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Date:   09 March, 2013  
Focus: Small animals - dogs, cats, hamsters, guinea pigs & rabbits
A Cavalier King Charles yelps when peeing  
Dr Sing Kong Yuen, BVMS (Glasgow), MRCVS
First written: 04 March, 2013
Date:   09 March, 2013 
Be Kind To Pets
Veterinary Education
Project 2010-0129

Monday, March 4, 2013

Calcium oxalate stones are radio-dense unlike urate stones which are radio-lucent (not visible in X-rays).

Yesterday, I had a case of a Cavalier King Charles, female, 6 years passing smelly cloudy urine. She yelped occasionally when she peed. So I asked the owner to send me a sample of the urine.

On March 2, 2013, she collected the urine in the clean pee tray and sent it to me. Urine analysis show pH=6.5 which is acidic and calcium oxalate crystals 2+. Bacteria was "occasional" and there was no blood in the urine.

I advised X-rays which showed no stones but I could see radiodense cloudy urine inside the bladder, suggestive of calcium oxalate crystals which are radio-dense. I palpated the bladder confirming no big stones or bladder pain at that time.

I turned the dog upside down on the examination table and discussed this case with Dr Daniel. I noted that she had unusually enlarged nipples as if the dog had given birth a few times. You can see the enlarged nipples on the lateral view of the X-ray below.  "She had never given birth," the lady owner in her late 30s said to me.

White cloudy discharge appeared at the vulval area but the owner did not want to see it. "This could be pyometra," I said to Dr Daniel who disagreed. He thought it was just white turbid urine. The dog could be incontinent but the owner did not complain about incontinence or leaking urine. She said that the dog no longer came into heat although it usually happened around February. I palpated the abdomen. The dog did not experience any abdominal pain but I could few swollen uterine horns of around 2 cm in diameter. 
tpvets_logo.jpg (2726 bytes)6012. Yelped occasionally when peeing tpvets_logo.jpg (2726 bytes)6013. Calcium oxalate crystals, no oxalate stones seen on X-rays. Calcium oxalate stones are radio-dense

This dog lived in a house with a garden and sometimes the owner might miss the bleeding as the dog cleaned herself well by licking. This would account for her swollen vulval lips.   

"So what to do now?" this was what the owner wants to know. She was a busy lady and all those technical information did not interest her.  

"Put the dog on U/D diet for 3 months and don't feed any treats or food. Monitor the urine 4 weeks later to check for the presence of calcium oxalate crystals. Monitor amount of water being drunk daily."

As to why the dog "yelped" occasionally when peeing, this was a mystery. This was the complaint. Not difficulty in urination or blood in the urine as in the 2009 case. My hypothesis was that the female stone had great difficulty passing out the calcium oxalate stones via her urethra. As she strained to pee out the stones, there was great pain and so she "yelped" during urination onto the grass.

But the X-rays (2 views) showed no large stones and so I had no evidence. If stones were large, it would not be passed out as the diameter of the urethra in this female dog would be around 3-4 mm. But the stones were smaller and must have been urinated out.

The owner ordered a packet of the dry U/D diet and drove home in a hurry as she was tired and although the children were grown up, she had lots of things to do. Monthly monitoring of urine every 4 weeks for the next 6 months and regular X-rays of the bladder and kidney are strongly advised but sadly, rarely do owners comply.

The owner phoned me as her dog would not eat the dry U/D diet at all.
"Shall I buy some cans of U/D to mix with the dry food?" she asked.
"No need," I said. "Give 90% of the old food and 10% of U/D. Increase U/D amount daily till she eats all U/D."
"I thought you said to switch all to U/D immediately?"
"Some dogs eat U/D immediately and so I had said to switch directly to U/D to prevent formation of the calcium oxalate stones. How's Pappy?" 
"She is OK" the lady replied. Evidence-based medicine using X-rays and blood tests are still the best practice to educate the owner.

As to how U/D will prevent calcium oxalate stone formation, the owner did not ask. Basically, it alkalinises the urine, preventing formation of the oxalate crystals and therefore preventing oxalate urolithiasis in this dog. Her urinary pH was 6.5 during urinalysis. A 4-weekly urine test will monitor the success of prevention but not many owners have time for such important matters. How many Singaporean senior citizens send their stool sample for colon cancer screening even when the bottles are free? Very few do.     

Updates will be on this webpage:

Read a case of calcium oxalate stones in 2009.
Calcium oxalate urinary stones are radiodense. Take X-rays. Toa Payoh Vets2009 case: Calcium oxalate urethral obstruction in a Chihuahua

Recurrence of Urate urolithiasis

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