6 Glossary of some medical terms
This is not required reading but is intended as a resource to help you understand material discussed in the course. Most of these definitions and many more can be found in online medical dictionaries. These pages are intended to present some of the terms that are most often used in considering gross lesions of animals, and to consider these terms in the nuanced way that they are sometimes used in veterinary medicine.
Organization of the glossary:
Descriptive terms:
- Distribution
- Size/extent
- Colour
- Shape/contour
- Texture
- Strength
Terms for morphologic diagnoses:
- Severity
- Time
- Distribution
- Pathologic process
- Tissue
Some words used in pathology:
- Words to describe abnormal location
- Materials deposited within tissues
- Death of tissue or cells
- Disorders of blood flow and coagulation
- Inflammation
- Tissue repair
- Neoplasia
- Disorders of growth and development
General, miscellaneous, organ-specific terms, and rambles
descriptive terms
Lesion: an observed abnormality within tissue. The biomedical literature sometimes uses “pathology” to mean disease-related changes within tissues, but don’t you blunder into that foolish trap. “Pathology” (Greek: pathos=disease, logia=study of) is the medical discipline involving the study of disease, or the study of morphologic and molecular changes within diseased tissues. The changes that we can observe in those tissues are called lesions.
Distribution
Localized and generalized are opposites:
Localized: affecting only one part or one region of an organ. A lesion affecting only the right middle lung lobe is localized. Getting hit with a baseball creates a localized bruise.
Generalized: affecting all parts or all regions of an organ. Generalized lesions can:
- be uniform throughout the organ (i.e. diffuse, see below)
- form multiple spots throughout the organ (i.e. multifocal generalized, see below)
- be patchy or irregularly distributed in the organ
- affect some lobules and not others throughout an organ
Locally extensive: this term is not often used, but refers to one or many lesions within a localized area. Multiple discrete abscesses the right middle lung lobe could be called locally extensive. Hemorrhages on the leg from a shotgun injury (multiple small projectiles) could be locally extensive.
Focal: one single lesion. If the lesion is discrete then focal is usually used, but a single irregular or poorly demarcated or large lesion might also called either focal or locally extensive.
Multifocal: multiple foci or multiple discrete lesions. Polka-dots are multifocal. Multifocal lesions can be randomly distributed, or uniform/non-random distribution (see zonal).
Diffuse: uniform throughout, like a poisonous gas diffusing throughout a room, or paint that completely covers a wall. Multifocal could be considered the opposite of diffuse.
Zonal: affecting one zone but not others. “Zonal” is mainly used for liver lesions that affect (for example) zone 3 of each hepatic lobule. This results in a regular alternating pattern of red and tan lesions.
Lobular: Mainly in lung. Lobular lesions affect some lobules completely while adjacent lobules are unaffected; this gives a “checkerboard” appearance or angular alternating areas of red and tan.
Lobar: Mainly in lung. Lobar lesions affect one lobe completely (or nearly completely). For example, a torsion or aspiration pneumonia might cause the right middle lung lobe to be dark red while adjacent lobes are normal.
Segmental: affecting one segment of a tubular organ. Eg. a 5-cm-long segment of small intestine is purple-red.
Other descriptive terms that are sometimes useful: bilateral, unilateral; symmetrical, asymmetrical; coalescing; patchy; cranioventral
size/extent
- Size in cm, mm, etc. Or, describe the range of sizes.
- Percentage of tissue affected (useful if the lesion compromises organ function simply because of its extent)
- Change from normal (eg a spleen might be 3-fold larger than normal, or a kidney half the size of normal)
- Ratio to another structure (eg. the normal ratio of adrenal cortex:medulla is 1:1; adrenocortical hypertrophy changes the ratio to 2:1)
Colour
- Tan, white, red, purple, black, green, yellow, brown, etc.
- Or, relative to normal (eg paler, or more reddened compared to the normal or adjacent tissue)
Shape/contour
- Raised, nodular, depressed, flat
- Well or poorly demarcated
- Round, oval, triangular, rhomboid, linear, serpiginous
- Surface texture: smooth, rough, papillated, villous, rugose, corrugated, fissured, pitted, cavitated (sunken), umbilicated (nodule with depressed centre)
- Polyp: a mass that grows outward. An anemone forms a polyp; most other cnidar- ians (eg jellyfish) start life as a polyp but later detach to become a free-swimming medusa.
