Idiopathic Adult Ileocolic Intussusception Mimicking Cecal Carcinoma: A Case Report and Literature Review.

Introduction: Adult intussusception is rare, accounting for approximately 5%-16% of all cases. Unlike pediatric intussusception, which is predominantly idiopathic, most adult cases are associated with organic lesions, nearly half of which are malignant. Idiopathic intussusception without a lead point is uncommon but appears to be increasingly recognized. We report a case of idiopathic adult ileocolic intussusception that mimicked cecal carcinoma in imaging studies.

Case presentation: A 63-year-old male with a history of gastric cancer recurrence presented with a 3-month history of abdominal pain. Contrast-enhanced computed tomography (CT) revealed circumferential thickening of the right colon, forming a "target sign," and invagination of the ileocecal region into the right colon, suggesting ileocolic intussusception. Colonoscopy identified a nodular lesion presumed to be cecal carcinoma; however, the biopsy did not provide a definitive diagnosis of malignancy. Preoperative ¹⁸F-fluorodeoxyglucose-positron emission tomography (¹⁸F-FDG-PET/CT) revealed high FDG uptake at the leading edge of the intussusception; however, no findings indicative of metastatic disease were observed. The patient underwent elective surgery, and a right colectomy with lymph node dissection was performed. However, the intussusception was found to have spontaneously resolved at laparotomy. Histopathological examination showed mild intramural congestion in the ileocecal valve. Postoperative imaging confirmed the absence of any lead point lesion, resulting in a final diagnosis of idiopathic intussusception.

Conclusions: This case highlights the diagnostic limitations of CT and PET/CT in evaluating lead points in adult intussusception, as false-positive findings are common. Given the possibility of spontaneous resolution, a conservative approach, including repeat imaging immediately before surgery, may be suitable in select cases of adult intussusception.