Human health and medicine

Anoscopy

Anoscopy is a quick bedside procedure in which a lighted tube called an anoscope examines the anal canal and distal rectum for hemorrhoids, fissures, and masses.

Anosmia is complete loss of the sense of smell, distinct from hyposmia and parosmia. Key facts: olfactory training helps about 26% of patients, head trauma causes anosmia in 4-16% of TBI cases, and smell loss predicts 5- and 10-year mortality.

Anosognosia

Anosognosia, from Greek 'without disease knowledge', is unawareness of one's own neurological or psychiatric deficits. Coined by Babinski in 1914 for hemiplegia denial; common in stroke, dementia, schizophrenia (50–90%), and bipolar disorder (40%).

Anovulation

Anovulation is absent ovulation, a leading treatable cause of female infertility (about a quarter of cases). Classified WHO Groups I–III; PCOS dominates; diagnosed by mid-luteal progesterone; letrozole now first-line therapy.

Anovulatory bleeding

Anovulatory bleeding (AUB-O, formerly dysfunctional uterine bleeding): irregular, often heavy uterine bleeding from unopposed estrogen when no ovulation occurs; common at menarche and perimenopause, treated with progestins.

Anovulatory cycle

Anovulatory cycle: a menstrual cycle without ovulation. Common after menarche and before menopause; PCOS causes about 70% of cases. Treated with letrozole, clomiphene, metformin, gonadotrophins, or IVF.

Anoxic-ischaemic encephalopathy

Anoxic-ischaemic encephalopathy (ICD-11 8B24.0), also called hypoxic-ischemic encephalopathy, is brain injury from combined cerebral hypoxia and ischemia, occurring after adult cardiac arrest and neonatal asphyxia, treated with cooling in newborns.

Anrikefon injection

Anrikefon injection (安瑞克芬注射液, HSK21542, brand Sishujing) is Haisco's peripheral kappa opioid receptor agonist, approved in China in May 2025 for post-abdominal-surgery pain and in September 2025 for dialysis-related pruritus, without narcotic control.

ANSWER study

ANSWER Program (American Norditropin Studies: Web-Enabled Research), NCT01009905, a 2002-2016 US observational registry of 19,847 Novo Nordisk Norditropin growth hormone patients, paired with Europe's NordiNet IOS.

Antacid

Antacid: over-the-counter medicines (aluminum, magnesium, calcium salts such as calcium carbonate, aluminum hydroxide) that neutralize stomach acid to relieve heartburn and indigestion; distinct from acid-suppressing H2 blockers and PPIs.

Antaitasvir phosphate capsules

Antaitasvir phosphate capsules (磷酸萘坦司韦胶囊, netanasvir phosphate, trade name 东卫卓) is a Chinese Class 1 NS5A-inhibitor drug approved by NMPA in February 2025, used with yiqibuvir for genotype 1, 2, 3, 6 chronic hepatitis C.

Antazoline

Antazoline, an imidazoline first-generation H1 antihistamine (C17H19N3), treats allergic conjunctivitis in eye drops and, as mesylate, converts recent-onset atrial fibrillation, in clinical use in Poland.

Antenatal corticosteroid therapy

Antenatal corticosteroid therapy gives betamethasone or dexamethasone to pregnant women at high risk of preterm delivery to speed fetal lung maturation, cutting neonatal death and respiratory disease by roughly 30 to 50 percent.

Antepartum fetal death

Antepartum fetal death (ICD-11 KD3B.0) is fetal death before the onset of labor, distinct from intrapartum death; maceration suggests antepartum timing, and it accounts for over half of stillbirths.

Oct 20, 2026

Antepartum haemorrhage

Antepartum haemorrhage (APH, ICD-11 JA41) is genital tract bleeding in late pregnancy before labour, complicating 2–5% of pregnancies; main causes are placental abruption and placenta praevia, with vasa previa and uterine rupture rarer.

Anterior cerebral artery

Anterior cerebral artery (ACA), artery of the circle of Willis supplying medial frontal and parietal cortex and corpus callosum; segments A1-A5, variants include azygous ACA and persistent primitive olfactory artery, associated with aneurysms.

Oct 20, 2026

Anterior cerebral artery syndrome

Anterior cerebral artery syndrome: stroke deficits from infarction in ACA territory, also called ACA infarction syndrome. Rare (0.3–4.4% of strokes), cardioembolic in origin, with leg-predominant weakness, abulia, alien hand, and akinetic mutism.

Anterior cervical discectomy and fusion

Anterior cervical discectomy and fusion (ACDF) is a spine operation that removes a herniated or degenerative neck disc through the front of the neck and fuses the adjacent vertebrae.

Anterior chamber paracentesis

Anterior chamber paracentesis (ACP) is an ophthalmologic procedure using a fine needle through the cornea to withdraw aqueous humor for diagnostic testing or to lower intraocular pressure.

Anterior cruciate ligament

The anterior cruciate ligament (ACL) is one of two cruciate ligaments of the knee, joining femur to tibia and stabilizing the joint against excessive movement.

Anterior cruciate ligament injury

Anterior cruciate ligament (ACL) injury: rupture of the knee ligament preventing tibial forward slide. Over 200,000 US cases yearly, 70% noncontact, females 2-8x higher risk; surgery versus rehabilitation compared in KANON, COMPARE, and ACL SNNAP trials.

Anterior cruciate ligament reconstruction

Anterior cruciate ligament reconstruction (ACLR) is an orthopedic surgical procedure that replaces a torn knee ligament with a tendon graft routed through bone tunnels, restoring knee stability.

Anterior cruciate ligament repair

Anterior cruciate ligament repair is a knee operation that reattaches a patient's own torn ACL rather than replacing it with a graft, as ACL reconstruction does.

Anterior cutaneous nerve entrapment syndrome

Anterior cutaneous nerve entrapment syndrome (ACNES), also called abdominal cutaneous nerve entrapment syndrome or intercostal neuralgia, is entrapment of T7-T12 intercostal nerve branches at the rectus abdominis border, causing chronic localized abdominal wall pain diagnosed by Carnett test and treated with injections or neurectomy.

Anterior horn motor neuron

Anterior horn motor neuron (anterior horn cell, ventral horn motor neuron): a lower motor neuron of the spinal cord's anterior horn, in Rexed lamina IX, with alpha and gamma types, that innervates skeletal muscle via acetylcholine at the neuromuscular junction as the final common pathway; targeted in ALS, SMA, and polio.

Anterior ischemic optic neuropathy

Anterior ischemic optic neuropathy (AION), also called NAION or AAION, is sudden infarction of the optic nerve head from posterior ciliary artery occlusion; the nonarteritic form is the most common acute optic neuropathy over age 50, while the arteritic form signals giant cell arteritis and is a steroid emergency.

Anterior pituitary

Anterior pituitary (adenohypophysis): front lobe of the pituitary gland in the sella turcica; five cell types secrete GH, prolactin, ACTH, TSH, FSH, and LH under hypothalamic portal control.

Anterior spinal artery syndrome

Anterior spinal artery syndrome (anterior cord syndrome) is infarction of the anterior two-thirds of the spinal cord, causing paralysis and pain-temperature loss with preserved vibration sense, most often after aortic surgery or atherosclerosis.

Oct 20, 2026

Anterior Temporal Lobectomy

Anterior temporal lobectomy (ATL), a neurosurgical resection of the anterior temporal lobe including amygdala, hippocampus, and parahippocampal gyrus, treats drug-resistant temporal lobe epilepsy; pioneered by Penfield and Falconer, it yields roughly 64% seizure freedom with visual field and memory risks.