The patient has a rectal mass of unclear etiology. Double-contrast barium enema may reveal the mass but will not allow a biopsy to be obtained. A CT or MRI scan of the abdomen is warranted once a diagnosis of rectal cancer is made to assess the extent of disease, but ordering them at this stage is premature. Flexible sigmoidoscopy allows visualization and biopsy of the lesion, but a full colonoscopy would accomplish both of these goals and also allows examination of the entire colon to rule out any synchronous lesions that also may require treatment.
