Patients with chronic large bowel obstruction complain of pain, distension, and constipation over several weeks. The distension is progressive dilation of the proximal large bowel by the closed-loop obstruction formed by a competent ileocecal valve. Because of the chronicity of this process, ischemia and gangrene of the cecum in association with tenderness and leukocytosis are usually absent. Vomiting is a late manifestation accompanying complete obstruction or involvement of the small bowel. Peritonitis may result from perforation at the site of the obstruction or of the cecum.

An abdominal radiograph is a simple and effective method of diagnosing large bowel obstruction. The proximal colon is often distended with air and a cutoff is seen at the level of the obstruction. The next step is to determine the degree, partial versus complete, and location of the obstruction using a water-contrast enema (with Hypaque or Gastrografin). Partial obstructions are amenable to endoscopic dilation (for strictures), endoscopic stenting (for strictures or carcinoma), and preoperative bowel preparations. Complete obstructions require early surgical intervention for proximal decompression. Location with respect to right colon, left colon, or rectum is important in planning any therapeutic intervention. In addition, length of the obstruction and presence of mucosal irregularities give clues to the etiology and candidacy for stenting.

Following the water-soluble enema, a computed tomography (CT) scan is performed, which provides extraluminal information about the cause and nature of the obstruction and associated pathology, such as extrinsic compression, tumor size, presence of metastases, perforation, or signs of diverticulitis. However, if the patient requires an exploratory laparotomy, then a CT scan of the abdomen and pelvis is unnecessary because the time can be spent resuscitating. Any pathology present can be evaluated intraoperatively, and appropriate decisions can be made at that time.