Cat Kidney Stones

"Cat kidney stones (called Nephrolithiasis, kidney calculi or renal calculi) is the accumulation of different minerals in parts of the kidney, including the cortex, medulla or pelvis. The actual cause of feline kidney stones is not fully known, but it may occur more commonly in breeds like Balinese, Burmese, and Persian cats. Obstructions in the urinary tract, hematuria (blood in cat urine), dysuria (difficulty urinating) and severe hind abdominal pain are signs associated with kidney stones. Diagnosis is based upon examination of x-rays, while clinical manifestations on the other hand can only help to indicate, not confirm the presence of stones. Treatment in mild cases can effectively be completed with the use of drug and dietary therapies. Surgical removal of kidney stones and/or the whole kidney may be required in severe cases."

Different Types of Cat Kidney Stones:

Calcium Oxalates, Magnesium Ammonium Phosphate and Urate are the three most common types of cat kidney stones. Until now, it was considered that in cats, kidney stones or calculi usually did not occur in a hard form. They were thought to be  small and sand like, with a consistency similar to a gel or a tooth paste. Recent research studies have proven that calcium oxalates are the most common type of feline kidney stone. These types of stones are not only hard, but are also small at approximately 3mm in size. 

 Calcium oxalates are more frequent in those cats which are  excessively fed a  urine - acidifying diet or those diets which contain reduced levels of magnesium it Adequate magnesium in cat food is good for reducing the chance of calcium oxalates formation in a cat's kidney, as it inhibits its (calcium oxalates) formation.

On the other hand, in case of stones comprised of magnesium ammonium phosphates, it may occur in cats depending on the form of magnesium delivered in the diet. There is less possibility that a cat may suffer magnesium ammonium phosphates stones, due to magnesium in the food. However, supplementation with magnesium may cause it.

Magnesium Ammonium Phosphates and Urates on the other hand are suspected in those cats with a sort of defect in the re–absorptive mechanism of the kidney. It is more susceptible in aged cats and cats with more fatty contents in their body that has accumulated within the cavities and organs.

Signs and Symptoms of Cat Kidney Stones:

Cat kidney stones is suspected in cats with signs of hematuria (cat blood in Urine), Dysuria (Difficult Urination), and obstruction in the urethra. Feline kidney stones can pass into the lower urinary tract and may causean  obstruction and  “Feline Lower Urinary Tract Disease” (FLUTD);  FLUTD can be characterized by hematuria, dysuria and mainly a reduced volumes of urine being passed frequently.

Abdominal pain can occur if the kidney stone is large enough to cause injury and obstruction, thus also causing an intractable secondary bacterial infection. Cats with kidney stones and who show symptoms of abdominal pain  should be screened for bacterial infection.

Diagnosis of Cat Kidney Stones:

If a cat is thought to have renal calculi, a diagnosis can be made on the basis of the clinical signs and symptoms.  Laboratory procedures such as urinalysis, urine culture and x-rays should be done, as this will not only confirm the type of cat kidney stone but these procedures will also help in differentiating a problem caused by stones with other common cat urinary tract problems such as  urinary tract infection or a neoplasm (tumor or cancerous growth).

Radiography, cystoscopy and/or ultrasounds may help in identifying the type of cat kidney stones, and will help in deciding an option for treatment.

Treatment of Cat Kidney Stones:

In most cases Calcium Oxalate stones can only be treated surgically. In cats with small sized oxalate stones, where calculi are identified, they can be effectively treated with adjusting the cat’s diet. Increasing the magnesium content in the food and by making cats drink more water before and after meals can assist with dissolving oxalate stones.

In chronic forms, calcium oxalate stones can only be treated with detailed surgical clearance of the kidney, or by a complete nephrectomy or removal of the kidney. Prevention can be handled by using special commercial diets for inhibition on a regular basis; which contain low amounts of minerals, vitamin C and vitamin D

Ammonium Magnesium Phosphates on the other hand can only be treated surgically; removal of the kidney is the most effective way in most cases. Dietary adjustments can help but are not therapeutically effective.

Cats with kidney stones should be allowed to drink and supplied with a lot of water, anytime, anywhere. These cats must not be forced to follow training commands, especially those regarding Litter Box Training.

Determination of stone type is essential for either feline kidney stone type.

Any of canned diet with chicken (avoid seafood since this type has more minerals) in preferred for cat's with stones. Canned foods contain more water.

There is a homeopathic remedy available that is designed to promote kidney health in cats.  The product, Kidney Support , promotes kidney and urinary tract health by combining ingredients associated with this outcome such as Burdock (for normal body fluid levels), dandelion (fluid levels), and Cleaver (urinary tract support).  Click on the link above for more information and related clinical studies.


The Merck/Merial Manual for Pet Health