Hooking intestine sign: a typical diagnostic CT finding of Petersen's hernia.

PURPOSE: To clarify typical diagnostic computed tomography (CT) findings of Petersen's hernia for differentiation from other causes of internal hernia observed in patients having undergone gastrectomy with Roux-en-Y gastric bypass. METHODS: We retrospectively reviewed CT findings of internal hernia in patients who had undergone both gastrectomy and Roux-en-Y reconstruction and a second surgery for bowel obstruction. Thirteen patients with Petersen's hernia and 6 with internal hernia other than Petersen's hernia were investigated. Six CT findings, viz. whirl sign, mesenteric fat haziness, intestinal distension in the upper abdomen, herniated intestinal loop above the gastric level, middle/distal ileum courses downwards from the left hypochondrium, and hooking intestine sign, which means two or more intestines pass through the inner side of J-shaped vessels consisting of mesenteric vessels of the elevated jejunum, were scored and evaluated regarding their diagnostic performance. RESULTS: The hooking intestine sign showed the highest sensitivity, specificity and accuracy (100%, 100% and 100%). We could detect J-shaped vessels in all Petersen's hernia patients. Inside the J-shaped vessels there were two or more intestinal tracts passing through in the Petersen's hernia group. There was only transverse colon inside the J-shaped vessels in the control group. CONCLUSION: The hooking intestine sign may be useful for diagnosing Petersen's hernia on CT.