Bladder Stones

Bladder stones, or calculi, are mineral accumulations that form in the urinary bladder as a result of alterations in an animal’s metabolism of various diets.  They can also occur from chronic urinary tract infections.  There are many different types of stones, although calcium oxalate and struvite are the most common. Several breeds of dogs including, Bichon Frises, Miniature Schnauzers, and Dalmations are at increased risk of developing bladder stones. 

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How do I know if my pet has a bladder stone?

Surprisingly, some pets do not exhibit symptoms until the bladder stones are large and/or numerous (See x-ray image).  Typical signs include straining to urinate, increased frequency of urination with relatively small volume, and licking of either the penis or vagina.   Some pets will become obstructed from the dislodging of the stone into the urethra (see diagram).  In this instance, the pet will not be able to produce urine during voiding.  Lack of urine production, especially if the pet is straining, should be taken very seriously.  

How are bladder stones diagnosed?

Many stones are visible on standard x-rays.  However, those that are not obvious on x-rays are visualized with an ultrasound of the urinary tract.  Occasionally, a dye enhanced x-ray study of the urinary tract is used to further investigate the presence of bladder stones.  A urine culture is often performed if a urinary tract infection is suspected to be the cause of the stone (struvite) or as a coexisting problem. 

How are bladder stones treated? 

Surgery is needed in a vast majority of cases.   Occasionally, prescription diets along with antibiotic medications are used to dissolve struvite stones.  Lithotripsy is a shock wave treatment routinely used in human medicine to dissolve kidney and ureteral stones.  While this technology is available in veterinary medicine, few institutions in the U.S. are equipped to provide this form of treatment on animals.

We use two different surgical approaches in the removal of bladder stones.  In both situations, the pets are placed under general anesthesia.  The standard or ‘open’ approach is when an incision is made into the caudal or lower third of the abdominal cavity.  Then, an incision is made into the urinary bladder, the stones are retrieved, and the lower urinary tract is copiously flushed with sterile fluid.  The bladder and abdominal cavity incisions are sutured and a post-operative x-ray is taken to ensure all of the stones have been removed.  The pet is then awakened from anesthesia.  The stones are sent to an outside laboratory to determine their mineral composition. The second type of surgery employs a laparoscopic camera that is introduced into the urinary bladder through small incisions.  The stones are then visualized and removed.  The incisions are closed in a manner similar to that described above.

In some instances, the bladder stones travel out of the bladder and become lodged in the urethra (see picture and x-ray).  This is a particular problem in male cats and dogs.  In these instances, emergency treatment is needed to flush the stones back into the bladder to relieve the obstruction.  Occasionally, the stones are so firmly lodged that they will not readily pass into the bladder.  In this case, emergency surgery (urethrotomy) is needed whereby an incision is made into the urethra and the stones are removed. The urethral incision is then either closed with fine gauge suture or allowed to heal on its own. 

What is involved in the recovery period following bladder surgery?

Pets are given pain medicine before surgery begins, immediately after surgery, and generally for several days after surgery.  The pets usually spend one night in the hospital so that pain medication can be administered and their urination habits can be monitored. Running, jumping, and rough play are prohibited for the first 10-14 days after surgery. Short, leashed walks may begin a couple of days after surgery.  Pets are kept from licking or chewing their incisions by using either an inflatable or Elizabethan (E)-collar. 

How do I prevent my pet from forming more stones in the future?

Once the stone type is identified, a specific and exclusive diet is generally recommended to help prevent new stones from forming.  The diets are generally prescription only, but occasionally tailored, homemade diets can be used as well.  One of the most important parts of preventing stones is by providing moisture to the diet which produces dilute urine.  Dilute urine (less yellow in color) has less of the mineral components which are the precursors to stones.  Moisture is provided by either using exclusively canned food and/or adding liberal amount of water to dry diets.  Human food and over the counter treats other than the type used in the specified diet are generally not allowed as they can predispose the pet to stone formation. 

We recommend a routine urinalysis to look for crystals which are the precursors to stones. The urine pH is also a very important parameter in assessing the effectiveness of the specified diet.  A repeat urine culture may be suggested to determine if an infection is present.  This information helps us determine if the pet is receiving an adequate, moist diet.  Some pets will form bladder stones despite following proper dietary recommendations.  In these instances, medications and supplements can be added to change the constituents of the urine.