Urinary Tract Stones in Cats

Kidney stones are always made up of calcium oxide minerals, whereas bladder stones can be composed of calcium oxide, struvite (magnesium-ammonium-phosphate), ammonium urate, cystine, or a compound of these.  The stones are formed when the body is overwhelmed with too many natural minerals for the urinary tract to process, leading to the development of crystals.

Urinary tract stones are clusters of mineral crystals that form anywhere in the kidneys, ureters (tubes from kidneys), bladder or urethra. Depending on the size of the stones, the condition can be life-threatening. They can vary in size from as small as a grain of sand to as large as a chunk of gravel. Male cats are more prone to life-threatening complications with urinary tract stones, referred to as complete blockages, due to their narrower urethra. Either one large single stone or many stones of different sizes can develop.

Bladder stones will exhibit more symptoms than kidney stones even if the stones are small. Kidney stones may not exhibit any symptoms until stones are quite large. Symptoms are as follows:

• Blood in urine
• Inappropriate urination (outside litter box)
• Frequent urination
• Dysuria (straining to urinate)
• Painful urination
• Unable to urinate
• Genital licking
• Crying

If the cat is unable to urinate, immediately take it to an animal hospital. The bladder could rupture, leading to a potentially lethal situation.

There are many different potential causes for the development of urinary tract stones. These issues are found far more often in domestic cats than in feral cats. The potential causes are:

• Genetic predisposition
• Dry food
• High carb diet
• Stress
• Sedentary lifestyle
• Disease or inflammation of the kidneys or bladder
• Abnormalities in diet
• Not enough water
• Not enough urination
• pH of the urine

Because most of these symptoms are present in cases of bladder inflammation without stones as well as when urinary tract stones are present, more information will be needed for your vet to make a proper diagnosis. They may obtain a full medical history on your cat and perform a complete physical examination. In this exam, they will feel the abdominal wall to check for stones or blockages.

Whether a stone has been discovered or not, the vet will need X-rays or an ultrasonic bladder examination (intravenous pyelogram) to find both the location and size of the stones, and to determine the best course of action. An intravenous pyelogram would be used after an X-ray, as some mineral composites do not show up on X-ray images. Dye is then injected through the veins, passing through the kidneys and then coming out as urine so that all stones will become visible on an ultrasound.

Your vet may choose to obtain a urinalysis to see if there is any blood, bacteria or crystals coming out in the urine. The vet may try to determine what type of stone exists, as struvite stones can be both sterile or infected with bacteria. If bacteria is present, additional treatment will be needed.

Depending on the size of stones present and the severity of the symptoms, various treatment methods may be used.

Catheter 

Smaller or soft stones can sometimes be removed by the administration of a catheter. If this is successful then no surgery is required.

Restricted Diet 

In cases where surgery is being avoided, the cat may be placed on an exclusive diet to help stones dissolve on their own. This method is not always successful as trial and error is the only way to know which type of stones are present. It is also a very slow process, taking several weeks or months, in which some patients get worse. Not all cats will eat the diet, as it is less appetizing than regular cat food.

Surgery 

Most often, the stones will be surgically removed in a procedure called a cystotomy. Your cat will be put under anesthetic and incisions will be made into the abdomen to remove the stones. Cats tend to recover from this type of surgery very well, and the risk is generally not substantial.

Antibiotics 

If bacteria is found in the urine, your cat will also be treated with antibiotics to stop any bacterial infections from progressing.

Painkillers 

Because this complication is quite painful for the cat, often your cat will be prescribed a painkiller such as Buprenex or Torbugesic.

It is important to note than in the case of kidney stones, treatment will only be administered if the stones are large enough to be causing significant damage, as kidney surgery is a complicated surgery bearing more risk.

If the cat has undergone surgery, a follow-up appointment will be needed several weeks later to access healing and ensure new stones are not present. If the cat has been on a special diet to dissolve stones, an X-ray or ultrasound will be needed to see if the stones are diminishing in size.

Urinary tract stones will recur if preventative measures are not taken. These measures include both dietary and medical therapies. Encourage your cat to drink lots of water and change it often as fresh water is more appealing to cats. Play with your cat to increase its daily exercise. Consider a diet consisting of no less than 50% wet food. Clean the litter box often to encourage urination. Your vet may recommend that periodic X-rays or ultrasounds be given to your cat to detect any new stone development early on.