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newSchoolWorks.com › VoTechWorks › Health & Personal Services › Veterinary Technology / Vet Assistant › Veterinary Laboratory Procedures & Diagnostic Radiology › Lesson 5
HLT-VET42-04 · Lesson 5 · 22 clock hours · lab

Urinalysis: Physical, Chemical & Sediment Examination

Objective. Students will perform a complete urinalysis including gross assessment, refractometer specific gravity, urine dipstick chemical evaluation, and centrifuged sediment microscopy, recording all findings on a standard urinalysis report form.

⚠ Pending professional review

This lesson, its worked examples and its practice questions has not yet been verified by a licensed clinician in the field or by a certification or approval body. It is a study draft and may contain errors. Do not use it to make decisions about any patient or medication. Always follow your instructor, your supervising professional, and current official references and regulations.

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Why Urinalysis Matters

Urinalysis (UA) is one of the most cost-effective and information-rich diagnostic tests in veterinary medicine. A complete UA has three parts: physical examination, chemical evaluation, and sediment microscopy. Together they give the veterinarian a snapshot of kidney function, hydration status, and the presence of infection, inflammation, or metabolic disease. As a veterinary technician or assistant, you will collect, process, and record UA findings accurately — errors at any step can lead to misdiagnosis and patient harm.

Part 1: Physical (Gross) Examination

Before touching any instrument, observe the sample with your eyes.

Record color and turbidity on the urinalysis report form before proceeding.

Part 2: Specific Gravity with a Refractometer

Specific gravity (SG) measures the concentration of dissolved solutes relative to pure water (SG = 1.000). The refractometer is the preferred veterinary instrument for this measurement.

Calibration first — always. Place one drop of distilled water on the prism, close the cover, and read the scale in good light. The reading must be 1.000. If it is not, adjust the calibration screw until it reads correctly, then wipe the prism clean with a soft lens tissue.

Place one to two drops of urine on the clean prism, close the cover, and read where the light-dark boundary crosses the urine SG scale. Use the correct species scale (canine/feline share one scale on most veterinary refractometers).

Part 3: Chemical Evaluation with Dipstick

Urine dipstick strips carry reagent pads that react with specific analytes. Timing is critical: dip the strip, tap the edge to remove excess urine, and read each pad at the manufacturer's specified time interval under white light against the color chart. Reading too early or too late gives inaccurate results.

Key pads in veterinary UA:

Caution: Human dipstick pads for leukocyte esterase and specific gravity are not reliable in dogs and cats. Always use the SG reading from the refractometer, and note that the leukocyte pad result should not replace sediment WBC counts in veterinary patients.

Part 4: Centrifugation and Sediment Preparation

Proper centrifuge technique preserves cells and casts.

1. Transfer 5 mL of well-mixed urine to a conical centrifuge tube.

2. Centrifuge at the speed and time recommended for urinalysis in your laboratory protocol (typically a low-speed, short spin — follow the manufacturer or laboratory standard operating procedure).

3. Carefully decant (pour off) the supernatant, leaving a small standard volume (commonly 0.5 mL or per SOP) over the pellet.

4. Resuspend the sediment by flicking the tube gently.

5. Place one drop on a clean glass slide and apply a coverslip without trapping air bubbles.

Safety note: Wear gloves and eye protection when handling urine samples. Urine can harbor zoonotic pathogens. Dispose of all biologic material and sharps per your facility's biosafety policy. Centrifuge tubes must be balanced before spinning.

Part 5: Sediment Microscopy

Examine the wet-mount slide using a compound microscope.

Recording Findings

All results go on the urinalysis report form immediately — never rely on memory. Record color, turbidity, SG value, each dipstick pad result, and sediment counts per HPF. The completed form becomes part of the patient medical record. Legibility and accuracy are professional and legal obligations.

Safety Summary

Key terms8

Specific gravity (SG)A measure of urine concentration expressed as the ratio of urine density to pure water density (1.000); measured with a refractometer in veterinary practice.
RefractometerAn optical instrument that measures the bending of light through a liquid to determine the concentration of dissolved solutes; must be calibrated with distilled water before each use.
IsosthenuriaUrine specific gravity fixed in the range of 1.008–1.012, indicating the kidneys are neither concentrating nor diluting urine, which may signal renal disease.
CastA cylindrical protein structure formed within renal tubules and flushed into urine; types include hyaline and granular, each carrying different diagnostic significance.
High-power field (HPF)The microscopic field of view observed at 40× objective magnification; used as the standard unit for reporting cellular elements in urine sediment.
TurbidityThe cloudiness or haziness of a urine sample caused by suspended particles such as cells, crystals, bacteria, or lipid droplets.
GlucosuriaThe presence of glucose in urine, detected by the dipstick glucose pad; in dogs and cats it commonly indicates diabetes mellitus or a renal tubular defect.
Hyaline castA nearly transparent, colorless cast composed primarily of Tamm-Horsfall mucoprotein; the least pathologically significant cast type and may appear after dehydration or vigorous exercise.

