UCN-01: An anticancer drug that belongs to the family of drugs called staurosporine analogues.

Ulcerative colitis: Chronic inflammation of the colon that produces ulcers in its lining. This condition is marked by abdominal pain, cramps, and loose discharges of pus, blood, and mucus from the bowel.

Ultrasonography (UL-tra-son-OG-ra-fee): A procedure in which sound waves (waves (called ultrasound) are bounced off tissues and the echoes are converted to a picture (sonogram).

Ultrasound energy: A form of therapy being studied as an anticancer treatment. Intensified ultrasound energy can be directed at cancer cells to heat them and kill them.

Ultrasound test: A test that bounces sound waves off tissues and internal organs and changes the echoes into pictures (sonograms).

Ultraviolet radiation (ul-tra- VYE-o-let ray-dee-AY-shun): Invisible rays that are part of the energy that comes from the sun. UV radiation can damage the skin and cause melanoma and other types of skin cancer. UV radiation that reaches the earth's surface is made up of two types of rays, called UVA and UVB rays. UVB rays are more likely than UVA rays to cause sunburn, but UVA rays pass deeper into the skin. Scientists have long thought that UVB radiation can cause melanoma and other types of skin cancer. They now think that UVA radiation also may add to skin damage that can lead to skin cancer and cause premature aging. For this reason, skin specialists recommend that people use sunscreens that reflect, absorb, or scatter both kinds of UV radiation.

Ultraviolet radiation therapy: A form of radiation used in the treatment of cancer.

Umbilical cord blood: Blood from the placenta (afterbirth) that contains high concentrations of stem cells needed to produce new blood cells.

Umbilical cord blood transplantation: The injection of umbilical cord blood to restore an individual's own blood production system suppressed by anticancer drugs, radiation therapy, or both. It is being studied in the treatment of cancer and severe blood disorders such as aplastic anemia. Cord blood contains high concentrations of stem cells needed to produce new blood cells.

Uncontrolled study: A clinical study that that lacks a comparison (i.e., a control) group.

Unilateral: Having to do with one side of the body.

Unresectable: Unable to be surgically removed.

Unresectable gallbladder cancer: Cancer that has spread to the tissues around the gallbladder (such as the liver, stomach, pancreas, intestine, or lymph nodes in the area) and cannot be surgically removed.

Upper GI series: A series of x-rays of the upper digestive (gastrointestinal, or GI) system that are taken after a person drinks a barium solution, which outlines the digestive organs on the x-rays.

Urachus (YOU-rah-kus): A fibrous cord that connects the urinary bladder to the umbilicus (navel). The urachus is formed as the allantoic stalk during fetal development, and lasts through life. Also called the median umbilical ligament.

Uraci: A fibrous cord that connects the urinary bladder to the umbilicus (navel). The urachus is formed as the allantoic stalk during fetal development, and lasts through life. Also called the median umbilical ligament.

Uracil: An anticancer drug that belongs to the family of drugs called alkylating agents.

Urethra (yoo-REE-thra): The tube through which urine leaves the body. It empties urine from the bladder.

Urinalysis: A test that determines the content of the urine.

Urinary: Of or relating to the function or production or secretion of urine.

Urinary tract (YOO-rin-air-ee): The organs of the body that produce and discharge urine. These include the kidneys, ureters, bladder, and urethra.

Urine (YOO-rin): Fluid containing water and waste products. Urine is made by the kidneys, stored in the bladder, and leaves the body through the urethra.

Urokinase: A drug that dissolves blood clots or prevents them from forming.

Urologic oncologist (yoor-uh-LAHJ-ik on-KOL-o-jist): A doctor who specializes in treao specializes in treating cancers of the urinary system.

Urologist (yoo-RAHL-o-jist): A doctor who specializes in diseases of the urinary organs in females and the urinary and sex organs in males.

Urostomy (yoo-RAHS-toe-mee)oe-mee): An operation to create an opening from inside the body to the outside, making a new way to pass urine.

Urothelium: The tissue layer that lines much of the urinary tract, including the renal pelvis, the ureters, the bladder, and parts of the urethra.