- Stalk or no stalk:
- Sessile: “no stalk”; a mass that has a broad attachment to the tissue or that bulges from the tissue
- Pedunculated: Halloween 101—a peduncle is the stalk on pumpkin. A pedunculated mass is attached by a stalk. (c.f., papillary, sessile)
- Papillary: “Greek: nipple-like”; a thin finger- like outward growth (c.f. pedunculated, sessile).
- Vegetative: refers to the rough-surfaced mass forming on heart valves affected by endocarditis. The true meaning seems controversial: “an abnormal growth upon a surface”, a “fungus-like growth on a part of the body” or “a cauliflower-like growth”. Your choice.
texture
A blinded pathologist has nary a hope of diagnosing tumours with her microscope. Yet her well-seeing fingers have no trepidation in detecting a lung with consolidation, or the friable nature of liver swollen with fat, or a knobbly old kidney from a now-deceased cat. So put on a glove, for your eyes need no crutch; your fingers will see if you just let them touch.
Please, palpate tissues in our labs, deeply and purposively.
- Hard (forehead), firm (nose), soft (lips)
- Other textures: rubbery, resilient, turgid, elastic, gritty, spongy, gelatinous
- Characteristics of fluids: serous (watery), viscid/viscous (sticky or thick and slow-flowing), inspissated, mucoid, creamy, clotted
- Inspissated: a fluid that has become thickened, like gravy or porridge. Pus is milky in the early stages, but can become creamy or porridge-like with age, and even form a solid friable mass.
Strength
- Tough, normal, friable
- Friable: lacking in normal strength; crumbly or easily torn
terms for morphologic diagnoses
severity
- Your estimate of mild, moderate, severe
- It can reflect how extensive the lesion is within the organ, or how serious the lesion is for the animal. Sometimes these two meanings are in conflict: it seems inappropriate to call a tiny lesion in the brainstem mild if it caused death. Similarly a visually dramatic lesion that is present throughout an organ might not be called “severe” if we knew it was functionally unimportant or would not result in any illness.
Time
- Acute, subacute and chronic are not precisely defined with respect to the number of days they have been occurring
- Not included for cases of neoplasia
- Peracute: appearing suddenly without prior clinical signs of illness
- Acute: a disease that has developed so recently that it hasn’t yet had a chance to resolve
- Subacute: between acute and chronic
- Chronic: persistent or recurrent or relapsing for a long time, or fails to respond
to treatment over a suitably long time. A disease that has gone on long enough that it has had a chance to resolve, but hasn’t done so. Some might call a disease chronic if it lasts for longer than 21 days; others might require it to last for more than 3 months; this probably depends on the specific illness.
Distribtuion
(See above)
Pathologic Process
- Inflammation (indicate where possible: fibrinous, granulomatous, neutrophilic/ suppurative)
- Necrosis, ischemia, infarct, infarction,
- Edema, hemorrhage
- Atrophy, hypertrophy, hyperplasia, dysplasia, metaplasia, neoplasia
- Aplasia, hypoplasia, atrophy
- Fibrosis
- Mineralization, lipidosis, melanosis
- Thrombosis, embolism
- Congestion, hyperemia, hemorrhage
Tissue
Noun: liver, skin, kidney cortex, grey matter of brain
or Adjective: hepatic, cutaneous, renal cortical
or Greek prefix: hepatitis, nephropathy, polioencephalitis
some words used in pathology
words to describe abnormal location
Torsion: a twist on its long axis. A screw made of weak metal undergoes torsion as
a screwdriver is applied. Christmas crackers and sausage links are nice examples of torsions. Torsion of the cecum is like twisting an inflated balloon, before you tie the knot to keep it inflated. The mesentery can also twist on its long axis, and the intestines will be caught up in the mess. Take all of the intestines and twist the whole armful clockwise, and you will create a mesenteric torsion.
Volvulus: a twist perpendicular to its long axis. To create an intestinal volvulus, grab
a fistful of intestine and rotate your wrist clockwise, the intestine twists upon itself. To create a balloon dog from a sausage-shaped balloon, first you have to make a few torsions, and then a volvulus to make the front legs, and another volvulus to make the back legs. And the ears.
