Veterinary terms dictionary

  • From A to Z

    • A – Acute through Atopy

      Having a sudden and generally severe onset. See also chronic.

      Substance that causes an allergic reaction, e.g., pollen.

      Loss of appetite.

      Anterior Cruciate Ligament (ACL), Medial Collateral Ligament (MCL)
      Major ligaments at the knee of the rear leg.

      Medication which kills certain types of intestinal worms; dewormer.

      Antibody Titer
      A measurement of the amount of antibodies in the blood. The test to measure antibodies is usually performed by making a number of dilutions of the blood and then measuring at what dilution there is sufficient antibody to react in the test. For example, a titer of 1:8 (one to eight) means the blood can be diluted to one part blood and seven parts saline and still produce a positive reaction in the test. The higher the titer (1:16 is higher than 1:8), the more antibody is present.

      An allergy to something that is inhaled such as pollen or house dust. Also called 'inhalant allergy'.

    • B – Beta-carotene through Bloat

      A plant pigment which can be converted to Vitamin A by many animals, but not by cats.

      Surgical removal of a small amount of abnormal tissue, usually of tumors, for diagnosis.

      A condition in dogs caused by twisting of the stomach that traps gases and contents.

    • C – Calcified through Cyst

      The hardening of tissue through the influx of calcium, usually as a result of chronic inflammation.

      The unit of measurement of energy derived from digested food. Fat contains about twice as many calories per gram as protein or carbohydrate.

      See Sarcoma.

      Diseases of the heart muscle; does not include diseases of the valves of the heart or congenital defects.

      An animal whose natural diet includes meat.

      Animal which harbors an infectious organism, such as a virus, bacteria or parasite. The animal does not appear ill but can still transmit the organism to other animals by direct contact or releasing the organisms (bacteria, protozoa, viruses) into the environment in the stool, urine, respiratory secretions, or vaginal discharges.

      A cloudiness of the lens of the eye, reducing vision and giving the eye a pearly appearance.

      Of a long duration: a chronic illness persists for weeks, months, or even for the life of animal. See also acute.

      Clotting factors
      Protein components in the blood which help it to clot. Clotting is a complex mechanism. In addition to platelets, clot formation is the result of a long chain of chemical reactions carried out by individual molecules called 'clotting factors'. Each factor is numbered such that factor I leads to a reaction with factor II forming a new substance. This then reacts with factor III and so on to factor XII.

      Central nervous system. Includes the brain, spinal cord, and the nerves leading from them.

      The process of clotting.

      Cognitive dysfunction
      A common medical condition in older dogs that results from abnormal brain function, causing certain behavior changes such as disorientation, housebreaking problems, and changes in sleeping patterns and interactions with others.

      Being in a state of unconsciousness.

      A characteristic of an animal that is present at birth. It may be inherited or induced by events that occur during pregnancy.

      The process in which a sample of fluid or tissue is taken from an animal and placed in special media which allows the bacteria, virus, etc. to grow (reproduce) in the laboratory.

      An abnormal sac structure containing fluid.

    • D – DEA through Dysplasia

      Drug Enforcement Administration. The federal agency which regulates the manufacture, dispensing, storage and shipment of controlled substances including medications with human abuse potential.

      An inflammation of the skin.

      A metabolic disease caused by failure of the pancreas to produce insulin, a hormone that allows blood sugar (glucose) to be taken up by cells that require it for function.

      Type I Diabetes
      A form of diabetes in which so little insulin is produced that supplemental insulin must be given for the animal to live. Also called insulin dependent diabetes mellitus (IDDM).

      Type II Diabetes
      A type of diabetes mellitus in which although the blood glucose levels are higher than normal, they are not immediately life-threatening, and the animal can survive without supplemental insulin. Also called non-insulin dependent diabetes mellitus (NIDDM).

      Expressed as a percent, is a measure of the content of food that is retained in the body after food is eaten. The difference between the weight of food eaten and the weight of stool produced, divided by the weight of the food.

