Diagnosing internal herniation after laparoscopic Roux-en-Y gastric bypass: usefulness of systematically reviewing CT scans using ten signs

Objectives: To evaluate if systematically reviewing CT scans using ten signs leads to a better accuracy in diagnosing internal herniation (IH), compared to the original report. Also, the difference in accuracy was analysed between experience levels. Methods: Patients were retrospectively included if they had undergone laparoscopic gastric bypass surgery between 2011 and 2014, and if additional radiological examination was performed for suspected IH between 2011 and 2016. Out of 1475 patients who had undergone laparoscopic gastric bypass surgery, 183 patients had one or more additional radiological examinations. A total of 245 CT scans were performed. All were reassessed by an abdominal radiologist, a radiology resident and intern. Assessment was done using ten signs from previous literature. Overall suspicion of IH was graded using a 5-point Likert scale. Accuracy was calculated using two-way contingency tables. Interobserver agreement was calculated using Fleiss’ kappa. Results: After 70 reoperations an IH was diagnosed in 48.6% (34/70). There was an increase in specificity for diagnosing IH with reoperation as reference from 52.8% (19/36; 95% CI 35.7–69.2%) in the original report to 86.1% (31/36; 95% CI 74.8–97.4%) for the radiologist (p = 0.002), 77.8% (28/36; 95% CI 64.2–91.4%) for the resident (p = 0.026) and 77.8% (28/36; 95% CI 64.2–91.4%) for the intern (p = 0.026). Interobserver agreement was good. Conclusions: Systematically reviewing CT scans using a list of ten CT signs can improve specificity and thereby reduce unnecessary reoperations, especially in a high pre-test probability population. The tool can be easily taught to less experienced readers. Key Points: • Computed tomography is useful to diagnose internal herniation(IH) after gastric bypass surgery • Ten signs are described to improve CT diagnosis of IH • Systematically reviewing CT scans improves specificity • There is no difference in experience levels when using these ten signs.