laboratory techniques small animal technology. laboratory tests used to diagnose & treat health...
TRANSCRIPT
Laboratory Techniques
Small Animal Technology
Laboratory Tests
Used to diagnose & treat health problems
Tests are performed in: Veterinary hospitals Zoos Research facilities Commercial labs
Who performs lab work?
Vet. technician is typically responsible for collecting samples & performing the tests.
Vet. tech must know: Proper collection techniques Specimen handling Knowledge of complex equipment (using &
maintaining) Accurately perform the tests (vet will decide
treatment based on results)
Different Types of Tests
Hematology
Urinalysis
Susceptibility testing
Circulatory System
Excretory System
Circulatory System Functions
Consists of: Heart Blood vessels Lymphatics
Circulatory System Functions
Respiratory- O2 & CO2 exchange
Excretory-removes waste from body cells
Protection-clotting, & transporting white blood cells to infections
Nutrition-carries energy & food throughout the body
Regulatory-helps to maintain pH & temperature
Hormonal-transfers hormones to organs
Circulatory System Components
Heart-muscular, four-chambered pump that drives the circulatory system
Pericardium-fibrous sac that encloses the heart
Artery-an elastic vessel with thick walls to maintain high pressure while carrying blood away from the heart
Vein-a thin-walled vessel that carries deoxygenated blood to the heart
Circulatory System Components
Capillary-a microscopic vessel that forms a network between arteries, veins, & body tissues
Lymph system-consists of lymphatic vessels & tissues (tonsils, thymus, spleen, lymph nodes) that play an important part in immunity & disease prevention
Lymph node-bean-shaped structures located throughout the body that produce lymphocytes & monocytes, & filters bacteria, foreign bodies, & malignant cells
Circulatory System Components
Spleen-largest lymph organ, produces lymphocytes & monocytes, stores red blood cells & iron, & destroys old red blood cells
Blood Circulation Through the Heart
Important when evaluating a sick animal
Problems in the right side of the heart will cause the abdomen to fill with fluid (ascites).
Problems in the left side of the heart will cause lung congestion.
Blood Circulation Through the Heart
Blood flows through the heart in this order:
Right atrium>right ventricle>pulmonary arteries>lungs>pulmonary veins>left atrium>left ventricle>aorta
Major Arteries & Veins
Aorta-the largest artery that sends blood from the heart to the body
Brachiocephalic-branches from the aorta to send blood to the head & right side of the body
Common carotid arteries-(left & right) run up both side of the neck & supply blood to the head
Coronary arteries-wraps around the exterior of the heart & supply blood to the heart muscle
Major Arteries & Veins
Facial artery-wraps under lower jaw & is used to take the pulse on a horse or cow
Femoral artery-runs down the inside hind leg; used to take the pulse on a cat or dog
Mesenteric-supplies blood to the intestines
Renal artery-supplies blood to the kidney
Pulmonary arteries-carry deoxygenated blood to the lungs
Major Arteries & Veins
Pulmonary veins-carry oxygenated blood to the left atrium
Cranial vena cava-returns blood to the heart from the head, neck, & forelegs
Caudal vena cava-returns blood to the heart from the thorax, abdomen, & hind legs
Cephalic vein-runs along the front of the foreleg
Major Arteries & Veins
Jugular vein-runs down the neck & returns blood from the head
Renal vein-returns blood from the kidney to the caudal vena cava
Femoral vein-runs along the inside of the hind leg
Saphenous vein-an extension of the femoral vein
Major Arteries & Veins
Arteries generally are located deeper in the body than veins.
The Structure of Blood
Blood is composed of cells & plasma (the liquid portion of blood).
Cells make up 40% of blood.
The cellular portion consists of erythrocytes (red blood cells), leukocytes (white blood cells), and platelets.
The other 60% is plasma.
The Structure of Blood
The amount of blood contained in an animal varies by species.
Usually blood volume comprises 6%-8% of the animal’s total body weight.
Health & age will cause variations in blood volume within a species.
