The diagnostic performance and interrater agreement of seven CT findings in the diagnosis of internal hernia after gastric bypass operation

Purpose: A reliable and immediate diagnosis of internal hernia is important for optimal and timely management of patients with a history of gastric bypass surgery. The aims of this study were to evaluate the interrater agreement and diagnostic performance characteristics of seven predefined CT findings of internal herniation in patients admitted on clinical suspicion of internal herniation after laparoscopic Roux-en-Y gastric bypass (LRYGB). Methods: Abdominal CT scans of 117 patients performed on clinical suspicion of internal hernia after LRYGB surgery were evaluated by three radiologists (two experts and one resident) for the following: (1) Swirl sign, (2) strangulation of superior mesenteric vein (SMV), (3) engorged mesenteric vessels and edema, (4) engorged lymph nodes, (5) ascites, (6) mushroom sign, (7) hurricane eye sign, and finally the overall conclusion. The CT findings were compared to the laparoscopic explorative findings. Results: The highest interrater agreements were seen for the swirl sign, SMV strangulation, ascites, and overall conclusion (all Kappa 0.82–0.83). The presence of internal hernia was significantly and independently associated with SMV strangulation (OR 18.3; 95% CI 4.3–78.1; p < 0.001) and mesenteric edema (OR 5.2; 95% CI 1.4–19.6; p < 0.001) on multivariate analysis, while the other CT findings were not independently associated with herniation. The highest sensitivity was observed for mesenteric edema (85.0%), while SMV strangulation had the highest specificity (94.8%). Conclusion: CT is an accurate diagnostic tool for detection of internal hernia after LRYGB. SMV strangulation and mesenteric edema are highly predictive and easily identified features of internal herniation.