The evaluation of a patient's urine is an essential component of a comprehensive health assessment, and a urinalysis (UA) should be included in both wellness examinations and diagnostic workups in dogs and cats. However, sample collection, handling, and processing can all impact findings, and a consistent approach is essential. In addition, practitioners need to be aware of the indications for additional urine-based tests, along with their requirements and limitations.

Sample collection

Urine samples should, whenever possible, be collected prior to any therapeutic interventions, particularly fluids, glucocorticoids, antibiotics, nonsteroidal anti-inflammatories (NSAIDS), or any drug with documented nephrotoxicity. Although a cystocentesis is generally preferred, this should not be performed in patients with evidence of a bleeding disorder (such as bruising, petechiation, or unexplained hemorrhage) until information is available regarding platelet number and/or clotting factor activity. Clinical findings suggestive of lower urinary tract neoplasia are also a relative contraindication for cystocentesis.

Although ultrasound guidance is not required, this should be considered if the history or examination suggest intra-abdominal pathology (e.g., free fluid, abdominal mass, pyometra). A free-catch urine sample is an acceptable option if a cystocentesis is not appropriate. Bacterial contamination may occur, but key information regarding renal function and metabolic status is unaffected. Samples can also be collected via catheterization; this should be performed using an aseptic technique to avoid iatrogenic infection.

If urine is not collected prior to any intervention, there is a tendency to abandon the effort. However, a sample collected a few hours after initiation of fluid or drug therapy can still be very informative. Similarly, ongoing evaluation of urine characteristics, such as specific gravity (USG), the presence or absence of analytes (e.g., glucose, ketones, protein), and findings on sediment examination (e.g., casts, cells, crystals), may be used to guide treatment decisions.