Abstract
BACKGROUND: Congenital transmesenteric hernia, an uncommon cause of acute abdomen with an incidence of less than 1%, is often identified only intraoperatively.We present a rare case of internal hernia through a congenital mesenteric defect posterior to the gastric antrum, precipitated by strenuous exercise after a meal in an adolescent. CASE PRESENTATION: A 17-year-old male developed sudden severe abdominal pain and distension after vigorous exercise following a meal. Abdominal computed tomography (CT) demonstrated an abnormally displaced duodenal loop, raising suspicion for internal herniation. Laparoscopic exploration revealed that a large segment of the small bowel had herniated through a congenital mesenteric defect posterior to the gastric antrum into the right upper abdomen. The herniated bowel exhibited clockwise torsion, forming a closed-loop obstruction with strangulated necrosis. Due to extensive necrosis and limited working space, the procedure was converted to an open laparotomy for definitive resection. Following resection of the necrotic bowel, only 6 cm of terminal ileum remained. To preserve the ileocecal valve function, after the viability of both ends was confirmed and with informed consent from the patient's guardians, an ileo-ileal side-to-side anastomosis was performed to restore intestinal continuity. By postoperative day 7, pelvic drainage was clear, without evidence of anastomotic leakage, and the patient had a smooth recovery and was subsequently discharged. CONCLUSION: Emergency physicians should maintain a high index of suspicion for transmesenteric hernia as a potential cause of acute strangulation and bowel necrosis in patients presenting with acute abdomen, and timely surgical intervention is essential. Although long-term outcomes require further evaluation, ileal resection near the ileocecal region with preservation of the valve using a side-to-side anastomosis may represent a salvage strategy under high-risk anatomical conditions.