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Urolithiasis in Cats

Abby’s Story and Urolithiasis in Cats

“Abby” was an affectionate big, long-haired Tabby cat. She had been brought into the surgery as she had been passing small pools of urine throughout the house and she had also been back and forth trying to pass urine in her usual litter tray. 

Abby was otherwise bright, active, and eating well, but she clearly had a urinary tract problem, which was further investigated.  

Urine samples were obtained using a clever, non-absorbent, cat litter tray sand and these were sent away for full examination including a microscopy examination of his urine. The results showed that Abby had a lot of crystals developing within her urine which were likely to be causing her recent symptoms. Her condition was termed Urolithiasis. 

Urolithiasis is a medical term referring to the presence of crystals or stones formed within the urinary tract.  

Feline urine is a complex solution in which salts, such as Struvite (magnesium ammonium phosphate) and calcium oxalate, can remain in solution under conditions of supersaturation. Their urine however does tend to form crystals from these dissolved salts. When these fine crystals clump together uroliths form. Uroliths are composed primarily of highly organized crystalloids and a small amount of organic material. They are identified based on their mineral composition: struvite and calcium oxalate and are the two most common feline uroliths. Struvite uroliths accounts for approximately 65% of uroliths causing this problem, and calcium oxalate uroliths account for about 20%. 

Uroliths are mostly found within the urinary Bladder or within the urethra (the passage from the Bladder to outside the body), but they may also be located within the kidneys and ureters (the passageways from each Kidney to the Bladder).  

Many animals do not display any signs or symptoms of the disease. However, some cases will have difficulty in passing urine and have more frequent urination. Blood in often seen within the urine, and affected cats can be vocal, agitated and unsettled and have an increased thirst. Symptoms depend on their size and number and on where they are located within the urinary tract. These uroliths can potentially irritate the bladder wall and can potentially cause an obstruction. Male cats are at a greater risk due to their narrower urethra and a cat who cannot urinate requires immediate veterinary attention. 

The median age for Struvite urolithiasis is around seven years old and it is more common in female animals than in males. It is thought that the uroliths can develop following recurrent urinary tract infections, along with a build-up of materials such as tissue, blood, and mucous plugs. Struvite Urolithiasis may affect as many as 25% of cats with a history of lower urinary tract disease. 

Older male cats (8–12 years) are most affected by calcium oxalate uroliths. Many older cats with a history of kidney disease can also have calcium oxalate uroliths. Dissolving and prevention of these uroliths can be much more difficult and recurrence of calcium oxalate uroliths in cats is a potential and concerning problem. 

To diagnose Urolithiasis urine samples are examined microscopically for any abnormalities. It is important that the main type of urolith is correctly diagnosed, so that the problem can be treated appropriately. It is also important to check the urine pH, and to also check a urine culture for any concurrent urinary infection. Ultrasound scans and X-rays can be used to determine the size, shape, and location of any stones for treatment options, and other underlying medical conditions, for example Kidney disease and Diabetes, can also be checked for. 

Depending on the size and type, some forms of uroliths can be dissolved or flushed out, while other forms such as calcium oxalate uroliths may have to be removed surgically. Urinary support supplements and antibiotics are also often prescribed to prevent infection. 

If Urolithiasis is diagnosed, sometimes, depending on the type of uroliths found, advised prescription diets and dietary management can be effective at adjusting the urine pH and dissolving and preventing some types of urolith formation. If this is the case all other cat treats and human food snacks should be avoided. Using such a “dissolution” diet uroliths may take anywhere from two weeks to five months to completely dissolve. However, some calcium oxalate uroliths cannot be dissolved and these will often have to be removed surgically. 

Thankfully, Abby was found to have Struvite urolithiasis, which responded well to an advised prescription dissolution diet regime. With regular urine checks Abby was managed very well and she was a lot more comfortable and had no further “accidents” in the house, which her owners were delighted about! 


Alison Laurie-Chalmers 

Senior Consultant 

Crown Vets 

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