An internal hernia may be either congenital or acquired. The reported incidence of such hernias is 1-2%. In rare cases, internal hernias are the cause of small bowel obstruction, with a reported incidence of 0.2-0.9%. Transmesocolic hernia of the ascending colon is especially rare. We report a case of transmesocolic hernia of the ascending colon with intestinal obstruction diagnosed preoperatively. A 91-year-old Japanese female was admitted to our hospital with abdominal distention and vomiting of 3 days duration. She had no past history of any abdominal surgery. Abdominal examination revealed distention and tenderness in the right iliac fossa. Abdominal computed tomography revealed ileus in the sac at the left side of the ascending colon and dilatation of the oral side of the intestine. We diagnosed a transmesocolic hernia of the ascending colon with intestinal obstruction and performed emergency surgery. At the time of operation, there was internal herniation of ileal loops through a defect in the ascending mesocolon, without any strangulation of the small bowel. The contents were reduced and the tear in the ascending mesocolon was closed. The postoperative course was uneventful and the patient was discharged 14 days after surgery. In conclusion, preoperative diagnosis of bowel obstruction caused by a congenital mesocolic hernia remains difficult despite the techniques currently available, so it is important to consider the possibility of a transmesocolic hernia when diagnosing a patient with ileus with no past history of abdominal surgery.
Keywords: Ascending colon; Intestinal obstruction; Transmesocolic hernia.