Left-sided transmesocolic herniation of small bowel in an otherwise unaffected abdomen.

Transmesocolic hernia is an uncommon type of internal hernia with incidence ranging from approximately 5-10%. To the best of our knowledge, this is the first reported case of a transmesocolic hernia through a gap within the descending mesocolon presenting clinically as an intestinal obstruction. A 75-year-old man was admitted with clinical features of intestinal obstruction. An abdominal X-ray showed multiple small bowel loops with air fluid levels. Contrast-enhanced CT of the abdomen revealed small bowel obstruction not only on the right, but also on the left side of the collapsed descending colon. Emergency surgery was performed. Strangulated bowel loops with gangrenous changes were resected and double-barrel ileostomy was carried out. The postoperative period was uneventful. Restoration of bowel was performed after 6 weeks. Preoperative diagnosis of bowel obstruction caused by a transmesocolic hernia remains difficult despite the currently available imaging techniques. Prompt surgery can prevent serious complications such as peritonitis and sepsis.