Use the A-Z list to browse more than 6,000 health-related topics in our library. Clicking on a term opens the definition and, in most cases, links to more information.
"OA" is more commonly referred to as "Osteoarthritis" in the medical community. Osteoarthritis
Also Known As: "Degenerative Arthritis, Osteoarthrosis, Arthrosis, Degenerative Joint Disease, Hypertrophic Arthritis, DJD"
The most common type of arthritis, caused by the breakdown of joint cartilage over time. Cartilage cushions the joint. When it deteriorates, bones rub against each other, causing pain, stiffness and loss of movement. It is more common after age 45. More Information on Osteoarthritis: Arthritis
"OAS" is more commonly referred to as "Oral Allergy Syndrome" in the medical community. Oral Allergy Syndrome
An allergic reaction to food that involves itchiness, redness and/or swelling of the mouth, lips and/or throat. People with OAS often have other allergies or asthma. Raw fruits and vegetables and nuts are common triggers. More Information on Oral Allergy Syndrome: Food Allergy & Intolerance
A type of oat that only includes the bran (outer shell), not the germ or endosperm contained in whole oats. More Information on Oat Bran: Functional Foods
"Oat Cell Cancer" is more commonly referred to as "Small Cell Lung Cancer" in the medical community. Small Cell Lung Cancer
Also Known As: "SCLC, Small Cell Lung Carcinoma, Oat Cell Carcinoma"
A type of lung cancer that accounts for 20 percent of all lung cancer diagnoses. It spreads more quickly than other types of lung cancer. There are several types of this cancer. More Information on Small Cell Lung Cancer: Lung & Chest Cancer
"Oat Cell Carcinoma" is more commonly referred to as "Small Cell Lung Cancer" in the medical community. Small Cell Lung Cancer
Also Known As: "SCLC, Small Cell Lung Carcinoma, Oat Cell Cancer"
A type of lung cancer that accounts for 20 percent of all lung cancer diagnoses. It spreads more quickly than other types of lung cancer. There are several types of this cancer. More Information on Small Cell Lung Cancer: Lung & Chest Cancer
A food made of whole oats that are either crushed or rolled. The oats are added to hot water and eaten as a type of porridge. More Information on Oatmeal: Functional Foods
A type of cereal grain that is an ideal source of soluble fiber. It may lower cholesterol levels, reduce the risk of heart disease and help control blood sugar levels. More Information on Oats: Functional Foods
Also Known As: "Goldenhar-Gorlin Syndrome, Lateral Facial Dysplasia, First Arch Syndrome, First And Second Branchial Arch Syndrome, Necrotic Facial Dysplasia, Franceschetti-Goldenhar Syndrome, Intrauterine Facial Necrosis"
A multiple congenital anomaly/mental retardation (MCA/MR) syndrome that could cause mild to severe physical and developmental problems. Some cases are complicated by one or more birth defects of the heart. More Information on OAV: Pediatric Heart
A physician specializing in the management of pregnancy labor and birth. Many also specialize in gynecology (care of the female reproductive system). More Information on OB: Pregnancy Basics
An excess of total body fat mass, as reflected in individuals with a body mass index (BMI) of 30 or greater. BMI is defined as weight in kilograms divided by height in meters squared (Wt/Ht2). More Information on Obesity: Weight & Obesity Basics
A major risk factor for diabetes, obesity is an excess of total body fat mass (defined as a body mass index [BMI] of 30 or greater). BMI is weight in kilograms divided by height in meters squared (Wt/Ht2). More Information on Obesity & Diabetes: Diabetes & Endocrine Risks
"Obesity in Children" is more commonly referred to as "Childhood Obesity" in the medical community. Childhood Obesity
It is estimated that 14 percent of American children aged 6 to 11 are overweight, a 6 percent increase over the last ten years. About 11 percent of adolescents (ages 12 to 17) are also thought to be overweight. More Information on Childhood Obesity: Pediatric Health Basics
A test that determines the amount of any given substance in the blood and identifies abnormally high or low levels that may affect normal body functions. Blood is usually collected from a vein (venipuncture). More Information on ObGyn Blood Tests: ObGyn Lab Tests
A modern adaptation of psychoanalytic theory that emphasizes human relationships - rather than the drives of aggression and sexuality - as the primary motivational force in life.
