Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.
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.
Melanosis coli is a condition usually associated with
chronic laxative use in which dark pigment is deposited in
the lamina propria
(one of the lining layers) of the large intestine
(colon). The pigment deposition results in a characteristic dark brown to black
discoloration of the lining of the large intestine. This condition is sometimes called
pseudomelanosis coli because the pigment deposits consist of a pigment known as
lipofuscin and do not contain melanin as implied by the term "melanosis."
Lipofuscin is a cellular pigment that forms when cells are destroyed, often
called "wear and tear" pigment that can be found throughout the body.
The dark color of the intestinal lining may be uniform
or patterned, and the discoloration may be slight or very pronounced. The
intensity and pattern of the discoloration may even vary among different sites
in the colon of a patient. The condition may also be reversed upon
discontinuation of laxative use. In some cases, the wall of the colon appears
normal to the eye, but microscopic evaluation of biopsies by a pathologist reveals areas of pigment in
the colon's lining. The pigment in melanosis coli does not accumulate in polyps
or tumors of the large intestine.
What are the symptoms of melanosis coli?
Melanosis coli does not cause
symptoms.
What causes melanosis coli?
Melanosis coli usually results from chronic use
of laxatives of the anthranoid group. Some examples of anthranoid laxatives are
senna and rhubarb derivatives. Many of these laxatives have been in use for
hundreds of years. In 1997, the U.S. Food and Drug Administration (FDA) banned
the use of the popular anthranoid laxative phenolphthalein due to fears that it
might be carcinogenic (cancer-causing). Animal studies had shown that extremely
high doses of phenolphthalein led to tumors in animals, but it has never been
shown to cause cancers in humans.
The anthranoid laxatives pass through the gastrointestinal tract unabsorbed
until they reach the large intestine, where they are changed into their active
forms. The resulting active compounds cause damage to the cells in the lining of
the intestine and leads to apoptosis (a form of
cell death). The damaged (apoptotic) cells appear as darkly pigmented bodies that may be taken up by
scavenger cells known as macrophages. When enough cells have been damaged, the
characteristic pigmentation of the bowel wall develops. The condition can
develop after just a few months of laxative use.
Abdominal pain is pain in the belly and can be acute or chronic. Causes include inflammation, distention of an organ, and loss of the blood supply to an organ. Abdominal pain can reflect a major problem with one of the organs in the abdomen such as the appendix, gallbladder, large and small intestine, pancreas, liver, colon, duodenum, and spleen.
Constipation is defined medically as fewer than three stools per week and severe constipation as less than one stool per week. Constipation usually is caused by the slow movement of stool through the colon. There are many causes of constipation including medications, poor bowel habits, low fiber diets, abuse of laxatives, hormonal disorders, and diseases primarily of other parts of the body that also affect the colon.
Colon cancer is a malignancy that arises from the inner lining of the colon. Most, if not all, of these cancers develop from colonic polyps. Removal of these precancerous polyps can prevent colon cancer.
A colon polyp is a benign tumor of the large intestine. Benign polyps do not invade nearby tissue or spread to other parts of the body. Benign polyps can easily be removed during colonoscopy and are not life threatening. If benign polyps are not removed from the large intestine, they can become malignant over time.
Laxatives for treatment of constipation include over-the-counter preparations such as bulk-forming laxatives, stool softeners, lubricant laxatives, stimulant laxatives, saline laxatives, enemas and suppositories. Some over-the-counter laxatives are not recommended for patients with specific diseases or conditions. Some laxatives may have negative adverse effects if taken over long periods of time.
Colonoscopy is a procedure that enables an examiner (usually a gastroenterologist) to evaluate the inside of the colon (large intestine or large bowel). The colonoscope is a four foot long, flexible tube about the thickness of a finger with a camera and a source of light at its tip. The tip of the colonoscope is inserted into the anus and then is advanced slowly, under visual control, into the rectum and through the colon usually as far as the cecum, which is the first part of the colon.
Why is colonoscopy done?
Colonoscopy may be done for a variety of reasons. Most often it is done to investigate the cause of
blood in the stool,
abdominal pain, diarrhea, a change in bowel habit, or an abnormality found on colonic
X-rays or a computerized tomographic (CT) scan. Individuals with previous history of polyps or colon cancer and certain individuals with a family history of some types of non-colonic cancers or co...
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