Thursday, June 26, 2014

1390. FINAL COPY TO MVA. Urolithiasis in dogs and cats.

Recent Advances in Veterinary Practice No.3
Myanmar Veterinary Association, July 5, 2014

Dr Sing Kong Yuen, BVMS (Glasgow), MRCVS
Founder of Toa Payoh Vets, Singapore.,

Urolithiasis is the formation of urinary stones (uroliths) within the urinary tract (kidneys, ureter, bladder and urethra). The outflow of urine is obstructed, leading to inflammation, septicaemia, shock and death. 

The 3 most common uroliths found in the canine cases in Toa Payoh Vets, Singapore are struvites (magnesium ammonium phosphate), calcium oxalate and urates. Cystine and silica urolithiasis are uncommon. (IMAGES). In feline cases, infection-induced struvites are the most common type seen but oxalate urolithiasis do occur in cats.

This paper shares my experiences with the treatment of urolithiasis  for the last 40 years. I graduated from Glasgow University in1974 and am still practicing.  My guidelines are as follows:

1. A correct diagnosis is important.

1.1 History. Do a thorough physical examination including weighing the dog, taking rectal temperature.
1.2 Clinical signs. Important ones are dysuria, haematuria and pollakuria.
2. Bladder palpation (large distended bladder, stones inside the bladder and crepitus). Abdominal pain or discomfort. Palpation of a likely “bladder” stone is not reliable and it is best to get radiography or ultrasonography performed to confirm its presence. For some owners who want the cheapest medical costs, I had removed bladder stones after bladder palpation without X-rays. I do not recommend this method. The bladder “stone” palpated may not be present  during surgery.  In any case, write in your case record under AMA (Against Medical Advice), that the owner does not want radiography as advised, to defend yourself against allegations of negligence.

3. Vaginal discharge (mucopurulent) may be seen with chronic lower urinary tract infections.

4. Blood test. CBC/Biochemistry. Leucocytosis, neutrophilia and thrombocytopenia indicate septicaemia and a poor prognosis.  High serum BUN and creatinine will point to kidney damage. Inform the owner about the poor prognosis if relevant, before surgery to remove the bladder stones.   

TIP. Always advise a blood test to screen the health of the dog and possible kidney damage to determine the anaesthetic risks and prognosis.  Leucocytosis, neutrophilia and thrombocytopenia indicate septicaemia and a poorer prognosis.    

5. Imaging
5.1 Survey radiography shows radio-dense stones such as struvites, calcium oxalate and silica.  Cystine and urate uroliths are radiolucent and the vet may need to perform contrast cystography or ultrasonography.

I prefer to inject 20 ml of air into the canine bladder via the urinary catheter, to show clearly the number of bladder stones (IMAGE). In female dogs, the use of a vaginal speculum or finger to guide the urinary catheter into the bladder will require more patience, time and practice as compared to the male dog’s urethral catherisation. I note that many vets do not catheterise females.  

TIP. Some vets perform only the lateral view to reduce medical costs. Two views must be done as radio-dense objects in the lateral view may not be located within the bladder.

TIP. If no radio-dense uroliths are seen on survey radiography, many vets diagnose that there is no urolithiasis. They don’t do contrast cystography or ultrasonography.  Perform routinely urinalysis which may reveal the presence of cystine or urates, both of which are radio-lucent.

TIP. I encountered cases where some vets just X-ray the bladder and urethra area. They miss radiography of the kidney area where uroliths may also be present. It is important to X-ray the abdomen and pelvis as uroliths may be present in the kidneys, ureters, bladder and urethra.

5.2 Ultrasonography shows the thickened bladder wall (chronic cystitis), location, number and size of uroliths. It will show the presence of bladder wall tumours which may be the cause of haematuria. Normal bladder wall cannot be detected by ultrasonography.

6. Urinalysis. I have heard from one client that her vet consider urinalysis unnecessary if surgery is to be done. Urinary pH and SG, presence of blood, bacteria and crystals can be useful in the post-surgical management and prevention of recurrence of urolithiasis.  

TIP. Some vets state that the absence of urinary crystals in the urine mean that no uroliths are present. This is not true as stones can be present without crystals in the urine.

7. Bacterial urinary culture and antibiotic sensitivity test are rarely done to reduce medical costs.

8. Chemical analysis of the uroliths.  Chemical analysis of the stones removed by surgery or passed out in the urine is one procedure that all vets should not forget. Some clients do not want to pay the cost of analysis and this should be recorded in the case notes under AMA (Against Medical Advice).  I heard from an Australian vet at his talk in 2013, that there was a vet who just removed the stones and not send them for analysis even though there was recurrence of urolithiasis. This vet lost a loyal client.