"Obligatory Exercise" is more commonly referred to as "Compulsive Exercise" in the medical community. Compulsive Exercise
A compulsory need to exercise, even when facing valid reasons to avoid exercise such as an injury. Patients may obsess over their exercise routine or continue added to it, even to the point of causing themselves physical harm. More Information on Compulsive Exercise: Exercise & Weight
"Oblique Fractures" is more commonly referred to as "Fractures" in the medical community. Fractures
Also Known As: "Simple Fractures, Closed Fractures, Compound Fractures, Stress Fractures, Open Fractures, Impacted Fractures, Converse Fractures"
A break, rupture or crack - especially in bone or cartilage - that is often painful. Most often caused by trauma, fractures may remain under the skin (closed) or break through (open). Types include: simple, compound, impacted, oblique, stress and converse. More Information on Fractures: Infection & Trauma Pain
"Obliterans" is more commonly referred to as "Peripheral Arterial Disease" in the medical community. Peripheral Arterial Disease
Also Known As: "Peripheral Arterial Occlusive Disease, PAD, PAOD, Peripheral Artery Disease"
Hardening or narrowing of the blood vessels in the arms, legs, abdomen, kidneys or carotid arteries (supplying blood to the brain). Like coronary artery disease (which affects the arteries of the heart), PAD can lead to a restriction of blood flow. More Information on Peripheral Arterial Disease: Vascular Disease
"Obscene Phone Calls" is more commonly referred to as "Telephone Scatalogia" in the medical community. Telephone Scatalogia
A type of paraphilia in which sexual arousal is associated with making sexually explicit phone calls to unwilling people. When both parties consent to this type of communication, it is called phone sex. More Information on Telephone Scatalogia: Impulse Control Disorders
Anxiety disorder marked by obsessions (recurrent and intrusive thoughts, feelings, ideas or sensations) and/or compulsions (conscious, recurrent pattern of behavior a person feels driven to perform). More Information on Obsessive Compulsive Disorder: Anxiety Disorders
An anxiety disorder marked by obsessions and/or compulsions in children. Children may struggle to complete homework or chores, and may feel out of control. It can cause significant loss of self-esteem. More Information on Obsessive Compulsive Disorder & Children: Anxiety Disorders
Condition marked by chronic preoccupation with rules, orderliness and control. Patients tend to be high achievers who become upset when rigidly ordered routines are disrupted. More common in men than women. More Information on Obsessive Compulsive Personality Disorder: Anxiety Disorders
"Obstetric Cholestasis" is more commonly referred to as "Intrahepatic Cholestasis of Pregnancy" in the medical community. Intrahepatic Cholestasis of Pregnancy
Also Known As: "IHCP, Cholestasis of Pregnancy, Extrahepatic Cholestasis of Pregnancy"
A rare, temporary condition that occurs when pregnancy hormones cause bile flow to stop or slow, leading to a build-up of bile acids. It causes intense itchiness without a rash, usually in the last trimester, and poses a risk to both mother and baby. More Information on Intrahepatic Cholestasis of Pregnancy: Pregnancy Management
A physician specializing in the management of pregnancy labor and birth. Many also specialize in gynecology (care of the female reproductive system). More Information on Obstetrician: Pregnancy Basics
Disorders that involve the partial or complete blockage of the esophagus. More Information on Obstructive Esophageal Disorders: Digestive Health Basics
"Obstructive Sleep Apnea-Hypopnea" is more commonly referred to as "Sleep Apnea" in the medical community. Sleep Apnea
Also Known As: "Sleep Disordered Breathing, Apnea, SDB"
A disorder in which a person's breathing stops and starts many times during sleep. The interruptions last from 10 seconds to two minutes. It is linked to some degree with coronary artery disease, hypertension, heart failure and stroke. More Information on Sleep Apnea: Sleep
A test that measures carbon dioxide levels in breath after the patient eats food containing octanoic acid (after a period of fasting). Octanoic acid is broken down and excreted through breath as carbon dioxide. Low levels indicate gastroparesis. More Information on OBT: Diabetes & Endocrine Tests
