Urine 1 Flashcards
Functions of the Kidney
- Eliminates of metabolic wastes from the body
- Maintains normal levels of body electrolytes and essential organic molecules (i.e. homeostasis)
- Produces important hormones
Urinary Tract Anatomy
Kidney
Ureter
Urinary bladder
Urethra
• Glomerular filtration
• Filtration of blood occurs at the glomerulus
• Driven by high blood pressure
• Permitted by semipermeable capillary membrane
allows passage of water and dissolved solutes of low molecular weight
Reabsorption (of the kidneys)
o The majority of small molecules in the glomerular filtrate are reabsorbed before they exit the body in urine
o ~ 90% of filtered molecules are reabsorbed in the renal tubule
Excretion (of the kidneys)
o Some molecules are excreted into the glomerular filtrate as it moves through the renal tubule
Voided Sample of urine
- Collect urine as animal urinates
- Contaminated by bacteria
- Preprandial (before meal)
a. Most concentrated
b. Not affected by eating or exercise - Midstream sample is the cleanest
Manual Express of urine
- Mainly used in cats and small dogs
- Must never exert too much pressure – bladder can be ruptured
- Never should be used with an animal with urinary tract obstruction
- Urine may contain RBC – bladder can be damaged during compression
Specimen Collection of urine
A. Voided Sample
B. Manual Express
C. Catheterization
D. Cystocentesis
Catheterization of urine
- One preferred method – sterile if done correctly
- Insert catheter into bladder via urethra
- Sterile catheter/sterile gloves
- Avoid trauma to urethral mucosa
- RBC common
Cystocentesis of urine
- Dogs/cats sterile collection
- Insert sterile needle directly into bladder through abdominal wall
- Surgical prep – remove as much urine as possible to avoid leakage through the needle hole
Biochemical Analysis of Urine
- Chemical substances excreted in urine can be measured
- Chemical assays are made using a dipstick w/ individual test pads for each chemical
- Deviations from normal expected levels can be an indication of disease
pH of urine
pH
• Measure of H+ concentration in urine
• Abnormally low pH associated w/ hypoventilation, starvation, prolonged vomiting and diarrhea
• Abnormally high pH associated w/ hyperventilation, bacterial UTI, postprandial urine sample
• May be falsely increased if urine is left out at room temperature for a long time before analysis
Urine is typically acidic or alkaline
pH < 7 in carnivores
pH > 7 in herbivores
Protein in urine
• A small amount of protein is excreted by an animal on a normal basis- Usually not detectable
• Method of urine collection affects protein level in urine
• Proteinuria usually indicates disease of the urinary system
o kidney damage (usu. glomerulus), urinary tract inflammation
• Falsely increased if urine has prolonged contact w/ the test pad on dipstick
Glucose in urine
• Not normally detected in urine
• Glucosuria occurs when blood glucose is
170-180 mg/dl in dog
260-310 mg/dl in cat
• Conditions associated w/ glucosuria include
o diabetes mellitus, stress/excitement, high carbohydrate meal
• May be falsely decreased in refrigerated urine
Ketones
• Ketone group-containing acids that result from fat breakdown
• Not normally detected in urine
• Ketonuria occurs when fat is metabolized for energy when carbohydrates are not available
o diabetes mellitus, pregnancy toxemia/ketosis, starvation/fasting
Bile pigments
- Chemicals derived from the breakdown of hemoglobin:
- Bilirubin
- Urobilinogen
- Bilirubinuria can be due to
- RBC destruction, hepatocellular damage,bile duct obstruction
- Small quantities of bilirubin can be detected in normal dogs
- Bilirubin is unstable in urine samples
Blood
- Red blood cells (RBC’s) and hemoglobin are detected by the same pad
- Hematuria can be due to
- bacterial UTI, urolithiasis, interstitial cystitis, neoplasia, renal disease, trauma
- Color of urine can be abnormal w/ hematuriaà wine, brown, cloudy red
- Abnormal urine color may disappear after centrifugation
Hemoglobin
- Hemoglobin is not normally present in urine
- Hemoglobinuria occurs w/ massive RBC destruction à autoimmune hemolytic anemia, blood transfusion incompatibility
- Color of urine containing hemoglobin can be abnormalà wine, brown, cloudy red
- The color of the sample doesn’t change after centrifugation
Myoglobin
- Oxygen-carrying molecule found in muscle that is similar to hemoglobin
- Detected by the blood test pad as hemoglobin and gives urine a dark brown to black color
- Myoglobinuria observed when significant muscle damage occurs- exertional rhabdomyolysis, trauma, toxicity
Nitrite
- Produced by bacteria from nitrate in urine
- Increased levels are supposed to indicate a bacterial UTI
- Not a reliable test in dogs and cats
Leukocytes
(i.e. White Blood Cells)
• Pyuria is indicative of infammation in the urinary tract
• Possible causes include- bacterial UTI, urolithiasis
• Test pad is not very sensitive in dogs, not reliable in cats
Urinary Sediment Analysis
- Performed as part of complete urinalysis procedure
- Detects abnormalities not seen on gross or biochemical analysis
- Confirms results of biochemical analysis
Urine collected for sediment analysis should be…
- Fresh sample
- Concentrated urine sample
- Collected by cystocentesis