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Date:   07 October, 2018  

 Small animals - dogs, cats, hamsters, guinea pigs, turtles & rabbits
A swollen glans penis is seen after retrograde hydrouropropulsion and cystotomy for calcium oxalate urolithiasis in a dog
First written: 20 Sep 2011
Update: 10 Oct 2018

Dr Sing Kong Yuen, BVMS (Glasgow), MRCVS 
Be Kind To Pets
Veterinary Education
Project 2010-0129
Each vet has his own way of handling a case of urethral obstruction in the dog. The outcome may be similar in that the dog can pass urine normally but the post-operation complications and implications vary.

In the following case of calcium oxalate urolithiasis, the Miniature Schnauzer dribbled urine. X-rays showed the urethra was blocked by more than 10 small stones 3x5 mm in diameter. The catheter was obstructed and could not be passed into the bladder.

1. Retrograde urohydropropulsion and cystotomy.
2. Urethrostomy and cystotomy.
3. Retrograde urohydropropulsion without surgery. This is possible if the stones are small as detected by X-rays and/or ultrasound is early. The small stones (<5 mm) are syringed from the urethra into the bladder and sucked out using the syringe.

1. Using Prescription Diet to dissolve the urinary stones cannot
be done in calcium oxalate urolithiasis. For struvite urolithiasis, this may be successful if the stones are small, preferably <1cm across.

Urethrostomy and Cystotomy.
When there are too many stones inside the urethra, I usually take the second surgical approach. There will be less trauma to the glans penis and urethra as the urohydropropulsion (syringing 20-35 ml of normal saline to push all the urethral stones from the urethra into the bladder).

I will make a 0.5 mm cut behind the os penis (urethrostomy), take out the stones with a forceps, close the urethra and skin. Then I take out the the bladder stones via the cystotomy. In my experience, the urethral wound heals well if proper post-op care is given. The urinary cathether must be inside the urethra for around 14 days to prevent closure of the urethra.   

However, in some cases, the dog is sent home within 2 days after surgery, either by the vet or the insistence of the owner. There is a lack of care by the owner due to inexperience in animal nursing. The urinary catheter is pulled out, the wound breaks down and the urine leaks from the wound perpetually. This is because some owners do not bother to refer to the vet on seeing the wound breakdown, owing to various reasons.

Retrograde urohydropropulsion and Cystotomy.
So, the first approach eliminates this post-op complication of an unnatural urethral gap as the penile urethra is not incised. All stones are taken out via the bladder in this approach. Repeated flushing of the urethra to push the stones into the bladder is needed. In this case, Vet 1 preferred the first approach.

There are more than one surgical approaches in treating urethral obstruction, depending on the size of the stones. Each has its own pros and cons.

However, on Saturday (my day off and 24 hours after surgery by Vet 1), I visited Toa Payoh Vets to check on this Miniature Schnauzer in the afternoon. I noted the glans penis was much swollen. 

In this case, the dog was scheduled to go home 48 hours after surgery. The owner was concerned about this swollen glans penis - reddish and not able to get back inside the prepuce. This swelling is a post-op complication of retrograde urohydropropulsion in some cases. What makes it occur? It is due to the traumatic pressure of gripping the glans as an anchor point in the process of retrograde urohydropropulsion.

Numerous small urinary stones inside the os penis (penile bone) were removed via flushing the stones back into the bladder (retrograde urohydropropulsion) and removed them via the bladder incision (cystostomy).

Calcium oxalate
stones were removed in this case.
The Miniature Schnauzer dribbled urine for the past 2 weeks. Partial urethral obstruction with >10 small stones were seen in the X-rays. Urohydropropulsion and cystotomy removed the stones.

The catheter was not able to pass through more than 10 cm inside the penis as its passage was obstructed by the numerous stones inside the penile urethra. To prevent it being dislodged as normal saline was pumped into the catheter to push the stones back into the bladder for removal. The glans penis has been gripped by Vet 1 as an anchor point, resulting in swelling. Gripping the penile bone may not be practical but would be preferred.

In any case, the outcome was excellent in the sense that after 3 flushings, the stones were pumped back into the bladder where they were removed. So, the penile urethra was not cut open.  