Materials deposited within tissues
Amyloid: innocent proteins are cleaved to make disease-causing peptides, which array themselves in β-pleated sheets. This arrangement is insoluble and resistant to degradation, and causes dysfunction of the organ.
Metastatic mineralization or calcification: mineral deposits within tissues because of high blood or systemic levels of calcium and/or phosphorus. Metastatic mineralization may occur throughout the body, but most frequently affects kidney, lung, stomach, and elastic arteries.
Dystrophic mineralization or calcification: mineral deposits within tissues because of necrosis or damage to to the tissue. Dystrophic mineralization can occur in whichever tissues are damaged.
Death of tissue or cells
Apoptosis: an active form of cell death initiated by the cell itself. Apoptotic cell death is initiated by caspase enzymes, does not stimulate inflammation, and leads to fragmentation of DNA. Apoptosis has characteristic morphology including shrunken cells with fragmented nuclei, condensed chromatin, and cell-surface blebs.
Necrosis: a passive form of cell death. The cell does not direct the process but is only an unfortunate victim. The key events are loss of membrane integrity, dysfunction of mitochondria, shrinkage or fragmentation of the nucleus, and release of inflammation- inducing cellular constituents into the extracellular space.
Coagulation (coagulative) necrosis: necrosis in which the microscopic architecture (i.e., the connective tissue and the ghost-like remnants of dead cells) is maintained and is histologically visible. Because the connective tissue is not dissolve, the dead tissue often retains its strength. Ischemia is a typical cause of coagulation necrosis.
Caseous necrosis: necrosis in which the microscopic architecture is lost, and the dead tissue has a friable or crumbly texture resembling cheese. In some cases, proteolytic enzymes degrade the dead tissue to create the crumbly caseum. The exact gross appearance varies: caseous lesions are usually moist and crumbly like feta, but as aging lesions become inspissated they may better mimic the curd of an aged cheddar.
Gangrene: a form of coagulation necrosis that is usually caused by ischemia or toxin-producing bacteria. In wet gangrene, bacteria invade the dead tissue and their enzymes putrefy the tissue into a liquid ooze. But in dry gangrene, there is no blood supply to bring tissue-debriding cells and proteases, nor are there saprophytes to return the dead tissue to dust, so it can only mummify— grey, dry, dull, cold and still.
Ulcer: full-thickness loss of a stratified squamous epithelium (eg skin), or full-thick- ness loss of the mucosa on a body surface with a simple epithelium (eg intestine or stomach). In both cases, the important consequence is that the regenerative cells are lost (i.e. basal cells in the epidermis, or cells within crypts of the intestine or foveolae of the stomach), so regeneration or healing will thus be delayed, and the risk of full-thickness perforation is greater.
Erosion: partial-thickness loss of a stratified squamous epithelium (skin), or partial-thickness loss of the mucosa (intestine, stomach). The great news is that the regenerative cells are still present and regeneration is more likely (that is, if there is an adequate blood supply, and damage to connective tissue can be repaired).
disorders of blood flow and coagulation
The flowing river of life brings sustenance and carts off waste. A dam upstream and the village starves; A dam downstream makes pestilence and flood. Poisons leaked from far away bring suffering to all. But life is good while the river flows forever.
Hyperemia: “Greek: hyper=increased, ‘emia=blood”; increased blood flow to a tissue such as from dilation of an arteriole (c.f. congestion, hemorrhage)
Congestion: increase blood within a tissue because of reduced drainage, such as from constriction of venules (c.f. hyperemia and hemorrhage)
Hemorrhage: “Greek: haima=blood, ‘rrhagia or rhegnunai=breaking out”; leakage of blood from a blood vessel into a tissue, into a body cavity, or from the body surface.
Hematoma: “Greek: haima=blood, ‘oma=mass”; a focal mass of blood (erythrocytes and plasma) within a tissue
Ecchymotic hemorrhage: ecchymoses are medium-sized splotches of hemorrhage within a tissue. Larger splashes of hemorrhage are sometimes called suggillations, but “bruise” is simpler and more often used.
Petechial hemorrhage: tiny spots of hemorrhage within a tissue. Petechia=singular, petechiae=plural.
