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Updated: 12/26/06 03:13 PM |
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Authors: S. Shimoda, F. Silverstein, and D.R. Saunders
Download Chapter ♦ Download Lecture Slides & Notes
Download Chapter ♦ Download Lecture Slides & Notes
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H. Diagnostic Methods
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In any colonic disorder the initial examination should be the "rectal" (digital palpation of the rectum with a gloved finger). The rectal examination should be a routine part of every complete physical examination. Many things can be felt with the examining finger: cancers, benign polyps, thrombosed external hemorrhoids, pararectal tender indurations (abscess, cellulitis), anal ulcers, intraabdominal masses (pelvic appendicitis, anterior shelf of metastatic cancer, etc.), uterine or ovarian disease and prostatic carcinoma. When the gloved finger is removed, some fecal material often adheres to it. If it is grossly bloody, there must be some bleeding lesion; if it is black, this indicates probable changed blood from a source some distance from the anus; if it smells like rancid butter, this suggests steatorrhea; if the patient is jaundiced and the stool is greyish or putty colored, this suggests absence of bile pigments due to complete biliary obstruction. The specimen of stool left on the finger can also be used for further examination. Approximately 85% of patients with colorectal cancers have blood in the stool, but colon cancers bleed intermittently so a negative occult blood test does not exclude colon cancer.
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Melenic = pitch black |
Examination of the feces affords important diagnostic information. The American attitude towards stool is ambivalent. In our culture many people are unnecessarily concerned about the desirability of a daily bowel movement, but at the same time the product produced is considered distasteful and often flushed away without even being observed. This attitude unfortunately is shared by doctors and nurses who forget how informative it may be to look at a total 24-hour stool and perhaps to examine it microscopically. In the absence of gastrointestinal disease, adults in the U.S.A. usually produce 75 to 170 gms of feces daily. If the 24-hour specimen is substantially heavier, malabsorption should be suspected. The brown color of the normal stool is derived from bilirubin by bacterial activity. Stool should not be tarry black or light-clay colored. The normal unpleasant odor is largely explained by the gases hydrogen sulfide and methanethiol, which are formed when dietary sulfates are reduced by colonic bacteria. The peculiar odor of steatorrhea or of changed blood in the stool is characteristic. Large parasites such as Ascaris and tapeworm segments maybe grossly obvious in the feces. Suspensions of stool emulsified in saline may be examined microscopically for excessive fat, for cysts and for neutrophils. A swab inserted into the anus can be used to culture for various bacterial diseases which affect the colon and small bowel. Viral pathogens can be sought by culturing stool or mucosal biopsies.
If distal colonic disease is suspected, the flexible sigmoidoscope can usually be passed to 45-50 cm. Sigmoidoscopy is especially useful in diagnosing inflammatory bowel disease because the mucosa can be inspected, and biopsies can be obtained. Flexible sigmoidoscopy is accepted as a technique to screen for distal colonic neoplasms in asymptomatic patients who have a negative occult blood test. Colonoscopy should be recommended for the patient with bleeding from the colon because the flexible colonoscope can examine the mucosa from the anus to cecum. Cancers can be biopsied for histological confirmation, and polyps can be removed with an electrocautery snare. One fifth of patients, who have one colonic neoplasm, harbor an additional neoplastic lesion. Prophylactic removal of neoplastic polyps interrupts the progression to colon cancer. |
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Barium causes foreign-body granulomata in the peritoneal cavity |
X-ray of the colon (Barium enema) can also be used to examine patients with suspected colonic dysfunction. Initial survey films (scout film) of the abdomen before barium has been introduced are of value when obstruction or perforation are suspected. In the former it may be helpful in localizing distended bowel loops and in the latter the diagnosis may be made by evidence of abnormal free air within the peritoneal cavity (usually under the diaphragm in the upright position). In these cases, a barium enema would not be performed. Why? The scout film is also helpful in the patient without evidence of obstruction or perforation to evaluate the amount of stool left in the colon and to see abnormalities such as calcifications which might be obscured by the barium. A barium enema can be accomplished with barium alone (single contrast) or with barium and air (double contrast). Double-contrast technique allows more precise evaluation of the colonic mucosa.
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Next Section (I): Some Colonic Diseases » |
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