Colocolic intussusception (invagination) secondary to a lipoma.

Clinical History

A 28-year-old man with left lower abdominal pain and rectal bleeding had experienced intermittent abdominal pain in the last five months and weight loss (15 kg).

Imaging Findings

A 28-year-old male patient was admitted to the hospital for severe, colicky left lower abdominal pain and rectal bleeding. He had experienced intermittent abdominal pain in the last five months, with 2 to 3 depositions per day, and weight loss (15 kg). His laboratory test results were unremarkable, although during his stay at the hospital, he had a discrete anaemia. His physical examination showed left lower abdominal tenderness without signs of acute abdomen. He had never underwent any surgery.
At computed tomography (CT), the typical bowel-within-bowel appearance was visualized at the level of the sigmoid colon (Fig. 1). The intussusceptum and intussuscipiens were well delimited by the strong enhancement of the mucosa. There was thickening of the wall. The lead point (head of intussusceptum), nicely shown, is an intraluminal 3.1 cm mass, of fat attenuation characteristic of a lipoma (Figures 2, 3). The intussusception was reduced during surgery and there were signs of suffering of the proximal segment of the colon. The proximal part of the intussusceptum was congested and a partial resection of the affected sigmoid colon was performed (Fig. 4). The gross pathologic specimen showed a lobulated, submucosal, sessile lipoma with overlying ulceration of the mucosa (Fig. 5, 6). The patient’s postoperative course was uneventful, and he was discharged seven days after surgery.

Discussion

Intussusception is a prolapse of a portion of the bowel into the lumen of an immediately adjacent segment of the bowel. The intussuscipiens is the part of the intestine into which the adjoining portion has prolapsed, and the intussusceptum is the prolapsed segment. The classic CT findings of intussusception include: (a) Sausagelike or targetlike mass, in which the inner central area corresponds to the invagenated intussusceptum, surrounded by its mesenteric fat and associated vasculature, all of which are surrounded by the thick-walled intussuscipiens [1]. (b) Oral positive contrast material trapped between the opposing walls of the intussusceptum and intussuscipiens [2]. (c) A soft-tissue mass secondary to intussusception, with the accompanying lead point, telescoping into the intussuscipiens [3, 4]. Nowadays, with the helical multislices CT-techniques, with the use of intravascular contrast agent injected with high velocity flows in early phase, and the use of negative contrast agents for the gastrointestinal tract, is possible to distinguish the mucosa by its strong enhancement, and delimitate the pathology associated to the intestinal wall [5]. This makes it possible to show the typical bowel-within-bowel appearance of intussusception at CT.
Intussusception is most often a disease of children, usually an ileocolic intussusception [2] without lead point. About 5% to 16% of intussusception occur in adults [2, 6, 7], accounting for 1% of all bowel obstruction [8], and usually there is a lead point [9].
Intussusceptions are classified according to location (enteroenteric, ileocolic, ileocecal and colocolic), cause (benign, malignant and idiopathic) [10] and presence of a lead point [6]. Intussusception without a lead point tends to be transient and with a lead point intussusceptum tends to be persistent or recurrent [6].
Unlike in children, symptoms in adults tend to be more chronic and intermittent [7]. Symptoms include cramping abdominal pain, nausea and vomiting, abdominal tenderness and distension, change in bowel habits [11] and weight loss [2]. Blood in stool is seen in the majority of patients and a palpable mass can be detected in up to one-half of patients [7].
More than one-half of large bowel intussusceptions are associated with malignant lesion, including primary tumours (adenocarcinoma, lymphoma) and metastasis [8]. Benign lesions constitute about 30 % and include neoplasm such as lipoma, leiomioma, adenomatous polyp, endometriosis (appendiceal) and previous anastomosis [10]. Colonic intussusception often manifests with abdominal pain due to a recurring intussusception that causes intestinal obstruction [2]. Identification of a lead mass at CT is often possible, although determination of an underlying cause is not easy with the exception of a lipoma [6]. Transient tumour-related colocolic intussusception has been reported [12].
Lipoma is the most common benign cause of colonic intussusception in adults. Lipomas are usually asymptomatic until they reach approximately 4 cm and cause abdominal pain, sometimes due to intussusception, and may result in chronic blood loss, due to ulceration of underlying mucosa in addition to intussusception [2]. Lipomas can appear either the large or the small bowel and may be easily diagnosed at CT due to their typical fat attenuation [6].

Differential Diagnosis List

Final Diagnosis

Colocolic intussusception (invagination) secondary to a lipoma.

URL:	https://www.eurorad.org/case/6852
DOI:	10.1594/EURORAD/CASE.6852
ISSN:	1563-4086