PANCE Blueprint GI and Nutrition (9%)

The diagnostic procedure of choice in this patient is a total colonoscopy to confirm a mass lesion, to determine the location of that lesion, and to obtain a biopsy specimen of the lesion if possible.

In this patient, the problem list at this point is as follows: (1) a middle-aged man with nonspecific feelings of “ill health”; (2) there is a right lower quadrant mass on physical examination, raising suspicion of carcinoma; (3) the liver is enlarged, possibly indicating metastases; (4) the pale appearance suggests anemia; (5) icterus suggests elevated conjugated bilirubin; and (6) the clinically apparent abdominal distention indicates possible ascites. With this constellation of symptoms and signs, the working diagnosis is adenocarcinoma of the colon, possibly the cecum, with liver metastases.

The definitive surgical treatment of choice in this patient (if feasible) is resection of the colonic mass. The preliminary location of the lesion based on physical examination is in the area of the cecum. If this proves to be correct, the colonic resection will involve the removal of the area from the vermiform appendix to the junction of the ascending and transverse colons. With the presence of liver metastasis, this procedure is palliative.

The majority of colonic adenocarcinomas evolve from adenomas. Adenomas are a premalignant lesion; in the large bowel, the sequence is adenoma, dysplasia in the adenomas, and adenocarcinoma.

Both adenomas and the subsequent evolved adenocarcinomas increase in incidence with age, and the distribution of adenomas and cancer in the bowel is similar. Overall, adenomatous polyps are found in approximately 25% of asymptomatic patients who undergo screening colonoscopy. The age-related prevalence of adenomatous polyps is 30% at age 50 years, 40% at age 60 years, 50% at age 70 years, and 55% at age 80 years.

The current U.S. Preventive Services Task Force recommends colorectal cancer screening for all people aged 50 years or older. Screening reduces mortality. Acceptable screening methods include annual fecal occult blood testing, colonoscopy, and contrast barium enema. Colonoscopy provides an alternative that will find abnormalities throughout the colon and allows removal of polyps at the same time; however, the major complication rate of 1 in 1000 procedures (under the best of circumstances) and the difficult preparation make many patients concerned about the process. Flexible sigmoidoscopy also provides a clear picture, but only of the distal third of the colon. So-called virtual colonoscopy done by a CT scan cannot replace colonoscopy at this time.

CEA is a glycoprotein found in the cell membranes of a number of tissues, a number of body fluids, and a number of secretions including urine and feces. It is also found in malignant neoplasms of the colon and rectum. Because some of the CEA antigen enters the bloodstream, it can be detected by the use of a radioimmunoassay technique of serum. Elevated CEA is not specifically associated with colorectal cancer; abnormally high levels of CEA are also found in patients with other gastrointestinal malignant neoplasms and nongastrointestinal malignant neoplasms. CEA levels are elevated in 70% of patients with an adenocarcinoma of the large bowel, but less than 50% of patients with localized disease are CEA positive. Thus, because of these difficulties with sensitivity and specificity, CEA does not serve as a useful screening procedure, nor is it an accurate diagnostic test for colorectal cancer at a curable stage. However, elevated preoperative CEA levels correlate with postoperative recurrence rate, and failure of CEA to fall to normal levels after resection implies a poor prognosis. CEA is helpful in detecting recurrence after curative surgical resection; if high CEA levels return to normal after operation and then increase progressively during the follow-up period, recurrence of cancer is likely.