Magnetic Resonance Imaging (MRI)
(mag-NEH-tik REH-zuh-nuns IM-uh-jing)
A test that takes pictures of the soft tissues in the body. The pictures are clearer than x-rays.

Malabsorption Syndromes
(MAL-ub-SORP-shun sin-drohmz)
Conditions that happen when the small intestine cannot absorb nutrients from foods.

Mallory-Weiss Tear
(MAH-luh-ree-WYSS tair)
A tear in the lower end of the esophagus. Caused by severe vomiting. Common in alcoholics.

Malnutrition
A condition caused by not eating enough food or not eating a balanced diet.

Manometry
Tests that measure muscle pressure and movements in the GI tract. See also Esophageal Manometry and Rectal Manometry.

Meckel's Diverticulum
A birth defect in which a small sac forms in the ileum.

Megacolon
A huge, swollen colon. Results from severe constipation. In children, megacolon is more common in boys than girls. See also Hirschsprung's Disease.

Melena
Blood in the stool.

Metabolism
The way cells change food into energy after food is digested and absorbed into the blood.

Motility
The movement of food through the digestive tract.

Motility Disorders
See Functional Disorders.

Mucosal Protective Drugs
Medicines that protect the stomach lining from acid. Examples are sucralfate Carafate, misoprostol (Cytotec), antacids (Mylanta and Maalox), and bismuth subsalicylate (Pepto-Bismol).

Mucous Colitis
(MYOO-kus koh-LY-tis)
See Irritable Bowel Syndrome.

Mucosal Lining
The lining of GI tract organs that makes mucus.

Mucus
A clear liquid made by the intestines. Mucus coats and protects tissues in the GI tract.