Proteinuria in Cats
Proteinuria is defined as the presence of excess protein in the urine. Cats can normally have a trace amount of protein in their urine. This represents small protein particles, those tiny enough to pass through the pores of the glomeruli (the kidney’s microscopic filtration units). The glomeruli prevent albumin and other larger protein particles from entering the urine.
The discovery of excessive protein in a cat’s urine warrants investigation to identify the underlying cause. The earlier the cause of the proteinuria is treated, the greater the likelihood of a positive outcome.
Causes of proteinuria in cats
Potential sources of excessive protein within the urine include all of the different structures within the urinary tract. The protein can also originate from portions of the reproductive tract that are anatomically connected to the urinary tract (prostate gland, uterus and vagina). Sampling the urine directly from the urinary bladder with a needle (cystocentesis) can help reduce contamination as the urine passes out of the body.
The most common causes of proteinuria include:
- Inflammation such as that caused by feline interstitial cystitis, stones, polyps or tumors
- Glomerular disease
- Too much protein within the bloodstream (hemoglobin, globulin, myoglobin, immunoglobulin) resulting in excess protein filtered into the urine
Symptoms of proteinuria in cats
In and of itself, proteinuria does not cause any symptoms. When symptoms do arise, they are typically as a result of the underlying cause of this disorder. For example, when proteinuria is caused by a cystitis (inflammation of the bladder wall), symptoms commonly include:
Increased frequency of urination
Straining to urinate/inability to urinate
Blood within the urine
Proteinuria caused by glomerular disease is often associated with chronic kidney disease. The following symptoms may be observed when chronic kidney disease is advanced:
Diagnosis of proteinuria in cats
The first step is documentation of proteinuria. This begins with the urinalysis. On appropriate urine samples, the amount of protein lost will be measured using a combination of the tests recommended by your veterinarian.
When honing in on the underlying cause of the proteinuria, in addition to a thorough physical examination, diagnostic steps may include:
- Complete blood cell count (CBC)
- Blood chemistry profile
- Urine culture
- Abdominal ultrasound
- Blood pressure measurement
- Infectious disease testing
A clear-cut diagnosis of glomerular disease requires a kidney biopsy. This can be accomplished via surgery, laparoscopy, or with ultrasound guidance. Whichever method is used, collection of a kidney biopsy has the potential to cause significant complications. Thoughtful discussion with a veterinarian about risks and benefits should always precede a kidney biopsy. Click here to learn more about glomerular disease.