Glossary of veterinary Terms


Addison’s Disease

Also known as hypoadrenocorticism, Addison’s Disease occurs when a pet’s adrenal glands (located just above the kidneys) do not produce enough of the steroid hormones cortisol and aldosterone.

These hormones play an important role in helping to regulate various bodily systems and organ functions so Addison’s Disease can be fatal to a pet who does not receive adequate treatment.


An allergen is a substance that causes an allergic reaction. Allergens can be unique to the individual pet, with one or more substances inducing allergic reactions. Allergens in pets typically fall into 4 categories: seasonal, environmental, food, or parasite-related.


Alopecia is a disorder that causes a pet to have partial or complete hair loss in areas where hair is normally present. Alopecia is fairly common in dogs and cats and is typically a sign of an underlying condition. 


When a pet has a reduced number of red blood cells or hemoglobin circulating in their blood they will be diagnosed as anemic. Hemoglobin (located inside red blood cells) carries oxygen from the lungs to the rest of the body and removes carbon dioxide from the cells to be expelled through the lungs.

There are various types of anemia in pets depending on the cause of the deficiency.


Analgesia is the inability to feel pain, or significant reduction in pain. The term analgesia is typically used in veterinary medicine when discussing severe or chronic pain management in pets.


Anaphylaxis in pets is a severe allergic reaction. Anaphylaxis can be localized to one part of a pet’s body, like the skin or throat, or it can be more widespread, causing major organs like the heart to shut down.


Anorexia in pets is a decrease or complete loss of appetite. The pet may be physically hungry but still refuse to eat, leading to severe weight loss and nutritional deficiencies. Anorexia in pets can be due to an underlying medical condition or caused by psychological stressors.


An antiemetic is a medication or natural substance that reduces or prevents nausea and vomiting in pets. Antiemetics are typically given to dogs and cats who suffer from motion sickness or to help manage the side effects of an illness.


Antifungal substances prevent the growth of fungi and yeasts. Antifungal medications and products are used to treat fungal infections that typically affect the skin, hair, and nails in pets.

An antigen is any substance outside of a pet’s body that induces an internal immune response. If an antigen is present, a pet’s immune system will produce antibodies to try to fight it away. Antigens can include bacteria, viruses, toxins, any other substances outside of the pet’s body.

For pets with allergies, their body recognizes the substance they are allergic to as an antigen, producing an immune response. 
An antipruritic is a medication or substance used to relieve or prevent itching in pets.
Also referred to as abdominal effusion, Ascites is the buildup of fluid in a pet’s abdomen. An abdominal fluid buildup (edema) can affect both dogs and cats and is typically caused by underlying medical problems.
Atrial Fibrillation
Atrial fibrillation, sometimes referred to as AFib, is a form of tachycardia (irregular heartbeat). AFib occurs when the muscles forming the walls of a pet’s atria (2 chambers within the heart) contract rapidly or twitch in a disorganized way causing an uneven flow of blood throughout the body.

Atrial fibrillation is usually caused by a pet’s underlying condition and requires medical intervention.
Atrophy in pets refers to the gradual decline in effectiveness or wasting away of part of their body or body processes.

Typically, atrophy occurs in the muscles of animals due to cells naturally breaking down with age or through lack of use, but can also occur in organ systems due to chronic illness (e.g., gastric atrophy).
Within the veterinary industry, the word attenuated is used to describe something that is weakened or thinned.

Veterinarians often refer to pet vaccines as “attenuated” strains of disease-causing bacteria/viruses as they stimulate an immune response within the cat or dog but are not strong enough to fully infect the animal with the disease.
Azotaemic describes elevated levels of nitrogen-based waste products, like urea and creatine, found in the blood of animals. These products are usually dispelled from a pet’s body through their urine, but several factors can lead to these substances building up to dangerous levels within the blood.

The primary cause of azotemia in pets is improper filtering of the blood due to decreased kidney function or kidney disease, which are very common in older cats. Other factors include feeding your pet a diet too high in protein, a urinary obstruction, or infections.



