Small Bowel Strangulation in an Adult From an Internal Hernia Caused by a Rare Congenital Mesenteric Defect.

Internal hernia occurs when a portion of the bowel herniates through a congenital or acquired opening within the abdominal cavity. This can lead to small bowel obstruction, bowel incarceration, and strangulation. We present a rare case of an adult patient presenting with an acute abdomen caused by small bowel strangulation due to a congenital transmesenteric defect. A 67-year-old female without any significant past medical or surgical history presented to the emergency department with an acute-onset worsening abdominal pain with nausea and vomiting. Physical examination revealed pain out of proportion to palpation of the abdomen. CT demonstrated internal hernia with moderate-volume ascites, concerning for ischemic bowel. The patient underwent an exploratory laparotomy, which demonstrated an internal hernia through a congenital mesenteric defect in the right hemiabdomen near the root of the mesentery with ischemic small bowel requiring resection. The patient was left in intestinal discontinuity and was returned for reexploration of the abdomen, open cholecystectomy, and right hemicolectomy. The patient's recovery and hospital course were uncomplicated, and she was discharged from the hospital on postoperative day five. The incidence of congenital mesenteric defects in adults is exceedingly low, resulting in a limited body of literature addressing their clinical presentation and complications. Timely and accurate preoperative diagnosis is critical to prevent acute obstruction and strangulation of the bowel. This case contributes valuable insights into the diagnosis and management of this uncommon condition.