Lactase
An enzyme in the small intestine needed to digest milk sugar (lactose).

Lactase Deficiency
Lack of the lactase enzyme. Causes lactose intolerance.

Lactose
The sugar found in milk. The body breaks lactose down into galactose and glucose.

Lactose Intolerance
Being unable to digest lactose, the sugar in milk. This condition occurs because the body does not produce the lactase enzyme.

Lactose Tolerance Test
A test for lactase deficiency. The patient drinks a liquid that contains milk sugar. Then the patient's blood is tested; the test measures the amount of milk sugar in the blood.

Laparoscope
A thin tube with a tiny video camera attached. Used to look inside the body and see the surface of organs. See also Endoscope.

Laparoscopic Cholecystectomy
An operation to remove the gallbladder. The doctor inserts a laparoscope (see above) and other surgical instruments through small holes in the abdomen. The camera allows the doctor to see the gallbladder on a television screen. The doctor removes the gallbladder through the holes.

Laparoscopy
A test that uses a laparoscope to look at and take tissue from the inside of the body.

Laparotomy
An operation that opens up the abdomen.

Large Intestine
The part of the intestine that goes from the cecum to the rectum. The large intestine absorbs water from stool and changes it from a liquid to a solid form. The large intestine is 5 feet long and includes the appendix, cecum, colon, and rectum. Also called colon.

Lavage
A cleaning of the stomach and colon. Uses a special drink and enemas. See also Bowel Prep.

Laxatives
Medicines to relieve long-term constipation. Used only if other methods fail. Also called cathartics.

Lazy Colon
See Atonic Colon.

Levator Syndrome
Feeling of fullness in the anus and rectum with occasional pain. Caused by muscle spasms.

Lithotripsy, Extracorporeal Shock Wave (ESWL)
A method of breaking up bile stones and gallstones. Uses a specialized tool and shock waves.

Liver
The largest organ in the body. The liver carries out many important functions, such as making bile, changing food into energy, and cleaning alcohol and poisons from the blood.

Liver Enzyme Tests
Blood tests that look at how well the liver and biliary system are working. Also called liver function tests.

Liver Function Tests
See Liver Enzyme Tests.

Lower Esophageal Ring
An abnormal ring of tissue that may partially block the lower esophagus. Also called Schatzki's ring.

Lower Esophageal Sphincter
The muscle between the esophagus and stomach. When a person swallows, this muscle relaxes to let food pass from the esophagus to the stomach. It stays closed at other times to keep stomach contents from flowing back into the esophagus.

Lower GI Series
X-rays of the rectum, colon, and lower part of the small intestine. A barium enema is given first. Barium coats the organs so they will show up on the x-ray. Also called barium enema x-ray.