All articles A–Z

Heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT), an immune adverse reaction to heparin mediated by anti-PF4/heparin IgG, causes thrombocytopenia with paradoxical thrombosis; diagnosed via 4Ts score, immunoassays, and functional assays, and treated with non-heparin anticoagulants.

Hepat Corona

Hepat Corona is a 150 km diameter corona on Venus at 2°S, 145.5°E, in quadrangle v36, IAU-approved in 1994 and named for a Hittite mother goddess.

Hepatectomy

Hepatectomy, also called major hepatectomy, is surgery to remove part of the liver, classically three or more of its eight segments, with mortality now 2 to 3%.

Oct 20, 2026

HEPATHER study

ANRS CO22 HEPATHER, a French national prospective observational cohort launched August 2012 (NCT01953458), follows about 21,000 patients with hepatitis B or C to assess real-life treatment effectiveness, safety, and liver disease outcomes.

Hepatic arterial infusion

Hepatic arterial infusion is a regional chemotherapy method that infuses cytotoxic drugs through a catheter in the hepatic artery, mainly for unresectable colorectal liver metastases and cholangiocarcinoma.

Hepatic arteriovenous malformation

A hepatic arteriovenous malformation is a rare vascular malformation in which arteries connect directly to veins in the liver, causing heart failure, portal hypertension, and complications often present from birth.

Hepatic artery aneurysm

Hepatic artery aneurysm (HAA), true or pseudoaneurysm of the hepatic artery; about 20% of splanchnic aneurysms, incidence 0.002%-0.4%, 25% rupture risk, treated first by endovascular repair.

Hepatic artery embolization

Hepatic artery embolization, also called bland transarterial embolization, is an interventional radiology procedure that blocks arterial blood flow to kill liver tumors that cannot be surgically removed.

Hepatic cystic hamartoma

Hepatic cystic hamartoma, also called mesenchymal hamartoma of the liver, is a rare benign multicystic liver tumor of children under 2, treated by complete resection, with rare sarcomatous transformation.

Hepatic encephalopathy

Hepatic encephalopathy (HE), also called portosystemic encephalopathy, is a reversible neuropsychiatric syndrome of liver dysfunction graded by West Haven criteria, treated with lactulose and rifaximin.

Hepatic fibrosis or cirrhosis

Hepatic fibrosis is the buildup of scar tissue in the liver from chronic injury, and cirrhosis is its advanced stage, marked by regenerative nodules and fibrotic septa.

Hepatic haemorrhage

Hepatic hemorrhage is bleeding from the liver tissue or its vessels, most often caused by hepatocellular carcinoma. The spontaneous form is an acute surgical emergency.

Hepatic lipase

Hepatic lipase (HL, LIPC, EC 3.1.1.3) is a hepatocyte-synthesized, heparan-sulfate-bound vascular lipase hydrolyzing triglycerides and phospholipids in IDL, LDL, HDL, and remnants, distinct from pancreatic and lipoprotein lipase.

Hepatic oval stem cell

Hepatic oval stem cells, also called hepatic progenitor or oval cells, are facultative bipotent liver cells with oval nuclei, activated in the canals of Hering when hepatocyte proliferation is impaired during chronic injury.

Hepatic portal system

Hepatic portal system (portal venous system): veins draining the stomach, intestines, pancreas, spleen, and gallbladder into the hepatic portal vein, which supplies about 75% of liver blood flow before blood returns to the inferior vena cava.

Hepatic stellate cell

Hepatic stellate cell (Ito cell, fat-storing cell, lipocyte), a perisinusoidal liver pericyte in the space of Disse storing 50-80% of body vitamin A; activates into collagen-producing myofibroblasts driving liver fibrosis.

Oct 20, 2026

Hepatic veno-occlusive disease

Hepatic veno-occlusive disease, or sinusoidal obstruction syndrome (SOS/VOD), is toxic sinusoidal endothelial injury causing nonthrombotic hepatic venular occlusion, mainly after HSCT conditioning or pyrrolizidine alkaloids, treated with defibrotide.

Hepaticogastrostomy

Hepaticogastrostomy is a procedure creating a connection between an intrahepatic bile duct and the stomach, usually performed endoscopically under ultrasound guidance to drain bile when ERCP fails, most often in malignant biliary obstruction.

Hepaticojejunostomy

Hepaticojejunostomy, also called the Rodney Smith operation when performed with transhepatic intubation, is a surgical operation connecting the hepatic bile duct to a Roux-en-Y jejunal limb to bypass strictures and repair bile duct injuries.

Hepatitis

Hepatitis: inflammation of the liver, mainly from viruses A through E. HBV (240 million chronic cases) and HCV (47 million) cause 95% of deaths; 1.3 million died in 2024; vaccines prevent A and B, drugs cure C.

Hepatitis A

Hepatitis A is an acute liver inflammation caused by the hepatitis A virus (HAV), a fecal-orally transmitted picornavirus. Distinguished from hepatitis B by its 28-day incubation, lack of chronicity, and preventability with vaccines licensed since 1995.

Hepatitis A virus internal ribosome entry site (IRES)

The hepatitis A virus (HAV) IRES, the type III picornavirus IRES, is a structured RNA in the 735 nt 5'UTR that drives cap-independent translation but uniquely requires intact eIF4G and eIF4E, is inefficient, and does not let HAV shut off host translation.

Hepatitis B

Hepatitis B, caused by the hepatitis B virus (HBV), a hepadnavirus, is a vaccine-preventable liver infection; 240 million chronic cases and 1.1 million deaths in 2024, vaccine since 1982.

Hepatitis B vaccine

Hepatitis B vaccine: recombinant HBsAg vaccine preventing HBV infection and liver cancer; first plasma-derived version 1981, recombinant 1986; birth dose recommended by WHO; US ACIP ended universal birth dose 2025.

Hepatitis B virus

Hepatitis B virus (HBV) is an enveloped DNA virus of the Hepadnaviridae family that infects the liver, chronically affecting 240 million people and preventable by vaccine.

Hepatitis C

Hepatitis C, liver inflammation caused by the bloodborne hepatitis C virus (HCV), formerly non-A, non-B hepatitis, identified in 1989; 47 million chronic infections, no vaccine, but direct-acting antivirals cure over 95% in 8–12 weeks.

Hepatitis C and HIV coinfection

HIV/HCV coinfection, simultaneous infection with HIV and hepatitis C virus, affects about 21% of US adults with HIV and up to 82% of those who inject drugs; HIV accelerates liver fibrosis, but direct-acting antivirals cure HCV in over 94% of coinfected patients.