The kidneys are two bean-shaped organs located near the spine in the abdomen. They are made up of tiny filtering units called nephrons. The kidneys perform many functions including filtering the blood, removing waste products, which are excreted out of the body via the urine.
Also known as nephroliths, kidney stones are fairly uncommon in cats. They are rock-like formations which accumulate in the kidneys. There are different types of kidney stone and can be made up of struvite, calcium oxalate, urate, bile pigment and calcium phosphate. The most common type of kidney stone is calcium oxalate.
There are several causes of kidney stones including dietary factors, urine retention (holding on too long to urinate), recurring urinary tract infections, certain medications, and genetics.
What are the symptoms of kidney stones in cats?
Cats with small stones may display no symptoms at all. Problems occur when stones pass from the kidney into the ureter, forming a partial or full blockage as they get stuck in the ureter. Symptoms are often associated with difficulty to urinate and may include:
Enlarged kidneys due to fluid backing up in the kidneys
This is a medical emergency, a blockage can cause irreversible damage to the kidneys, along with a build up of toxins in the bloodstream causing uremia. Veterinary attention should be sought urgently if your cat is displaying any of the above symptoms.
How are kidney stones diagnosed?
Your veterinarian will perform a physical examination, which may reveal swollen and/or tender kidneys. He will obtain a medical history from you including any symptoms you have noticed. He will need to run some diagnostic tests which may include:
Ultrasound or x-rays, which may reveal the presence of kidney stones.
Complete blood count.
Urinalysis to check kidney function, it may also reveal blood in the urine, bacteria and the presence of small kidney stones.
Analysis of the stones if a stone is passed.
How are kidney stones treated?
Treatment depends on the type of stones present, and if your cat is displaying symptoms. In some cases, there may be no treatment. However, where treatment is necessary, it may include:
Medication or diet to dissolve the stones.
Severe cases will require surgery to remove the stones.
Extracorporeal shock wave lithotripsy (ESWL) is a technique using sound waves to break up the stones. This will need to be done at a specialist centre.
Increasing your cat’s water consumption so the urine is less concentrated.
Ensure your cat always has access to a clean litter tray so that he doesn’t hold onto urine for too long.
If your cat has become blocked he will need to be catheterised. Uremia is life threatening and your cat will need to be stabilised with IV fluids to treat fluid and electrolyte imbalances. Painkillers may be prescribed.
Cats will need to return to their veterinarian regularly for monitoring as kidney stones often will return. The test will include X-rays, urinalysis, and blood work. You may also be required to regularly monitor your cat’s urine pH and specific gravity (concentration).