A complete urinalysis integrates three components — urine specific gravity (USG), dipstick chemistry, and sediment examination — and each must be interpreted in the context of the others and the patient's clinical presentation. Veterinary Clin…
Urine Specific Gravity
USG is measured by refractometer at room temperature before centrifugation, unless the sample is discolored or turbid, in which case testing on the supernatant is preferable to avoid interference. MSD Vet Manuals In chinchillas, USG measured by refractometer before centrifugation does not differ significantly from post-centrifugation values, so pre-centrifugation measurement is acceptable in that species; USG ranges from 1.014 to >1.060 in clinically normal chinchillas, with 41% of samples at ≥1.050. Journal of the… For dogs and cats, USG is a critical modifier of dipstick protein results — a positive dipstick protein finding in dilute urine carries different clinical weight than the same result in concentrated urine, because USG directly influences the apparent protein concentration. Veterinary Clin…+1
Dipstick Chemistry
Dipstick results are semiquantitative and colorimetric, making them vulnerable to interference from sample color, turbidity, and temperature. Discolored or turbid samples can render reagent strips unreadable, as seen with dark red hemoglobinuric urine where pH, glucose, ketones, and urobilinogen strips become uninterpretable due to color interference. Journal of the…+1 Performing dipstick analysis on supernatant after centrifugation mitigates this problem. MSD Vet Manuals
For protein, dipstick results cannot be used alone to predict the urine protein-to-creatinine ratio (UPCR). Within any given dipstick protein category, USG does not allow accurate prediction of UPCR in dogs. Journal of Vete… A calculated dipstick urine protein-to-USG ratio (DUR) improves on raw dipstick protein alone: in dogs, a DUR cutoff of 1.4 detects a UPCR >0.5 with sensitivity 89%, specificity 83%, positive predictive value 96%, and negative predictive value 63%; in cats, a DUR cutoff of 2.1 detects a UPCR >0.4 with sensitivity 70%, specificity 100%, positive predictive value 100%, and negative predictive value 75%. Journal of Vete… Because the negative predictive value is poor in both species, DUR cannot be used to exclude proteinuria — a negative or low DUR does not rule out a clinically significant UPCR. Journal of Vete… Dipstick protein principally detects albumin, while UPCR also captures immunoglobulins and other inflammation-associated proteins; macroscopic hematuria can elevate UPCR up to 0.3 even without true glomerular proteinuria. Journal of Vete…
For leukocyte esterase, dipstick has high specificity (93.2%) but low sensitivity (46%) for pyuria in dogs, meaning a positive result is meaningful but a negative result does not exclude urinary tract infection or inflammation. Journal of Vete… Leukocyte esterase dipstick has little or no diagnostic value in dogs and cats as a standalone test, and limiting sediment examination to cases with a positive leukocyte dipstick will miss urogenital inflammatory conditions. Journal of Smal…
Bilirubin at 3+ (100 μmol/L) on dipstick, combined with hemoglobinuria confirmed by ammonium sulfate precipitation, points toward hemolytic disease — in the ammonium sulfate test, hemoglobin separates from the fluid leaving the supernatant clear, whereas myoglobin produces uniform dark coloration throughout the sample. Journal of the…
In chinchillas, dipstick protein is unreliable — protein is detected on dipstick in 100% of normal chinchilla samples, yet the sulfosalicylic acid precipitation test is negative in all of those same samples, and quantitative protein results do not correlate with dipstick results. Protein concentration in chinchillas must be determined by quantitative protein analysis. Journal of the… Similarly, chinchilla urine pH is consistently at 8.5, which is the upper detection limit of standard reagent strips, so pH cannot be meaningfully graded above that threshold. Journal of the…
Sediment Examination
Sediment examination is the most technically demanding component of urinalysis and is associated with high interobserver variability, including in veterinary practice, due to limited training in formed-element identification and microscope technique. Journal of Vete… Approximately 20% of clinicians who perform in-house urinalysis do not always include sediment examination, most commonly reserving it for cases with positive dipstick protein, white blood cells, or red blood cells — an approach that will miss crystals, casts, and urogenital inflammation in a subset of patients. Journal of Smal…
An active sediment (pyuria, hematuria, bacteriuria) directly affects interpretation of proteinuria. Urinary tract infection elevates UPCR, and UPCR should be repeated after infection resolution before attributing proteinuria to renal disease. Journal of Vete… Urinalysis alone — including sediment — should not be used to exclude bacteriuria; in dogs with chronic kidney disease, 11% of culture-positive cases showed neither a positive leukocyte esterase test nor microorganisms on sediment examination. Journal of Vete… Microorganisms visible on sediment examination are significantly associated with a positive urine culture in dogs. Journal of Vete…
Crystals and casts are only detectable by sediment examination and cannot be identified by dipstick or USG alone — omitting sediment examination eliminates the ability to recognize these indicators of disease. Journal of Smal… In clinically normal chinchillas, 68% of urine samples contain crystals, with 27 of 28 crystal-containing samples showing amorphous crystals, so crystal presence alone is not pathological in that species. Journal of the…
| Component | Key Cutoff or Finding | Performance / Significance | Critical Caveat |
|---|---|---|---|
| USG (refractometer) | Chinchilla normal: 1.014–>1.060; 41% ≥1.050 | Modifies dipstick protein interpretation in all species | Must be at room temperature; use supernatant if sample discolored MSD Vet Manuals+1 |
| Dipstick protein (DUR, dogs) | DUR 1.4 for UPCR >0.5 | Sensitivity 89%, specificity 83%, PPV 96%, NPV 63% | Cannot exclude proteinuria (poor NPV) Journal of Vete… |
| Dipstick protein (DUR, cats) | DUR 2.1 for UPCR >0.4 | Sensitivity 70%, specificity 100%, PPV 100%, NPV 75% | Cannot exclude proteinuria (poor NPV) Journal of Vete… |
| Leukocyte esterase (dogs) | Positive result | Specificity 93.2%, sensitivity 46% for pyuria | Negative result does not exclude UTI or inflammation Journal of Vete… |
| Dipstick protein (chinchillas) | Any positive result | Not clinically meaningful — 100% of normal samples positive | Use quantitative protein analysis only Journal of the… |
| Ammonium sulfate precipitation | Clear supernatant = hemoglobin; uniform dark = myoglobin | Differentiates hemoglobinuria from myoglobinuria | Required when dipstick blood is positive and source is uncertain Journal of the… |
| Sediment examination | Crystals, casts, bacteria, cells | Only method to detect crystals and casts | High interobserver variability; should not be omitted based on dipstick alone Journal of Vete…+1 |
Would you like guidance on when to proceed from an abnormal urinalysis to a urine protein-to-creatinine ratio versus urine culture as the next diagnostic step?