Indications for colorectal resection for adenoma before and after polypectomy

Adenomas presenting in colon and rectum require different strategies. Those in the rectum are accessible to local endoanal excision while those in the colon can be removed by endoscopic polypectomy. Essentially the decision in both cases centres around the risk of malignancy. Does the tumour itself contain a focus of malignancy? Where invasion has been demonstrated in the tumour, are the regional lymph nodes involved? Rectal adenomas can be assessed by clinical examination, rectal ultrasound and magnetic resonance imaging. Colonic adenomas on the other hand, are assessed by endoscopic appearances amplified by chromoand zoom-endoscopy techniques and by endoscopic endosonography. In both locations the decision for surgical resection may be necessary in two clinical circumstances: the preoperative assessment of invasion and following the histopathology report where invasion has been demonstrated. With any adenoma with malignant change, a surgical opinion should be obtained. The decision for surgery depends on the risk of failure of the local excision balanced by the risk of morbidity and mortality following major surgery. Patients’ wishes in the light of discussion of clinical and pathological prognostic factors are crucial in making the decision. Surgery is more frequently applied for Tech Coloproctol (2004) 8:S291–S294 DOI 10.1007/s10151-004-0179-9 S292 R.J. Nicholls et al.: Indications for colorectal resection for adenoma muscularis mucosae [5]. Thus it is not reliable in differentiating between an adenoma that, by definition, is still confined to the mucosa, and an early T1 carcinoma. Magnetic resonance (MR) imaging adds nothing to the assessment of these early tumours [6]. Thus the suspicion of malignity is still based largely on clinical factors. Obviously only the histological examination will resolve the doubt. It is mandatory to provide an adequate specimen. If the adenoma is uniformly soft and accessible to local removal then it is justified to excise it locally. A submucous technique is the preferred method [7]. Occasionally during the dissection the submucosal plane may be found to be obliterated at a certain point. This suggests the possibility of malignant invasion. At this point the dissection should be carried out through the full thickness of the rectal wall. The excised specimen must be properly oriented for the pathologist. A suitable method is to pin it out on a corkboard, recreating its gross morphology [1]. The cork is then placed upside down in a container of formalin. Any further decision should wait upon the histopathological report. Where the preoperative assessment indicates that the lesion is an established carcinoma, then the criteria for local excision should be applied. These include size of tumour (<3 cm), accessibility to endoanal removal, not ulcerated and clinical and ultrasonic evidence of T1 stage as well as the age and general fitness of the patient for major surgery [8]. The simple morphology is a crucial factor in deciding whether local excision is adequate. In a series of 165 rectal cancers treated by local excision the cancer specific death was 0% in polypoid or sessile and 30% in flat or ulcerated lesions [9]. A large villous adenoma, which is not amenable to local excision, should be treated by anterior resection. Where the tumour encroaches on the upper anal canal, the most distal part can be removed by submucous resection in continuity with the main specimen and intestinal continuity established by a manual coloanal anastomosis.