U

Ulcerative colitis: An inflammatory bowel disease in which the colon is inflamed over a long period, increasing a person's risk of developing colon cancer.

Ultrasonography: (See: Ultrasound.)

Ultrasound: Imaging method using high-frequency sound waves to outline a part of the body. Sound wave echoes are picked up and displayed on a television screen.

Umbilical cord blood transplant: Use of stem cells in blood removed from the umbilical cords of newborns (a very rich source of stem cells) to replace blood-forming cells in patients whose own blood-forming cells have been destroyed by radiation or chemotherapy.

Unilateral: One sided. A unilateral ovarian cancer, for instance, occurs in only one ovary. (See: Bilateral).

Unproven therapy: Any treatment not been scientifically tested and approved.

Uracil: A nitrogenous base normally found in RNA but not DNA; uracil is capable of forming a base pair with adenine.

Urethra : Tube that carries urine to outside the body from the bladder. In women, it is fairly short; in men it is longer, passing through the penis, and also carries semen.

Urinary system: Kidneys, bladder, ureters, and urethra.  

Urinary tract: All organs and ducts participating in the secretion and elimination of urine from the body.

Urine cytology : Microscopic examination of urine to look for cancerous and precancerous cells. Cytology is also done on bladder washings, which are samples are taken by placing a salt solution into the bladder through a tube (catheter) and then removing the solution for testing.

Urologist : Doctor specializing in treating problems of the urinary tract in both sexes and of the genital area of men.

Urostomy : Surgical diversion of urine through a new passage and then through an opening in the abdomen. In a " continent urostomy", urine is stored inside the body and drained a few times a day through a tube placed into an opening called a stoma.

Uterine: Pertaining to the uterus, a female reproductive organ. See: uterus.

Uterus: Female organ for containing and nourishing the embryo and fetus from fertilization to birth. The muscular, pear-shaped structure is lined with a mucous membrane called the endometrium. It has three areas: the body or upper part; the isthmus or the narrowed central area; and the cervix, the lower portion.