Bacterium is the singular term for bacteria, which are tiny living organisms (microorganisms). They are only one cell large and have most of the features of our human and animal cells but no distinct nucleus.

Bacteria can have positive or negative effects on our pets when inside their bodies, either causing diseases and illnesses like leptospirosis or helping enhance pets’ bodily processes like digestion and immune functioning.


When something affects two or both sides of something, it is referred to as “bilateral”. You may often hear or read this term during a veterinarian’s diagnosis or in pet insurance coverage when referring to “bilateral conditions” which affect parts of your pet’s body for which they have two.

Bilateral conditions in pets include any injuries or diseases that affect your pet’s eyes, legs, kidneys, or ears like hip dysplasia and cataracts.


Bile is a fluid made by a pet’s liver to help aid their digestion of fat. When not in use, this yellow-green fluid is stored in a pet’s gallbladder before being secreted into the duodenum (an area in the small intestine just below their stomach) when food needs to be digested.

If you ever see your pet vomit yellow liquid, it is most likely bile. This happens when their stomach is empty of food but irritation or inflammation within their GI tract is causing them to vomit. Many conditions can cause vomiting of bile in pets, including allergies, intestinal blockages (like large hairballs), or internal diseases and infections.


Bloat is a common serious condition in dogs that can be fatal if not treated urgently. Bloat occurs when gas, food, or fluid fills a dog’s stomach, making it expand so much that pressure is put on other organs.

Sometimes when bloat occurs, a dog’s stomach can twist, which is referred to as gastric dilatation-volvulus (GDV). This traps blood flow into and out of the stomach, sending the dog into shock. Any dogs, especially larger dogs at higher risk, should be taken to an emergency veterinarian immediately if displaying signs of bloat.


Borborygum, or borborygmi, is the medical term for natural stomach noises caused by gas, food, or water moving through a pet’s digestive tract. These stomach rumblings are a very normal part of digestion that you will likely hear more clearly if your pet is hungry or they have just eaten a large meal.  

If your pet’s stomach is continuously making noises, or their rumbling is louder than usual, they may be having some digestional upset and you will want to keep an eye out for other signs of digestive problems like vomiting or diarrhea.


Bradycardia is the term used when a pet’s heart rate is slower than normal. When observing a pet’s heart rate, a veterinarian will consider the pet’s size, activity level, and previous rates recorded to determine what speed is typical or atypical for them. 

There are many potential causes of bradycardia ranging from low body temperature and head injuries to gastrointestinal diseases and underlying heart problems.



The caecum (or cecum) is a small portion of a pet’s intestinal tract located between the ilium (the final part of the small intestine) and the colon.
After complete digestion within the small intestine, the caecum absorbs additional fluid and salts from the food mass and mixes the remaining products with a lubricating substance to promote smooth movement of feces through the pet’s colon.


Calculus is another name for tartar, a rough substance that can buildup above and below the gum line in pets. Calculus develops when food is left between a pet’s teeth and is a breeding ground for harmful bacteria.

Oral inflammation, infection, periodontitis, and tooth loss can result from an untreated development of calculus within a pet’s mouth.


Candida is a type of fungal yeast that naturally occurs within pets’ bodies. This yeast is typically found within a pet’s mouth, nose, ears, and GI tract as part of their normal microbial flora.

Although candida is not typically harmful to our pets due to the balance of “good” bacteria within their flora, some pets with poor immune systems or underlying health conditions may become infected (candidiasis).


The carpus is the medical term for the wrist or an animal’s equivalent to a human wrist. If your pet is suffering from a condition of their carpus, you will likely hear the term “carpal” within the diagnosis (e.g. carpal hyperextension).

The physiology and function of your pet’s carpus will differ depending on their species. For example, a dog’s carpus (on their lower front limbs) are responsible for carrying a large proportion of their body weight, whereas in cats, they help maintain a normal range of motion and flexibility.


