Arye Blachar, MD ; Michael P. Federle, MD ; S. Forrest Dodson, MD

PURPOSE: To review the clinical and radiologic features of internal hernia and to derive useful radiographic and CT criteria to assist in diagnosis.

MATERIALS AND METHODS: Retrospective review of medical records revealed 17 patients with surgically proved internal hernia (three paraduodenal, 14 transmesenteric) who had 15 computed tomographic (CT) scans and three small-bowel follow-through (SBFT) images.

RESULTS: CT signs common to all types of internal hernia included evidence of small-bowel obstruction; clustering of small bowel; stretched, displaced, crowded, and engorged mesenteric vessels; and displacement of other bowel segments, especially the transverse colon and fourth portion of the duodenum. Left-sided paraduodenal hernias demonstrated a saclike mass of small-bowel loops interposed between the stomach and pancreatic tail and a posterior mass effect on the stomach. All three paraduodenal hernias were diagnosed confidently at retrospective review of CT and SBFT findings. Transmesenteric hernias demonstrated clustered small-bowel loops adjacent to the abdominal wall without overlying omental fat and central displacement of colon and were frequently complicated by small-bowel volvulus (five of 14) and bowel ischemia (six of 14). CT demonstrated signs of volvulus in four of six patients with ischemia. CT findings considered definitive or suggestive of internal hernia were demonstrated in 15 patients.

CONCLUSION: Internal hernia is an important and underdiagnosed condition. Transmesenteric hernia is most common in our experience and is usually related to prior abdominal surgery, especially with creation of a Roux-en-Y anastomosis. CT may allow confident diagnosis in most patients.