When evaluating the significance of proteinuria, it is important to review the urine sediment. This is a crucial part of a complete urinalysis and is required for proper interpretation of other variables. Presence of hemorrhage1 or inflammation2 (infectious or noninfectious) in the sample can confound the ability to identify whether presence of protein is due to glomerular leakage or poor tubular reabsorption rather than an active sediment. In this situation, the cause of hematuria and/or pyuria must be identified and addressed, then proteinuria reassessed. If proteinuria persists in the absence of these confounders, it can be assumed that the protein is present due to kidney disease.
In addition, proteinuria must be interpreted in the context of urine specific gravity.2 Although a 1+ dipstick reaction might not be concerning in a well concentrated sample, the same reaction in dilute urine should be taken seriously and further evaluated. Other prerenal causes of mild proteinuria (eg, fever, strenuous exercise) must also be considered.
The results of this study suggest that proteinuria occurs frequently in dogs with cancer, although the clinical significance in most cases may be minimal. Establishing baseline protein loss at cancer diagnosis, with subsequent monitoring for progression during therapy, may be warranted to ensure worsening kidney disease does not impact patient quality of life or management of underlying neoplasia. Other biomarkers of kidney disease should also be taken into consideration.