Blood Cells
The formation & development of blood cells is called hematopoiesis: hem=blood, poiesis=formation & development
All blood cells develop in the bone marrow from one type of cell called a hemocytoblast.
In young animals, blood is produced in all the bones.
Adults produce blood in the pelvis, ribs, vertebrae, femur, & humerus.
Erythrocytes
The red blood cell is the most abundant blood cell.
Its function is to transport O2 throughout the body.
Erythrocytes contain hemoglobin, a pigment that contains iron & gives blood its red color when combined with O2.
In mammals the red cell is non-nucleated, while reptiles & birds have nucleated red cells.
A red cell’s life span in dogs & humans is 120 days, but this varies among different species.
Leukocytes
Are colorless, nucleated cells that are capable of moving throughout the body.
Their function is mainly body defense.
Divided into 2 categories: Granulocytes & Agranulocytes
Granulocytes
Produced in the bone marrow, have lobed nuclei, & granules in their cytoplasm.
Neutrophils, basophils, & eosinophils are granulocytes.
Neutrophil
Has red & blue granules in cytoplasm.
Function is to stop or slow down foreign organisms.
How they work- 1) Phagocytosis-to eat bacteria & dead cells 2) Bactericidal-kill bacteria
How they get to infection site- 1) sticky & can migrate through vessel walls 2) release chemials to attract other neutropils
to the infection site
Basophil
Has dark purple granules in cytoplasm.
Functions are phagocytosis, to mediate allergic reactions, & to produce heparin & histamine
Eusinophil
Has organish-red granules in the cytoplasm.
Function is to moderate the inflammatory response & phagocytosis.
Agranulocytes
Produced in lymphatic organs, have rounded nuclei, & no granules in cytoplasm.
Lymphocytes & monocytes are agranulocytes.
Lymphocyte
Has a round nucleus & plays a vital role in immunity
Divided into 2 categories: 1) T-cells, also called memory cells, are long-
lived & once they are sensitized to an antigen remember it so that the next time they can fight off that antigen.
2) B-cells encounter an antigen & divide to form many cells that all produce the same antibodies to fight the antigen.
Monocyte
Has an irregular shaped nucleus.
The largest cell in the blood, its function is phagocytosis.
Thrombocytes (platelets)
Main function is hemostasis (clotting)
Platelets are 1/3 the size of a red blood cell
Stop bleeding by adhering to damaged vessels & clumping together & releasing proteins that help form a clot
Average life span of a platelet is 10 days
Hematology
Study of the structure of blood & the tissues that produce blood.
Clinical hematology is a division of medicine that uses lab tests performed on blood to determine the cause of an illness.
To correctly evaluate lab tests, it is necessary to have a working knowledge of the circulatory system.
Hematology
The lab tests are most commonly performed in veterinary medicine are: PCV or hematocrit White cell count TPP (total plasma protein) Blood film evaluation
PCV (Packed Cell Volume)
Measures the % of red blood cells in the total blood volume.
A capillary tube is filled with fresh anticoagulated blood, sealed with clay, & centrifuged for 5 minutes.
The results are read using a special scale.
An animal with a PCV that is below normal is said to have anemia.
Normal PCV Values
Dogs: 37-55
Cat: 30-45
Horse: 32-48
Bovine: 24-46
TPP (Total Plasma Protein)
Measurement of proteins produced mainly by the liver.
Measured using a capillary tube of blood.
The tube is scored with the edge of a microscope slide, broken at the plasma layer, and the plasma is placed on a refractometer.
The refractometer takes a measurement in g/dl.
An elevated TPP is a sign of inflammation, infection, or dehydration.
A decreased TPP occurs normally in newborns, pregnant animals.
Blood Film Evaluation
Used to determine the size, color, & shape of cells & abnormalities in their formation.
Blood films are also used to look for blood parasites such as the microfilaria of the heartworm.
Blood films are prepared by spreading a drop of blood on a slide, drying the slide, & then staining with Wright’s stain.