In Singapore, Hills’ Science Diet provides a free stone analysis to be done by the University of Minnesota. I send the stones to the local laboratory for analysis as results come back much earlier.

9. Client Education & Informed Consent Form.
9.1. Outflow obstruction caused by urolithiasis is a medical emergency. Prognosis depends on the health of the dog as shown in the blood test results of CBC/Biochemistry as well as physical examination.

9.2  Informed consent for anaesthesia and surgery explaining the high risks involved esp. for old dogs. This is important as there have been litigation against Singapore surgeons who have not fully explained the risks of anaesthesia and surgery.

9.3  An estimated amount of medical costs must be given to the owner before the surgery. A pyometra surgery and anaesthesia in small breeds cost around $800 in Toa Payoh Vets in 2014.  

1. Immediate I/V fluid therapy, antibiotics and pain-killers for 1-2 days. I usually give Hartmann’s, dextrose and amino acids, baytril and spasmogesic IV. The dog is an in-patient.

11.1   I use 25-50% of the calculated dosage I/V for sedation/induction depending on the health of the dog. Then I intubate and maintain with isoflurane + oxygen anaesthesia. If the dog is very weak and lethargic, I use entirely isoflurane + O2 anaesthesia and find this to be very effective and safe.

11.2 My calculated dosage is as follows: For a young 10-kg dog, Domitor + Ketamine IV = 0.4 ml + 0.5 ml respectively.

11.3 For very old (over 10 years) dogs and/or in poor health, I use only isoflurane + oxygen gas.

11.4  Clipping and cleaning to be done before sedation outside the operating room reduce anaesthetic time and risks.


12.  URETHRAL OBSTRUCTION IN DOGSOutflow obstruction due to stones obstructing the urethra is a common situation in male neutered cats at Toa Payoh Vets. Some dogs do have this problem too.

Briefly, the procedures after diagnosis of urolithiasis are as follows: Sedation, urethra catheterization, syringe normal saline to flush the stones into the bladder (use 30-ml syringe instead of 10-ml) and remove all stones from the bladder surgery. It may be very difficult to flush larger urethral stones into the bladder (voiding urohydropropulsion) when they are lodged at the bend of the urethra. I know of one case of recurring urolithiasis where the vet used a hard catheter and rupture the urethra, leaking urine into the skin (IMAGE). 

Some vets prefer incising the urethra behind the os penis to remove the stones and open up the bladder to remove the bladder stones. I had one case of the owner wanting to euthanase the male dog that had a urethral opening performed by another vet, as the dogs keeps dribbling urine from this opening, soiling the apartment floor. Voiding urohydropropulsion (flushing uroliths back into the bladder) might have prevented euthanasia in this case.

A most common problem in male neutered cats seen at Toa Payoh Vets. Sedation, urethral catherisation to unblock the urethra followed by bladder irrigation several times normal saline till the bladder is cleared of blood and debri. I stitch up the catheter to the prepuce, put the cat on an Elizabeth collar and ward the cat for 2-3 days. I removed the stitched catheter before sending the cat home.

Some vets send the cat home on the same day and in one case, the cat just bite out the urinary catheter despite the wearing of the Elizabeth collar. It is important that the vet do urinalysis and teach the client how to switch over to the Prescription Diet. Follow up by phone calls is necessary but sometimes not done by the busy vet. The owner must be warned about recurrence if he does not comply with medical (not able to give antibiotics)  and dietary instructions (feeding same dry food).

In recurrence, survey radiography and more detailed tests to check other types of uroliths such as calcium oxalate may be present, instead of struvites, may need to be done. 

A video of a case of urethral obstruction handled by Dr Aung of the Royal Asia Veterinary Surgery will be screened.

14. UROCYSTOLITHIASIS. BLADDER SURGERY14.1 Empty the full bladder before surgery. In male dogs, I may inflate the bladder with 20 ml of normal saline to enable it to be easily accessed.  

TIP. The full bladder may be just below the skin. If the vet is not careful, the bladder may be cut spilling urine into the peritoneum.
TIP. Be careful. Avoid contamination of the peritoneum with urine and small uroliths by packing the surgical area next to the bladder with many sterile swabs.  

14.2 Sutures. For closure of the bladder wall, I usually use two layers of continuous inverting suture if the bladder wall is thickened by inflammation. I use 3/0 braided absorbable sutures (Polysorb) in all my bladder closures. My associate vet, Dr Daniel prefers the 3/0 monofilament absorbable sutures (Monosyn).

14.3  I use Anti-sedan IM to reverse and abolish the effects of Domitor sedation in cases where the dog is still not conscious after the surgery. The dog is usually awake within 5 minutes of the injection.

