Canine Urolithiasis: Caught Between a Rock and a Hard Place?

by Dr Penny Dobson BVSc MACVSc (Canine), Hill’s Helpline Manager

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Bladder stones are a frequent cause of concern for dog owners. However they often remain undetected until the pet exhibits pain and discomfort.

Common signs include:

  • Haematuria
  • Frequent and /or painful urination, with vocalisation and straining
  • Inappropriate urination
  • An Inability to urinate

There are two common crystal and stone types in dogs:

  • Struvite or Triple-phosphate: A stone composed of magnesium, ammonium and phosphate. These are often associated with urinary tract infections by urease – producing bacteria, such as staphlocococci or proteus spp.
    • Management can be achieved with:
      • medical dissolution by controlling the infection; and
      • dietary intervention
    • To manage recurrence the single most important aspect is to prevent urinary tract infections and retreat if they do recur.    
  • Calcium oxalate: A metabolic stone associated with either increased gastrointestinal  calcium absorption, excessive renal calcium loss or defective function of nephrocalcin, a glycoprotein that inhibits calcium oxalate growth in the bladder.
    • Currently calcium oxalate uroliths cannot be medically dissolved.
    • Treatment includes:
      • voiding urohydropropulsion if the stones are small; or
      • surgery if large and the pet is symptomatic
    • Recurrence of calcium oxalate uroliths in dogs is common.
    • Management includes:
      • transitioning to a prescription urinary diet; and
      • 6 monthly monitoring with radiographs and urine analysis

There are many reasons why urinary crystals and stones form, with genetics and diet playing a key role. You may remember from vet school how genes can be switched on by internal environmental factors such as hormones and regulators or by external factors such as diet, water, stress and exercise.

Urine analysis is an essential diagnostic tool in assessing urinary tract health and should be performed with every annual health check. When investigating lower urinary tract disease it is the responsibility of the healthcare professional, not the pet owners, to collect a urine sample. This will minimise unknown variables, such as contamination, temperature, length of storage and changes in urine pH.

Remember, fresh is best!  

Assessing the sample within 15 minutes of collection reflects in vivo crystalluria, pH and specific gravity. While refrigeration can preserve physical, chemical and morphologic properties of urine sediment, it can also enhance in vitro formation of various crystals, which have no relationship to events occurring in the urinary tract.

ALWAYS measure urine specific gravity.

Now for the good news:  We can educate pet owners to lower their pets’ risk for a recurrence of bladder stones by following these 6 steps:

  1. Diagnosis: The type of stone the pet is prone to forming impacts the treatment options. Making adjustments to the pets diet may be sufficient to dissolve some types of stone, whereas others may need to be removed surgically. Hill’s Pet Nutrition offer a Free Quantitative Urolith Analysis Service through Minnesota Urolith Centre. Contact your local Hill’s representative to find out more.
  2. Diet: Prescription urinary health diets are formulated to reduce the likelihood of crystal/ stone formation by minimising levels of specific potential stone forming nutrients and minerals. Also feeding a pet multiple small meals a day can help maintain more consistent urine pH levels throughout the day.
  3. Supplements: Avoid using  nutritional supplements particularly those containing calcium or Vitamins C or D.  Occasionally to decrease stone recurrence supplement options maybe prescribed. For example, potassium citrate is a calcium oxalate inhibitor and urinary alkaliniser.
  4. Water intake: Sediment and inflammatory products in the urine can contribute to the formation of stones. This can be reduced by increasing water intake, to dilute the urine. Water intake can be increased by:
    • Feeding canned food
    • Adding extra water to the pet’s food
    • Providing  a drinking fountain
  5. Exercise: By walking your dog multiple times a day, you will give them more frequent opportunities to urinate. This will decrease urine retention, which is a factor in crystal precipitation.
  6. Follow up: Even on a urinary diet, never set and forget. Monitor regularly. Routine blood and urine testing along with bladder imaging allows you to screen for indicators of subclinical bladder health issues.  

  Reference

Sanderson, S Canine urolithiasis overview and update (Proceedings), CVC IN SAN DIEGO PROCEEDINGS, 2008 http://veterinarycalendar.dvm360.com/canine-urolithiasis-overview-and-update-proceedings

Nwaokorie E, Osbourne C 21 Tips to enhance your crystalluria interpretation, DVM360 MAGAZINE, 2013  http://veterinarynews.dvm360.com/21-tips-enhance-your-crystalluria-interpretation

Reyes, N 5 steps to reduce the recurrence of bladder stones,  Firstline

http://veterinaryteam.dvm360.com/5-steps-reduce-recurrence-bladder-stones-1

 

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