Abaxial
Situated away from the axis of the body.

Abdominocentesis
Insertion of a trocar through a small incision in the abdominal wall into the abdominal cavity to collect abdominal fluid for evaluation.

Aboral
Away from the mouth.

Abortion
Termination of a pregnancy prior to the fetus being viable.

Abrasion
A wound caused by rubbing or scrapping of the skin or mucus membranes.

Abscess
Localized collection of pus in a cavity formed by the disintegration of tissue.  Most are formed by bacteria that invade tissues.

ACTH
Adrenocorticotropic hormone produced by the pituitary gland. Elevated blood levels can be diagnostic in horses with Cushing’s Disease.

Acupuncture
The Chinese practice of inserting needles into specific points along meridians in the body to relieve discomfort.

Acute Renal Failure
The result of an abrupt decrease in filtration (glomerular) of blood through the kidneys resulting in elevated BUN and creatinine (azotemia) and fluid and electrolyte imbalances.

Adhesion
Any fibrous band that connects two surfaces that are normally separate.  In surgery, adhesions may form inelastic bands between loops of intestines.  These bands often times cause no clinical signs but can lead to colic.

Aerobe
A bacteria that grows only in the presence of oxygen.

Agalactia
Failure of lactation or lack of milk production after giving birth.

Albumin
A plasma protein formed in the liver that is responsible for maintaining and regulating the exchange of water between the blood vessels and the rest of the body.

Alopecia
Loss of hair.

Anaerobe
A bacteria that grows in the absence of oxygen.

Anaphylaxis
An unusual or exaggerated allergic reaction of an animal to a foreign protein of other substance.

Anemia
Decreased number of red blood cells.

Anesthesia
Loss of feeling or sensation.  It is induced to permit the performace of painful procedures.

Anhidrosis
The inability to sweat effectively in response to stimulation of the sweat glands.

Anorexia
Lack or loss of appetite for food.

Antibiotic
A chemical substance that has the capacity to kill or inhibit the growth of bacteria.

Aortic Regurgitation
Occurs when the aortic valve of the heart becomes insufficient or incompetent thus allowing blood to leak back into the heart (left ventricle) during the relaxation or filling phase (diastolic phase) of the heart. This leads to a left sided murmur heard during diastole.

Arthritis
Inflammation of a joint.

Ascarids
Roundworms capable of infesting the small intestinal tract. Seen primarily in foals and weanlings 6-9 months of age.

Aspiration pneumonia
May develop after inhalation of foreign material (feed) and bacteria into the lower respiratory tract (lungs).

Ataxia
Failure of muscular coordination.

Atrial Fibrillation
A common heart arrhythmia characterized by an irregularly irregular heart rhythm.

Auscultation
Listening for sounds produced within the body with a stethoscope.

Axial
Situated toward the axis of the body.

Azotemia
The accumulation of nitrogenous wastes such as BUN (Blood Urea Nitrogen) and creatinine in blood most often due to either 1. decreased perfusion of the kidneys seen with dehydration, 2. Renal failure or insufficiency, or 3. Rupture of the bladder or any other part of the urinary tract.

Bile
Clear yellow fluid produced by the liver.

Block
Regional anesthesia.

Blood Urea Nitrogen (BUN)
The urea concentration of blood or plasma. It is an important indicator of renal function. An elevated BUN is indicative of compromised renal function. Normal value (7-25 mg/dl).

Botulism
Gradual or acute generalized weakness in horses caused by the potent toxin produced by Clostridium botulinum bacterium characterized by difficulty swallowing and progressive weakness leading to an inability to stand.

Bradycardia
Slow heart rate.

Bronchoalveolar Lavage (BAL)
A lavage of the lower respiratory tract (small airways and alveoli) with saline. Samples are collected and cell counts and cytology performed to determine whether there is inflammation present in the lungs. Bacterial culture of the fluid can also be performed however this is not a sterile procedure, thus the sample may be contaminated with bacteria from the upper respiratory tract. Commonly performed in patients with Heaves or inflammatory airway disease.

