A colonic submucosal lipoma presenting with recurrent intestinal obstruction attacks

Abstract

Colonic submucosal lipomas are rare benign tumours of the colon, which may be discovered incidentally at colonoscopy, through imaging such as CT or at autopsy. These tumours can cause complications such as bleeding, intussusception and bowel obstruction. We describe the case of a patient in whom a small submucosal lipoma was identified at the time of colonoscopy and who did not receive follow-up treatment. The patient presented 1 year later with intussusception and obstruction resulting from this polyp and required urgent surgery. With the increasing use of colonoscopy and CT, such lesions are likely to be discovered more often. As complications can ensue, guidelines should be developed to advise on the management of such polyps in order to prevent consequent complications.

BACKGROUND

Although submucosal lipomas represent the second most common benign tumour of the colon,^1,2 they remain rare and are usually detected incidentally at colonoscopy, surgery or autopsy.³ They can cause complications, including bleeding, abdominal pain, bowel obstruction or intussusception. There are currently no recommendations as to how patients with incidental lipomas should be managed. We report here the case of a patient with an incidental submucosal lipoma that was not followed up. The patient subsequently presented with obstructive symptoms secondary to intussusception of the lipoma and required urgent surgery.

CASE PRESENTATION

A 62-year-old man presented in 2007 with a 1-year history of intermittent bleeding per rectum and abdominal pain. A colonoscopy demonstrated a 2 cm polypoidal tumour in the descending colon in keeping with a submucosal lipoma. Biopsy of this lesion showed normal colonic mucosa. On the basis that this was a benign condition and the patient’s symptoms had resolved, no further follow-up was arranged. He presented a year later as an emergency admission with colicky abdominal pain and constipation. On examination, a mass was palpable in the left iliac fossa. A CT scan of the abdomen demonstrated an intussuscepting lesion in the left colon. The CT appearances showed a lipoma as the possible lead point for this intussusception (fig 1). A flexible sigmoidoscopy was performed and, although it was not possible to reach the left colon because of looping of the sigmoid, the patient’s symptoms resolved and he was discharged with colonoscopy arranged as an out-patient. Two weeks following discharge, he was re-admitted with symptoms of bowel obstruction. A colonoscopy was performed under general anaesthetic and a large polyp was found at 90 cm. It was not possible to remove this polyp endoscopically due to its size. Biopsies were taken, which showed ischaemic changes of the colonic mucosa only. Due to persistent symptoms of bowel obstruction, he underwent a left hemicolectomy. The postoperative period was complicated by an adhesive obstruction, which did not settle with conservative management and required a further laparotomy and adhesiolysis from which the patient made an unremarkable recovery. Histopathological examination revealed a 2.5 cm submucosal lipoma (fig 2–4).

Figure 1.

CT section demonstrating intussusception of the submucosal lipoma (arrow) in the left colon.

Figure 2.

Macroscopic image of polypoid lesion. The surface of the “polyp” is ulcerated. Distal to the polyp there are areas of erythematous mucosa secondary to intussusception.

Figure 4.

On the surface of the polyp are the remnants of colonic epithelium (crypts). The mucosa is necrotic and many of the crypts have disappeared completely leaving empty spaces behind.

Figure 3.

Cross-section through polypoid lesion showing core of pale yellow adipose tissue.

OUTCOMES AND FOLLOW-UP

The patient consequently made a full recovery and was discharged home.

DISCUSSION

Although rare, lipomata represent 4% of benign lesions of the gastrointestinal tract and can occur throughout its length.⁴ The incidence has been reported between 0.15% and 4.4%.^2,5

The colon is most commonly affected, followed by the small bowel and stomach.^6,7 Ninety per cent of colonic lipomas arise from the submucosa.¹ The most common age of presentation is in the 5th or 6th decade and there is a slight female preponderance.⁴

Most lipomas are found in the right side of the colon.^1,8 To our knowledge, sarcomatous change in theses lesions has not been reported. Therefore, accurate preoperative diagnosis of these lesions may avoid unnecessary extensive surgery.

Most lipomas do not produce symptoms and are often found incidentally during colonoscopy, surgery, radiological examination or autopsy.³ Larger lipomas (>2cm) are more likely to cause symptoms of abdominal pain, obstruction, bleeding or intussusception.²

On endoscopic examination, lipomas typically appear smooth, yellow and may be sessile or pedunculated. The polyp may be easily indented when probed with biopsy forceps but then regain their original shape (cushion sign).⁹ On biopsy, fatty tissue may protrude through the biopsy site giving rise to the so-called “naked-fat sign”.¹⁰ However, appearances on colonoscopy may be misleading as the lesion may appear ulcerated resulting in suspicion of malignancy.⁸

Lipomas can be diagnosed on CT. A lipoma is seen as a mass with well-defined margins and an absorption density between −40 and −120 HU, which is characteristic of fatty tissue.^6,11 Barium studies may reveal a filling defect with a well-circumscribed border and this lesion may change in size and shape on peristalsis and pressure.^6,8 The use of endoscopic ultrasonography can help delineate the size, border and layer of origin of these colonic submucosal lesions and may improve diagnostic accuracy.^12,13

Lipomas are only usually treated when they become symptomatic. They can be removed endoscopically but this may not always be possible, particularly in larger lipomas where the base may be broad. Endoscopic resection of large lipomas was found in a case series¹⁴ to be associated with an increased risk of colonic perforation. Resection of symptomatic lipomas has not been shown to be associated with recurrence.¹⁵ Where there is a suspicion of malignancy, or endoscopic resection is not possible, operative resection is normally performed with a radical rather than segmental resection if malignancy has not been excluded. Frozen section at the time of laparotomy may be helpful in making a tissue diagnosis prior to radical resection.

LEARNING POINTS

• With the number of colonoscopies and CT colonoscopies performed increasing rapidly, the detection of submucosal lipomas is likely to increase.

• To our knowledge, there are no guidelines for the management of those patients in whom submucosal lipomas have been demonstrated but are deemed to be insignificant. However, as this case demonstrates, such lesions may consequently present at a later date as an emergency supporting a case for follow up and early intervention.