Abstract
Mucosal prolapse syndrome (MPS) is a group of diseases caused by occult and obvious mucosal prolapse with fibromuscular obliteration determined histologically. The endoscopic appearance of MPS varies (polypoid type, ulcerative type and flat type), and a differential diagnosis for cancer and other inflammatory bowel diseases is necessary. Almost all large polypoid types of MPS have an irregular surface, erosions and sloughs mimicking rectal cancer. If the rectal lesion is diagnosed as MPS endoscopically or clinically without fibromuscular obliteration determined from a biopsy specimen, a large specimen obtained by polypectomy, endoscopic mucosal resection or transanal local resection is necessary to demonstrate fibromuscular obliteration histologically. If MPS is misdiagnosed as rectal cancer, there is a possibility that an unnecessary operation will be performed. The flat type of MPS is classified according macular redness just above the anus and circular redness on the Houston valve. If these findings are not recognized, a differential diagnosis is necessary for other inflammatory bowel diseases.