Bruised sole
Injury to the laminae of the horse’s foot caused by stepping on sharp objects.

Bruxism
Behavior characterized by rhythmic grinding of the teeth. It is often a manifestation of pain. In foals it is most often associated with ulceration of the stomach or small intestine. In adult horses it can also be seen but not limited to the pain associated with gastric ulceration.

Bursa
A small fluid filled sac situated in placed to prevent friction.

Calcification
The deposit of calcium salts in a tissue.

Canker
Excessive proliferation of the frog portion of the sole of the foot.

Capillary refill time
Physical examination procedure that estimates peripheral circulation.

Cartilage
Specialized connective tissue in joints that prevents concussive forces of bone on bone interaction.

Castration
Excision of the gonad.

Catheter
Plastic cannula inserted into a blood vessel to allow for the administration of medications and fluids.

Caudal
Towards the tail.

Cecum
Proximal portion of the large intestine forming a dilated pouch distal to the ileum and proximal colon.

Cellulitis
A diffuse inflammatory process within solid tissues causing redness, pain, and interference with function.

Cervical Vertebral Malformation
Malformation of the vertebrae of the neck region resulting in compression of the spinal cord in the neck (cervical) region, leading to neurologic signs of stumbling and incoordination. 

Chip Fractures
Small pieces of bone that are chipped off that can cause lameness and swelling.

Choke
See Esophageal Obstruction.

Clostridial Myositis
An infection of muscle tissue caused by Clostridium Spp of bacteria. Occurs most frequently in association with or as a complication of an intramuscular injection.

Clostridium difficile
Bacterium capable of causing inflammation and diarrhea of the colon in both foals and adults via production of a toxin.

Colic
Broad term used for abdominal pain.
 
Colitis/Enterocolitis
An inflammatory condition involving the large colon resulting in a variety of clinical signs, of which diarrhea is usually the most significant.

Congenital
A condition present at birth.

Contagious
Able to be transmitted from animal to animal.

Creatinine
A nitrogenous compound formed from the breakdown of creatine. It is formed in the muscle and excreted in the urine. It is used as a measurement of kidney function. An elevated level indicates compromised renal function. (Normal value 0.6-2.2 mg/dl)

Cribbing
An acquired habit in stabled horses where the horse grips a solid object with his incisor teeth, arches the neck, pulls upwards and backwards and swallows air.

Cryptorchid
A developmental defect characterized by the failure of the testes to descend into the scrotum.  The testicle can either be found in the inguinal region or abdomen.

Cushing’s Syndrome
A syndrome associated with a functional abnormality of the pituitary gland, resulting in excessive production of hormones such as ACTH. Clinical signs often include abnormal haircoat shedding pattern, laminitis, and increased sweating, drinking and urination.

Cyanosis
A bluish discoloration of mucus membranes due to decreased oxygen.

Cyst
Closed epithelium lined sac containing liquid, usually harmless but can cause disease.

Degenerative Myelopathy (also Equine Degenerative Myelopathy or EDM)
A neurologic disease of young growing horses resulting in degeneration of spinal cord tissue. Suggestive role of low blood Vitamin E levels in the development of the disease. Lack of access to green pasture during developmental stages may predispose foals to development of disease.

Dehydration
The state when the body loses more water than it takes in (negative fluid balance).

Dermatitis
Inflammation of the skin.

Diarrhea
Rapid movement of fecal material through the intestine resulting in poor absorption of water, nutritive elements and electrolytes.

Diastema
Space between the incisiors and canine teeth.

Disseminated Intravascular Coagulation (DIC)
Disruption of the blood clotting system leading to clotting factor consumption. It results in often fatal bleeding throughout the body. It is seen as a secondary complication to severe cases of colic and diarrhea.

Dummy
State of depressed conciousness in which a still mobile animal is non-responsive to normal stimuli.

Dysmaturity
The term applied to foals born after 320 days that show clinical signs of immaturity such as ligamentous laxity, pliable ears and fine haircoat.

Dystocia
Any difficult foaling with or without assistance.

Dyspnea
Labored breathing.

