Teaching Case

The patient was a 45-year-old lady who presented with a history of dyspepsia and vague abdominal pain for the past three months. During this period, she was having anorexia and weight loss (not quantified). However, there was no history of any vomiting/ constipation/ obstipation/ haematochezia/ Malena/ recurrent fever/ abdominal lump.

US (ultrasonography) abdomen showed telescoping of the ileum into the large bowel loops giving a sandwich appearance. A homogeneously hyperechoic lesion was noted at the distal end which is likely to represent a lipoma that may have acted as a lead point for this intussusception [Fig 1a,1b]. The proximal bowel loops were not dilated. CECT (contrast-enhanced computed tomography) abdomen revealed herniation of the distal ileal loop into the ascending and proximal transverse colon. The lipoma measured 38.0mm x 40.0mm x 56.0mm in size, qualifying it to be a giant lipoma[1]. Its average attenuation was -46 HU. [Fig 2a]. A delayed radiograph of the abdomen after the CECT scan showed a pulled-up caecum and the typical coiled appearance of the bowel loop with lipoma as a lead point [Fig 3].

Macroscopically, there was a yellow globular mass [Fig 4]. Histopathology revealed predominantly mature adipocytes and interspersed by fibrous septae [Fig 5].

A lipoma is a benign non-invasive, encapsulated mesenchymal tumour that resembles normal fat. Lipoma complicating as intussusception is extremely rare [2].  Among adults, intussusception contributes to 1% of all bowel obstructions [3]. It is a rare condition in adults compared to that in children. Intussusception can be primary when a definite cause cannot be delineated or secondary when pathology can be identified. In children, the cause is usually a primary post-viral illness. However, in adults, primary intussusception accounts for only 8%-20% of cases whereas secondary intussusception, where a lead point can be identified accounts for the majority. The lead point can be a benign lesion like polyp, enlarged lymph node, an intra-luminal lipoma, appendix, Meckel’s diverticulum, or malignant tumours, such as lymphoma, gastrointestinal stromal tumour, primary or metastatic adenocarcinoma [4].

Clinical perspective

Lipomas of the intestine are infrequent, with an incidence ranging from 0.2 to 4.4% [5].  One-third of cases with larger tumour size may present with anaemia, abdominal pain, diarrhoea, constipation, bleeding, or intussusceptions [6]. Most commonly, they occur in 50 to 60-year-old women with the most common site of occurrence being the caecum and ascending colon[7]. Giant lipomas are associated with more complications of abdominal pain, bleeding, and intussusception. Hence they are to be approached surgically[2].

Imaging perspective

Radiological investigations including US and particularly CT are essential for characterizing the fatty nature of the mass.

Radiographs may demonstrate dilated bowel loops in case of obstruction. Barium meal follow-through may reveal a stacked coil or coiled spring appearance, whereas barium enema may show a cup-shaped filling defect or the typical claw sign[8]. US will show a target sign in the transverse view or a hay fork sign in the longitudinal view. CT scan will show a target or soft tissue mass with a layering effect. It also helps in looking into surrounding tissues and local invasion if any [8].

Adult patients are usually subjected to surgical treatment rather than reduction under sonography due to increased chances of malignancy. Paediatric intussusception may be managed by hydro reduction or pneumatic reduction [8].

Take home message

Lipoma has to be considered in the differential diagnosis of a fatty intra-abdominal mass. Imaging aids in correctly localizing and characterizing the pathology and also to identify any complications. It helps to avoid extensive surgical interventions.

The patient has given her informed consent to publish this article.