Introduction
Ureteral ectopia is a congenital condition where the ureters bypass the bladder and open into the proximal urethra and vagina.
It is one of the most common causes of juvenile urinary incontinence in the dog and cat.
Ectopic ureters are thought to result from the abnormal differentiation of mesonephric and metanephric duct systems, resulting in inappropriate ureteral tube termination and malposition of the ureteral orifice.
The condition can be unilateral or bilateral, and ureteral openings can be single, double or elongated (trough).
In dogs, the ectopic ureter usually runs within the bladder wall: intramural ectopic ureter.
Whereas in cats, the distal ureter is not usually associated with the bladder wall: extramural ectopic ureter.
It affects both sexes but is 20 times more common in females than in males.
An inherited basis is suspected, and breeds such as Siberian Huskies, Poodles, Golden Retrievers, Skye terriers and other Terriers are more commonly affected.
Concurrent abnormalities such as urethral sphincter mechanism incompetence, hydronephrosis, hydroureter and ureterocoeles can also be present.
Clinical Signs
The commonest presenting sign is continual dribbling incontinence. Animals can void urine normally but amounts may be smaller.
The incontinence can also be intermittent.
There will be skin soiling and common sequels include vaginitis and a urinary tract infection.
Animals will lick at their vulva and may show dysuria, haematuria and a vaginal discharge.
Diagnosis
History and clinical signs are suggestive.
A full physical examination should include checking for a palpable bladder and examining for urine soiling.
Urinalysis should be performed, preferably by cystocentesis, for culture and sensitivity.
Radiography is a useful method of diagnosis, especially contrast studies such as:
- intravenous urography: visualise the abnormal ureter draining into the urethra or vagina
- retrograde vagino-urethrocystogram: there may be retrograde filling of ectopic ureters
Fluoroscopy enables to visualise active movement of contrast within the urinary system.
Ultrasonography is very useful to visualise the ureters emptying.
Treatment
Treatment depends on the type of ectopic ureter.
Intramural ectopic ureter:
The aim is to create a new stoma between the intramural portion of the ureter and the bladder. The intramural ureter distal to the stoma is occluded or surgically excised.
This is the technique of choice for the majority of bitches as the ureter usually enters the bladder wall at the normal external site and runs intramurally, bypassing the trigone, before entering the urethra.
Fine suture material, fine instruments and magnification are required.
Extramural ectopic ureter:
In these cases, the ureter is transected and re-attached directly to the bladder urothelium via a tunnel through the detrusor muscle. This can be performed via an intravesical or extravesical approach.
This is the technique of choice for most feline ectopic ureters and some ectopic ureters in male dogs.
For both surgeries:
Post-operatively: fluids should be continued for 24 hours to promote diuresis, and urination should be closely monitored.
Complications:
- Ascending infection can occur so it is essential to eradicate any existing urinary tract infection preoperatively.
- Bladder oedema can lead to ureteral obstruction or bladder outflow obstruction, which is usually temporary. This is a reason not to reimplant two ectopic ureters at the same time.
- Recanalisation can occur which lead to a recurrence of the incontinence
- Continued incontinence may indicate that another abnormality is present, such as urethral sphincter mechanism incompetence. Phenylpropanolamine may be helpful in those cases.
Ureteronephrectomy can be performed instead of reimplanting the ureter if severe renal disease is present.
Prognosis is difficult to predict due to the varied nature of the condition and the various surgical techniques. Generally, response to surgery is good.
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Small Animal Soft Tissue Surgery Q&A 13 |
References
Pasquini, C. (1999) Tschauner's Guide to Small Animal Clinics Sudz Publishing
Gregory, S. (2010) Ureteral disorders RVC student notes
Merck and CO (2008) The Merck Veterinary Manual Merial