A continuous, throbbing pain along the occipital nerve (in the back of the head) that is periodically accompanied by sharp, severe jabs of pain. It is a type of cranial neuralgia. Due to the pain location, it may be mistaken for a tension headache. More Information on Occipital Headache: Ear, Eye & Face Pain
A continuous, throbbing pain along the occipital nerve (in the back of the head) that is periodically accompanied by sharp, severe jabs of pain. It is a type of cranial neuralgia. Due to the pain location, it may be mistaken for a tension headache. More Information on Occipital Neuralgia: Ear, Eye & Face Pain
X-rays that show nearly the full arch of teeth in the upper or lower jaw. The x-ray machine points straight down from near the nose (to show upper jaw and teeth) or straight up from under the chin (to show lower jaw and teeth). More Information on Occlusal X ray: Oral Health Basics
The process of covering the skin with a thin shield, dressing or film. It may be used with a topical solution to increase the medication's effectiveness or to preserve skin moisture and prevent evaporation. More Information on Occlusion Therapy: Skin Drugs & Medications
Impenetrable. In skin-related conditions it usually refers to a shield or film that is applied to the skin to preserve moisture and prevent evaporation. More Information on Occlusive: Skin & Hair Basics
"Occlusive Cerebrovascular Disease" is more commonly referred to as "Cerebrovascular Disease" in the medical community. Cerebrovascular Disease
Also Known As: "Cerebrovascular Occlusion, Cerebral Vasculitis, Cerebral Arteriosclerosis, Cerebral Vascular Disease, Cerebral Arteritis"
A form of peripheral arterial disease (PAD) that affects the blood vessel within and leading to the brain. It involved the hardening and narrowing of arteries, usually due to plaque buildup. It can increase the risk of a stroke or TIA. More Information on Cerebrovascular Disease: Vascular Disease
The process of covering the skin with a thin shield, dressing or film. It may be used with a topical solution to increase the medication's effectiveness or to preserve skin moisture and prevent evaporation. More Information on Occlusive Therapy: Skin Drugs & Medications
"Occlusive Thromboaortopathy" is more commonly referred to as "Takayasu Disease" in the medical community. Takayasu Disease
Also Known As: "Takayasu Arteritis, Aortic Arch Syndrome, Pulseness Disease"
An inflammatory disease of the aorta and its branches. Its cause is unknown. It is most common in Asian women between the ages of 15 and 30, but cases have been reported worldwide. More Information on Takayasu Disease: Heart Injuries & Infections
Hidden blood in stool detected through laboratory analysis. This may be a sign of various diseases, including colorectal cancer. More Information on Occult Bleeding: Digestive Health Basics
"Occult Spinal Dysraphism Sequence" is more commonly referred to as "Tethered Spinal Cord Syndrome" in the medical community. Tethered Spinal Cord Syndrome
A progressive neurological disorder caused by tissue attachments that limit the movement of the spinal cord within the spinal column. These attachments cause an abnormal stretching of the spinal cord. Surgery may help. More Information on Tethered Spinal Cord Syndrome: Birth & Genetic Disorders
Asthma that is caused by factors in the patient's work environment (e.g., working with chemicals) as opposed to other factors. The airways become blocked or narrowed, causing shortness of breath and difficulty breathing. More Information on Occupational Asthma: Asthma Basics
"Occupational Factors" is more commonly referred to as "Environmental Risk Factors for Cancer" in the medical community. Environmental Risk Factors for Cancer
External factors that increase the risk of cancer. These include smoking and pollution, exposure to radiation or toxic wastes, among others. Those encountered at the workplace are called occupational risk factors. More Information on Environmental Risk Factors for Cancer: Cancer Risk Factors
Allergic reactions to seafood that take place in occupational settings. Those who work with the processing of crabs, prawns, mussels, fish and fishmeal are often exposed to skin and aerosolized contact with these foods More Information on Occupational Seafood Allergy: Food Allergy & Intolerance
