Large bowel obstruction secondary to colon cancer

Erect and supine abdominal radiographs demonstrate distension of the large bowel with feces without definite feces or gas seen within the rectum. No extraluminal gas identified. Left pelvic side wall surgical clips.

While the appearances could be due to colonic pseudo-obstruction, an obstructing lesion in the distal large bowel requires consideration and could be further assessed with CT.  

There is a 2.5cm long stenotic segment of circumferential wall thickening in the distal sigmoid colon that causes moderate grade bowel obstruction. The large bowel proximal to the stenosis is distended with feces. No pathologically enlarged draining lymph nodes. Sub-centimeter hypoattenuation foci in segment VIII, VII and IVb of the liver have a benign appearance but this should be confirmed with ultrasound.  There is a moderate volume of ascites.  No peritoneal thickening or a nodular appearance of the peritoneum. There is a 11 x 8 x 14 mm well-circumscribed cystic lesion in the body of the pancreas without duct dilatation. Rest of the pancreas has a normal appearance.  The gallbladder, spleen, adrenal glands and kidneys demonstrate normal postcontrast enhancement. Small hiatus hernia.  Multiple surgical clips in the left pelvic wall presumably related to previous hysterectomy/oophorectomy. Correlation with previous surgical history is essential.