Purpura: widespread distribution of petechial hemorrhages, either throughout the skin (clinically) or throughout the body (at postmortem). Inadequate numbers of platelets or defects in platelet function interrupt coagulation and are thus frequent causes of purpura, but don’t neglect consumptive coagulopathy and widespread injury to blood vessel walls (eg vasculitis) as other important mechanisms of purpura. Whereas platelet and blood vessels diseases often manifest as purpura, disorders of coagulation factors such as anticoagulant rodenticides (warfarin) or inherited coagulopathies (hemophilia) typically cause hematomas or bleeding into body cavities. Thus, the subtle morphology of bleeding informs us of the cause.
Cardiac tamponade: fluid in the pericardial sac prevents the heart from filling with blood during diastole, and may lead to right heart failure. The offending pericardial fluid can be blood (hemopericardium), exudate (pericarditis) or transudate (hydropericardium).
Aneurysm: the bulging of an artery due to weakening of its wall. In humans, hemor- rhage from an aneurysm in the brain can cause stroke, and emergency surgery can reinforce an aneurysm of the abdominal aorta to prevent a catastrophic rupture.
Thrombus: a mass within a blood vessel formed of activated and aggregated platelets enmeshed in a web of fibrin. An antemortem thrombus is usually white-tan and crumbly, whereas a postmortem clot is gelatinous, red-purple or yellow, and elastic but snaps easily. “Clot” is not recom- mended in precise conversations like ours because it is ambiguous: it can mean an antemortem thrombus, or a postmortem blood clot.
Embolism: an intravascular mass (an embolus) that has been carried by flowing blood to lodge within the narrow- ing branches of an artery. A thromboembolism—embolism of a thrombus—may continue to grow “upstream” as additional platelets and fibrin are added. Other forms of emboli include fat, tumour cells, air/gas, and intravenously injected substances. Emboli that obstruct an artery can cause ischemia/infarction.
Consumptive coagulopathy: the bleeding tendency that results from consump- tion of coagulation factors and platelets. In sepsis, widespread activation of endothelial cells triggers disseminated intravascular coagulation (“DIC”), which uses up all of the available platelets and coagulation factors. Ironically, excessive coagulation thus leads to widespread hemorrhage—i.e. purpura.
Edema: excessive fluid with tissue. Low- protein edema results from reduced oncotic pressure (eg. hypoproteinemia), increased hydrostatic pressure (eg, heart failure, or increased blood volume) or obstruction of lymphatic vessels. Protein-rich edema results from increased vascular permeability
(eg. from inflammation).
Effusion: fluid within a body cavity. A transudate is a watery clear effusion with low protein concentration and low cellularity, with similar causes as for low-protein edema. An exudate is an opaque or murky effusion with high protein concentration and high cellularity, usually caused by inflammation.
Ascites: a transudate (or modified transudate) in the abdominal cavity
inflammation
Catarrhal: a exudate of mucus mixed with pus (neutrophils) that clings to a mucosal surface. Hearing a Scottish veterinary pathologist say catarrhal (and also diphtheritic) is a happy memory of my time in Saskatoon.
Cellulitis: inflammation of subcutaneous tissues and the adjacent loose connective tissues
Granulomatous: inflammation dominated by activated (“epithelioid”) macrophages, usually with lymphocytes, and sometimes with multinucleated macrophages (“giant cells”) and/or fibrosis.
Granuloma: a form of granulomatous inflammation in which the activated macrophages (and other cells) form a nodular mass.
Neutrophilic: inflammation dominated by neutrophils, especially when the neutrophil infiltrate is microscopic and leads to pale- ness and swelling of tissue. Suppurative and purulent refer to the formation of pus— that grossly visible, white-yellow, watery or creamy or inspissated ooze that forms when many many neutrophils accumulate and liquefy.
Abscess: a package of pus; a focal accumulation of liquefied neutrophils enclosed in a capsule.
Fistula: a tract within tissue that opens to a surface, such as an infection in the muscle with a pus-filled fistula extending through the subcutaneous tissue to the drain onto the skin surface.
Bacteremia: bacteria within the blood, with or without observable illness.
Septicemia: bacteremia that results in clinically observable illness.
