The operation is performed under general anaesthesia. The patient is placed in the dependent position, as described during the pre-operative examination. The most difficult position is the prone position. This position, for tumours of the anterior wall, requires strong support of the hips and chest so the abdomen itself is mobile. When the lateral Simms position is necessary, it is important that the anus is accessible and the table or legs of the patient do not impede mobility of the instruments. Suitable positioning of the patient is necessary because of the angulation of the optics and the specific design of the instruments.
A careful digital sphincter dilatation is performed. The operative rectoscope is introduced and the tumour is localised. The position of the rectoscope is fixed by a special retractor. The operative instruments and the optics are introduced and connected to the different lines.
The type of excision depends on the type and position of the tumour. The standard is the full-thickness excision because tearing of the tumour is prevented and precise histological evaluation is possible. In the case of a carcinoma inside an adenoma, full-thickness
excision is mandatory to guarantee complete excision. Full-thickness excision of an anterior wall above 10 cm is not possible because of the contact to the peritoneal cavity. In women this limit could be even lower. The resection line for the dissection is defined by placing marking dots using a high frequency cautery device. The line should be 5 mm long for adenomas and at least 10 mm long for early cancers. After placement of the marking dots the bowel wall is transected to the appropriate layer by use of the standard technique. A monopolar cutting device is used. When bleeding occurs, the suction device, which is positioned at the entrance of the rectoscope, is advanced and the bleeding is localised and stopped by monopolar coagulation. Dissection from the perirectal tissue is usually performed in a layer close to the longitudinal muscles of the bowel wall and the tumour lifted upward (Fig. 6). Any bleeding must be stopped immediately by monopolar coagulation to guarantee optimal overview during the whole procedure.
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