Partial obstruction with colicky abdominal pain or complete obstruction may be the presenting picture. The stool may be streaked or mixed with blood. In cancer of the rectum the most common presenting symptom is bleeding with defecation. Whenever rectal bleeding occurs, even with obvious hemorrhoids or known diverticular disease, coexisting cancer must be ruled out. Simple, inexpensive testing of the stool for occult blood is advised as part of screening and high-risk surveillance programmes.
Positive tests require further studies.
Fiberoptic colonoscopy should be done whenever cancer is suspected in any portion of the bowel and in every patient with symptoms referable to the colon. Barium enema x-ray examination is unreliable to detect rectal cancer, but it is an important initial step to diagnose colonic cancer. If CEA is high preoperatively and low after removal of a colonic tumor, monitoring CEA may help to detect recurrence. Treatment and Prognosis Primary treatment consists of wide surgical resection of the colon cancer and its regional lymphatic drainage after preparation of the bowel. Chemotherapy and immunotherapy have not proven effective as surgical adjuvants in properly controlled trials of colon and rectal cancer treatment.