U-Z

Uhthoff phenomenon: Acute worsening of multiple sclerosis symptoms on exposure to heat because high body temperatures may exceed the capacitance of the demyelinated nerve and conduction may fail.

Ultrasound: An imaging method that uses high-frequency sound waves to produce images of structures within the body.

Unknown-onset seizures: Seizures where the onset (ie, focal or generalized) cannot be determined.

Unstable angina: Pathogenically similar to non-ST segmentmyocardial infarction but without muscle damage, therefore troponins are not elevated.

Uremia: A condition that results from accumulation of metabolic waste products and endogenous toxins in the body resulting

from impaired kidney function. Symptoms of uremia include nausea, vomiting, weakness, loss of appetite, and mental confusion.

Urethral stricture: Narrowing of the urethra.

Urgency: A compelling desire to void, which is difficult to defer.

Uricosuric: Pertaining to, characterized by, or promoting renal excretion of uric acid.

Urticaria: Itchy, raised, swollen areas on the skin, also known as hives.

Uterine tachysystole: Uterine hyperstimulation with frequent contractions, hypertonus and non-reassuring fetal heart rate pattern.

Uveitis: An inflammation of the uvea. Uveal structures include the iris, the ciliary body, and the choroid.

Valsalva maneuver: A forceful attempt at exhalation while keeping the mouth and nose closed.

Valvular heart disease: Damage or defects in one or more of the heart valves, disrupting blood flow into and out of the heart. The most common valves affected are the aortic and mitral valves. Valvular stenosis is a narrowing of the valve opening restricting the forward flow of blood. Valvular regurgitation or insufficiency occurs when there is inadequate closure of the valve leaflets leading to blood “leaking” backward.

Vasculitis: Inflammation of the walls of blood vessels.

Vasomotor symptoms: Menopausal symptoms that include both hot flashes (flushes) and night sweats for which women most commonly seek therapy.

Vasopressors: Medications that cause constriction of blood vessels, increase in vascular resistance, and increase in blood pressure.

Vegetation: Infectious mass comprised of protein, cellular components, and microorganisms attached to the endocardial surface of a heart valve which may be visualized on an echocardiogram.

Ventilation/perfusion ratio (VA/Q): A comparison of the proportion of lung tissue being ventilated by inhaled air to the rate of oxygenation of pulmonary blood.

Ventricular depolarization: Change in the membrane potential of a ventricular myocyte, resulting in loss of polarization. Under normal conditions, depolarization of ventricular myocytes is followed by ventricular contraction.

Vertigo: Sensation of spinning or feeling out of balance.

Vesicants: Chemotherapy drugs that cause significant tissue damage if extravasation occurs.

Virilization: Production or acquisition of virilism, which is masculine characteristics.

Viscoelastic testing: Point-of-care testing devices utilizing thromboelastography principles to evaluate clot formation and dissolution.

Volvulus: Twisting of the intestine causing obstruction and possible necrosis.

Vulvovaginal atrophy: Thinning of vaginal tissue due to a lack of estrogen stimulation.

Wernicke syndrome: Neurologic condition caused by thiamine deficiency and characterized by mental confusion, ataxia, and ophthalmoplegia.

Wheeze: A high-pitched whistling sound caused by air moving through narrowed airways. Wheezes are usually heard at the end of expiration but may be heard during inspiration and expiration in acute severe asthma.

White coat hypertension: A persistently elevated average office blood pressure of greater than 140/90 mm Hg and an average awake ambulatory reading of less than 135/85 mm Hg.

Wild-type virus: The phenotype of naturally occurring, nonmutated strain of the HIV virus.

Wilson disease: A disorder of copper metabolism, characterized by cirrhosis of the liver and neurological manifestations.

Xanthomas: Firm raised nodules composed of lipid-containing histocytes.

Xerostomia: Unusual dryness of the mouth.

ZAP-70 expression: An intracellular tyrosine kinase found in CLL B-cells.

Zymogen: An inactive protein precursor of an enzyme that is converted into an active form.