A woman in her 40s presented to our department with lower abdominal pain, lasting for a few weeks, with nausea and vomiting but no diarrhea or fever. Her medical history was unremarkable; in particular, she had no history of endometriosis. She had visited the emergency department of another hospital 2 weeks before with the same symptoms and had received conservative treatment. On physical examination in the present visit, she had lower abdominal tenderness but no sign of peritoneal irritation. A mass was palpable in the lower right abdominal quadrant. The results of routine blood investigations, including white blood cell count, hemoglobin concentration, and C-reactive protein level, were within normal limits, as they had been in the previous hospital. Abdominal ultrasonographic examination was performed, followed by abdominal computed tomography; the results were suggestive of an ileal intussusception (Figure, A). A colonoscopy revealed the presence of a bulge in the cecal lumen (Figure, B).