Edema
An abnormal accumulation of fluid in cavities and spaces of the body.

EEE
Eastern Equine Encephalitis

Effusion
Escape of fluid into a part.

EHV
Equine Herpes Virus

EIA
Equine Infections Anemia

EIPH
Exercise Induced Pulmonary Hemorrhage

Emaciation
Excessive leanness, wasted condition of the body.

Embolism
The sudden blocking of an artery by a clot of foreign material.

Emphysema
Accumulation of air in tissues that don’t normally contain air.

Endocarditis
A bacterial infection of the heart valves or inner lining of the heart (endocardium).

Endometritis
Infectious/noninfectious inflammation of the lining or the uterus (endometrium). It a major cause of infertility in broodmares.

Endotoxemia
The presence of endotoxin in the bloodstream, and the subsequent effects that the toxin has on the various organ systems of the body. Endotoxemia commonly occurs in horses that are systemically ill (colic, diarrhea, pneumonia). The endotoxin is released from certain types (Gram –ve) bacteria when their cell walls are disrupted during multiplication or death. The endotoxin is either absorbed into the bloodstream or released directly into the bloodstream.

Endotoxin
Portion of the cell wall of certain bacteria that can get into the blood stream and cause systemic disease.

Enema
Introduction of fluid into the rectum to evacuate fecal material.

Epiglottic Entrapment
The epiglottis is trapped by the arytenoepiglottic fold and fails to function normally.

Equine Granulocytic Ehrlichiosis
Seasonal tick-borne disease caused by the Rickettsial organism Anaplasma phagocytophilium, formerly known as Ehrlichia Equi.

Equine Multinodular Pulmonary Fibrosis
A form of pneumonia characterized by the presence of nodular lesions of fibrosis in the lungs associated with the presence of Equine Herpesvirus 5.

Equine Protozoal Myeloencephalitis
Neurologic disease caused by invasion of the central nervous system by the protozoal organism Sarcocystis neurona. Clinical signs vary with migration of the organism through the nervous system.

Esophageal obstruction (Choke)
An inability to swallow as a result of partial or complete obstruction of the esophageal lumen by feed material or a foreign body.

Estrus
Time in the reproductive cycle where an animal displays interest in mating.

Eupneic
Normal respiration.
Euthanasia
The deliberate ending of life of an animal suffering from an incurable disease.  An easy or painless death.

EVA
Equine Viral Arteritis

Exercise Induced Pulmonary Hemorrhage (EIPH)
Hemorrhage from the lungs associated with exertion. It is characterized by blood in the airways, and occasionally by bleeding out of the nostrils.

Failure of Passive Transfer (FPT)
Inadequate absorption of maternal antibodies (Immunoglobulin) from colostrum by foals during the first 24 hours of life. Complete FPT is defined as an immunoglobulin G concentration of less than 200 mg/dl.

Fasciculation
Involuntary muscular contractions visible under the skin.

Fescue Toxicosis
Toxicosis in pregnant mares associated with ingestion of fescue infected with a fungus (Acremonium coenophialum) during late gestation. It can result in prolonged gestation, a thickened placenta, birth of a dysmature foal, and lack of milk production (agalactia).

Fever
An elevation in core body temperature, due to resetting of the body’s thermostat (hypothalamus). Normal rectal temperature in adult horses is 99.5-101F, and in foals can be as high as 102F depending on the ambient temperature.

Fibrin
An insoluble protein that is formed when being clotted.

Fibrinogen
A non-specific indicator of acute inflammation of infection. Elevated levels are usually associated with a bacterial infection. Blood levels usually peak between 5-7 days in association with an infection. Normal value ranges from 200-400 mg/dl.

Flexion test
The act of bending the limb to test for pain in the flexed joint.

Flexural Deformity
Fixation of the joints in flexion (contracted tendons).

Float
An instrument used to file or rasp a horses teeth.

Follicle
A fluid filled structure in the ovary that grows until it is ready to ovulate.

