Facts on File Encyclopedia of Health and Medicine

(pelvic area) can damage the colon, causing symp-
toms such as diarrhea and cramping. Symptoms
typically resolve as the damaged tissue regener-
ates. Treatment targets symptom relief. Radiation
colitis typically resolves when radiation therapy
ends.

Ischemic Colitis

Impaired blood flow to the intestinal tract, such as
might occur with serious ATHEROSCLEROSIS, can
impede intestinal function. Ischemic colitis is most
common in people age 70 and older. Treatment
focuses on restoring adequate circulation and
minimizing symptoms, such as diarrhea, that can
result in nutritional deficits and dehydration.

Inflammatory Bowel Disease (IBD)
Chronic inflammation of the colon takes the form
of ulcerative colitis or Crohn’s disease, collectively
called IBD. Crohn’s disease can affect the entire
gastrointestinal tract but most commonly involves
the terminal ileum and the ascending colon.
Ulcerative colitis can affect the whole colon but
usually starts in the rectum and left colon. IBD is
an autoimmune disorder in which the IMMUNE
SYSTEMattacks sections of the intestinal tract and
destroys the mucus lining. This creates ulcerations
that cause PAIN, diarrhea, and MALABSORPTION.
Treatment for inflammatory colitis typically
includes CORTICOSTEROID MEDICATIONS and some-
times immunosuppressive agents such as
methotrexate or cyclosporine to suppress the
IMMUNE RESPONSE. IBD is a serious and lifelong dis-
order that requires continuous management
through medications and diet.
See also ANTIBIOTIC MEDICATIONS; AUTOIMMUNE DIS-
ORDERS; ENTERITIS; FOOD SAFETY; GASTRITIS; GASTROEN-
TERITIS; INCUBATION PERIOD; IRRITABLE BOWEL
SYNDROME(IBS); NUTRITIONAL NEEDS; NUTRITIONAL SUP-
PLEMENTS; PATHOGEN; PERSONAL HYGIENE; PROCTITIS;
VIRUS; WATER SAFETY.

colon The large intestine, which extracts water
from and consolidates the waste byproducts of
digestion. The colon extends from theILEUM, the
final segment of the SMALL INTESTINE, to the ANUS,
the exit from the body for solid digestive waste
(feces or stool). The colon goes up the left side of
the abdomen (the ascending colon), across the

abdomen at the lower ribs (the transverse colon),

and down the right side of the abdomen to about

the level of the hip JOINT(the descending colon).

The final segments of the colon are the sigmoid

colon and the RECTUM. The colon is about five feet

long in the average adult.

COMMON CONDITIONS AFFECTING THE COLON

COLITIS COLORECTAL CANCER

CONSTIPATION Crohn’s disease

DIARRHEA DIVERTICULAR DISEASE

FECAL IMPACTION FECAL INCONTINENCE

HIRSCHSPRUNG’S DISEASE ILEUS

INFLAMMATORY BOWEL DISEASE(IBD) INTESTINAL POLYP

IRRITABLE BOWEL SYDROME(IBS) PROCTITIS

RECTAL FISTULA RECTAL PROLAPSE

TOXIC MEGACOLON ulcerative colitis

For further discussion of the colon within the

context of gastrointestinal structure and function,

please see the overview section “The Gastrointesti-

nal System.”

See also ANAL ATRESIA; ANAL FISSURE; BORBORYG-

MUS; BOWEL ATRESIA; BOWEL SOUNDS; COLONOSCOPY;

STOMACH.

colonoscopy An examination of the COLON(also

called bowel or large intestine) to detect and

remove INTESTINAL POLYPS, fleshy growths that may

become cancerous, and to biopsy or remove small

adenocarcinomas (cancerous polyps). Conven-

tional colonoscopy is an endoscopic procedure in

which the gastroenterologist inserts a flexible,

lighted tube (endoscope or colonoscope) through

the ANUSand into the large intestine.

Reasons for Doing This Test

Colonoscopy is a diagnostic procedure to detect

intestinal polyps, COLORECTAL CANCER, and other

conditions affecting the colon. Cancer experts

believe screening colonoscopy, performed at age

50 (or earlier, when there is family history of colo-

rectal cancer) and every 5 to 10 years thereafter,

can prevent 80 to 90 percent of colorectal cancers.

Preparation, Procedure, and Recovery

The gastroenterologist performs conventional

colonoscopy in an ENDOSCOPY center or hospital

unit, with intravenous general sedation to mini-

26 The Gastrointestinal System