Systemic inflammatory response syndrome (SIRS): systemic consequences of inflammation (eg fever, increased blood neutrophils, malaise, elevated acute phase proteins in blood). The inflammation can affect either one organ or multiple organs. If it is caused by infection, let’s call it sepsis.
Sepsis: SIRS due to infection. The infection can be either localized (eg mastitis), or disseminated (eg bacteremia/septicemia).
Mycosis: disease caused by fungal infection
Tissue repair
Contraction: reduction in size of a wound over time (due to shrinkage of the tissue itself from myofibroblast contraction).
Contracture: fixation of a joint due to shortening of a muscle or tendon.
Stricture: chronic narrowing of a lumen due to contraction of fibrous tissue.
Organization (of fibrin): the transformation of fibrin to fibrous tissue. Specifically, infiltration of fibrin by new blood vessels and fibroblasts, with synthesis of collagen, and removal of the fibrin.
Debridement: “French: remove the bridle from”; removal of necrotic or damaged tissue, either by surgical excision, or by the body’s own processes using proteases and macrophages.
Recanalization: in a blood vessel occluded by a thrombus, the process by which the thrombus becomes organized and a new blood vessel lumen develops.
Regeneration: in damaged tissue, the formation of new functional tissue. When regeneration fails, a non-functional fibrous scar may take the place of the damaged tissue, or there may be permanent loss of the tissue, or an ulcer may remain on a mucosal surface.
Neoplasia
Tumor: a mass, which could be either neoplastic or non-neoplastic
Neoplasm: a mass resulting from cellular proliferation. Specifically, cellular proliferation that is permanently independent of the normal control mechanisms. The concept is that even if the cause were corrected, neoplastic cells would continue to prolife ate (whereas, dysplastic cells could return to normal if the cause of the dysplasia was corrected).
Malignant; cancer: those neoplasms that are capable of invading and destroying adjacent tissues, or spreading to establish neoplasms in other parts of the body. Although malignant classically means “capable of causing death”, we conventionally use it for neoplasms that could invade or metastasize.
Adenoma: “Greek: adeno=glandular, ‘oma= mass”; a benign epithelial neoplasm with a glandular pattern of differentiation (or, origin).
Papilloma: a benign epithelial neoplasm that forms a nipple-like, finger-like or frond-like projection from the tissue.
Carcinoma: malignant epithelial neoplasm. Also: adenocarcinoma (carcinoma of glandular origin or glandular differentiation), squamous cell carcinoma (carcinoma with differentiation to form keratin-producing squamous cells), etc.
Sarcoma: malignant mesenchymal neoplasm. Sarcomas are further named for:
- what the neoplastic cells produce (osteosarcoma cells produced osteoid, myxosarcoma cells produce myxoid or proteoglycan-rich matrix)
- their pattern of differentiation (hemangiosarcoma cells form blood-filled channels, liposarcoma cells produce lipid)
- their presumed origin (synovial sarcoma is presumed to originate from synoviocytes).
Metastasis: in a malignant neoplasm, the seeding of distant sites with neoplastic cells, and growth of those cells to form a new tumour.
Paraneoplastic syndrome: clinical signs or other observed changes that are an effect of a tumour on a distant site, but not as a result of spread of the neoplastic cells. Paraneoplastic syndromes result from secretion of hormones by neoplasms (eg. renal neoplasm secretes erythropoietin that causes polycythemia, or a anal sac adenocarcinoma secretes a parathyroid hormone-like protein that causes hypercalcemia and tissue mineralization), dysfunction of nerves, triggering of autoimmune responses (thymoma leading to immune-mediated polymyositis and thus megaesophagus), or strange and unusual lesions that no one quite understands (eg. paraneoplastic alopecia in cats with pancreatic carcinoma).
Anaplastic: “Greek: backward formation”; in reference to a malignant neoplasm, it indicates lack of differentiation, in which the rebellious cells neglect to follow the usual conventions of respectable cells, and have abnormal shapes, abnormal arrangements with one another, and abnormal orientation with the rest of the tissue.
Atypia: refers to cells that are morphologically different from their normal appearance (i.e. atypical appearance).
Desmoplasia, desmoplastic reaction: “Greek: knot/restraint formation”; connective tissue that induced by a malignant neoplasm, particular carcinomas. “Scirrhous” has a similar meaning of hard fibrotic tissue, although it can be used for both neoplastic and non-neoplastic causes.
