Predictive value of abdominal CT in evaluating internal herniation after bariatric laparoscopic Roux-en-Y gastric bypass.

Background: Internal herniation, a serious complication after bariatric surgery, is challenging to diagnose. The aim of this study was to determine the accuracy of abdominal CT in diagnosing internal herniation.

Methods: The study included consecutive patients who had undergone laparoscopic gastric bypass surgery between 1 January 2011 and 1 January 2015 at a bariatric centre of excellence. To select patients suspected of having internal herniation, reports of abdominal CT and reoperations up to 1 January 2017 were screened. CT was presumed negative for internal herniation if no follow-up CT or reoperation was performed within 90 days after the initial CT, or no internal herniation was found during reoperation. The accuracy of abdominal CT in diagnosing internal herniation was calculated using two-way contingency tables.

Results: A total of 1475 patients were included (84·7 per cent women, mean age 46·5 years, median initial BMI 41·8 kg/m ). CT and/or reoperation was performed in 192 patients (13·0 per cent) in whom internal herniation was suspected. Internal herniation was proven laparoscopically in 37 of these patients. The incidence of internal herniation was 2·5 per cent. An analysis by complaint included a total of 265 episodes, for which 247 CT scans were undertaken. CT was not used to investigate 18 episodes, but internal herniation was encountered in one-third of these during reoperation. Combining the follow-up and intraoperative findings, the accuracy of CT for internal herniation had a sensitivity of 83·8 (95 per cent c.i. 67·3 to 93·2) per cent, a specificity of 87·1 (81·7 to 91·2) per cent, a positive predictive value of 53·4 (40·0 to 66·5) per cent and a negative predictive value of 96·8 (92·9 to 98·7) per cent.

Conclusion: Abdominal CT is an important tool in diagnosing internal herniation, with a high specificity and a high negative predictive value.