Worked examples4

1. You read a urine SG of 1.024 on the refractometer, but you forgot to calibrate first. When you then test distilled water, the refractometer reads 1.004. What is the corrected SG of the urine sample?
  1. Identify the calibration error: distilled water should read 1.000, but reads 1.004, meaning the instrument reads 0.004 too high.
  2. Subtract the error from the urine reading: 1.024 − 0.004 = 1.020.
  3. Report the corrected SG and recalibrate the instrument before the next reading.
Answer: The corrected specific gravity is 1.020. Always calibrate before measuring patient samples to avoid this error.
2. You are reading urine sediment at 40× (high dry) and count RBCs in 10 consecutive HPFs: 3, 5, 4, 6, 4, 5, 3, 4, 6, 5. What is the average RBC count per HPF, and is it above the commonly cited normal threshold?
  1. Add all counts: 3 + 5 + 4 + 6 + 4 + 5 + 3 + 4 + 6 + 5 = 45.
  2. Divide by the number of fields: 45 ÷ 10 = 4.5 RBCs/HPF.
  3. Compare to the general reference: > 5 RBCs/HPF is commonly considered abnormal.
  4. 4.5 is below 5, so this result falls within the normal range, though it is near the threshold and should be interpreted with clinical context.
Answer: Average = 4.5 RBCs/HPF, which is below the commonly cited threshold of > 5/HPF and is within normal limits for most references.
3. You have 7 mL of urine in a conical tube and your SOP states to use 5 mL for centrifugation. After spinning and decanting, you should leave 0.5 mL over the pellet. How many milliliters of supernatant do you pour off?
  1. Starting volume in tube: 5 mL (you used the SOP-specified amount, discarding the extra 2 mL or saving it).
  2. Volume to retain: 0.5 mL.
  3. Volume to decant: 5.0 − 0.5 = 4.5 mL.
Answer: Decant 4.5 mL of supernatant, leaving 0.5 mL to resuspend the sediment pellet.
4. A dipstick protein pad is read at the correct time and matches the 1+ color block. The glucose pad matches the negative color block. Record these findings in standard format and state what follow-up the technician should flag for the veterinarian.
  1. Record protein: 1+ (positive).
  2. Record glucose: Negative.
  3. A single 1+ protein finding on a concentrated sample may be less significant than on a dilute sample; compare protein result to the SG.
  4. Flag persistent or unexplained proteinuria (1+ or higher) for veterinary evaluation, especially if SG is low (isosthenuric range), which would make the protein finding more significant.
Answer: Record Protein: 1+, Glucose: Negative. Flag the protein result for the veterinarian, noting the SG so clinical significance can be assessed in context.

The math in this lesson1

Learners correct a refractometer reading of 1.024 by a 0.004 calibration error to report specific gravity 1.020.
N-Q.3
Brush up in the math halls at newSchoolWorks.com:
In class: Students receive three simulated or preserved urine samples varying in color and turbidity; they measure specific gravity with a refractometer (calibrating with distilled water first), read the dipstick at the correct time interval under white light, and record all findings before handling any sediment. · Centrifuge technique: students spin each sample at the standard urine speed for the prescribed time, decant the supernatant to the correct volume, resuspend the sediment, and prepare an unstained wet-mount slide using a standardized coverslip. · Sediment review: using a microscope under low and high dry power, students identify and count red blood cells, white blood cells, epithelial cells, casts (hyaline and granular), bacteria, and crystals on three pre-made sediment slides; they record counts per high-power field on the report form.
Materials: Refractometer, distilled water, urine dipstick strips and color chart, simulated or preserved urine samples, conical centrifuge tubes, centrifuge, slides, coverslips, compound microscopes, urinalysis report forms, Sirois Ch. 8; AAHA Urinalysis Reference Guide
Check: Completed urinalysis report form for each of the three samples evaluated by instructor against answer key; specific gravity reading within ±0.002 of control value, dipstick readings 100% accurate for protein and glucose, sediment findings within ±1 structure per HPF. Overall 80% or higher required.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.

Laboratory Procedures
1. Before measuring urine specific gravity with a refractometer, the technician should first:
Laboratory Procedures
2. A urine sample has a specific gravity of 1.010 in a dog that is not receiving any fluids. This result is best described as:
Laboratory Procedures
3. Which urine dipstick pad result is considered unreliable in dogs and cats and should NOT be used in place of microscopic sediment examination?
Laboratory Procedures
4. During sediment microscopy, you observe large, nearly transparent, colorless cylindrical structures. These are most consistent with:
Laboratory Procedures
5. When preparing urine sediment, the technician decants the supernatant and leaves a small volume over the pellet, then resuspends by flicking the tube. What is the primary reason for leaving residual supernatant rather than pouring everything off?
Laboratory Procedures
6. A student reads the urine glucose dipstick pad 90 seconds after dipping instead of at the manufacturer-specified time. The most likely consequence is:
Laboratory Procedures
7. A veterinary technician counts WBCs in 10 HPFs and records: 8, 10, 9, 11, 8, 9, 10, 8, 9, 8. What is the average WBC count per HPF?
Safety and Professional Standards
8. Which of the following personal protective measures is required when processing urine samples in a veterinary laboratory?
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