Dysplasia: “Greek: bad formation”; cells that misbehave by not differentiating in an orderly way, or piling up on each other when they should be side by side. Dysplastic cells are like teenagers in the dim light of a suburban park: they try to look troublesome but mostly respect the law, and will eventually become normal again. In contrast, anaplastic cells have crossed the line: they are neoplastic and can never return to a normally regulated life.
disorders of growth and development
Congenital: present at birth. In contrast to a developmental lesion that resulted from failure of the initial organ development in the fetus, “acquired” lesions develop in an organ that developed normally. Although developmental lesions are often congenital and vice versa, it is not always so because organs continue to develop after birth. For example, in utero ischemia and toxins can necrosis of the late-gestation kidney to cause renal disease that is acquired but congenital, while some dogs with breed- specific (and presumably inherited) developmental renal diseases are normal at birth and only develop clinical signs at several months of age.
Teratogen: something that causes an abnormality of development, such as a chemical toxicant or a virus.
Agenesis: “Greek: a=no, genesis=origin/ creation”; failure of an organ to form, with an absence of even a primordial structure (c.f., aplasia, hypoplasia.
Aplasia: “Greek: a=no, plasia=growth”; failure of growth of an organ, but there is a primordium to suggest that the original formation of the organ occurred, even if it didn’t grow properly. I recommend to not spend time on the subtle beauty of this distinction.
Atresia: failure to form the lumen of a tubular organ. Colonic and rectal/anal atresia occurs in newborn calves and can be induced by palpation of the fetus during a pregnancy check. In tricuspid atresia— I’ve seen a few cases in calves—there is no communication between the right atrium
and ventricle.
Stenosis: narrowing of a tubular organ because of compression, hypercontraction of smooth muscle, an obstructing mass, or stricture. It is an acquired condition, whereas atresia is developmental.
Atrophy: reduction in size of an organ that developed normally (c.f. hypoplasia). It is an acquired condition, whereas hypoplasia is developmental.
Hypoplasia: failure of an organ to develop to its normal size. Small because of a lack of development.
Hyperplasia: proliferation of cells, or enlargement of an organ because of proliferation of cells.
Hypertrophy: increased cell size, or enlargement of an organ because of increased cell size.
Ectopic: normal-appearing tissue or organ in an abnormal location. Related but obscure words that you should definitely not memorize include hamartoma, a mass formed by excessive normal-appearing tissue within the expected location of that tissue; and choristoma, a mass formed by excessive normal-appearing tissue in an abnormal location for that tissue.
Cyst: a fluid-filled cavity lined by epithelial cells. This can be developmental or acquired, for example traumatic implantation of epithelial cells into subcutaneous tissue, with continued growth of the epithelial cells and secretion into a central lumen.
general, miscellaneous, organ-specific terms, and rambles
Diagnosis: recognition of a specific disease based on observed evidence.
Differential diagnosis: one of several possible causes or diagnoses. A particular set of clinical signs or lesions may be the result of several different diseases. We create a list of these differential diagnoses as an important step in developing a plan to distinguish among them, in our quest to identify the one true cause of the patient’s illness.
Diagnostic method: the method that we use to investigate a clinical case in order to establish the diagnosis.
One diagnostic method is based on pattern recognition: we look at the clinical signs or pathologic lesions, and hope that the first disease or cause that pops into our head is the correct answer for this case. Please recognize this approach is tunnel-visioned and unlikely to reliably arrive at the correct answer, until you have seen enough of these cases to be well-familiar with the characteristic appearances. Even then, we use pattern recognition only as a first line of diagnosis, but then take care to consider other possibilities or verify the diagnosis by another method.
A second approach is to create an exhaustive (a huge and complete) list of all diseases that could cause what we are observing. But, this approach is … well, it is exhausting and so big that it paralyzes our diagnostic investigation.
Usually, we use the third approach: we consider a smaller list of those differential diagnoses that are most common for the circumstances and best fit the observed clinical findings or pathologic lesions, and then we narrow this list of differential diagnoses (that is, we exclude some possibilities but keep others) by (a) more detailed or directed consideration of information already at hand, (b) performing additional tests or procedures to rule in or rule out some of the differential diagnoses, and (c) further considering other “less likely” differential diagnoses if the more likely ones are excluded or as more information comes to light. In this way, we consider many likely possibilities and then gradually narrow in on the correct diagnosis.