Blood Film Evaluation
The film is evaluated by scanning under high power for abnormalities.
Abnormalities appear in the RBC as color changes in the cell, abnormal cell shape & size, & foreign bodies within the cell.
WBC numbers are tallied & provide information about infection.
Platelet numbers are also evaluated.
The Urinary System
Consists of the: Kidneys Ureters Urinary bladder Urethra
The Urinary System
Main function is to extract & remove waste from the blood.
The kidneys are responsible for extracting & collecting waste.
They are paired organs located on both sides of the spinal column & are bean-shaped in most species of animals.
The kidneys of cattle have several lobes instead of the bean shape.
The Urinary System
The Urinary System
Kidneys
Consist of a cortex, medulla, & renal pelvis.
Throughout the cortex & medulla are located nephrons; nephrons are the functioning units of the kidneys & are directly responsible for the filtering & collection of wastes from the blood.
Collecting ducts run through the medulla & drain into the renal pelvis.
Kidneys
Nephrons
The Urinary System
Urine then passes into the ureters & proceeds to the bladder.
The ureters are smooth muscled tubes that extend from each kidney.
They use peristalsis to move urine to the bladder.
Urine is pushed into the bladder every 10-30 seconds depending on the species.
It flows in spurts rather than continuously.
The Urinary System
The bladder, consisting of smooth muscle, is an extremely elastic sac that is capable of holding large volumes of urine.
The bladder has 3 openings: 2 that receive urine from the ureters, & 1 used to excrete urine to the urethra.
The Urinary System
The urethra carries urine from the bladder to the exterior.
The urethra varies in length & circumference in males & females.
The female urethra is shorter in length & runs directly from the bladder to the exterior.
Males have a narrower urethra that is longer to extend through the accessory sex glands.
3 Phases of Urine Production
1) filtration
2) reabsorption
3) secretion
These phases occur in the nephrons, the functioning unit of the kidneys.
1) Filtration
Blood enters the glomerulus through the afferent arteriole
Under various pressures, water, salt, & small molecules move out of the glomerulus & into Bowman’s capsule
2) Reabsorption
Occurs in the proximal convoluted tubule & the loop of Henle
Substances needed by the body such as water & electrolytes will be reabsorbed by the body from the loop of Henle
3) Secretion
Substances are secreted into the collecting tubules & transported to the renal pelvis
Urinalysis
Provides information about how the kidneys are functioning & if wastes are being properly filtered from the body.
Specimen Collection
1) Free Catch-simplest method of collecting urine.
Samples from dogs can be caught with a pan or soup ladle.
Use a metal pie plate for females.
To collect from a cat, replace the cat litter with a shredded plastic bag or plastic pellets.
Specimen Collection
2) Manual Expression-involves palpating the bladder through the abdomen then applying pressure to it to encourage urination.
Manual expression is mainly used for animals that are unable to urinate on their own due to an injury or illness.
Animals with obstructions should never be manually expressed.
Specimen Collection
3) Catheterization-performed by inserting a plastic, or rubber catheter through the urethra into the bladder.
The size & type of catheter used depends on the sex & species of animal.
Catheterization is performed aseptically to prevent infection & is used in emergencies & for immobile animals that need long-term care.
Specimen Collection
4) Cystocentesis-performed by inserting a needle through the abdomen into the bladder.
Aseptic technique is used to prevent infection.
Is performed to obtain a pure urine sample or to relieve bladder pressure on an obstructed animal.
Urinalysis
Evaluation-ideally evaluation of a urine sample should occur within 30 minutes of collection, however samples can be refrigerated overnight if necessary.
Refrigerated samples should be brought to room temperature before they are evaluated.
Urinalysis
Samples are evaluated on the following: Color Transparency Specific Gravity Chemistry Sediment
Color
In most species urine is a pale yellow to amber color.
The color of the urine correlates to specific gravity. Lighter colored urine=lower specific gravity Darker colored urine=higher specific gravity Red urine=hematuria (red blood cells in urine) Yellowish-brown foamy urine=presences of
bile pigments
Some species, like the rabbit, have urine that is normally a darker orange to reddish-brown.