Immediately after giving birth, a female mammal produces a nutrient-rich fluid called colostrum that is typically passed to their newborns through breast milk. Colostrum is packed with antibodies and growth factors (proteins) that help build a youth’s immune system and prepare them for the world.

Colostrum can also be consumed by older animals, including our pets, to help support their immune system, digestive health, and their response to environmental allergens.


A trait or condition is congenital if it has been present since birth. Congenital disorders, also called birth defects, can be passed to offspring through the genes of their parents or can develop within the womb due to mutations or malfunctions during fetal development.



The term ‘dermal’ refers to the inner layer of our pet’s skin and is often called the dermis. This skin layer is thick and lies underneath the epidermis - the outermost, protective layer of skin.

An animal’s dermal skin layer contains nerve endings, hair follicles, sweat glands, blood vessels, and other essential regulatory and protective cells.


Dermatitis is an umbrella term used to describe skin conditions that cause itching and inflammation of a pet’s skin, ears, or paws. There are several types of dermatitis in pets which are categorized depending on the root cause of the pruritic (itchy) skin disease.

  • Atopic dermatitis (also called allergic dermatitis or atopy) is associated with allergies.
  • Parasitic dermatitis is caused by parasite infestations like fleas, mites, or mange.
  • Dermatitis caused by skin infections (pyoderma) is typically named after the bacteria or fungi causing the initial infection, such as staph dermatitis and Malassezia (yeast) dermatitis.


Ear Canal

The ear canal is part of your pet’s ear structure that funnels sound from their environment towards the inner parts of their ear.

Ear canals are thin tube-like structures that are much longer in cats and dogs than those in human ears. Our pet’s ear canals also contain a sharp angle, forming an L-shape within their head; this provides greater auditory sensitivity but also provides greater opportunities for blockage and infections.

Ear Drum

The eardrum, or tympanic membrane, is a thin, flexible, oval membrane located deep inside your pet’s ear canal. Eardrums act as dividers between the outer and middle parts of the ear, transforming sound waves into vibrations. Pet’s eardrums are very fragile and can be easily damaged during an incautious ear cleaning or by infection.

Ear Mites

Ear mites are a highly contagious type of parasite that lives inside pets’ ears, feeding off blood, tissue, wax, and oils within their ear canal. Ear mites are very tiny creatures and cause excessive itching and inflammation in and around pets’ ears.


The outer layer of your pet’s skin is called the epidermis. This layer of skin is the one visible to us as pet parents and is designed to help protect your pet’s inner body parts from injury, diseases, UV light damage, and water. The epidermis of cats and dogs tend to be thinner than our human surface skin and can become more fragile with age.



Gastritis is a common condition in dogs that occurs when the lining of their stomach becomes irritated and inflamed, causing abdominal pain, vomiting, and other stomach-related symptoms.

Gastritis can be short-term with acute symptoms appearing suddenly with, typically seen after a pet consumes a toxic or spoiled substance. It can also be chronic, becoming increasingly worse over time, which is usually linked to underlying infections, allergies, or more serious health problems.


Gastrointestinal (GI.) is a collective term used in veterinary medicine for the 5 parts of an animal’s body involved in the digestion and absorption of food and nutrients: The mouth, esophagus, stomach, small intestines, and large intestines.



Immunodeficiency is the inability for an animal’s immune system to adequately protect its body from infection. This occurs when their immune system is lacking important components or substances necessary to work effectively against foreign threats.


A substance is immunosuppressive if it partially or completely suppresses the immune response of an animal.

Immununosuppressive therapies are typically used in veterinary medicine to help pets with  autoimmune diseases, severe allergies, and inflammatory conditions by reducing the overactivity of their immune system, preventing it from attacking or negatively effecting their own body.


The intestine in cats and dogs is a long, tube-like organ connecting the end of the stomach to the anus. It consists of two distinct parts, the small intestine and large intestine, each with distinct functions.

The small intestine comes straight off the stomach, is highly folded, and has an average length of 13 feet (in dogs)! This is where the majority of food digestion and nutrient absorption occurs.

