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BLADDER STONES

Reprinted with permission by Dr. Osbourne  -  Article was written originally for the Bichon Frise

 

This condition is called urolithiasis 

uro = Greek meaning urine, lith = Greek meaning stone, iasis 

= a process or condition
  

What are uroliths ?

Several different minerals can form stones within the urinary tract of dogs, including magnesium ammonium phosphate (struvite), calcium oxalate, ammonium urate, cystine, calcium phosphate and others. In uroliths, 

these minerals may occur singly or in combination.

  

Key Point :

Knowledge of the mineral type(s) comprising the stones is recommended to determine the best treatment and

preventative therapy. Currently the two most common minerals found in uroliths  are magnesium ammonium

phosphate (struvite) and calcium oxalate. In the past decade, an increased occurrence of calcium oxalate

urolithiasis has been recognized in several breeds of dogs and several breeds of cats. The causes associated with 

this increased occurrence of calcium oxalate uroliths are currently under investigation. To date, studies indicate 

that multiple genetic, environmental, dietary and drug related factors may be involved. Of the uroliths submitted 

in 1998 to the Minnesota Urolith Center for analysis from the Bichon Frise breed, 51% were struvite, 37% were 

calcium oxalate and the remaining 22% were composed of other minerals. 

Calcium oxalate is more likely to form in males, struvite is more likely to form in females

In a recent survey of the Minnesota Urolith Center database, 10% of male Bichons formed struvite uroliths, 

80% of male Bichons formed calcium oxalate uroliths. Conversely, 50% of female Bichons formed struvite uroliths, 

36% of female Bichons formed calcium oxalate uroliths. These percentages refer to stones removed from Bichons 

and therefore they do not apply to all Bichons.

 

Key Point

Calcium oxalate uroliths are increasing in occurrence. Multiple factors are associated with this change in prevalence 

of mineral types in stones and studies are underway to identify risk factors. 

    

Struvite uroliths :  

In dogs, struvite uroliths are primarily associated with a diagnosis of infections caused by urease producing bacteria.

although other factors may predispose a dog to struvite uroliths, bacterial infections with staphylococcus and other

urease producing pathogens are clearly the most important. 

 

Once a diagnosis of struvite uroliths has been made, at least 3 therapeutic options are present.  

 

Medical and dietary dissolution of uroliths
Non-surgical procedures for removal of uroliths
Surgical removal of uroliths

    

Medical and dietary dissolution consists of feeding a special diet, available from veterinarians, along with treatment

with an appropriate antibiotic. Your veterinarian will perform a urine culture to determine which antibiotic will most

likely be effective in treating the infection. 

These antibiotics should be administered until the stones are completely dissolved

The time required for medical dissolution is dependent on the number and size of the stones and compliance with

dietary and antimicrobial treatment by the owner. Some have been dissolved within a few weeks, whereas others

may require up to 2 months or more. Non-surgical procedures have been developed to remove stones small enough 

to pass through the urethra. Best results may be obtained from veterinarians who have experience with these techniques.

Surgery consists of removal of uroliths from the urinary tract. Once struvite uroliths are dissolved medically or removed

surgically, prevention of the urinary tract infection will prevent recurrence. Prevention of urinary tract infections may

require periodic urinalysis and urine culture. Periodic radiographs (i.e. x-rays) may also be indicated. Antibiotics and/or a

diet designed to lower urine pH and restrict certain minerals may be recommended on the basis of these test results.

   

Key Point

If the infection can be eradicated, struvite uroliths will not form or recur even if secondary factors persist.
     

Calcium oxalate uroliths :

Once a diagnosis of calcium oxalate uroliths has been made, at least 2 therapeutic options are present :

  

Surgical removal of uroliths

Non-surgical procedures for removal of uroliths

( Note that calcium oxalate uroliths cannot yet be dissolved by medical treatment )

   
Non-surgical procedures have been developed to remove stones small enough to pass through the urethra of the pet.

( Best results may be obtained from veterinarians who have experience with these techniques. )

Surgery consists of removal of uroliths from the urinary tract. Once calcium oxalate uroliths have been removed,

urinalysis and urine culture should be a part of follow-up visits. Periodic x-rays may also be indicated. 

Owner compliance with feeding special diets designed to minimize risk factors associated with calcium oxalate urolith

formation will help prevent recurrence. In general, certain drugs should be avoided including corticosteroids,

furosemide, ascorbic acid (vitamin C), vitamin D, and acidifiers because they increase the risk of calcium

oxalate urolithiasis.

   

Key Point : 

It is not yet possible to dissolve calcium oxalate uroliths by dietary management. 

However, compliance with feeding special diets and avoiding use of certain drugs will minimize risk factors 

known to be associated with calcium oxalate urolith formation.
      

What about water sources ?

In a case-controlled epidemiological study performed at the University of Minnesota, the source of water ingested was

not found to be a risk factor for formation of calcium oxalate uroliths. However, the volume of water ingested usually

plays a significant role. By increasing water consumption, the urine concentration of urolith-inducing constituents will

be decreased or diluted. We highly recommend feeding a canned diet and providing ready access to fresh water

at all times to increase water consumption and urine voiding

Both of these goals decrease the risk factors for urolith formation.

   

What about pH testing ?

Ask your veterinarian about testing urine pH at home. Struvite uroliths tend to occur in alkaline urine. 

Calcium uroliths are associated with acid urine.
      

What about collecting urine samples ?

Urinalysis is an important part of preventative therapy. Because external factors such as temperature, delay in sample

analysis, evaporation of the sample, contaminated collection container, contaminants from hair or skin, and other

factors may affect the urine, urine samples should be collected (preferably by the veterinarian) and evaluated as soon

as possible.  Samples may also be collected at the veterinary hospital by a procedure called "cystocentesis". 

A sterile needle is inserted into the bladder and a urine sample is withdrawn into a sterile syringe. This is the 

preferred method for collecting a urine sample for culture. Identification of crystalline material is best performed at

the veterinary hospital.Screening samples may be collected by the owner using a clean cup or container. 

These samples should be capped, labeled with the date and time collected, and taken promptly to your veterinarian 

for evaluation.

 

Key Point

For best results, fresh urine samples should be analyzed.

   

What about analysis of stones ?

Any stones that are removed surgically or voided during urination should be evaluated by quantitative methods 

of analysis. Proper analysis of the uroliths is vital to successful treatment. Unfortunately most veterinary

laboratories perform qualitative analysis which is a highly unreliable test.

   

Key Point : 

Have uroliths analyzed by quantitative analysis.
   

Veterinary laboratories qualified to perform quantitative analysis are :

 

  Minnesota Urolith Center
Dr. Carl Osborne DVM, PhD, Director
Department of Small Animal Clinical Sciences
College of Veterinary Medicine
University of Minnesota
1352 Boyd Avenue
St. Paul, MN 55108
Lab Phone : 612/625-4221

 

Urinary Stone Analysis Laboratory
Gerald V. Ling PhD, Director
College Of Veterinary Medicine
University of California-Davis
Davis, CA 95616
Lab Phone 530/752-3228

    

  

Where can my veterinarian get more information ?

The Veterinary Clinics of North America

" Small Animal Practice"

" The ROCKet Science of Canine Urolithiasis "
Volume 29:1  -  January 1999
Available from : 
W. B. Saunders Publishing Company
Phone 800/654-2452
  

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