Founder
See Laminitis

Gastric Ulceration/Erosions
Defects in the mucosal (inner) lining of the stomach that extend into the underlying muscular layer. In contrast, erosions do not extend into the muscular layer.  These occur when there is an imbalance of digestive factors such as hydrochloric acid and protective factors such as mucus, protective prostaglandins and blood flow to the mucosal lining.

Gastroscopy
Inspection of the stomach with an endoscope.

Gestation
The period of development from fertilization of the egg to birth.

Glucose Tolerance Test
Performed to evaluate a horse’s ability to metabolize glucose efficiently. Dextrose is administered intravenously, and the horse’s glucose and insulin are monitored every 30 minutes for the next 4 hours. It is used primarily to determine whether a horse is insulin resistant, as seen in some horses with Cushing’s Disease.

Guttural Pouch Empyema (GPE)
Accumulation of purulent material or pus within the guttural pouches, usually due to a bacterial infection. The most common bacterial infections seen in association with GPE are Streptococcus zooepidemicus, and Streptococcus equi, the organism that causes Strangles.

Guttural Pouch Mycosis (GPM)
A fungal infection of the guttural pouch, which often affects important nerves and arteries (carotid) that course through the guttural pouch. It can lead to sometimes fatal hemorrhage preceded by intermittent low-grade bleeding from the nostrils as well as neurologic signs associated with the affected nerves e.g An inability to swallow due to damage to the nerves responsible for control of swallowing.

Guttural Pouch Tympany
A non-painful accumulation of air within the guttural pouches seen in foals. The swelling is usually visible in the throatlatch region.

Heart Failure
Inability of the heart to maintain a circulation sufficient to meet the body’s demand.

Heaves
A manageable inflammatory condition of the lower airways characterized by spasming of the airways and excessive mucus production leading to airway obstruction and respiratory compromise. Occurs secondary to inhalation of dusts/molds that trigger an inflammatory response within the respiratory tract. Usually seen in older horses > 7years.

Hematoma
A localized collection of extravasated blood.

Hemolysis
Rupture of red blood cells.

Hemorrhage
The escape of blood from a ruptured vessel.

Hepatitis
Inflammation of the liver.

Hereditary
Transmissible from parent to offspring.

Hernia
The abnormal protrusion of a part of an organ or tissues through the structures normally containing it.

Herpesvirus myeloencephalopathy
Spinal cord disorder due to infection with Equine Herpesvirus 1, giving rise to signs of incoordination, weakness, and in severe cases an inability to stand and death.

Hyper
Increased

Hypo
Decreased

Hypothyroidism
Insufficient production of thyroid hormones to support the metabolic needs of the horse.

Hypoxia
Diminished availability of oxygen to the tissues.

Hypoxic Encephalopathy
A condition that arises as a result of transient damage to the brain secondary to oxygen deprivation either while in utero or at the time of parturition. Also referred to as dummy foal syndrome.

Icterus
Yellow discoloration of the sclera and mucous membranes due to elevated levels of bilirubin in the bloodstream. It can be seen in cases of liver disease and diseases causing destruction of red blood cells.

Idiopathic
Disease occurring with no known cause.

Ileus
Intestinal obstruction or failure of the intestine to contract.

Impaction
Obstructed lumen of the intestine by feed material.

Incontinence
Inability to control excretory function.

Incoordination
Lack of normal adjustment of muscle reaction so that the intended movement of a limb is made smoothly.

Inflammation
A localized protective response elicited by injury or destruction of tissues which serves to destroy, dilute, or wall the injurious agent and injured tissue.

Inflammatory Airway Disease
A recurrent reversible allergic airway disease characterized by accumulation of inflammatory cells leading to excess mucus production and increased responsiveness of the airways. Can lead to poor performance. Similar to heaves, but is seen in younger performing horses.

Influenza
A highly contagious upper respiratory tract viral disease caused by the Equine Influenza Virus.  It is the most important respiratory disease seen worldwide.

Injection
The forcing of a liquid into a part be it intravascular, subcutaneous, intradermal, intramuscular.

