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Paper text:
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 .
endoscopic submucosal dissection ( esd ) is considered to be effective for treating large lipomas ; however , esd is also associated with the risk of perforation and bleeding .
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 .
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 .
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 ) .
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 ) .
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 .
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 ) .
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 ) .
endoscopic unroofing is simple and safe , and a useful method of treatment that also enables pathological examinations .
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 .
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 , but treating those 2 cm using endoscopic procedures is associated with increased risk of complications such as perforation and hemorrhage . 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 . 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 .
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 .
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 .