      Distemper (Canine)
      A viral disease that caused a severe and often fatal systemic illness in dogs and their close relatives. Distemper is also fatal in animals such as raccoons, and mustelids including skunks, mink and ferrets.

      An abnormal tissue development, common in the bones of the canine. See also hip dysplasia

    • E – Ear Canal through Exotic

      Ear Canal
      The tube that connects the external ear with the ear drum.

      Ear Drum
      The membrane that divides the outer ear from the inner ear, where the mechanism of hearing takes place. The membrane prevents infection from reaching the inner ear, as well as vibrating to amplify sounds.

      Ear Mites
      Small parasitic insects that live in the ear canal of an animal, and that are able to survive outside the ear for only very short periods of time.

      The image produced by performing an ultrasound examination of the heart.

      A parasite that lives on the outside surface or skin of another animal. Ectoparasites include fleas, ticks, lice, and mange mites.

      Non-malignant tissue growing in an unusual location (e.g., an ectopic pregnancy is conception of a normal embryo outside the normal location, which is the uterus).

      Electrocardiogram (EKG)
      A printout of an analysis of the electrical activity in the heart.

      Elbow Dysplasia
      See fragmented coronoid process.

      Chemically, an element that, when dissolved in water, will cause the solution to transmit electricity. In medicine, certain elements in the blood which are critically important to life, including sodium, potassium, chloride, calcium, and phosphorous.


      A long flexible instrument which can be passed into the body to view various structures through the use of fiber optics.

      Condition of the eyelids where they roll in or out from the eyeball.

      Enzymes are special proteins produced by cells which cause chemical changes in other substances, but which are not themselves changed in the process.

      Esophageal Reflux
      A condition in which stomach contents move backward into the esophagus, i.e., heartburn.

      A female hormone produced by the ovaries, which results in the onset of estrus.

      An animal not native to the geographical area where it is living.

    • F – Flatulence through Fragmented Coronoid Process

      Increased stomach or intestinal gas.

      Foreign Body
      Any abnormal substance within the body. Examples include wood slivers, ingested cloth, balls, glass in the feet, etc.

      Fragmented Coronoid Process
      Small piece of bone broken off the ulna, often referred to as elbow dysplasia.

    • G – Gastritis through Glaucoma

      Inflammation of the stomach.

      An upset of the gastrointestinal system usually from ingestion of toxic or non-food items, causing acute vomiting and diarrhea which can lead to severe dehydration.

      Gastrointestinal Tract
      Pertaining to the stomach and intestines. The term 'digestive system' includes the mouth, gastrointestinal tract, anus, pancreas, and liver.

      Gastric Dilatation-Volvulus (GDV)
      is also known as "bloat," "stomach torsion," or "twisted stomach". GDV is an extremely serious condition, and should be considered a life-threatening emergency when it occurs. Dogs can die of bloat within several hours. Even with treatment, as many as 25-33% of dogs with GDV die.

      Increased pressure within the eye, very painful and can lead to blindness.

    • H – Heartworm through Hip Dysplasia

      A species of parasitic worm that lives and reproduces in the chambers of the heart of an animal. Microscopic, immature worms (microfilariae) circulate in the blood and are taken in by mosquitoes that bite the animal. Microfilariae mature in the mouth parts of the mosquito and infect another susceptible animal bitten by the same mosquito.

      To bleed excessively; may be the result of injury or blood clotting abnormalities.

      An inflammation or infection of the liver.

      The protrusion of an organ through an abnormal opening.

      High Titer Vaccine
      A modified live vaccine that contains a higher number of virus particles than the 'average' vaccine. High titer vaccines can generally elicit an immune system response in young animals who have a maternal antibody level that would prevent them from responding to an 'average' vaccine.

      Hip Dysplasia
      Ball of the hip joint is not properly seated in the socket of the pelvis. See also dysplasia.

    • I – Immune through Isoflavone

      Immune-mediated reaction or disease
      A condition or disease caused by abnormal activity of the immune system in which the body's immune system either over-reacts (e.g., immune-mediated contact dermatitis) or starts attacking the body itself (e.g., autoimmune hemolytic anemia). Related to 'Autoimmune'.

