Two Patients with Large Colonic Lipomas for which Endoscopic Unroofing was Ineffective.

Endoscopic unroofing is effective for treating large colonic lipomas. However, additional endoscopic resection is occasionally required when the outcomes of initial unroofing are incomplete. The colonoscopy of an 82-year-old woman with abdominal pain revealed a yellowish lipoma of about 20 mm in the transverse colon. The mass was treated by unroofing, but a follow-up colonoscopy 5 days later revealed residual lipoma. One month later, the regenerated surface had become covered with mucosa, and the status of the lipoma had returned to that before unroofing. The colonoscopy of a 74-year-old man with abdominal pain and melena revealed a 50-mm-wide protruding lipoma in the transverse colon. The mucosa of the upper third of the lipoma was excised using an electric knife and snare, which allowed the immediate partial drainage of adipose tissue. Unroofing proceeded, but 7 days later, the unroofed surface had become coated with a white substance, and the residual lipoma required additional endoscopic resection. Colonic lipomas are often asymptomatic. However, patients with abdominal pain and hemorrhage should be treated in consideration of complete resection, but not by unroofing, which could leave a residual tumor. Drainage should be confirmed after unroofing and any residual lipoma should be treated by additional resection.

Introduction

Colonic lipomas are benign mesenchymal tumors that might not require treatment if asymptomatic, whereas large colonic lipomas that cause abdominal pain, hemorrhage, constipation and intussusception require surgical resection. Therefore, it is desirable to treat large colonic lipomas with endoscopic resection [1]. Endoscopic submucosal dissection (ESD) is considered to be effective for treating large lipomas [2]; however, ESD is also associated with the risk of perforation and bleeding [3].

Endoscopic unroofing is a simple, safe and effective procedure that comprises the excision of the upper third of a large lipoma to allow remaining adipose tissue to gradually extrude from the resected stump [1, 4, 5, 6]. Nonetheless, the outcomes of this procedure are not always positive, and we describe the failure of unroofing to treat two large colonic lipomas.

Case Reports

Case 1

The colonoscopy of an 82-year-old woman with abdominal pain revealed a 40-mm pedunculated lipoma in the ascending colon and a 20-mm sessile lipoma in the transverse colon (fig 1a). The pedunculated mass in the ascending colon was resected en bloc by ESD using an electric knife (Dual Knife, Olympus, Tokyo, Japan), and the sessile mass in the transverse colon was treated by unroofing. The upper third of the tumor was resected using an electrocautery snare (Olympus, Tokyo, Japan) (fig 1b). Follow-up colonoscopy 5 days later revealed an open surface on the unroofed stump and residual lipoma (fig 1c) that persisted for up to 1 month. By that time, the regenerated surface had become covered with a mucosa, and the lipoma looked the same as it had been before unroofing (fig 1d). The residual lipoma was not resected because the patient no longer had abdominal pain and requested only follow-up observation.

Fig. 1

Colonoscopy findings of lipoma in an 82-year-old woman. a A smooth, yellowish submucosal tumor of about 20 mm in the transverse colon. b The upper third of lipoma body was excised using a snare. c The unroofed surface was open, but the lipoma persisted for 5 days. d The lipoma was covered with regenerated mucosa at 1 month after unroofing.

Case 2

A 74-year-old man who presented with abdominal pain and melena was diagnosed with a lipoma in the transverse colon and referred to our Department. The colonoscopy revealed a 50-mm-wide lipoma accompanied by mucosal hypertrophy and erosion in the transverse colon (fig 2a). The mucosa of the upper third of the tumor was circumferentially incised using an electric knife (Dual Knife, Olympus) and resected using an electrocautery snare (Olympus) (fig 2b, c). Adipose tissue in the lipoma partially drained immediately thereafter (fig 2d). Seven days later, the unroofed surface had become coated with a white substance (fig 3a). Since residual adipose tissue was not likely to drain, the lesion was resected piecemeal using an electrocautery snare (fig 3b, c). One month thereafter, the patient was free of abdominal pain and melena, and the colonoscopy showed that the resected region had become a scar without residual lipoma (fig 3d).

Fig. 2

Colonoscopy findings of lipoma in a 74-year-old man. a A protruding mass with a 50-mm-wide base and thickened, erosive mucosa in the transverse colon. b Mucosa of the upper third of lipoma after circumferential incision using an electric knife. c The upper third of lipoma body excised using a snare. d Adipose material extrudes from the cut surface.

Fig. 3

Colonoscopy findings of lipoma in a 74-year-old man at 1 week after unroofing and 4 weeks after piecemeal EMR. a The unroofed surface was coated with white substance, and the residual lipoma was evident after 1 week. b, c The lipoma was removed by piecemeal EMR. d Four weeks thereafter, the resected region was cicatrized without residual lipoma.

Discussion

Endoscopic unroofing is simple and safe, and a useful method of treatment that also enables pathological examinations [1]. The procedure is applicable to a diagnosis not only of lipomas, but also of submucosal masses such as gastrointestinal stromal tumors, leiomyomas, and neuroendocrine carcinomas [7, 8].

We treated colonic lipomas in 2 patients using unroofing, but the outcomes were insufficient in both. We therefore investigated why the remaining lipoma failed to drain. In the 1st patient, the unroofed area of the transverse colon lipoma was small, and only the surface was resected, which might have prevented the drainage of adipose tissue despite it being exposed. Adipose tissue partially drained immediately after unroofing in the 2nd patient, but a hard, thickened mucosa was encapsulated by a submucosal layer that might have prevented the spontaneous drainage of residual fat. Adipose tissue can take several days to weeks to drain from lipomas, but this did not occur within a period of about 1 week in either patient. The mucosa regenerated on the unroofed surface after 1 month in the 1st patient, whereas endoscopic findings showed that adipose tissue had not drained in the 2nd patient within 1 month, and additional endoscopic mucosal resection (EMR) was required. Unroofing resulting in incomplete resection that requires additional EMR has been reported [9]. More investigation is needed about lipomas treated by endoscopic unroofing, particularly those from which adipose tissue does not drain.

Large colonic lipomas can spontaneously detach [10], but treating those ≥2 cm using endoscopic procedures is associated with increased risk of complications such as perforation and hemorrhage [11]. Therefore, in addition to standard EMR, attempts have been made to reduce complications by applying a detachable nylon endoloop or a long clip to the base of large colonic lipomas [12, 13]. In addition, recent improvements in ESD have allowed the safe resection of large lesions, and large colonic lipomas are now included among the indications for this procedure [14]. However, the risk of complications remains high for endoscopic procedures, and surgical resection is recommended for lipomas with a base that is ≥4 cm or patients with an unclear diagnosis, intussusception-induced obstruction, expansion into the muscle layer and serosa, and incomplete endoscopic resection [15].

Colonic lipomas are often asymptomatic. However, patients with abdominal pain and hemorrhage should be treated in consideration of complete resection, but not by unroofing, which could leave a residual tumor. Drainage should be confirmed after unroofing and any residual lipoma should be treated by additional resection.

Statement of Ethics

The authors have no ethical conflicts to disclose.

Disclosure Statement

The authors have no conflicts of interest to declare.