14.4   Post-op Nursing. The dog is hospitalised around 3 days to lower the medical costs. She goes home with antibiotics for another 10 days and an Elizabeth collar. Tolfedine pain-killers are given for the first 4 days.

15. Outcome. If the dog is not extremely ill, she recovers very well from the surgery. The blood test is useful in client education as regards any permanent kidney damage (high serum BUN and creatinine and phosphous).

16.  Practise evidence-based medicine as clients are better educated and have high expectations. Some 10 years ago, in one case, the dog kept vomiting and died despite being spayed. I did not do the blood test to check for kidney damage as the owner wanted the cheapest medical cost. Her family members sent mass e-mails to everyone in Singapore advising them to avoid me. There are strangers and a doctor who phone me to let me know.  Nowadays, they use Facebook or pet forums to voice their grievances against the vet.

16.1 AMA (Against Medical Advice). Nowadays, I give the client a written record that he does not want blood tests, X-rays or procedures as advised by me. I have the written evidence in case of litigation or complaint. In computerized records, there is the allegation of falsifying evidence by deleting the earlier record but vets using manual records need to keep proper records to protect their reputation.

Nephrolithiasis is rarely seen at Toa Payoh Vets and I have no experience of the surgery to remove kidney stones. I had two cases in 2013/2014 (IMAGES). One involved a Miniature Schnauzer with recurring cystourolithiasis. Another was an old Poodle. Both owners did not want to spend money on further tests and the dogs died soon.  A senior vet had done the rare case and said that the dog felt great pain post-surgery. Also, he said that the kidney was swollen and infected (nephritis). An Australian vet who gave a talk in 2013 said that he would operate only if 70% of the kidney tissues are still functional.     

TIP. Shock wave lithotripsy to blast and break up kidney stones is too expensive for almost all  dogs and cats.

Ureteroscopy and lithotripsy may be used to remove the ureteric stones in people. I have not encountered cases of ureteral stones in dogs and cats. 

19.1  Presently, only struvite stones can be dissolved/prevented using prescription diet that acidifies the urine, e.g. Hills’ S/D and C/D or Royal Canin Urinary S/O (no pork ingredients important for certain religions). 

In my opinion, bigger struvite stones of over 1 cm diameter cannot be dissolved using dietary means although the Minnesota Urolith Center had mentioned this could be done in 2-3 months. Many clients don’t have the time to monitor the progress and do more survey radiographs. Surgery is usually the best way.  

19.2  One of my clients did not want the bladder stones in her Miniature Schnauzer removed by surgery and the dog had one episode of urethral obstruction but is OK now without surgery (IMAGE). Another client had a male Pekinese keeps peeing out stones for many months as the owner did not want any radiography or urinalysis (IMAGE). He had to rush the dog as he developed urethral obstruction after midnight.  He died during attempts to unblock the bladder by the emergency vet who was “blamed” for the death.   

19.3  Non-compliance by clients. Many Singapore clients do not know how to get the dog or cat to eat the prescription diet and so give up. The vet has to advise on how to do it. Mix 10% of the new diet and increase to 100% in 2-4 weeks. No other food or dog treats.

19.4  Feed canned food only.  No more dry food if possible. Feed home-cooked food. No more treats or sharing other pet’s dry food.

19.5 Get the dog or cat to drink more water e.g. more exercise, add ice.

20. Urine monitoring
every month for the first 3 months so as to confirm that the prescription diet is effective in acidifying the urine and to check for bacteria and crystals in the urine.

21. Survey radiography every 3-monthly so that small stones can be removed by retrograde urohydropropulsion (eliminate stones via the catheter). None of my clients in the past 40 years bother to adopt this advice! 

22. Diet management. Some will just buy the Prescription Diet regularly and that is all they do.

My paper shares some of my urolithiasis experiences in practice. Much more detailed research and advices on treatment and prevention can be obtained from the website of the Minnesota Urolith Center, University of Minnesota

e.g. urate urolithiasis in cats is at:

A video of a case of recurring urethral obstruction handled by Dr Aung of the Royal Asia Veterinary Surgery will be screened. I happened to visit him at that time and filmed the video for discussion at this talk.   

Recurring urolithiasis is a complex  problem to resolve. The owner doctor-hops to find a solution and previous treatment by the other vet may be hard to obtain.

In this case, in retrospective review today as I write this paper some 7 days after my visit, I have the following questions:

What was the composition of the uroliths in the urine as seen by the first vet?
Did the first vet do a survery radiograph and urinalysis? Ultrasonography? Blood test?
What was the urinary pH on the first visit?
He or she had prescribed Royal Canine Urinary S/O for this cat and so the pH was acidic now. Was the urethral plug or urolith confirmed struvites? Or oxalate or urate stones?  Were there stones in the kidneys?  

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