Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.
Colitis means inflammation of the colon. The colon, also
known as the large intestine or large bowel,
constitutes the last part of the digestive tract. The colon is a long, muscular
tube that receives undigested food from the small intestine. It removes water
from the undigested food, stores the undigested food, and then eliminates it from the body through
bowel movements. The rectum is the last part of the colon adjacent to the anus. The common symptoms of colitis include:
ischemic colitis (such as blockage of an artery in
the colon by a blood
clot. If the blood clot
interrupts the flow of blood to a segment of the colon, the result is
inflammation of that segment and, sometimes, even death [gangrene] of the
Crohn's disease and ulcerative colitis (two related
conditions that are caused by abnormalities of the body's immune system in which the body is inappropriately making antibodies and
chemicals that attack the colon). Crohn's disease and ulcerative colitis are
also referred to as
inflammatory bowel disease (IBD).
Infectious, radiation, ischemic, ulcerative, and Crohn's colitis all have
visible abnormalities of the inner lining of the colon. These abnormalities
include edema (swelling of the lining),
redness, bleeding from the lining with gentle rubbing (friability), and ulcers.
These abnormalities can be seen during either colonoscopy (examination of the
entire colon using a long flexible viewing tube) or flexible sigmoidoscopy
(examination of the rectum and the sigmoid colon - the segment of the colon closest to the rectum).
Edema and inflammation of the colon's lining interferes
with the absorption of water from the undigested food, and the unabsorbed water
exits the rectum as diarrhea. Pus and fluid also are secreted into the colon and
add to the diarrhea. The redness, bleeding from the lining with gentle rubbing
(friability), and ulcerations in the lining of the colon contribute to rectal