Apolipoprotein-E genotype and the risk of developing cholelithiasis following bariatric surgery: a clue to prevention of routine prophylactic cholecystectomy.

BACKGROUND: Obesity and especially rapid weight loss following bariatric surgery are known risk factors for cholelithiasis. Since the risk may be high, prophylactic cholecystectomy has been advocated. Apolipoprotein (Apo) E, an important carrier protein in cholesterol metabolism and trafficking, is believed to play a role in gallstone pathogenesis. In particular, the Apo E4 allele has been suggested to be associated with cholesterol cholelithiasis. The aim of this study was to assess the incidence of postoperative cholelithiasis in our patient population and to determine a possible correlation with the Apo-E genotype.

METHODS: 134 morbidly obese patients undergoing gastric restrictive surgery [laparoscopic assisted gastric banding (LAGB) or silastic ring vertical gastroplasty (SRVG)] had abdominal ultrasound before and 6 to 12 months after operation, to determine the presence of gallstones. None of the patients enrolled in the study had gallstones before surgery. They did not have a prophylactic cholecystectomy or receive bile salt treatment. Apo-E genotypes were determined by Polymerase Chain Reaction restriction enzyme analysis.

RESULTS: 10 patients (7.5%) developed postoperative cholelithiasis. The incidence of cholelithiasis in each ApoE genotype was: E2/E3--1/20 (5%), E3/E3--3/91 (3%), E3/E4--6/21 (29%), and E4/E4--0/2. ApoE allele frequencies in the study population were identical to those of a healthy control population. The mean BMI dropped from 43.6 to 29.4 kg/m2.

CONCLUSIONS: The occurrence of postoperative gallstones was low in our population. However, in subjects with the Apo-E3/E4 genotype, the incidence is of practical significance. These data suggest that Apo-E genotyping may be useful in selecting patients for gallstone prevention (surgical or medical) when undergoing bariatric surgery. Further testing in larger patient populations may be able to give more definite guidelines in the future.