U-Z

Uhthoff phenomenon

Acute worsening of multiple sclerosis symptoms on exposure to heat due to high body temperatures exceeding the capacitance of demyelinated nerves.

Ultrafiltration

The movement of plasma water across a semipermeable membrane

Uncomplicated acid-base disorder

See simple disorder

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 (i.e., focal or generalized) cannot be determined.

Unstable angina

Pathogenically similar to non-ST segment myocardial infarction but without muscle damage; therefore, troponins are not elevated.

Uremia

A condition resulting from the accumulation of metabolic waste products and endogenous toxins due to impaired kidney function, with symptoms including 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 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 a non-reassuring fetal heart rate pattern.

Uveitis

An inflammation of the uvea, which includes the iris, ciliary body, and 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 heart valves disrupting blood flow; includes valvular stenosis and regurgitation.

Vasculitis

Inflammation of the walls of blood vessels.

Vasomotor symptoms

Menopausal symptoms including hot flashes and night sweats.

Vasopressors

Medications that cause vessel constriction, increase vascular resistance, and raise blood pressure.

Vegetation

Infectious mass of protein, cellular components, and microorganisms attached to heart valves, visible on echocardiogram.

Ventilation/perfusion ratio (VA/Q)

A comparison of lung tissue being ventilated to the rate of oxygenation of pulmonary blood.

Ventricular depolarization

Change in membrane potential of a ventricular myocyte leading to loss of polarization.

Vertigo

Sensation of spinning or feeling out of balance.

Vesicants

Chemotherapy drugs that cause tissue damage if extravasation occurs.

Virilization

Production or acquisition of masculine characteristics.

Viscoelastic testing

Testing using thromboelastography principles to evaluate clot formation and dissolution.

Volvulus

Twisting of the intestine causing obstruction and possible necrosis.

Vomiting

A reflexive rapid and forceful oral expulsion of upper gastrointestinal contents due to powerful and sustained contractions in the abdominal and thoracic musculature.

Vulvovaginal atrophy

Thinning of vaginal tissue due to lack of estrogen stimulation.

Wernicke syndrome

Neurological condition caused by thiamine deficiency, characterized by mental confusion, ataxia, and ophthalmoplegia.

Wheeze

High-pitched whistling sound caused by air moving through narrowed airways.

White coat hypertension

Elevated average office blood pressure and lower ambulatory reading.

Wild-type virus

The naturally occurring, nonmutated strain of the HIV virus.

Wilson disease

Disorder of copper metabolism characterized by liver cirrhosis and neurological manifestations.

Xanthomas

Firm raised nodules composed of lipid-containing histiocytes.

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 converted into an active form.