Large bowel obstruction caused by a small bowel internal hernia

Internal hernia is a rare complication of laparoscopic colorectal surgery with an incidence of less than 1%. However, it is associated with a mortality rate of up to 20% largely due to the risk of strangulation of the herniated bowel resulting in bowel ischaemia.1-4 Early recognition and timely operative management where appropriate is therefore crucial. Here we describe a case a small bowel internal hernia causing volvulus of a colonic conduit and secondary large bowel obstruction (LBO). A 79-year-old male presented with abdominal pain, distention and obstipation for 4 days. His significant history includes an anterior resection for sigmoid adenocarcinoma 20 years prior with no adjuvant chemotherapy and no history of a recent colonoscopy. A computed tomography (CT) scan showed a LBO with a markedly distended large bowel from the caecum to the descending colon with no obvious mass. However, a single mesenteric swirl was observed in keeping with volvulus of the colonic conduit as well as loops of small bowel located lateral and posterior to the colonic conduit thus raising suspicion of an internal hernia (Fig. 1a). The patient subsequently underwent operative management for the LBO. A flexible sigmoidoscopy was performed initially with evidence of a swirl consistent with a volvulus with normal mucosa (Fig. 1b). The flexible sigmoidoscope was unable to advance beyond the volvulus and hence proceeded to diagnostic laparoscopy. Loops of small bowel were adherent to the colonic conduit and thereby caused the colonic conduit to twist on its longitudinal axis when these small bowel loops herniated under the conduit, that is, an internal hernia, and causing a LBO (Fig. 2). Small bowel adhesive bands were divided and the internal hernia was reduced and returned to its normal anatomical position. There was no requirement for bowel resection and the case was successfully managed laparoscopically without compromising the colonic conduit. After left-sided colorectal resection and anastomosis, the distal transverse and proximal descending colon forms the colonic conduit with its mesentery lying on the retroperitoneum.2, 4 Postoperatively, the small bowel should lie anterior and medially to the colonic conduit, however, the small bowel mesentery which is normally anchored to the posterior abdominal wall from posterior to anterior and from left to right, tends to direct the small bowel loops to the left and explains the predisposition of developing a small bowel internal hernia underneath the colonic conduit mesentery.1-3, 5 Internal hernia after colorectal resection is uncommon however a systematic review conducted by Toh et al., demonstrated that more than half of cases were left-sided colonic resection of which all patients required operative intervention, and of those approximately one-third requiring bowel resection.2 Furthermore, in approximately half of these cases, the mesenteric defect was closed at the second operation. LBO caused by internal hernia and colonic conduit volvulus is rare but can lead to severe complications or mortality. We need to recognise the possibility of internal herniation in patients presenting with LBO who have had previous colonic resection to prompt further investigations including imaging and flexible sigmoidoscopy as a prelude to timely operative correction. We are grateful to the patient who consented to use their clinical information and images. Yui Kaneko: Writing – original draft. Neil Strugnell: Writing – review and editing. Toan Pham: Conceptualisation; writing – review and editing.