Ultrasonographic diagnosis of pure inversion of Meckel's diverticulum without obstruction in a child: a case report and literature review.

Introduction: Meckel's diverticulum (MD) is the most common congenital malformation of the gastrointestinal tract. Most cases are asymptomatic, while a minority may develop complications such as hematochezia, diverticulitis, and intestinal obstruction. When a Meckel's diverticulum inverts into the lumen of the ileum rather than protruding outward from the intestinal wall, it is referred to as an inverted Meckel's diverticulum, which is a very rare condition. Although inverted MD frequently presents with intestinal obstruction, cases of pure inversion without obstruction are exceptionally rare. However, even in the absence of obstruction, such cases may still manifest with non-specific symptoms, posing a significant diagnostic challenge. This report describes a case of complete MD inversion in a child that was accurately diagnosed by high-frequency ultrasonography (HFUS), with preoperative ultrasound findings consistent with intraoperative observations. Case description: A 5-year-old child presented with recurrent abdominal pain and diarrhea for 4 months, having been evaluated at multiple hospitals without a definitive diagnosis. Ultrasound examination at our institution revealed a Meckel's diverticulum in the terminal ileum; however, instead of protruding outward, the diverticulum was inverted into the intestinal lumen. This invagination into the lumen explained the patient's clinical manifestations of abdominal pain and diarrhea. Ultrasound diagnosis was MD inversion. After preoperative evaluation, the patient underwent transumbilical single-port laparoscopic partial small bowel resection and anastomosis, which intraoperatively confirmed the diagnosis of inverted MD. Conclusion: This case demonstrates that high-frequency ultrasonography can accurately identify an inverted Meckel's diverticulum by revealing the characteristic morphological changes of the diverticulum within the ileal lumen. This imaging modality proved valuable in establishing the correct preoperative diagnosis and guiding timely surgical intervention.