefit from prophylactic antibiotic cover. The analysis defined populations of high risk (45 patients) and low risk (136 patients) in which the incidence of infected bile was 67 and 19 per cent respectively (P less than 0-001). Eight variables were more common in the high risk than in the low risk group (P less than 0-001). These "high risk factors" were: jaundice at operation, recent rigoors, emergency operation or one within 4 weeks of an emergency admission, age over 70 years, previous biliary operation, common duct obstruction and stones in the bile duct. In 67 patients where one or more "high risk factors" was present, the bile contained organisms in 37 (53 percent); when 4 "high risk factors" occurred in the same patient (16 cases) biliary organisms were isolated in 14(87 per cent). We conclude that the presence of one or more "high risk factors" indicates a patient in whom prophylactic antibiotics would be advised during an operation on the biliary tract.