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. Tenesmus or a sensation of incomplete evacuation may be present. Pain is noticeably absent until perirectal tissue is involved. Simple, inexpensive testing of the stool for occult blood is advised as part of screening and high-risk surveillance programs.
Positive tests require further studies.
Fiberoptic colonoscopy should be performed when cancer is suspected in any portion of the bowel and when symptoms are referable to the colon. If a lesion is detected on sigmoidoscopy, total colonoscopy and complete removal of all colonic lesions should follow. Endoscopic excision of synchronous polyps may reduce the amount of bowel that needs to be resected. If a lesion is sessile or not removable at colonoscopy, surgical excision should be strongly considered. Barium enema x-ray examination is often unreliable to detect rectal cancer but may be an important preliminary step to diagnose colon cancer.