A healthcare professional trained to evaluate and treat people whose abilities are impaired by physical illness injury or developmental deficiencies. Certification standards vary by state and some states require a license to practice. More Information on Occupational Therapist: Pain Basics
Techniques that help people with impaired ability to perform everyday activities to rehabilitate using exercise, activity and general motor control. The goal is to regain or maintain fine motor skills. More Information on Occupational Therapy: Pain Management
Anxiety disorder marked by obsessions (recurrent and intrusive thoughts, feelings, ideas or sensations) and/or compulsions (conscious, recurrent pattern of behavior a person feels driven to perform). More Information on OCD: Anxiety Disorders
An anxiety disorder marked by obsessions and/or compulsions in children. Children may struggle to complete homework or chores, and may feel out of control. It can cause significant loss of self-esteem. More Information on OCD & Children: Anxiety Disorders
Also Known As: "OBT, Gastric Motility Breath Test"
A test that measures carbon dioxide levels in breath after the patient eats food containing octanoic acid (after a period of fasting). Octanoic acid is broken down and excreted through breath as carbon dioxide. Low levels indicate gastroparesis. More Information on Octanoate Breath Test: Diabetes & Endocrine Tests
A fatal condition in which the lower jaw is completely or almost complete absent. The condition is considered fatal because the airway cannot function properly. More Information on Octocephaly: Pediatric Brain & Nerve
"Ocular Cancers" is more commonly referred to as "Eye Cancers" in the medical community. Eye Cancers
There are two main types of eye cancer. Intraocular melanoma develops in the eye's uvea (middle layer) and occurs in middle aged people. Retinoblastoma is a tumor of the retina (nerve tissue in the rear eye) and usually occurs in children. More Information on Eye Cancers: Head, Neck & Mouth Cancer
"Ocular Larva Migrans" is more commonly referred to as "Toxocariasis" in the medical community. Toxocariasis
Also Known As: "Toxocara Canis, Visceral Larva Migrans, Toxocara Cati, Toxocara Infection, Covert Toxocariasis"
Infection caused by roundworms found in dog or cat intestines. Major forms are ocular larva migrans (OLM), an eye disease causes blindness; and visceral larva migrans (VLM), which causes swelling of the body's organs or central nervous system. More Information on Toxocariasis: Infectious Disease Basics
"Ocular Pain" is more commonly referred to as "Eye Pain" in the medical community. Eye Pain
Also Known As: "Eyeache, Eye Pressure, Eye Discomfort, Ophthalmalgia"
Pain that is located in or around the eye. It may involve visual disturbances. It may be due to many different conditions including multiple sclerosis, migraine, cluster headache, glaucoma and shingles. More Information on Eye Pain: Ear, Eye & Face Pain
"Oculo Genito Laryngeal Syndrome" is more commonly referred to as "Opitz Frias Syndrome" in the medical community. Opitz Frias Syndrome
Also Known As: "Hypertelorism Hypospadias Syndrome, X Linked Opitz Syndrome, XLOS, Hypospadias Dysphagia Syndrome, Telecanthus Hypospadias Syndrome"
A type of multiple congenital anomaly/mental retardation (MCA/MR) syndrome that may include one or more heart conditions, such as septal defects, heart murmurs, patent ductus arteriosus, tetralogy of Fallot, coarctation of the aorta and others. More Information on Opitz Frias Syndrome: Pediatric Heart
Also Known As: "OAV, Goldenhar-Gorlin Syndrome, Lateral Facial Dysplasia, First Arch Syndrome, First And Second Branchial Arch Syndrome, Necrotic Facial Dysplasia, Franceschetti-Goldenhar Syndrome, Intrauterine Facial Necrosis"
A multiple congenital anomaly/mental retardation (MCA/MR) syndrome that could cause mild to severe physical and developmental problems. Some cases are complicated by one or more birth defects of the heart. More Information on Oculoauriculovertebral Dysplasia: Pediatric Heart
"Oculoplethysmogram" is more commonly referred to as "Plethysmogram" in the medical community. Plethysmogram
Also Known As: "Impedance Plethysmogram, Body Plethysmogram"
A noninvasive test widely used to measure the blood flow in the veins of the arms or legs, in order to detect and assess the presence of any blockages. More Information on Plethysmogram: Vascular Disease
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