Intern
A recent veterinary graduate serving and often residing in a hospital with the objective of getting a concentrated, supervised, postgraduate, inservice training in a particular field of veterinary medicine. 

Intramuscular
Injection into the muscle.

Intravenous
Injection into the vein.

Jaundice
Yellowness of the skin, sclerae, mucus membranes.

Joint
The site of union of two or more bones that provide motion and flexibility to the skeletal frame.

Knuckling
Forward bending at the fetlock joint.

Laceration
A wound produced by the tearing of body tissue.

Lame
Incapable of normal locomotion, deviation from normal gait.

Laminitis
Inflammation of the laminae of the foot, which may lead to degeneration and subsequent failure of the attachments between the coffin bone and hoof wall.

Lateral
Position farther from the midline of the body, towards the outside.

Lavage
Washing out of an organ or cavity.

Leptospirosis
A bacterial disease caused by various strains of Leptospira. It has been associated with recurrent uveitis, abortions, stillbirths and neonatal infections.

Lethargy
Decreased energy.

Leukocyte
A white blood cell.

Lipoma
Benign fatty tumor that can occasionally strangulate small intestine.

Lyme Disease
A condition caused by the spirochete Borrelia bugdorferi. Reported clinical findings include arthritis, shifting limb lameness, limb swelling and lethargy. Definitive diagnosis can be difficult due to accuracy of available tests, and is usually based on clinical signs and response to treatment.

Lymphangititis
Inflammation of a lymphatic vessel that may lead to edema within a limb or body cavity.

Lymphosarcoma
The most common form of cancer/neoplasia seen in horses. It can affect various organ systems of the body including the skin, intestinal tract and mediastinum.

Malformation
An anatomical aberration.

Malignant
Tending to become progressively worse and may result in death.

Mastitis
Inflammation of the mammary gland.

Meconium
The first fecal material produced by a newborn foal. It’s retention can give rise to signs of abdominal discomfort and distension.

Medial
Towards midline, the inside aspect.

Melanoma
A tumor arising from pigmented cells, occur commonly in the skin of grey horses but can be in the abdominal cavity.

Mesentary
A membranous sheet attaching various organs to the body wall.

Metritis
Inflammation of the uterus.

Mucus
The free slime secreted by mucus membranes.

Murmur
An auscultatory sounds that is abnormal during cardiac function.

Myelogram
Contrast enhanced radiography of the cervical spinal cord. It is utilized in cases of suspected cervical vertebral malformation or wobblers to determine the site of spinal cord compression. 

Nasogastric Intubation
Passing a tube through the nose and into the esophagus and down into the stomach.

Necropsy
The examination of a body after death.

Necrosis
Cell death.

Neonatal Isoerythrolysis
Destruction of red blood cells in a newborn foal by the immune system. It is triggered by antibodies (IgG) acquired from the mare through ingestion of colostrum.

Nerve
A macroscopic cordlike structure of the body that carries electrical impulses.

Obesity
Excessive accumulation of fat in the body.

Obstetrics
The aiding of parturition.

Ointment
A semisolid preparation for external application to the body.

Open
Not pregnant.

Osteoarthritis
Noninflammatory degenerative joint disease marked by degeneration of the articular cartilage, hypertrophy of the bone at the margins and changes in the synovial membrane.

Ovary
Female gonad that produces eggs.

Pain
A feeling of distress, suffering or agony, caused by stimulation of specialized nerve endings.

Pallor
Paleness of the skin, commonly associated with anemia.

Paralysis
Loss or impairment of motor function due to disease with the nervous system.

Parturition
The act of giving birth.

Patent Urachus
Congenital or acquired failure of the urachal remnant to close, resulting in leakage of urine from the umbilical stump.

Pathogenic
Capable of causing disease.

Per os
By mouth.

Perforation
A hole or leak in the walls of an organ.

Peristalsis
The coordinated movement of the intestines to move food particles along the tract.

Peritonitis
Inflammation of the peritoneum.

Phlebitis
Inflammation of a vein.

Photosensitization
The development of abnormally heightened sensitivity of the skin to sunlight.

