ulcer - sore on the skin surface or on the stomach lining.

ultraviolet radiation - invisible rays that come from the sun. UV radiation can damage the skin and cause melanoma and other types of skin cancer.

upper GI endoscopy - examining into the esophagus, stomach, and duodenum with an endoscope. (See also endoscopy.)

upper limb tension test (ULTT) - test to assess pain.

urea breath test - test used to detect Helicobacter pylori infection. The test measures breath samples for urease, an enzyme H. pylori produces.

ureters - two tubes that carry urine from the kidneys to the bladder.

urethra - narrow channel through which urine passes from the bladder out of the body.

urge incontinence - the inability to hold urine long enough to reach a restroom.

urgent surgery - an operation performed immediately as a result of an urgent medical condition. (See also emergency surgery.)

urinary retention - the inability to empty the bladder.

Usher's syndrome - a hereditary disease that affects hearing and vision.

uterus (Also called the womb.) - the uterus is a hollow, pear-shaped organ located in a woman's lower abdomen, between the bladder and the rectum, that sheds its lining each month during menstruation and in which a fertilized egg implants and grows into a fetus.