The management of obstructing or perforated colon cancer presents unique considerations.When patients present with urgent evidence of obstruction without the opportunity to prepare the bowel, they must be expediently resuscitated and undergo immediate surgical exploration. If the obstruction is due to a proximal lesion near the ileocecal valve, a right hemicolectomy with primary anastomosis may be performed safely in most cases, even with an unprepared colon. More distal obstructions are problematic because the proximal colon is dilated and typically full of stool.

Once the involved segment of colon is resected, ontable lavage can be performed. This involves mobilization of the colon, attachment of large bore sterile tubing to drain the effluent, and instillation of a large volume of warm saline through a catheter placed through an appendicostomy

or the terminal ileum. The distal segment of bowel can be washed out from below. This technique can allow for a primary anastomosis in some cases provided the bowel is not dilated and appears relatively healthy.

Perforations at the tumor site can present either as locally contained abscesses or as free perforation with peritonitis. In addition, obstructing tumors can result in

colonic perforation, typically proximal to the tumor or at the cecum. In the case of contained perforations, abscesses can be drained percutaneously with subsequent investigations

and elective surgical management. Free perforation with peritonitis is a surgical emergency that necessitates rapid resuscitation and operation. In the setting of gross fecal contamination, resection of the tumor and perforation are performed when possible with a proximal colostomy or ileostomy (Hartmann's procedure). In some cases, a primary anastomosis can be performed with a protecting proximal ostomy. An unprotected anastomosis without diversion is ill advised in these unstable patients.