Teaching Case

A 73-year-old female was diagnosed with a right pertrochanteric fracture and treated with intramedullary nail fixation. On the 5th postoperative day she developed progressive abdominal distension with worsening of the general condition.
With the clinical suspicion of adynamic ileus, plain abdominal film and computed tomography (CT) of abdomen and pelvis were performed.

Plain abdominal film showed a large number of dilated air-containing bowel loops and dilatation of the right and transverse colon, suggesting mechanic intestinal obstruction.

Contrast-enhanced CT revealed large bowel obstruction with ileocecal valve incompetent and transition point at distal transverse colon secondary to a colo-colonic intussusception. A 4 cm lobulated fat density intramural colonic mass was seen as the lead point of the intussusception. The right colon was markedly dilated with cecum measuring 10 cm and showing pneumatosis. Open extended right hemicolectomy was performed uneventfully. Pathology confirmed the diagnosis of submucosal colonic lipoma. Many other submucosal lipomas smaller than 0.2 cm were seen in the hemicolectomy piece.

Intussusception is defined as the invagination of an intestinal loop (termed the intussusceptum) into the distal portion of the same intestinal segment (known as the intussuscipiens). In adults, in contrast to children, it is relative rare, accounting for only 5% of all cases of intussusception and 1-5% of all causes of mechanical intestinal obstruction. [1, 2] A demonstrable cause is found in 70-90% of adult cases. Malignant lesions are responsible for 66% of cases of adult intussusceptions occurring in large bowel and for 30% occurring in small bowel. [1, 2]

Lipomas are benign adipose tumours, most often localized in the submucosa of the gastrointestinal tract. Approximately 65-75% of the gastrointestinal lipomas are located in the colon, most commonly in the ascending colon and cecum. [3] However, colo-colonic intussusception due to colonic lipoma has been described more frequently in the transverse or descending colon as in our case. [4] Multiple lipomas have been shown in 10-20% of the patients. [3]

The majority of colonic lipomas are diagnosed in the fifth and sixth decades and more often in women. [1, 4] Lipomas are usually asymptomatic, often discovered incidentally in routine procedures or in pathological specimens. Uncommonly, they can cause abdominal pain, bleeding, intestinal obstruction and intussusception. The risk of bowel obstruction, intussusception and clinical symptoms correlates with its size, usually larger than 2 cm. [5, 6] Lipomas larger than 4 cm are considered giant and are symptomatic in 75% of cases. [5, 6]

Imaging techniques are key in the diagnosis of intussusception. Ultrasound is essential in children, being less accurate in adults due to their larger size and the presence of intestinal gas. CT is the imaging technique of choice in adults. At CT, the presence of a target-like mass with a bowel-within-bowel configuration with or without mesenteric fat and mesenteric vessels is pathognomonic for intussusception. In addition, it may identify the lead point responsible for the intussusception.[7]
Lipomas typically appears in CT as a round or ovoid, smooth, well-demarcated, homogeneous mass with characteristic fatty densitometric value (Hounsfield units between -80 and -120).[3] CT scan is particularly useful in the detection of lipomas larger than 2 cm.

Most authors recommend surgical resection for colonic lipomas greater than 2 cm in size due to the risk of colonic intussusception and also for intussusceptions in adults, as they usually have a lead point with a high incidence of malignancy. [6]

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