      Immune system
      The body's defense system which recognizes infectious agents and other 'foreign' compounds (such as pollen), and works to destroy them.

      A condition in which the animal's immune system has been primed and is able to protect the body from a disease-causing agent such as a certain virus or bacteria. An animal could have immunity to one agent, such as parvovirus, but not have immunity to another agent, such as rabies.

      The process of rendering an animal protected (immune) against a certain disease. Vaccination is a way to produce immunization. However, just because an animal has been vaccinated (received a vaccine) does not necessarily mean the animal is immune. If the body did not correctly react to the vaccine or if the vaccine was defective, immunity would not occur. No vaccine produces immunity in 100% of the population to which it was given. 'Vaccination' is not the same as 'immunization'.

      Reduced function of the immune system of an animal, making it more susceptible to infectious disease. Can be an inherited defect or caused by drugs, radiation or viruses.

      A compound which stimulates the immune system to work more effectively to kill bacteria, viruses or cancer cells.

      Something, for instance a drug, hormone, or virus, that reduces the function of the immune system of an animal.

      A term used to describe an invasion of parasites.

      A condition in which tissue reacts to injury and undergoes changes during the healing process. As an example, a toe with a sliver of wood in it would be inflamed and show the signs of inflammation which include redness, increased temperature, pain, swelling and a loss of or disordered function. The toe is swollen, red, hot, painful, and the animal is reluctant to walk on that toe.

      A trait passed from one generation to the next in the genes from each parent.

      A hormone produced by the pancreas which is necessary for glucose to be able to enter the cells of the body and be used for energy.

      Into the muscle (IM).

      Into the nose.

      Into a the blood stream via a vein.

      The colored portion of the eye is called the iris. As with humans, dogs' iris colors vary. In the center of the iris is the black opening called the pupil. This opening can be made larger or smaller by muscles called ciliary bodies, that attach to the colored iris, causing it to expand or contract.

      An estrogen-like substance produced by pasture plants; a type of phytoestrogen.

    • J – Jaundice

      The condition in which there is a build up of waste products in the body called bilirubin. Bilirubin is yellow in color, therefore an animal with jaundice will have yellow gums, skin (often seen on the inside flap of the ear), and a yellowish cast to the 'whites' of the eyes. It can occur if a large number of red blood cells are destroyed, the liver is not functioning normally, or the bile ducts are blocked.

    • L – Large Intestine through Lymph Nodes

      Large Intestine
      The lower part of the intestinal tract, usually made up of the colon, cecum and rectum. Bacteria that live harmlessly in the large intestine help to digest complex carbohydrates.

      Legg-Perthes Disease
      Blood supply to the hip joint is disrupted causing degeneration in the joint.

      Liver Shunt
      Abnormal condition where the blood bypasses the liver.

      Lymph Nodes
      Part of the immune system of an animal. Small masses of tissue that contain white blood cells called lymphocytes. Blood from the nearby area is filtered through the lymph node allowing foreign or infectious material to be recognized and destroyed if possible.

    • M – Malignant through MAOI

      A process that does harm to nearby tissues. Usually synonymous with cancer, a tumor that grows quickly and spreads both in the original area where it occurred and in remote parts of the body.

      Ill health due to dietary deficiency or imbalance.

      Pertaining to the breast.

      Any of several skin and ear conditions caused by a variety of mites.

      Mast cell tumor
      A nodular growth, usually on the skin, which involves cells (mast cells) which contain large amounts of histamine and normally play a role in allergic reactions. All mast cell tumors in dogs should be considered potentially malignant.

      When referring to food ingredients, means a ground-up preparation. Chicken meal is ground up chicken, which might include bones and feathers. Meat meal means ground up muscle meat.

      Medial Collateral Ligament (MCL)
      See Anterior Cruciate Ligament.

      Monoamine oxidase inhibitor (MAOI)
      Substances that inactivate the enzyme monoamine oxidase which regulates certain transmitter chemicals between nerves. These compounds include certain types of antidepressants and also insecticides containing amitraz (such as Mitaban and Preventic collars).

