Medicine

Nasal septum: anatomy, function, and clinical significance Nasal septum The nasal septum is the internal partition that divides the left and right nasal cavities and nostrils. It consists of cartilage and bone, supports airflow, and has clinical import…

Nasopharyngeal carcinoma Nasopharyngeal carcinoma is a malignancy of the nasopharynx with distinct epidemiology and biology; linked to Epstein–Barr virus, dietary and genetic factors, and typically managed…

National Institute for Minamata Disease (Japan) National Institute for Minamata Disease Japanese research institute based in Minamata that studies Minamata disease, mercury toxicity, environmental health, clinical care, epidemiology and public outreach. Part of the Mi…

Nausea: overview, causes, and management Nausea Nausea is a common symptom of unease in the upper abdomen often with an urge to vomit. This article explains what nausea is, typical causes, underlying mechanisms, assessment and p…

Nebulizer (aerosol drug-delivery device) Nebulizer A nebulizer is a device that converts liquid medication into an inhalable mist for direct delivery to the airways; used in asthma, COPD, cystic fibrosis, pediatric and other respir…

Necrosis: causes, types, clinical features and treatment Necrosis Necrosis is pathological death of body tissue due to injury, infection, toxins, or impaired blood flow. This article summarizes causes, types, signs, diagnosis, treatment, preventi…

Neglect: omission of care and its effects Neglect Neglect is harm caused by failing to provide necessary care or protection. This article explains types, common signs, causes, consequences, and approaches to prevention and interve…

Neoplasm (Tumour): Overview, Types, and Clinical Insights Neoplasm A neoplasm is abnormal tissue growth that can form benign or malignant tumours. This article covers definitions, classification, causes, diagnosis, treatment, and notable examples…

Nephrectomy: Surgical removal of a kidney Nephrectomy Nephrectomy is the surgical removal of a kidney. This article explains types, indications, techniques, risks, recovery, history, and when surgeons choose partial versus radical nep…

Nephritis — inflammation and disorders of the kidneys Nephritis Nephritis is kidney inflammation that disrupts filtration. This article explains types, causes, symptoms, diagnosis, treatment, and outcomes in clear, neutral terms.

Nephrology: the medical specialty focused on kidney health and disease Nephrology Nephrology is the medical discipline that studies kidney function, diagnoses and treats kidney disorders, and manages therapies from medication and diet to dialysis and transplanta…

Neuroblastoma: a pediatric cancer of the sympathetic nervous system Neuroblastoma Neuroblastoma is a childhood cancer arising from neural crest–derived sympathetic cells, most often in the adrenal medulla; presentation, biology, and outcome vary widely with age,…

Neuroendocrine tumor (NET) Neuroendocrine tumor Neuroendocrine tumors are neoplasms that arise from hormone-producing neuroendocrine cells. They occur throughout the body—commonly in the gastrointestinal tract, pancreas and lung…

Neurological disorder A neurological disorder is any condition affecting the nervous system—brain, spinal cord or peripheral nerves—causing symptoms from pain and weakness to seizures and altered consci…

Neurology: study and medical practice of the nervous system Neurology Overview of neurology: scope, anatomy, common disorders, diagnostic methods, treatments, history, subspecialties and comparative (animal) neurology.

Neurosarcoidosis Inflammatory disease in the nervous system caused by sarcoidosis; covers symptoms, diagnosis, treatments (including corticosteroids) and prognosis.

Neurosurgery: surgical care of the brain, spinal cord and peripheral nerves Neurosurgery Neurosurgery is the medical specialty that treats disorders of the brain, spinal cord and peripheral nervous system through operative and minimally invasive techniques.

Nicotine replacement therapy: overview, forms, effectiveness and safety Nicotine replacement therapy Nicotine replacement therapy (NRT) supplies controlled nicotine without tobacco smoke to reduce withdrawal, increase quit rates, and support smoking cessation through patches, gum,…

Nocturnal enuresis (bedwetting): causes, evaluation and management Nocturnal enuresis Nocturnal enuresis (bedwetting) is involuntary urine loss during sleep. This article explains types, common causes, when to seek evaluation, and evidence-based management options f…

Non-Hodgkin lymphoma Non-Hodgkin lymphoma is a diverse group of cancers of the lymphatic system that arise from B or T lymphocytes; presentation, classification, diagnosis, and treatment vary widely.

Non-penetrative sex: forms, safety, history, and distinctions Non-penetrative sex Overview of non-penetrative sexual activities: types, health considerations, historical and social contexts, and how it differs from penetrative sex.

Nonsteroidal anti-inflammatory drug (NSAID) Nonsteroidal anti-inflammatory drug NSAIDs are a broad class of medicines that relieve pain, reduce fever and, at higher doses, reduce inflammation. Common examples include aspirin, ibuprofen and diclofenac and they…

Northwestern Memorial Hospital — Chicago academic medical center Northwestern Memorial Hospital Northwestern Memorial Hospital is a major academic medical center in Chicago, Illinois, affiliated with Northwestern University's Feinberg School of Medicine. It provides tertiary…

Nose-picking (rhinotillexis) and related behaviors Nose-picking Overview of nose-picking: terminology, causes, health considerations, social attitudes, and practical hygiene and behavioral strategies to reduce the habit.

