Understanding Urinalysis: Guidelines for Accurate Diagnosis and Effective Monitoring in Pets

Urinalysis is a standard laboratory test that provides information regarding the pet’s urinary-renal system. It is performed to evaluate any conditions related to the pet’s urinary tract, assess animals with systemic illnesses, or monitor an animal’s response to a treatment. Urinalysis can be easily conducted but the results must be interpreted differently.This article will serve as a guideline for veterinary professionals in performing urinalysis. 

Indications:

• Evaluation of urinary tract conditions (e.g., UTIs)
• Assessment of systemic illnesses (e.g., diabetes, liver disease).
• Monitoring the response to treatments or medications.

Purpose:

• To detect abnormalities in urine composition, which may indicate underlying health issues. 
• To aid in the diagnosis and management of urinary and systemic diseases.
• To monitor the effectiveness of treatments and track disease progression.

Urine Sample Collection & Management 

Method of Collection:

Urine collection methods vary in contamination risk. Collecting off the floor is the least ideal, often leading to high contamination. Free catch, especially midstream, reduces contamination but can still include bacteria from the urinary or genital tract. Catheterization is more controlled and sterile, but cystocentesis is the most ideal, minimising contamination for the most reliable sample.

Appropriate Time for Urine Collection:

Timing is crucial for accurate results. Collect urine in the morning or after fasting for a concentrated sample. Examine the sample within 30 minutes or refrigerate it for up to 24 hours, returning it to room temperature before testing. Avoid adding preservatives.

Handling and Interpretation Considerations:

Use a sterile container for urine collection, preferably via cystocentesis, catheterization, or voiding. Record the collection method, as it affects result interpretation. Improper storage can lead to crystal formation, potentially skewing results, so careful documentation and handling are essential

In-House Analysis vs. External Lab Analysis

In-House Analysis: 

Common test: 

• Routine Urinalysis (color, pH, specific gravity, protein, glucose)
• Complete Blood Count (CBC)
• Basic Chemistry Panels (electrolytes, glucose, kidney function markers)
• Fecal Analysis (parasites, bacteria)

Pros: Immediate results, convenient for rapid diagnostics, and can be more cost-effective for routine tests.

Cons: May have limitations in terms of test variety and accuracy compared to specialised external labs.

External Lab Analysis: 

Common test: 

• Advanced Biochemical Tests (detailed metabolic profiles)
• Specialised Hormone Assays
• Genetic Testing (genetic disorders, predispositions)
• Advanced Microbiological Testing (culture and sensitivity)
• Toxicology Screening (drugs, toxins)
• Complex Histopathology (cancer, detailed tissue examination)

Pros: Often offers more advanced testing and higher accuracy, especially for complex or rare conditions.

Cons: May involve longer turnaround times and higher costs.

Reasons for Sending Samples:

Complex Testing:

Complex testing often requires specialized equipment and expertise not available in-house. For detailed biochemical profiles, genetic analysis, or advanced toxicology screening, samples are sent to external labs, ensuring access to advanced diagnostic tools and providing deeper insights than routine evaluations.

Specialized Analysis:

Specialized tests, such as hormone assays, advanced microbiological testing, or in-depth histopathology, are sent to external labs for detailed analysis or validation. These labs offer higher precision, especially for complex or rare conditions, ensuring accurate and comprehensive results.

Quality Control:

Quality control is vital for accurate diagnostics. Sending samples to external labs for confirmation or higher accuracy ensures consistent, trustworthy results. This is crucial when initial in-house findings need validation or when the highest level of diagnostic certainty is required.

Urinalysis involves 3 type of analysis:

Physical analysis 

Physical analysis of urine samples involve direct observation of the sample visual characteristics, such as volume, colour, or odour. This provides valuable information, including the pets hydration status or presence of potential diseases.  

Chemical analysis

Chemical analysis of urine is often performed using chemical reagent test strips, which are basic diagnostic tools. These strips have multiple pads for testing various parameters such as pH, specific gravity, glucose, and proteins. When exposed to a reagent, the strip pads change  colour to indicate the presence and concentration of substances. To ensure accuracy and reliability, test strips must be stored in a dry, covered compartment, as they are highly reactive and sensitive to moisture.