Placenta
The organ formed during pregnancy that allows the diffusion of nutrients and oxygen to the fetus.

Placentitis
Inflammation of the placenta, usually due to a bacterial infection, however viral and fungal causes are seen as well. Can lead to vulvar discharge and premature lactation.

Pleuropneumonia
Inflammation and infection of the pleural/chest cavity extending from infected lung tissue (pneumonia). This gives rise to fluid build-up within the chest cavity and associated respiratory distress.

Pneumonia
Inflammation of the parenchyma of the airways leading to difficulty breathing.

Polyarthritis
Inflammation of several joints.

Polydipsia (PD)
Excessive fluid intake defined as greater than 50 liters per day for the average sized horse.

Polyuria (PU)
Excessive urine output defined as greater than 25 liters per day for an average sized horse.

Post-partum metritis
Acute infection and fluid accumulation of the uterus resulting from retained fetal membranes or contamination of the uterus after foaling.

Potomac Horse Fever
A syndrome of fever and/or diarrhea caused by the organism Neorickettsia risticii. The disease is seasonal with most cases occurring between June and September. The organism has a predilection for the cecum and large colon. Infected horses are at very high risk for the development of laminitis.

Premature Placental Separation
Premature detachment of the chorioallantoic membrane from the endometrium of the uterus before delivery of a term fetus. Occurs mostly as a result of placentitis, and results in decreased delivery of oxygen and nutrients to the fetus.

Prematurity
Foals born at a gestational age of less than 320 days. These foals may experience clinical problems such as respiratory distress due to lack of surfactant and incomplete ossification of cuboidal bones of the hocks and carpi.

Prepubic Tendon Rupture
Separation of the prepubic tendon from its attachment to the pubis, which typically occurs in late gestation as the fetus enlarges and that quantity of fetal fluids increases.

Pruritis
Intense itching.

Purpura Hemorrhagica
An immune mediated vasculitis most often associated with infection of vaccination against Streptococcus equi, the organism that causes Strangles. Clinical signs include hot painful edema or swelling of the head and limbs and hemorrhages on the mucous membranes (gums).

Pyrexia
Fever

Quidding
Dropping feed due to a problem with being able to chew the food.

Rabies
A virally induced neurologic disease seen in mammals.  It occurs rarely in the horse, and clinical signs are variable.

Recumbency
Clinical term used to describe an animal lying down.

Recurrent Uveitis
Equine recurrent uveitis (ERU) (also known as moon blindness, iridocyclitis and periodic ophthalmia) is a major ophthalmic disease of the horse and is the most common cause of blindness in this species. It is an immune-mediated disease of multiple origins, with an approximately 8 to 25% prevalence rate in horses in the United States.

Rhabomyolysis (Tying-up)
A complex syndrome characterized by varying degrees of muscular dysfunction ranging from mild stiffness to rigid immobility and sometimes an inability to stand. Muscles may be firm on palpation.

Reflux
Stomach contents and fluid that is obtained when using a nasogastric tube.

Rhodococcus equi
An important cause of respiratory disease in foals less than 6 months of age. Infection may also result in septic joints, diarrhea, osteomyelitis and intra-abdominal abscessation.

Right Dorsal Colitis
Localized ulcerative inflammation of the right dorsal colon. Some cases have been associated with the administration of high doses of phenylbutazone.

Ringbone
Osteoarthritis of the first and second phalanx.

Rostral
Towards the head

Salmonellosis
Refers to clinical syndromes that may arise as a result of infection with Salmonella species. The gastrointestinal tract is most commonly affected, leading to fever, lethargy and diarrhea.

Scratches
Excoriations along the back of the pastern also known as greasy heel.

Seedy toe
Defect in the wall of the hoof.

Seizure
A conculsion or sudden onset of uncontrolled motor function.

Sepsis
Present of pathogenic organisms in the blood and other tissues.

Septicemia
Systemic disease associated with the presence of bacteria or their toxins in the bloodstream. Typically seen in neonatal foals. It can lead to fevers, lethargy and infected joints.