A fourth approach—also commonly used and a variant of the above—is to use a clinical algorithm, or a somewhat-standardized approach to sorting out the likely causes of a frequent or well-studied clinical problem. For example, most clinical veterinarians have a somewhat-standardized approach to investigating acute vomiting in dogs, or anorexia and vague illness in older cats.
Biopsy: a sample of tissue from a live animal (typically, a live-animal sample used for diagnosis)
Etiology: the branch or discipline of medicine that deals with the causes of disease. Etiology is the study of disease causation. It is sometimes used to mean the thing that induces the disease (like a virus, or a toxicant, or a thermal burn, or trauma) but these are more properly and more simply termed “causes”. Simple, clear, precise, happy.
Idiopathic: of unknown cause. (“cryptogenic” is a British equivalent)
Iatrogenic: “Greek: healer, caused/origin”. You did it, Doc — illness or bad things that were caused by the veterinarian or the well- meaning medical procedure.
Some words to describe infectious diseases:
Pathogen: an infectious agent that causes disease. A primary pathogen causes disease on its own. An opportunistic pathogen needs some predisposing factor before it can cause disease (eg. a bacterium needs a primary viral infection before it can cause disease). A secondary pathogen typically colonizes the lesions caused by a different pathogen (a primary pathogen), but it can be important by perpetuating or worsening the disease.
Contagious: an infections that spread from one individual to another. Infectious diseases are those diseases caused by infectious agents (such as viruses, bacteria, fungi, protists, metazoan parasites). Some infectious diseases are not contagious (eg, fungal infection acquired from the environment but not spread from animal to animal), and some contagious diseases are not infectious (eg the facial tumour of Tasmanian devils or transmissible venereal tumours of dogs, where neoplastic
cells spread from one animal to another). A zoonosis is a disease that affects humans and other animals.
Infectivity: the ability of a microbe to infect a host, with or without disease.
Pathogenicity: the ability of a microbe to cause disease.
Virulence: the severity of the resulting disease.
Autolysis: self-digestion of tissues, caused by the tissues own enzymes. Contrast with putrefaction, which is the dissolution of tissues as a result of postmortem invasion of bacteria.
Involution: reduction in size of a once- large organ, usually as part of a normal process. Examples are thymic involution at puberty, or involution of the uterus after delivery of a baby.
Cachexia: wasting of the body, such as severe loss of muscle and fat due to chronic illness.
Hypoxia: abnormally low levels of oxygen within tissues.
Icterus: yellow discoloration of skin, sclera, and other tissues; results from bilirubin in tissues; typically due to liver disease or lysis of erythrocytes. The word is apparently derived from the name of a yellow bird that was thought to cure the disease. Interestingly (and completely unrelated), an bunan bui (the yellow bittern) is an epic Irish poem about a man’s refusal to give up drink even though he knows it will be his death (death from alcoholic liver disease? …maybe there is a link after all?).
Jaundice: same as icterus. Not all medical words are Greek! (from the French, jaune).
Infarct: tissue death because of ischemia (lack of blood or oxygen supply). An infarct is typically a focal lesion, but “infarction” can affect an entire organ.
Ischemia: suffering of tissue because of a lack of blood (or oxygen) supply. A pound for the first to explain to me why the Brits spell it ischaemia.
Ischemic necrosis: death of tissue because of a lack of blood (or oxygen) supply (see also: infarct).
Atelectasis: “Greek: ateles=failure, ectasis=dilation/distention”. For the lung, failure of the alveoli to dilate with air.
Consolidation: solidification or firmness of a tissue, typically firmness of the lung due to filling with inflammatory cells or fibrin.
Malacia: softening of tissue, mostly used to describe brain lesions
Intussusception: swallowing of one segment of intestine by the adjacent segment.
Melena: black tarry feces. The tarry appearance results from digested blood, due to bleeding from the esophagus, stomach or proximal small intestine. The woman’s name Melana has the same etymology, from the feminine of the Greek word for black. It seems that veterinarians’ daughters are not often named Melana.
