Kidney Disease Symptoms in Cats

Although many signs of kidney disease are the same as those for any problem with the urinary tract, there may be some differences. Cats with kidney disease may show these symptoms:

  • Increased drinking and urination (polydipsia and polyuria)
  • Urination outside the litter box
  • Decreased or even complete lack of urination
  • Blood in the urine
  • Vomiting
  • Loss of appetite, probably due to nausea
  • Weight loss
  • Pain in the lower back area
  • Sitting hunched or walking stiffly
  • Poor haircoat, partly due to decreased grooming
  • Ulcers in the mouth and/or drooling
  • High blood pressure, possibly with associated retinal damage
  • Anemia


Pyelonephritis is a bacterial infection of the kidney and renal pelvis (the urinary collection system). It usually ascends from an infection in the bladder. Occasionally, it is blood-borne.

Acute pyelonephritis begins with fever, vomiting, and pain in the kidney area (the lower back). A stiff-legged gait and a hunched posture are characteristic signs. The cat's urine is often bloody.

Chronic pyelonephritis is an insidious disease that may or may not be preceded by signs of acute infection. When the disease is of long duration, you will see weight loss and signs of kidney failure. If it is diagnosed before irreversible changes occur in the kidneys (that is, during a regular health checkup), treatment may prevent complications, or at least slow the progression of the disease.

Treatment: The cat's urine should be cultured. Antibiotics that concentrate in the urine will be selected by your veterinarian based on bacterial sensitivity testing. Chronic pyelonephritis should be treated for at least six weeks. Many cats will require dietary adjustments. Most cats will need added fluid therapy-this may be done in the veterinary hospital intravenously or at home with subcutaneous injections.

Nephritis and Nephrosis

Nephritis and nephrosis are a group of diseases of the kidneys that produce scarring and kidney failure. Many cats with these conditions also have high blood pressure and a tendency to develop blood clots. Abdominal ultrasound and a kidney biopsy may be required to make an exact diagnosis.

Nephritis is an inflammation of the kidneys, regardless of cause. Chronic interstitial nephritis is perhaps the most common form, but even this may not be a single disease, but rather, the result of various toxins, drugs, poisons, or viruses. In cats with this condition, the kidneys become small and scarred due to repeated insults.

Glomerulonephritis is an inflammatory disease affecting the filtering mechanism of the kidneys. The disease appears to be related to the cat's immune system, and is found in association with feline leukemia, feline infectious peritonitis, feline progressive polyarthritis, some types of infections, and certain types of cancer. This tends to be a disease of cats in their prime, with the mean age about 4 years old.

Nephrosis refers to kidney diseases accompanied by destruction of the nephrons and loss of functioning kidney cells. In a cat with nephrotic syndrome, protein leaks through the kidney filtering system in large amounts and is lost in the urine. This results in abnormally low serum proteins. Protein in the serum maintains osmotic pressure that keeps fluid from passing out of the bloodstream into the cat's tissues. Because of the low serum protein, fluid accumulates beneath the skin of the legs (edema) and inside the abdomen (ascites). The signs are like those of right-sided heart failure. Laboratory studies will distinguish between these conditions. Hydronephrosis is caused by an obstruction in the ureter (such as a urolith), which causes urine to back up into the kidney, destroying its architecture.

Treatment: Nephritis and nephrosis are not usually recognized until a cat develops signs of kidney failure. Steroids and special diets may be of temporary help.

This article is excerpted from “Cat Owner’s Home Veterinary Handbook” with permission from Wiley Publishing, Inc.

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