Mesenteric Meckel's Diverticulum as a Missed Diagnosis in a Child With Recurrent Rectal Bleeding: A Report of a Challenging Case.

Meckel's diverticulum is a common congenital anomaly of the gastrointestinal tract and is a remnant of the omphalomesenteric duct. One of the classical identification and diagnostic criteria of Meckel's diverticulum is its location along the anti-mesenteric border of the ileum. Mesenteric Meckel's diverticulum (MMD) is an unexpected occurrence, rarely reported, with confounding diagnostic tests due to the atypical location, often forming a gray zone in diagnosis due to its similarity to an enteric duplication cyst. A 1.5-year-old male child presented to the pediatric surgery outpatient department (OPD) with complaints of intermittent episodes of painless rectal bleeding and melena for five months. On examination, the child was pale, and the abdomen was soft, with no tenderness or palpable mass. Digital rectal examination showed dark melena stool staining. The patient had a history of prior admissions in outside hospitals, where he underwent an upper gastrointestinal (UGI) endoscopy and colonoscopy, both of which were normal. A Meckel's scan done in an outside hospital was positive, and therefore, the patient underwent a diagnostic laparoscopy in the center, wherein no Meckel's diverticulum nor other bowel abnormalities were identified. Thereafter, the patient was referred to our hospital due to persistence of symptoms. Evaluation was repeated to ensure a thorough investigative protocol. Repeat UGI endoscopy and colonoscopy revealed no abnormality. A red blood cell (RBC) tagged radionuclide scan (Tc99) was done, which showed pooling of blood in the small bowel (possibly ileum) and hepatic flexure. The child underwent an exploratory laparotomy, which showed an obscure diverticulum in the mid-ileum, on the mesenteric side, buried within the mesentery. The diverticulum had a wide base with luminal communication with adjacent ileum, with a separate vascular supply within the mesentery, suggestive of an MMD. The patient underwent resection of the Meckel's diverticulum with end-to-end anastomosis of the ileum. The postoperative period was uneventful, and the child thereafter had no further episodes of rectal bleeding or melena. Histopathology confirmed a 3.5 cm Meckel's diverticulum with ectopic gastric mucosa. Anti-mesenteric location of a diverticulum is a classical diagnosis of Meckel's diverticulum. The rare entity of mesenteric location can confound the diagnosis due to similarity with an enteric duplication cyst. While clinical presentation remains the same irrespective of mesenteric or anti-mesenteric location, it can often be missed intraoperatively due to the unexpected location. Diagnostic evaluation and planned surgical intervention are prudent to ensure complete resection and clinical recovery.