2,701 articles
Discectomy
Discectomy: surgical removal of herniated disc material pressing on spinal nerves, first performed planned in 1932; evolved into microdiscectomy (Yasargil, 1977) and endoscopic techniques; relieves sciatica faster than non-surgical care short-term.
Dislocation of lens
Dislocation of lens (ectopia lentis): displacement of the eye's crystalline lens from zonular weakness or rupture. Subluxation is partial, luxation complete; trauma is the most common cause, FBN1/Marfan syndrome the leading genetic cause.
Disorders of Eustachian tube
Disorders of Eustachian tube (ICD-11 AB10) cover Eustachian tube dysfunction and related conditions. ETD has three subtypes (dilatory, baro-challenge-induced, patulous), affects about 1% of adults, and is diagnosed clinically without a gold-standard test.
Dissection
Dissection is cutting and separating tissues for surgery, autopsy, or anatomy teaching. Revived at medieval Bologna, advanced by Vesalius, sustained today by body donation, prosections, and virtual dissection tables.
Distributive shock
Distributive shock, also called vasodilatory shock, is circulatory shock from widespread vasodilation with normal blood volume. Subtypes are septic, anaphylactic, neurogenic, and toxin-induced shock; it is the most common shock type and is treated with fluids and vasopressors.
Diuresis
Diuresis is increased urine excretion, from Greek diourein. Distinguished as water diuresis (urine osmolality 300), caused by glucose, mannitol, urea, or diuretic drugs, and induced therapeutically in heart failure and SIAD.
Diving reflex
Diving reflex (mammalian diving response, diving bradycardia): apnea, bradycardia, and peripheral vasoconstriction triggered by facial water immersion, found in all vertebrates studied; human heart rate falls with a 10.4 s time constant, down to 6 beats/min in extremes.
Dix–Hallpike test
Dix–Hallpike test (also Dix-Hallpike maneuver, Hallpike-Dix test): bedside head-positioning test introduced by Dix and Hallpike in 1952; gold standard for diagnosing posterior canal BPPV via provoked positional nystagmus resolving within 60 seconds.
Dofetilide
Dofetilide, sold as Tikosyn, is a Class III antiarrhythmic drug that blocks a cardiac potassium current to convert atrial fibrillation and must be started in hospital under monitoring.
Door-to-balloon
Door-to-balloon (D2B) time measures hospital arrival to angioplasty balloon inflation in STEMI. Guideline target 90 minutes (120 for transfers); total ischemic time predicts mortality better.
Doppler echocardiography
Doppler echocardiography measures cardiac blood-flow velocities via the Doppler effect to estimate valve gradients and pulmonary pressures noninvasively; modes include continuous-wave, pulsed-wave, color-flow, and tissue Doppler, validated against right heart catheterization.
Dorsal cochlear nucleus
Dorsal cochlear nucleus (DCN), part of the cochlear nucleus with the ventral cochlear nucleus; a laminar, cerebellum-like auditory brainstem nucleus processing spectral cues for sound localization and implicated in tinnitus and hyperacusis.
Dorsal column–medial lemniscus pathway
Dorsal column–medial lemniscus (DCML) pathway: ascending CNS tract carrying fine touch, vibration, two-point discrimination, and conscious proprioception from the body (excluding the face) via dorsal root ganglion, dorsal column nuclei, medullary decussation, thalamic VPL, to postcentral gyrus.
Dorsal root ganglion
Dorsal root ganglion (DRG, spinal ganglion): cluster of pseudo-unipolar sensory neuron cell bodies in each spinal nerve's dorsal root, within the neuroforamen; also the stimulation target FDA-approved in 2016 for chronic CRPS pain.
Dorsal root of spinal nerve
Dorsal root of spinal nerve (posterior root): the entirely sensory bundle of afferent axons, with cell bodies in the dorsal root ganglion, carrying touch, pain, and temperature from the periphery into the spinal cord's dorsal horn.
Dorsal veins of the penis
Dorsal veins of the penis: the superficial and deep dorsal veins, midline vessels draining the penile skin, glans, and corpora; deep vein empties into the prostatic venous plexus, with additional cavernosal and para-arterial veins described.
Dorsalis pedis artery
The dorsalis pedis artery, also called the arteria dorsalis pedis, is the artery on the upper surface of the foot and a continuation of the anterior tibial artery.
Dorsolateral prefrontal cortex
Dorsolateral prefrontal cortex (DLPFC, dlPFC), Brodmann areas 9 and 46 in the middle frontal gyrus: executive-control hub for working memory manipulation, planning, and self-control, and a leading tDCS/TMS target in depression and other neuropsychiatric disorders.
Dorzolamide
Dorzolamide, sold as Trusopt, is a topical carbonic anhydrase inhibitor eye drop first approved in the United States in 1994 to lower elevated intraocular pressure in glaucoma.
Double aortic arch
Double aortic arch: a congenital heart defect with two aortic arches forming a vascular ring around the trachea and esophagus, causing breathing and swallowing symptoms; treated surgically with excellent outcomes.
Double eyelids
Double eyelids, also called creased upper eyelids, are upper eyelids with a visible supratarsal crease; about 50% of people of Asian descent lack one, and surgery can create it.
Double outlet left ventricle
Double outlet left ventricle (DOLV) is a rare congenital heart defect in which the aorta and pulmonary artery both originate from the morphologic left ventricle, usually with a ventricular septal defect.
Double outlet right ventricle
Double outlet right ventricle (DORV), also called double-outlet right ventricle, is a congenital heart defect where both the aorta and pulmonary artery arise from the right ventricle, usually with a VSD; treated by biventricular repair, single-ventricle palliation, or palliation.
Dream
Dream: spontaneous experiences, mostly visual and emotional, occurring during sleep, most vividly in REM sleep. Key theories include Freud's 1900 psychoanalysis, Hobson and McCarley's 1977 activation-synthesis, and memory-consolidation accounts.
Dronedarone
Dronedarone (Multaq) is a non-iodinated amiodarone analog antiarrhythmic approved in 2009 to reduce AF hospitalization; contraindicated in decompensated heart failure and permanent AF, where it doubles mortality risk.
Drug-eluting stent
Drug-eluting stent (DES): coronary stent coated with sirolimus, paclitaxel, everolimus, or similar drugs released to prevent restenosis after angioplasty; first implanted 1999, reduces repeat revascularization versus bare-metal stents but requires dual antiplatelet therapy.
Drug-induced and toxic bradycardia
Drug-induced and toxic bradycardia is a slow heart rate caused by drugs such as beta-blockers and digoxin, or by conditions like hypothyroidism and hypothermia, and is often reversible.
Drusen
Drusen are yellow-white extracellular deposits of the aging retina, the hallmark of age-related macular degeneration; hard, soft, and reticular pseudodrusen (subretinal drusenoid deposits) differ in location, size, and progression risk.
Dual consciousness
Dual consciousness: the hypothesis that one person can contain two conscious subjects, tested mainly in split-brain (callosotomy) patients, where evidence remains divided between two-agents and single-agent split-perception models.
Ductus arteriosus
Ductus arteriosus: fetal vessel linking pulmonary artery and aorta; normally closes 24-72 hours after birth via oxygen rise and prostaglandin E2 fall. Persistent patency (PDA) affects 0.3-0.8% of term infants, up to 80% of those born before 28 weeks.