Protein-Losing Nephropathy

What Is Protein-Losing Nephropathy?

Protein-losing nephropathy (PLN) is a kidney problem in which the tiny filters of the kidney, called glomeruli, become damaged and let protein, mainly albumin, leak into the urine. Healthy kidneys keep almost all protein in the blood. Ongoing protein loss harms the kidneys further and can lead to low blood protein, fluid buildup, high blood pressure, and blood clots.

PLN is a syndrome rather than a single disease. Common triggers include long-running infections such as Lyme disease, ehrlichiosis, and heartworm; cancer; chronic inflammation; and amyloidosis. Inherited forms are recognized in Soft-Coated Wheaten Terriers and are also seen in breeds such as Bernese Mountain Dogs, Labrador and Golden Retrievers, English Cocker Spaniels, and Samoyeds. It is less common in cats.

Signs Owners Notice

• Often none at first; protein in the urine is found on routine tests
• Weight loss and muscle wasting, especially along the back and hips
• Drinking and urinating more as kidney function declines
• A swollen belly or puffy legs from fluid when blood protein drops very low
• Sudden trouble breathing or back-leg weakness from a blood clot
• Sudden blindness from very high blood pressure

Diagnosis

Your vet will check a urinalysis and a urine protein-to-creatinine (UPC) ratio, which measures how much protein is being lost. A UPC that stays high on repeat tests, after ruling out a urinary infection or blood in the urine, points to glomerular disease. Bloodwork shows albumin levels and kidney function, and blood pressure is measured. Tests for tick-borne disease and heartworm, imaging, and sometimes a kidney biopsy help find the cause.

PLN is different from protein-losing enteropathy, where protein is lost through the gut rather than the urine. Both can cause low albumin, so your vet checks the urine and the intestines to tell them apart. Advanced PLN can progress to the signs described in dog kidney failure symptoms.

Treatment and Outlook

• Reduce protein loss: medicines such as ACE inhibitors or angiotensin receptor blockers lower pressure inside the kidney filters.
• Kidney diet: a prescription diet with controlled, high-quality protein and added omega-3 fatty acids.
• Blood pressure control: extra medicine if blood pressure remains high.
• Clot prevention: low-dose antiplatelet medicine to reduce the risk of dangerous blood clots.
• Treat the cause: clearing infections, managing cancer, or, in selected cases, immune-suppressing medicine after a biopsy.

The outlook varies widely. Dogs found early, with normal kidney values and a protein level that drops on treatment, can live comfortably for years. Dogs diagnosed with advanced kidney failure, very low albumin, or blood clots have a more guarded prognosis. Regular UPC and blood pressure rechecks guide treatment.

Practical Tips for US Pet Owners

• Ask for a yearly urinalysis, and a UPC if protein shows up, from middle age onward.
• Wheaten Terrier owners can ask breeders about DNA testing for a gene variant linked to PLN.
• Use tick control and heartworm prevention year-round to lower infection-related risk.
• Find a nearby practice through veterinary clinic listings.

Key Takeaways

• PLN means damaged kidney filters are leaking protein into the urine.
• Infections, cancer, inflammation, amyloidosis, and genetics can all cause it.
• Early UPC testing and medicine to cut protein loss give the best long-term results.

FAQ

Is protein in my dog’s urine always PLN?
No. A urinary infection, blood in the urine, or a concentrated sample can raise protein. Your vet repeats the test after ruling those out.

Should I feed a very low-protein diet?
Not without guidance. Prescription kidney diets control protein while still meeting your dog’s needs.

Can cats get PLN?
Yes, but it is less common than in dogs. Most kidney disease in cats starts in other parts of the kidney.