Teaching Case

We performed an abdominal CT examination on a 42 year old female patient complaining of abdominal pain. Laboratory analyses and past medical history were unremarkable.

The examination was performed after oral and intravenous contrast administration and revealed an ovoid (long axis 5.2 cm), well defined, fat density mass in the lumen of the splenic flexure of the colon. There was also a "bowel in bowel" configuration of transverse colon.

Lipomas are benign fatty tumors enclosed by a thin capsule. When localized in the gastrointestinal tract they may cause symptoms due to bleeding, obstruction or intussusception. Intussusception is a condition characterized by the invagination of an intestinal segment into the adjacent intestinal lumen. About 95% of all intussusceptions occur in children and are usually idiopathic [1]. Adult intussusception is usually caused by a factor (lead point) that alters the normal propagation of the peristaltic wave such as a tumor or scar tissue. Patients may present with symptoms of bowel obstruction (abdominal pain, nausea, vomiting). Diarrhea, hematochezia, constipation and weight loss may also be present [1].

Radiographic findings may include dilated bowel loops and air fluid levels suggestive of intestinal obstruction. Although sensitivity of conventional radiography is low it may help identify complications such as perforation (indicated by free intraperitoneal air) [2]. In children with suspected intussusception ultrasound is considered the imaging modality of choice. The classic ultrasonographic finding is the target (donut) sign (short axis US) and the pseudokidney sign (long axis US) [2]. The diagnostic accuracy of ultrasound is high with sensitivity and specificity as high as 97.9% and 97.8% respectively [3]. In adults intussusception is rare and symptoms may be chronic. Thus it is usually diagnosed with abdominal CT which is an imaging modality often used in patients with vague abdominal symptoms. The "bowel in bowel" configuration on CT is virtually pathognomonic [4]. CT may also be useful in identifying a lead point that caused the intussusception. Timely diagnoses is important due to potential life threatening complications (bowel obstruction, perforation, vascular compromise). Treatment options in children include therapeutic hydrostatic or pneumatic enemas but sometimes surgical reduction may be required [5]. Adults are usually treated with resection of the involved segment. Colonic intussusception should be carefully approached due to high probability of underlying malignant pathology [6].