Learner's URINALYSIS objectives: 1) identification of abnormal urinalysis findings 2) basic understanding of methodologies as described in these notes including artifacts 3) interpretation of results with regards to likely rule-outs Methods of Collection Cystocentesis - best method bladder back to kidney use for culture and sensitivity Catheterization bladder back to kidney ( urethra if immediately performed) "traumatic catheterization" - urethral/trigone tumors Voided / Free catch external opening back to kidney FRESH is BEST! Bacterial populations multiply Urease-producing bacteria increase pH Casts and cell degenerate in alkaline urine Analyze urine at room temp If sample is not to be read within 30 minutes, then refrigerate If sample has been refrigerated, allow to warm to room temperature prior to analysis Physical Exam Color Turbidity Odor Specific Gravity Color yellowish brown/orange/green increased bilirubin, biliverdin, Pseudomonas red/brown/black hematuria; should clear following centrifugation hemoglobinuria, myoglobinuria, or porphyrinuria Many drugs have also been reported to change urine color, so recent drug history is indicated with urine discoloration. Specific Gravity the ratio of the weight of urine compared to that of an equal volume of pure water the specific gravity of pure water is 1.000 addition of solute increases the specific gravity refractive index is an estimate of specific gravity more solute slows down the passage of light (refracted) through the solution refractometers are designed for human or animals human scale is very similar to that used for dogs and large animals THE URINE SPECIFIC GRAVITY PAD ON DIPSTICKS IS NOT ACCURATE, DON'T USE IT!
Obtain USG before any treatment fluids, diuretics, steroids, etc. can SG Isothenuria 1.008-1.012; SG of filtrate is not altered Hyposthenuria <1.008; kidney is functional, diluting urine Baruria appropriately concentrated urine for a given species If the animal is dehydrated, kidneys should concentrate the urine above an expected threshold to conserve H2O cat >1.035 dog >1.030 horse >1.025 cattle >1.025 If not then either the kidney is damaged the kidney's ability to concentrate is functionally compromised Urine pH Dependent on diet horse/cow 7.5 8.5 dog/cat 6.0 7.5 Acidic urine acidosis herbivores on milk diet/starvation paradoxical aciduria hypokalemia/furosemide therapy Alkaline urine alkalosis post-prandial (monogastrics) urease (+) bacteria renal tubular acidosis delayed processing (bacteria/CO2 loss) Proteinuria Most commonly measured by dipstick based upon pH reaction that is altered by the presence of negatively charged proteins alkaline urine may have a falsely elevated protein reading, but likely only a minor effect may underestimate proteins other than albumin (~ as sensitive for hemoglobin) abnormal urine color may interfere with reading Newer more sensitive species-specific ELISA-based strip tests (E.R.D) for the dog and cat that can identifies low levels of proteinuria normally undetectable by traditional strips that in theory could aid in diagnosis of early renal disease; studies are ongoing to determine the clinical utility as well as accuracy of this test Dogs can have up to 1+ in concentrated urine prerenal (overflow of small proteins) light chains/hemoglobin/myoglobin/post-colostral/transient* renal glomerular albumin/globulins/antithrombin lost can produce hypoproteinemia
tubular small amounts of albumin not resorbed as normal post-renal hemorrhage inflammatory
* transient causes include fever, strenuous exercise, shock, cardiac or central nervous system disease
Blood Sensitive to hemoglobin, myoglobin, and intact RBC's Use urine appearance, serum appearance, and centrifugation to differentiate RBC's centrifuge urine clear RBC's in sediment; may lyse if alkaline, old sample, or if SG < 1.008 Hb centrifuge urine colored and serum is pink amm. sulfate to urine clear PCV Mb centrifuge urine colored and serum is clear amm. to sulfate urine colored CK, muscle pain, history Bilirubinuria Measured by Multistix or the more sensitive Ictotest Dogs (esp. males) can have trace to occasionally moderate Br in concentrated urine lower renal threshold canine renal epithelium can conjugate and secrete some albumin-bound Br may be present Always a significant finding in other common species Conjugated bilirubin is filtered by the glomeruli False negative if urine is left standing in direct light Glucosuria Glucosuria Normoglycemia/renal tubular dysfunction (rare) Congenital Primary renal glucosuria Fanconi syndrome Toxic tubular damage Gentamycin/Amoxicillin Ischemic induced tubular damage Note: residual urine volume may show glucosuria with normoglycemia in previously excited/stressed Hyperglycemia (most causes) Renal proximal tubular threshold dog 180 mg/dl cat 280 mg/dl horse/calves 150 mg/dl cattle 100 mg/dl Diabetes mellitus Stress or excitement Glucose-containing fluids
Ketonuria Multistix and Acetest tablets don't detect -hydroxybutyrate Not in urine of healthy animals on good nutritional plane Indicative of fat degradation hyperglycemic DKA (usually type I) normo- to hypoglycemic starvation bovine ketosis pregnancy ketosis of ewes insulinoma low carb, high fat diet Old School Urobilinogen from GI breakdown of Br might indicate a patent bile duct, but too much variability to be useful test Nitrate and Leukocyte esterase are not dependable tests for assessment of bacterial infections Sediment Evaluation Use ~5-10 ml with a low speed spin (1000 to 1500 rpm for ~5 minutes) Analyze within a few hours ideally Express most findings per hpf RBC's WBC's Epithelial cells Squamous from voided and catheterized Transitional Some normal, but higher numbers may indicate TCC especially with atypia (dysplasia with WBC?) Catheterized may have more, ouch... Cylindruria (Casts) Recorded per low powered field (lpf) 10x Remnants of cells and/or protein that filled tubules Hyaline casts Clear, colorless; Tamm-Horsfall mucoprotein A few are normal very soluble in alkaline urine WBC casts Neutrophilic inflammation within the nephron RBC casts Hemorrhage within the nephron; renal hemorrhage/inflammation Tubular epithelial cell casts Degeneration, necrosis, and sloughing of tubular epithelium; ischemia, toxins Granular casts Former cellular casts Waxy casts Former granular casts Fatty casts Former granular casts (e...