Kidney and Bladder Stones (Uroliths) in Cats

Key Takeaways

Urinary tract stones (uroliths) are clusters of minerals excreted in urine. They may be localized to any region of the tract, including the bladder and kidneys.

• Stones form as a result of variations in the chemical composition of the urine

• Uroliths vary in size and mineral composition and occur throughout the urinary tract

• Small stones often pass without complication

• Larger stones are more likely to cause a life-threatening urinary blockage

• Diagnostics include physical examination, diagnostic imaging, and urinalysis

• Surgery or flushing of the urinary tract are performed to remove stones when necessary

• Dietary modification is sometimes successful for dissolving particular types of stones

• Uroliths are often a chronic, recurrent problem, but the prognosis is good as long as there is no urinary obstruction

• Nutritional therapy is critical for preventing stone recurrence

A Closer Look: What are Uroliths in Cats?

Up to one quarter of cats suffering from lower urinary tract disease are also affected by uroliths.  Urinary tract stones do not always constitute an emergency or even require treatment. Small stones may resolve on their own, expelled in the animal's urine. If small urinary stones are noted in the urine, prompt veterinary care is recommended to begin a treatment plan before an emergency occurs. 

Bloody urine may occur intermittently or consistently.  It may be more pronounced at the beginning or end of the stream. A pet may exhibit significant straining and discomfort, then suddenly recover if a stone passes. 

It is sometimes difficult to distinguish the symptoms of a urinary tract infection or urinary stones from a urinary obstruction. A urinary obstruction is a life threatening emergency requiring immediate veterinary attention.

Risk Factors

Uroliths often form and pass without any symptoms. If the stone is large enough, it can cause a blockage. Urinary blockage is an emergency, and immediate medical attention is warranted. The main symptom of a urinary blockage is unproductive straining to urinate, usually accompanied by distress. Cats with a urinary obstruction typically spend a lot of time in the litter box, straining and vocalizing, but producing little to no urine.  

Urolithiasis is less problematic for female cats than male cats because they are less likely to experience a urinary obstruction.  Males have a longer, narrower, and more tortuous urethra that is more likely to collect stones and crystals.

Possible Causes

Some cases of urolithiasis have no identifiable cause. Stones more commonly form as a result of alterations to the chemical make-up of the urine. Minerals that are normally dissolved in the urine fall out of solution, primarily in response to changes in the pH. Even though the minerals are initially microscopic, they can aggregate and form much larger crystals and stones. 

The chemical composition of urine is heavily influenced by diet and bacterial urinary tract infections. Most stones form in response to dietary influence or bacterial urinary tract infections. Female cats are less prone to urinary obstruction as their urethra is shorter, straighter, and wider in comparison to males.

Main Symptoms

Main symptoms of uroliths:

• Often asymptomatic • Blood in urine • Frequent urination, often in tiny amounts

• Urination outside of the litter box • Straining to urinate, which may or may not be productive 

• Vocalizing during urination

Testing and Diagnosis

Cats presenting with symptoms of uroliths will typically undergo the following tests:

• Physical examination  • Urinalysis • Urine culture • Diagnostic imaging • Stone analysis

Steps to Recovery

Urolithiasis does not always require treatment. Treatment varies depending on the chemical composition, location, and size of the stone(s).

Options include: 

• Flushing the lower urinary tract to remove stones • Surgical removal of stones • Pain medication

• Antibiotics for stones caused by a bacterial UTI • Dietary modification

Some stones can be dissolved with dietary therapy and antibiotics.  Extracorporeal shock wave lithotripsy (ESWL), which is commonly used in people to blast kidney stones into smaller pieces, is not typically performed in cats.

In the majority of cases, the prognosis for uroliths is generally very good. Frequent monitoring and ongoing therapy are  necessary as it is often a recurring condition.

Prevention

A healthy and balanced diet plays a central role in preventing the formation of urinary tract stones. Specialized, prescription diets are available to prevent certain types of uroliths, depending on the type of stone the cat is predisposed to. 

Increasing water consumption is helpful for lowering the risk of urinary tract stone formation. Frequently cleaning and refreshing the cat's water bowl increases the chances of adequate water consumption. Preventing frequent urinary tract infections is another important preventive strategy.

Are Uroliths Common in Cats?

Up to one quarter of cats suffering from lower urinary tract disease are also affected by uroliths.

Typical Treatment

• Benign neglect • Dietary changes • Surgery  • Urinary tract flushing (retrohydropropulsion) • Antibiotics  

• Pain medication

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