The 'difficult' polyp: pitfalls for endoscopic removal.

Adenomatous polyps are early neoplasias of colorectal cancer (adenoma-carcinoma sequence). The majority of adenomas or early invasive cancers (T1sm1) can be resected by endoscopy. Endoscopic resection techniques include classic loop polypectomy, endoscopic mucosectomy with preceding lifting of the (almost flat) lesion, endoscopic submucosal dissection and transanal microsurgical resection, an alternative to endoscopic submucosal dissection in the rectum. Endoscopic polyp removal should always aim to resect the lesion in 'one piece' and avoid, whenever possible, 'piecemeal resection'. One-piece polypectomy is the basis for a precise histopathological analysis and for proving complete removal of the lesion. Preceding injection of saline solution into the submucosa to lift the targeted polyp is a therapeutic modality to remove even-flat and flat-depressed adenomas. In addition, a positive lifting sign is regarded as a criterion of lower superficial malignancy. Lifting of a polyp can be negatively influenced by an already advanced cancer (T1sm3/T2) in the deep parts of the submucosa as well as by scars and connective tissue in the upper two layers of the colorectal wall. Hence, a negative lifting sign may lead to incorrect macroscopic evaluation of the lesion before removal. Endoscopic submucosal dissection is mostly performed in large laterally spreading tumors in the rectum and in the preanal region. The technique has a relatively long learning curve and is somewhat time consuming. A 'difficult polyp' may be characterized by: (1) the size (>3 cm), pedunculated or sessile (Ip/Is); (2) morphological type (classification of Paris 2003), in particular the flat type II lesions IIa-c flat, flat depressed; laterally spreading tumors and the large sessile-serrated lesions; and (3) the difficult assessment of the grade of malignancy before removal [e.g. dysplasia-associated lesions or masses (DALMs), sporadic adenoma, colitis carcinoma]. Chromoendoscopy (with indigo carmine) represents an adequate method to differentiate advanced flat and depressed type II lesions from those with lower malignancy, and to better identify DALMs and sporadic adenomas in patients with long-lasting ulcerative colitis. To reduce the risk of resection (hemorrhage 0-6%, perforation 0.2%; Munich Polyp Study 2005) the application of hemoclips to visible vessels or injection of adrenaline (1:10,000) in the polyp stalk before removal are methods to prevent bleeding. In case of immediate bleeding, the treatment with hemoclips, injection (adrenaline or fibrin sealant) or endoloops are efficacious to manage this problem. Small perforations can be treated at once by the application of hemoclips, or, in case of larger or difficult leakages by Ovesco clips to avoid surgical interventions.