Adult colonic intussusception is rare and often originates from neoplasms. In emergency situations it can be difficult to diagnose. Our aim was to show how the integration of readily available diagnostic means in emergency situations can help in making a correct diagnosis of this disease. A 68-year old male patient presented with vomiting and abdominal pain. The abdomen was distended, with pain to palpation in the left quadrants without a mass. Plain radiographs of the abdomen showed a large amount of gas in the small bowel and in the right and transverse colon. A barium enema demonstrated an endoluminal filling defect in the descending colon. Abdominal ultrasonography revealed the presence of intraperitoneal fluid and thickened left colonic wall at the site of the lesion, with an aspect of a "double ring" consistent with intussusception. A solid formation was also revealed at a point distal to the thickened colonic wall. At emergency laparotomy an approximately 8-cm-long mass was palpable through the left colon. A colostomy was fashioned, and subsequently colonoscopy revealed the presence of a left colon tumor. At the subsequent operation an invagination of the left transverse colon into the descending colon was confirmed. The left transverse and descending colon were resected with high ligation of the left colic artery. Macroscopic examination of the invaginating head showed a vegetating transverse colon neoplasm. We conclude that in emergency settings the association of readily available diagnostic means such as plain abdominal radiography, water soluble contrast enema and ultrasonography may yield reliable information for diagnosing colonic intussusception.