Transparency
Terms used to describe urine transparency are clear, cloudy, or flocculent.
Clear, fresh urine is normal for most species.
Cloudy urine indicates the presence of cells, bacteria, crystals, or fats, but in the horse, rabbit & hamster cloudy urine is normal.
Flocculent describes urine that has pieces of floating debris in it caused by the presence of cells, fats, or mucus.
Specific Gravity
Measures the concentration or density of urine compared to distilled water.
There are 3 ways to measure sg.
Specific Gravity
1) Refractometer-a tool that refracts light through urine & measures density by comparing it to the amount of light that will pass through distilled water.
The refractometer is also used to measure total plasma protein.
Specific Gravity
2) Urinometer-a bulb is floated in a cylinder filled with urine.
Specific gravity is read off a scale attached to the bulb.
This method requires a larger sample than the other methods.
Specific Gravity
Reagent strips-contain a chemical pad that changes color when dipped into urine.
The color change is read using a scale on the reagent container.
Specific Gravity
Average Specific Gravities:
Dog: 1.025
Cat: 1.030
Horse: 1.035
Cattle & swine: 1.015
Sheep: 1.030
Specific Gravity
An increased sg could indicate dehydration, decreased water intake, acute renal disease, or shock.
A decreased sg could indicate increased water intake, chronic renal disease, or other diseases.
Specific Gravity
4) Chemistry
The chemical components evaluated in urine are: pH Protein Glucose Ketones Bile Blood Yeast sperm
Specific Gravity
Chemistry tests are performed using reagent strips.
Several companies produce strips that will evaluate all the chemical components on one strip.
The chemical components provide information used to diagnose problems such as diabetes, renal failure, liver infections, muscle disease, inflammation of the urinary tract, & ketosis.
Specific Gravity
5) Sediment
An examination of urine sediment provides information on the types & numbers of cells present.
Cells commonly seen are: RBC’s WBC’s Epithelial cells
Specific Gravity
All of these cells are normal in small amounts; large amounts indicate disease or infection.
Excess RBC’s indicate hemorrhaging of the urinary tract.
Excess WBC’s indicate inflammation of the urinary tract.
Epithelial cells are sloughed from the urinary tract as they wear out, but trauma to the urinary tract will also cause sloughing.
Other components found in sediment are bacteria, crystals, & casts.
Bacteria
Indicate infection or contamination of the sample by improper handling.
If bacteria are present with an increased number of WBC’s then infection is likely.
Crystals
Form due to influences from pH, urine concentration, & diet.
Crystals do not necessarily indicate a disease, but they do cause problems in large amounts by irritating the urinary tract, causing blood in the urine (hematuria) & pain.
Crystals bond together creating stones that can block urine low & may eventually cause death.
Stones & crystals are especially serious in males due to the size & shape of the urethra.
Casts
Tubular clumps of cells or other materials that form in the collecting tubules of the kidney.
Large numbers of casts indicate a problem in the collecting tubules.
The types of casts are: Hyaline Fine granular WBC/RBC
Susceptibility Testing
Performed to determine how bacteria will respond to an antibiotic since some types of bacteria do not respond in a predictable manner.
Testing is important so that an effective antibiotic can be found.
The main methods used to test antibiotic sensitivity are broth dilution & agar diffusion.
Broth Dilution
Uses a series of test tubes that contain varying concentrations of the same antibiotic.
The test tubes are inoculated with bacteria & incubated.
The test tube that has the lowest antibiotic concentration with no bacteria growth indicates the minimum amount of antibiotic that is effective.
Agar Diffusion
Uses petri dishes coated with bacteria.
Disks containing antibiotics are placed on the petri dishes & incubated.
After incubation, the “zone of inhibition” is measured to determine which antibiotic is most effective.
The “zone of inhibition” is an area of no growth around an antibiotic disk.
The larger the “zone of inhibition”, the more effective the antibiotic.