Shock
A condition of acute peripheral circulatory failure.

Soundness
Having the capacity to perform the function for which the animal is used for.

Strangles
An acute upper respiratory tract infection caused by Streptococcus equi infection. Infection is characterized by fever, lethargy, submandibular lymph node abscessation and/or purulent nasal discharge.

Synchronous Diaphragmatic Flutter (SDF)
Also known as the “thumps”. It is a contraction of the diaphragm synchronous with the heartbeat. Most often due to electrolyte (low blood calcium and potassium) and acid base abnormalities.

Synovial Fluid
Fluid in joints that aids to lubricate and protect the joints.

Synovitis
Inflammation of a synovial membrane.

Tachycardia
Increased heart rate.

Temporohyoid osteoarthropathy
Bony proliferation of the petrous temporal and stylohyoid bone and often fusion of the temporohyoid joint. Most likely occurs secondary to a middle ear infection (otitis media).  Bony proliferation leads to microfractures of the petrous temporal bone resulting in damage to the facial (facial paralysis) and vestibular nerves (loss of balance, head tilt).

Tendon
Fibrous sheet of tissue that convey support and muscle action to the joints.

Tetanus
A disease caused by the toxins of the bacterium Clostridium tetani. It is characterized by muscular rigidity and sometimes death due to respiratory paralysis. The vaccine is highly protective and increases survival in affected animals.

Theriogenology
The branch of veterinary medicine dealing with reproductive medicine.

Thrombocytopenia
Low peripheral blood platelet count, generally less than 100,000 platelets/uL. Potential causes are numerous, however generally due to decreased production (bone marrow disease), increased consumption (bleeding) and increased destruction (immune mediated disease).

Thrombus
An aggregation of blood products that cause a vascular obstruction.

Transtracheal Wash
Sterile lavage and aspiration of fluid from the trachea. Samples are collected and cell counts, cytology and bacterial culture performed to determine whether there is inflammation and/or infection present in the lungs. Routinely performed in patients with pneumonia.

Tricuspid Valve
The valve separating the right atrium and ventricle of the heart. When the valve becomes insufficient  blood can leak from the ventricle into the right atrium during contraction of the heart.

Thrombus
An aggregation of blood products that cause a vascular obstruction.

Tying Up Syndrome
Disease in which horses become stiff in the their limbs while performing exercise.

Ulcer
Local defect through the level of mucosa.

Ultrasonography
Imaging technique in which deep structures are visualized by recording the reflections of ultrasonic waves.

Urinalysis
Evaluation of selected urinary parameters (protein, glucose, blood etc) via dipstick. Also includes microscopic evaluation of sediment.
Urolith (urolithiasis)
A calculus or stone located in any portion of the urinary tract. The stome may be located in the kidneys (nephrolith), ureters (ureterolith), bladder (cystolith) and urethra (urethrolith). Accumulation of a large volume of thick urinary sediment in the ventral aspect of the bladder of a horse affected with bladder paresis is referred to as sabulous urolithiasis.

Uroperitoneum
Free urine in the abdominal cavity. Most often seen in neonatal foals when the bladder or urachus ruptures leading to urine leakage into the abdomen.  It can also occur due to ureteral or urethral tears. Rupture of either the bladder or urachus requires surgical correction.

Vaccine
A suspension of attenuated, killed, or modified live organisms that produces immunity to a specific disease.

Vasculitis
Inflammation of the blood vessels of the body. It can be associated with a variety of disease such as purpura hemorrhagica, and Equine arteritis Virus (EAV), leading to clinical signs of warm/painful limb edema (swelling) and mucosal hemorrhages.

West Nile Virus
Seasonal viral disease borne by mosquitoes. Results in neurologic signs indistinguishable from other more common neurologic diseases such as EPM, Wobblers and Equine Herpesvirus.

Wobblers
Syndrome of incoordination in young horses associated with a variety of pathological processes leading to compression of the cervical (neck) spinal cord.

Winking
Uncontrolled movement of the vulva in a mare in heat.

Zoonosis
Disease of animals transmissible to humans.