Diagnosis



Carcinoma of the bowel must be suspected in any patient over age 40 who presents with change of bowel habits or in the caliber of stools, ill-de­fined abdominal pain, hematochezia, or iron de­ficiency anemia. Bright red blood on the stools should not be attributed to hemorrhoids or div-erticulosis until malignancy has been carefully excluded. If the patient has any of the special risk factors listed in Table 41-2, the threshold for sus­picion is further lowered. Even in the absence of such symptoms or findings, careful testing of stools for occult blood (using the Hemoccult test, for example) may pick up early malignant lesions.

Diagnostic studies usually start with a careful digital rectal examination followed by proctos­copy or sigmoidoscopy, since radiographic stud­ies are often not satisfactory for the rectum or lower sigmoid. If no lesion is found, a double-contrast barium enema is performed after careful bowel cleansing. If a suspicious lesion is noted, or indeed even if the study is normal and the sus­picion is high, colonoscopy is performed with multiple biopsies and brush cytological prepara­tions from abnormal sites. These combined stud­ies are successful in the detection of the vast ma­jority of carcinomas of the colon. Measurement of carcinoembryonic antigen (CEA) is not useful in diagnosis but may be of value in following a pa­tient after resection of a tumor, as a rise in CEA may then herald recurrence.