    • N – Neuter through Nutrient

      Sterilization by surgical removal of the testicles of a male animal.

      Animals that are active during the night and sleep during the day.

      Compounds in foods which are essential for life. Nutrients include protein, fats, vitamins, minerals, etc.

    • O – Obsessive through Over the Counter

      Obsessive compulsive
      A behavioral condition in which a pet repeatedly performs an action out of context. It is thought that the behavior is an expression of stress, frustration and/or conflict. Certain breeds more prone to these behaviors. The behaviors include tail-chasing, some cases of excessive barking, continual licking, and biting the air as if snapping at an invisible fly.

      Off label
      Term used to describe the use of a medication for a condition for which it was not FDA approved. A large number of medications used in veterinary medicine are used 'off label'. If veterinarians only used FDA approved medications, options for treatments of certain conditions would be severely limited or nonexistent. The safety and efficacy of off-label uses of medications is often determined in university research settings, but the manufacturer of the drug does submit the results or go through the elaborate FDA approval process.

      Over the counter
      Can be purchased without a prescription, like aspirin and vitamins. 

    • P – Pancreatitis through Pulmonary

      Inflammation of the pancreas, a severe and sometimes life threatening disease often associated with eating fatty foods. Signs include vomiting and a painful abdomen.

      A contagious disease affecting the intestinal lining in dogs but is more severe to puppies. Parvo causes diarrhea and can infect the heart. 

      Patellar Luxation
      Dislocation of knee cap of the hind legs.

      Pet Insurance
      Health insurance for pets that covers costs of veterinary treatments and procedures, typically for accidents and illnesses. 

      A build-up of bacteria, saliva and food on the teeth. Also known as 'Tartar'.

      In dogs or cats, refers to inflammation within the lung tissue. Pneumonia can be caused by an infection or irritation in the lungs. 

      After surgery.

      Pulmonary edema
      Fluid accumulation in the lungs.

      Pulmonary emboli/embolism
      Blood clot that travels to the blood vessels in the lung and obstructs them.

    • R – Rabies

      A fatal virus disease of warm blooded animals, sometimes including humans, that affects the brain and is spread in the saliva of infected animals. Rabid animals have a temperament change. Wild creatures become bold enough to attack human beings, and docile domestic animals may turn on their owners. Rabies is a preventable disease through vaccination and is required by law. 

    • S – Sarcoma through Spay

      Cancer in connecting tissues. In dogs and cats sarcoma usually refers to tumors in the soft tissue.

      Abnormal muscle spasms and sensations which are a result of unusual nerve activity in the brain.

      Separation anxiety
      A behavioral condition in which the pet becomes anxious when separated from the owner. Dogs with separation anxiety tend to 'shadow' their owners, greet them exuberantly when they return after being gone, and sometimes vocalize, chew destructively, and urinate or defecate when separated from their owners.

      A condition caused by an infection e.g., with bacteria or fungi, or toxins they produce.

      Sterilization by surgical removal of the ovaries and uterus of a female animal.

    • T – Titer

      A measurement of the amount of antibodies in the blood. The test to measure antibodies is usually performed by making a number of dilutions of the blood and then measuring at what dilution there is sufficient antibody to react in the test. For example, a titer of 1:8 (one to eight) means the blood can be diluted to one part blood and seven parts saline and still produce a positive reaction in the test. The higher the titer (1:16 is higher than 1:8), the more antibody is present. (NOTE: The word 'titer' may also be used when discussing the amount of antigen present, e.g., a high titer vaccine has a large number of virus particles.)

    • U – Ulcer through Ultrasound

      A lesion in which the tissue surface is eroded away.

      A technique used to get the image of a deep structure within the body by directing ultrasound waves at it and recording the reflections (echoes) from it.

    • V – Vaccination through Virus

      The act of giving a vaccine. See also 'immunization' since the two words have different meanings and are often confused.

      The smallest form of life, invisible with an ordinary microscope. An infectious unit that enters and uses cells of plants or animals for replication. Some viruses cause disease in animals or plants.

    • W – Whelping

      In dogs, the act of giving birth.

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