The Relationship Between Cancer and Proteinuria

Several causes of proteinuria are documented in canine patients, including neoplasia. Specifically, studies have identified increased prevalence of proteinuria in dogs with lymphoma, mammary carcinoma, and osteosarcoma.

In a recent study presented in the Journal of Small Animal Practice, clinical oncologists at the University of Georgia (UGA) College of Veterinary Medicine examined the prevalence, severity, and contributing factors of proteinuria in canine oncology patients during initial evaluation.

Methods

Client-owned dogs with neoplasia that were referred to the UGA Oncology Service were included in the study. Patients were excluded from enrollment if they had lower urinary tract neoplasia or if cystocentesis could not be performed.

The following data were recorded for each patient:

• Signalment
• Body weight
• Clinical history (including administered medications)
• Date of cancer diagnosis
• Type and location of cancer
• Previous cancer treatments performed at other clinics

Initial evaluation included a physical examination, systolic blood pressure measurement, and blood collection. A single urine sample was also collected via cystocentesis for urinalysis, measurement of urine protein: creatinine (UPC) magnitude, and aerobic urine culture for proteinuric patients or those with suspected urinary tract infection. UPC levels were classified as nonproteinuric (< 0.2), borderline proteinuria (0.2—0.49), or overt proteinuria (≥ 0.5) based on International Renal Interest Society guidelines.

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Results

Thirty-one male and 29 female dogs representing 24 pure breeds and several mixed breeds were assessed in the study. Median age and weight at presentation were 9 years and 24.5 kg, respectively.

The most commonly diagnosed neoplasia types were cutaneous mast cell tumor (25%), lymphoma (13%), squamous cell carcinoma (10%), and soft tissue sarcoma (8%). Seventeen dogs had received previous surgical treatment for neoplasia, while 8 dogs had been treated with chemotherapy.

Just over half of the dogs were either borderline (37%) or overtly (15%) proteinuric. Median UPC of all dogs measured at the cutoff value of 0.2. Two nonproteinuric dogs were diagnosed with lower urinary tract infection based on aerobic urine culture results, whereas urine cultures from 10 borderline or overtly proteinuric dogs were all negative for bacterial growth.

Hypertension was diagnosed in 18 dogs, 12 of which were either borderline or overtly proteinuric. None of the examined dogs were azotemic. When the authors examined possible associations between proteinuria and medication administration, they found that 5 of 8 dogs receiving corticosteroids (namely prednisone) were borderline or overtly proteinemic.

Clinical Impact

Over half of dogs with cancer were found to be proteinuric at initial presentation to the UGA Oncology Service. Most cases were borderline, suggesting that proteinuria in canine cancer patients is typically mild and does not require immediate intervention. However, many proteinuric patients were also hypertensive and/or receiving corticosteroids, which are both documented risk factors for proteinuria. The authors stressed that “diagnosis of proteinuria should prompt further testing to help identify potential underlying conditions,” including neoplasia, hypertension, and side effects from corticosteroid treatment.

Dr. Stilwell received her DVM from Auburn University, followed by a MS in fisheries and aquatic sciences and a PhD in veterinary medical sciences from the University of Florida. She provides freelance medical writing and aquatic veterinary consulting services through her business, Seastar Communications and Consulting.