In this case, there was a complication post-op. I had to intervene to resolve this problem. I decided to give an anti-inflammatory pred injection which is not normally used after surgery. Leaving the glans penis to shrink will take many days and any traumatic injury to it will lead to much unhappiness for the owner.

Although the dog has a big size 20 elizabeth collar, the owner disagreed with me that the dog could  reach his surgical area to bruise it. There was a small bruised area near his sutures (see picture). The owner told me that there was no way her dog could have licked that area since he had the biggest collar. I said it was possible that the dob could have rubbed the penile glans on the flooring to relieve his pain.

Within 24 hours of the prednisolone injection, the glans penis had shrunk by 50% and was much less inflamed (see picture). He peed normally and had a good appetite. He went home the next day.  

For dogs with swollen glans penis, it is best not to send home till the dog has recovered but that would take many days and trauma could still occur. NSAID does not work very well in such cases although they are standard offers for pain killer effect. NSAID was prescribed for the home stay.

P.S. Results of the case:

pH=7 (5-8), SG 1.030 (1.005 - 1.030).
Protein +, Blood 4+, WBC 504, RBC 1440, Bacteria +, Crystals Nil

Miniature Schnauzer, not neutered, male, 8 years, small urinary stones, x-ray, dysuria, toapayohvets, singaporeX-RAY. Small stones seen.

Urea = 7 (4.2 - 6.3)
Creatinine = 61 (89-177)
WBC = 13.6 (6-17) with neutrophils 93%. Absolute 12.6, lymphocytes 6.5%. Absolute 0.88
No hypercalcaemia

16.9.11 Cystotomy and retrograde urohydropropulsion. Urinary stones removed by Vet 1 after flushing all urethral stones into the bladder.

cystotomy, uro-hydropropulsion, urinary stones, miniature schnauzer, male, 8 years, toapayohvets singaporeSTONE ANALYSIS - multiple fragmented uroliths

Calcium oxalate monohydrate 100% stone, 5% shell
Calcium oxalate dihydrate 95% shell.



o urinalysis and X-rays regularly.

If the urine SG >1.020, give canned food or add water to the dry food. Give 300 - 400 ml water daily if the small-breed dog does not eat the dry food with water.

If the urine pH <6.5, consider diets that produce less acidic urine e.g. Hills' U/D or use urinary alkalinizers eg. Potassium citrate.

If the urine pH >6.5, urine SG <1.020, with no urinary crystals present, repeat urinalysis monthly, then every 3-6 months.

Repeat X-rays every 6-12 months to detect urolith recurrence early.
Repeat urine test and X-rays if signs - haematuria, pollakiuria and dysuria recur.

For calcium oxalate prevention:
1. Diets promoting urine pH <6.59 were at the highest risk for recurrence.

2. Avoid risk factors like hypercalciuria due to hypercalcaemia, metabolic acidosis, high sodium consumption and Vit D excess.

3. Feed canned foods and/or add more water to food so that urine pH is consistently <6.5. You will need to do urine pH tests regularly.

4. Consider hydrochlorothiazide (2mg/kg q 12 hr) with highly recurrent urolithiasis in dogs without hypercalcaemia.

5. Consider potassium citrate (75mg/kg q 12-24 hr) if urine pH is consistently <6.5.

Many dog owners in Singapore stop doing regular X-rays and urine tests, leading to recurrence of urinary stones and surgeries or euthanasia. Feeding Hills' C/D is not advised in calcium oxalate urolithiasis as it is an urine acidifying diet. There is no Prescription Diet to dissolve calcium oxalate stones.

In Singapore in 2018, Hills' C/D diet is no longer available. Royal Canin still produces Urinary S/0 diets. These diets are acidifying diets used mainly for struvite stone prevention.

It is best to consult your veterinarian to prevent recurrence of calcium oxalate urolithiasis as each case is different. E-mail or SMS +65 9668-6468 to make an appointment for consultation of your case or for a second opinion.


urinary stones again despite home-cooked food diet. why? toapayohvets miniature schnauzer

Recurrent urolithiasis 4 months later - struvite stone case study. This is not a calcium oxalate stone case study.

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