Nurse: Roles, Education, Specialties, and Practice Nurse A nurse is a licensed health professional who provides clinical care, advocacy and health promotion across settings. This article outlines roles, training, specialties, workplaces…

Nuss procedure: minimally invasive repair of pectus excavatum Nuss Procedure A minimally invasive chest-wall operation to correct pectus excavatum. Describes technique, history, indications, risks, recovery, and comparisons with open repairs.

Nyctalopia (Night Blindness) Nyctalopia Nyctalopia, or night blindness, is impaired vision in low light caused by rod dysfunction, vitamin A deficiency, genetic retinal disorders, eye injury, or other conditions; diagnos…

Nystagmus: Causes, Types, Diagnosis, and Management Nystagmus Nystagmus is an involuntary, rhythmic movement of the eyes that can reduce visual acuity and affect daily life. This article explains types, causes, diagnosis, treatment, and pract…

Obesity: causes, measurement, health effects, prevention and treatment Obesity Comprehensive overview of obesity: definition, measurement (BMI and alternatives), causes, health risks, prevention, management options, and public health context.

Obstetric fistula: causes, symptoms, treatment and prevention Obstetric fistula An obstetric fistula is an abnormal connection between the birth canal and the urinary or intestinal tract that most commonly follows prolonged, obstructed labor without timely med…

Obstetrics Obstetrics is the medical specialty focused on pregnancy, labor, delivery and immediate postpartum care, integrating clinical assessment, surgical and non-surgical interventions to…

Oedema: causes, types, mechanisms and management Oedema Oedema (edema) is tissue swelling from excess fluid. This article explains its mechanisms, common locations and causes, clinical signs, diagnostic approaches and general treatment…

Off‑label use of prescription drugs Off-label use Off‑label use is prescribing a legally approved drug for a different indication, population, dose, or route than authorized. It raises medical, regulatory, and ethical consideratio…

Olanzapine (Zyprexa): an atypical antipsychotic used for schizophrenia and bipolar disorder Olanzapine Olanzapine is an atypical antipsychotic prescribed for schizophrenia, bipolar disorder and some anxiety-related conditions. It is effective but has notable metabolic and sedative s…

Ommaya reservoir: intraventricular access device for cerebrospinal therapies Ommaya reservoir An implanted device that provides direct access to the cerebral ventricles for delivery of drugs, sampling cerebrospinal fluid, or draining fluids. Common uses, placement, benefits…

Oncology: The Study and Treatment of Cancer Oncology Oncology is the medical field concerned with the diagnosis, management, research and prevention of cancer. It encompasses clinical care, laboratory science, and supportive services…

Online pharmacy: how it works, regulations, benefits, risks, and consumer guidance Online pharmacy A comprehensive overview of online pharmacies: definition, services, regulatory differences, benefits, risks such as counterfeit drugs, and practical tips for safe use and comparis…

Ophthalmology — the medical and surgical specialty of the eye Ophthalmology Branch of medicine concerned with the anatomy, physiology, diagnosis and treatment of the eye and orbit, including medical therapies, laser procedures, and eye surgery.

Opioid (drug class): pharmacology, uses, risks, and history Opioid Opioids are drugs that act on opioid receptors to relieve pain and produce sedation. This article explains their pharmacology, medical uses, side effects, historical development, a…

Oral cancer: causes, signs, diagnosis and treatment Oral cancer Oral cancer affects the lips, mouth and oropharynx. This article outlines common types, risk factors (tobacco, alcohol, HPV), symptoms, diagnosis, treatment options, prevention and…

Oral rehydration therapy: purpose, composition, history, and use Oral rehydration therapy Oral rehydration therapy (ORT) is a simple, life‑saving treatment for dehydration using a balanced solution of water, salts and glucose; recommended by WHO and UNICEF and widely us…

Oropharyngeal cancer: causes, diagnosis, treatment, and prevention Oropharyngeal cancer An impartial overview of cancers arising in the oropharynx: anatomy, HPV and non‑HPV causes, common symptoms, diagnostic steps, treatment approaches, prognosis, and prevention meas…

Orthodontist: dental specialist in teeth alignment and bite correction Orthodontist A dental specialist who diagnoses, prevents, and treats misaligned teeth and bite problems using braces, aligners, retainers and other orthodontic appliances after additional postg…

Orthopedic cast: purpose, materials, application, care, and history Orthopedic cast Orthopedic casts immobilize and protect injured bones and joints during healing. This article explains types, materials (plaster, fiberglass), application, care, removal, and commo…

Osteogenesis imperfecta (brittle bone disease) Osteogenesis imperfecta Osteogenesis imperfecta is a genetic disorder that weakens bone due to defective type I collagen. It causes fragile bones, variable extra‑skeletal features, and requires multidisci…

Osteopathy: principles, history, techniques, and clinical uses Osteopathy Osteopathy is a system of manual healthcare emphasizing the body’s self-healing, structural relations, and manipulative techniques. Covers principles, history, treatments, training…

Otitis: ear inflammation — types, causes, symptoms, diagnosis, and treatment Otitis Otitis is inflammation or infection of the ear. This article explains outer, middle and inner ear disease, common causes and symptoms, diagnostic methods, treatments, prevention an…

Ovarian cancer: overview, types, risk factors and management Ovarian cancer Ovarian cancer is a group of malignant tumors arising in the ovary or related tissues. This article explains types, origins, symptoms, diagnosis, treatment options and factors that…