The large intestine is shorter but wider than the small intestine and is the final passage of food waste before excretion. No nutrient absorption occurs here, instead water is is absorbed from foods that could not be digested within the small intestine, packaging it into solid form that is then passed out of the body when your pet poops.  



The jejunum is the longest part of your pet’s small intestine where the majority of digestion and absorption of nutrients occurs. The main function of the jejunum is nutrient absorption which is achieved with the ticker, more textured surface of the intestinal walls during this portion.


Large Intestine

The large intestine in pets includes the cecum, colon, rectum, and anal canal. The primary function of this portion of a pet’s digestive tract is to absorb water from the partially digested food exiting the small intestine, forming it into a solid-formed feces that can be excreted through the anal canal during defecation.

The ceum is responsible for fermentation of the remaining food, the colon contains thick muscles that move feces through the canal, and the rectum stores feces before defecation.


Non-steroidal anti-inflammatory drugs (NSAIDs)
Non-steroidal anti-inflammatory drugs (NSAIDs) are medications that help to reduce or relieve pain and inflammation in animals. Veterinary NSAIDs are typically prescribed to help pets suffering from osteoarthritis, post-operative pain, and sometimes for the management of severe seasonal allergies.

While NSAIDs cannot cure a pet’s condition, they can help manage symptoms and improve mobility, similar to the effects of ibuprofen and aspirin for humans.


Otic is an anatomical term to describe anything relating to, or located around the ear.
Often, pet products labeled with “otic” are used to treat ear infections, or are specialized for ear cleaning.


Perianal Fistula
Also known as anal furunculosis, perianal fisulas are abnormal, tunnel-like connections that form between tissues around a pet’s anus. They may start as small holes that ooze puss, but can grow larger over time and become inflamed and irritated. Perianal fistulas are a serious medical condition and can be incredibly painful for your pet.

Perianal fistulas can be caused by impaction or infection of a pet’s anal glands, an autoimmune disease, or having a genetic predisposition (German Shepherds are significantly more likely to develop this condition). Age and gender can also be contributing factors, with males and middle-aged pets being more at risk.
The perineal area, or perineum, is the region on a pet’s body stretching from the base of their tail to their genitals. It includes everything from their pelvic floor muscles and scrotum, to their external rectum and anal sacs.
Prolapsed Rectum
A rectal (or anal) prolapse is a medical condition in dogs (and occasionally cats) in which part of the rectum, the final part of the large intestine, turns inside out and protrudes from their anus. A prolapsed rectum can be incredibly painful for pets and requires prompt medical attention.


Sebaceous Glands
Sebaceous glands are a veterinary term for a pet’s oil glands. These glands are located within the lower levels of their skin and secrete sebum, an oily substance, up through the hair follicles and out onto the skin surface.

The oily substance these glands produce and secrete is essential for helping lubricate a pet’s skin, adding an extra layer of protection, and releasing their unique scent.
Separation Anxiety
Separation anxiety is a type of anxiety disorder that can develop in pets due to a prior negative life experience or a genetic predisposition to anxious behavior. A with with separation anxiety will become excessively upset, distressed, or disruptive when separated from their guardian or someone they attached to.

Some pets with separation anxiety may go to extreme measures to escape when left alone, or to prevent their guardian from leaving, which can result in them hurting themselves or damaging areas of the home.
Skin Cytology
Skin cytology is a common type of diagnostic dermatological (skin) test. For pets with abnormal skin lesions, masses, or inflammation, veterinarians take a swab or sample from the area and perform a microscopic examination. Findings from a skin cytology can help determine what type of skin condition your pet is suffering from and help direct appropriate treatment options.


The term zoonotic is often used in relation to infections or diseases where it describes the diseases’ ability to be transmitted from animals to humans. All common domestic animals can spread zoonotic diseases to humans around them including dogs, cats, horses, birds, rabbits, and farm animals.

Common zoonotic diseases effecting household pets and their families include ringworm, leptospirosis, tapeworm, and scabies.