Colorectal Cancer

Colorectal cancer is the second most common solid malignancy in adults and the second leading cause of cancer death in the US.

Clinical evaluation of colorectal cancer

Flexible sigmoidoscopy for screening is indicated for asymptomatic, healthy adults over age 50. All adults with anemia or guaiac positive stools should be evaluated for colorectal cancer; older adults (>40) should be evaluated even if other sources of bleeding have been found. Hemorrhoids and cancer can coexist.

Flexible sigmoidoscopy plus air contrast barium enema is adequate to evaluate the colon when the source of bleeding is thought to be benign anorectal disease.

Total colonoscopy should be performed for any adult with gross or occult rectal bleeding and no apparent anorectal source.

Left sided or rectal lesions are characterized by blood streaked stools, change in caliber or consistency of stools, obstipation, alternating diarrhea and constipation, and tenesmus.

Right sided lesions are characterized by a triad of iron deficiency anemia, a right lower quadrant mass, and weakness. Cancers occasionally present as a large bowel obstruction, perforation or abscess.

Laboratory evaluation

CBC with indices (hypochromic, microcytic anemia). Liver function tests may sometimes be elevated in metastatic disease.

Carcinoembryonic antigen (CEA) may be elevated in colorectal cancer, but it is a nonspecific test (also elevated in other malignancies, some inflammatory bowel disease, cigarette smokers, and some normal persons). It is valuable in monitoring the response to treatment and as a marker for recurrence or metastases, requiring adjuvant therapy. It should be measured prior to resection of the tumor and at intervals postoperatively.

Colorectal cancer is detected by total colonoscopy with biopsies. Barium enema may complement colonoscopy since BE shows the exact anatomic location of the tumor. A chest X-ray should be done to search for metastases to the lungs.

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