Sediment Analysis

In this analysis, urine samples are spinned down and analysed under a brightfield microscope to detect the presence of sediments such as blood cells, casts, crystals, and microorganisms. 

Urinalysis Parameters and Interpretation

Physical Analysis:

Volume:

Indicates patient's hydration status and renal concentrating ability. Regular urine volume ranges differs for each pet, for example:

• Cats: 10–20 mL/kg body weight per day
• Dogs: 20–100 mL/kg body weight per day

Increased urine volume is a normal response to increased water consumption or drug effects such as diuretics. However, abnormal increase in urine volume could indicate renal injury, hyperadrenocorticism, or diabetes insipidus. A decrease in urine volume could indicate regular dehydration. However, abnormal decrease in urine volume could also indicate renal injury or urinary obstruction.

Colour:

Reflects the patient’s hydration status. A healthy urine colour would be transparent, yellow, or amber coloured. An abnormal urine colour could indicate the presence of disorders such as dark red/brown (hemoglobinuria, myoglobinuria), yellow-brown (bilirubinuria), or unusual colours (medication effects)

Odour:

Provide clues regarding a patient's health. A healthy urine would be odourless. An abnormal urine odour would be putrid or ammonia odour, indicating sepsis, or acetone, indicating ketosis. 

Transparency:

Indicates hydration status and presence of substances. A healthy sample would be clear, while a cloudy or turbid sample could indicate the presence of cells, crystalks, organisms, or mucus. 

Chemical Analysis:

Sediment Analysis:

Interpretation and Follow-up

Review Results:

• Objective: Compare the urinalysis findings against standard normal ranges.

• Purpose: Identify any abnormalities that could indicate underlying health issues.

Consultation:

• Objective: Discuss the urinalysis results with a healthcare provider.

• Purpose: Determine the next steps, which may include further testing or immediate diagnosis.

Additional Testing:

• Objective: Conduct further diagnostic tests as recommended.

• Purpose: Achieve a definitive diagnosis based on the initial urinalysis findings.

Treatment:

• Objective: Implement the treatment or management plan advised by the healthcare provider.
• Purpose: Address or manage any conditions identified through the urinalysis and subsequent tests.

Further Reading:

1. 1. Barsanti JA, Shotts EB, Crowell WA, Finco DR, Brown J. Effect of Therapy on Susceptibility to Urinary Tract Infection in Male Cats with Indwelling Urethral Catheters. Journal of Veterinary Internal Medicine. 1992;6(2):64–70. doi: 10.1111/j.1939-1676.1992.tb03153.
   2. Erickson HH, Goff JP, Reece WO, Uemura EE. Dukes’ Physiology of Domestic Animals. 13^th ed. Wiley-Blackwell; 2015.
   3. Lekcharoensuk C, Osborne CA, Lulich JP. Epidemiologic study of risk factors for lower urinary tract diseases in cats. Journal of the American Veterinary Medical Association. 2001;218(9):1429–35. doi: 10.2460/javma.2001.218.1429
   4. ‌Mayer-roenne B, Goldstein R, Erb H. Urinary tract infections in cats with hyperthyroidism, diabetes mellitus and chronic kidney disease. Journal of Feline Medicine & Surgery. 2007;9(2):124–32. doi: 10.1016/j.jfms.2006.09.004.
   5. Milani DAQ, Jialal I. Urinalysis. StatPearls Publishing. May 1 2023. Accessed 29 Aug 2024. https://www.ncbi.nlm.nih.gov/books/NBK557685/
   6. Reppas G, Foster SF. Practical urinalysis in the cat. Journal of Feline Medicine and Surgery. 2016 Mar;18(3):190–202. doi: 10.1177/1098612X16631228
   7. Simerville JA, Maxted WC, Pahira JJ. Urinalysis: A Comprehensive Review. American Family Physician. 2005;71(6):1153–62. Accessed 29 Aug 2024. https://www.aafp.org/pubs/afp/issues/2005/0315/p1153.html
   8. ‌‌Yadav SN, Ahmed N, Nath AJ, Mahanta D, Kalita MK. Urinalysis in dog and cat: A review. Vet World. 2020;13(10):2133–41. doi: 10.14202/vetworld.2020.2133-2141.