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Both of these presentations can lead to electrolyte imbalance, dehydration, and infection, which add on to a surgical procedure, performed under emergent conditions. Perforation and obstruction cause an increase in morbidity and mortality. 279 In the Massachusetts General Hospital series, the actuarial 5-year survival for patients with obstructing and perforating carcinomas was 31% and 44%, respectively, whereas it was 59% in the control group. The GITSG reported that perforation was a prognostic factor for disease-free survival. Perforation is another untoward sign in patients with colorectal carcinoma. 260 After multivariate analysis, the Gastrointestinal Tumor Study Group (GITSG) concluded that obstruction was an independent prognostic factor for survival independent of Dukes stage. 259 Because tumors in the right colon can grow to a larger size, and therefore be present longer before causing symptoms of obstruction, it has been postulated that it is because of advanced stage at presentation rather than mechanical obstruction that these patients have a worse prognosis. The occurrence of bowel obstruction in the right colon was associated with a significantly diminished disease-free survival, whereas obstruction in the left colon demonstrated no such effect. 259 These investigators also reported that the effect of bowel obstruction was influenced by the location of the tumor. In two prospective randomized trials of Dukes Band C colorectal trials, the National Surgical Adjuvant Breast and Bowel Project (NSABP) reported that patients with bowel obstruction were at greater risk for treatment failure than were those patients without obstruction. 257, 258 Prospective studies are needed to clarify the significance of molecular detection of lymphatic micrometastases.Ĭolorectal cancer presenting with obstruction or perforation has an adverse effect on survival. Similar to reports of micrometastases in the bone marrow of patients with colorectal carcinoma undergoing curative resection, a report from The Netherlands suggests that lymphatic micrometastases adversely affect prognosis. 255, 256 The significance of lymph node micrometastases in colorectal carcinoma is unknown. In both single-institution and multiinstitutional studies it has been shown that lymphatic mapping is feasible and indeed may upstage 14% to 18% of node-negative tumors to node-positive status. By identifying the sentinel lymph node, immunohistochemical techniques and molecular techniques can be used to evaluate for the presence of micrometastases otherwise not diagnosed by conventional pathologic examination. Lymphatic mapping identifies the lymph node(s) that has(ve) the highest probability of harboring metastatic disease. Lymph node metastases in colorectal cancer appear to be an orderly process. Descending and upper sigmoid colon cancers can be treated with left hemicolectomy with ligation of the IMA at its origin from the aorta or by segmental resections as long as the principles outlined above are followed. Tumors in the transverse colon may require transverse colectomy or, at times, an extended right colectomy where the cecum, ascending colon, hepatic flexure, transverse colon, splenic flexure, and upper descending colon are resected together with its lymphatic drainage. If the middle colic artery is ligated at its origin, consideration should be given to extend the resection of the bowel just to the distal third of the transverse colon in order to ensure viable bowel for the anastomosis. It is important to note that for tumors in the cecum, ascending colon, hepatic flexure, and proximal transverse colon, the right branch of the middle colic artery is divided along with the right colic and the ileocolic arteries. 254 Figures 106-2 and 106-3 note the extent of resection. 254 For right-sided tumors, the length of ileum apparently does not influence the local recurrence rate. It is therefore recommended that at least a 5-cm margin of normal bowel be obtained on either side of the tumor in order to minimize the possibility of an anastomotic recurrence. More common are para-anastomotic recurrences reflecting possibly an inadequate lymphadenectomy. True colonic mucosal recurrences are rare. The basic surgical principles are removal of the major vascular pedicle feeding the tumor along with its lymphatics, obtaining a tumor-free margin, and en bloc resection of any organs or structures attached to the tumor. Radical surgery with curative intent is the treatment of choice in the majority of colon cancers.