Bladder Stones In Cats

Dogs and cats, like humans, can develop bladder and kidney stones.

Bladder stones are rock-like collections of minerals that form in the urinary bladder. These stones can obstruct the outflow of urine when they block the neck of the bladder or get lodged in the narrow urethra.




Bladder stones may be in the form of a single large stone or multiple small stones. They can rub and damage the lining of the bladder or urethra , causing painful inflammation and bleeding. Cats with bladder stones often strain to urinate and pass out blood in urine.

The 2 most common types of bladder stones are:


  • more likely to develop in alkaline urine
  • made up of magnesium, ammonium and phosphate
  • can be dissolved by prescription diet
  • prescription diet low in magnesium to produce a more acidic (low pH) urine to dissolve the crystals or stones


  • more likely to develop in acidic urine
  • could be caused by excessive intake of calcium, protein, sodium or Vitamin D
  • cannot be dissolved by diet
  • prescription diet to minimise calcium oxalates in urine and produce a more alkaline (high pH) urine

Obstruction of the bladder is a painful condition. Your cat may cry in pain when she strains to urinate or if the abdomen is pressed. 16-year-old Isabelle being prepared for surgery to remove her bladder stones.

How do bladder stones form?

Certain diets or diseases in the bladder may cause an increased level of stone-forming minerals in the urine. When the concentration of such minerals becomes very high, the undissolved particles unite and form tiny crystals. As more crystals join together, they gradually enlarge into stones.

How are bladder stones diagnosed?
  • Palpation: Some bladder stones can be palpated (felt) through the abdominal wall.
  • Urinalysis: To check urine pH and detect presence of blood, bacteria and crystals.
  • X-Ray: Most bladder stones are visible on X-Ray. 
  • Ultrasound:  Stones that are radiolucent (not visible on X-Ray) can be detected by ultrasound.

Dogs develop bladder stones too. Dr Ng Yilin, assisted by Andy, Mount Pleasant Animal Clinic (East), performs an ultrasound which can detect sediments that may not show up on X-Rays.


Bladder stones come in different shapes & sizes. A year ago, Isabelle developed a single large stone in her bladder which was surgically removed via a surgery called cystotomy.


6 months after her first surgery, new stones developed in Isabelle’s bladder. They were again removed by cystotomy.

This is the third time stones developed in Isabelle's bladder. Smaller stones are more likely to exit the bladder & get lodged in the bladder neck or urethra. If this obstruction is not relieved, urine builds up & the bladder may rupture. It can also lead to irreversible kidney damage & eventual death.

This is the third time stones developed in Isabelle’s bladder. Smaller stones are more likely to exit the bladder & get lodged in the bladder neck or urethra. If this obstruction is not relieved, urine builds up & the bladder may rupture. It can also lead to irreversible kidney damage & eventual death.

How are bladder stones treated?


  • Usually prescribed to dissolve struvite stones (not effective for other types of stones)
  • Slow to work and not the best option if your pet is already in pain or there is life-threatening obstruction
  • Must be fed exclusively for it to be effective but not all pets will eat the prescription diet
This boy is so loveable, Dr Sarah Wong can't bear to let him to go home!

Dr Sarah Wong with Simba Sean at Mount Pleasant (East). Simba was having difficulty urinating. Struvite crystals were detected in the urine culture. Fortunately, Simba’s condition was not severe & he is doing well on prescription diet which helps dissolve struvite stones.


Very small stones can be flushed out of the bladder via a non-surgical procedure called voiding urohydropropulsion – using a liquid to expel something from the urinary tract. 


  • A sterile urinary catheter is placed via the urethra.
  • Saline solution is instilled into the bladder. * Avoid over distending or rupturing the bladder.
  • The bladder is manually expressed to flush out the stones.

A small amount of numbing agent (lidocaine) may help to ease the passage of the urinary catheter through the urethral opening. Blood-tinged urine is often a sign of bladder stones, urinary tract infection, urethral plug or cancer, collectively known as feline lower urinary tract disease (FLUTD).


The size of stones that can be flushed out depends on the size of the patient’s urethra. Male cats’ urethras are often too narrow for urohydropropulsion to be successful. Sediments or crystals collected should be analysed so that appropriate medication or diet can be prescribed.


Larger stones need to be removed surgically through an operation called a cystotomy.


During the surgery, tiny stones trapped in Isabelle’s bladder neck are flushed into the bladder (retrograde) & removed. As this is her third cystotomy, Isabelle’s bladder wall is not smooth but thickened by scar tissues.


All the stones are successfully removed & Isabelle’s bladder is closed up with absorbable sutures.


Some of the stones removed from Isabelle’s bladder. Most of them measure 2 to 5mm.


All the stones are successfully removed after surgery & a combination of retrograde & normograde flushing to loosen the stones wedged in the bladder neck.

Bladder stones may be in the form of multiple small stones or in Roxy’s case, a palm-sized ‘rock’. Dogs with bladder stones often strain to urinate and may pass out blood. Everyone is relieved to see this 5cm ‘rock’ surgically removed by Dr Ng Yilin.

The bladder stones should be sent to the laboratory for analysis to determine if prescription diet will be helpful in lowering the chance of recurrence. Regular urine tests and ultrasound are useful. There are also medications to control urine pH and bacterial infections. However, it is not uncommon for bladder stones to recur. Some breeds are genetically predisposed to developing stones.

How can we help prevent bladder stones in our cats?
  • Provide plenty of fresh water at all times to keep your cat well hydrated so that the urine is dilute.
  • Keep litter trays in a quiet and safe area in the house.
  • Keep litter trays clean.
  • If you have more than one cat, provide more litter trays to encourage them to urinate frequently and freely without fear of “invading” another cat’s territory.