Veterinary Task Force for Urinary Incontinence
The Istituto Veterinario di Novara hosts the Veterinary Task Force for Urinary Incontinence
Urinary incontinence is the involuntary loss of urine and is frequent in dogs and cats. Urinary incontinence decreases quality of life both of owners and animals. The Veterinary Task Force for Urinary Incontinence has been established to provide owners of dogs and cats with urinary incontinence the diagnostic and therapeutic aid that is necessary to live with good quality of life.
Urinary incontinence is a pathological condition that can affect either the dog or cat, with the former being mostly represented. Causes of urinary incontinence are several and can act on their own or via their combinations. Because of the multifactorial and complex nature of the disease, a pluridisciplinary clinical approach is required to achieve the correct diagnosis and to plan the most successful therapeutic regimen. Therefore, the interaction between the internal medicine specialist, the radiologist, the neurologist, the endoscopist and the surgeon plays a chief role in the management of urinary incontinence.
The clinical sign that is immediately recognized by the owner is the loss of urine, which can be continuous (the dog loses urine when playing, during a walk, when sleeping), intermittent (urine is lost only when sleeping, for instance) or sporadic. Females seem to be most often affected, probably because the female urethra (the tube that allows urine to flow from the bladder out of the body) is shorter than in males and therefore clinical signs become earlier evident.
The diagnostic protocol includes different phases, from physical and neurological examinations to laboratory exams and diagnostic imaging. The latter comprises several methods, such as ultrasonography, radiographs with or without contrast medium, uro-CT (computed tomography) and cystoscopy (bladder endoscopy).
There are several forms of urinary incontinence. The classification is based on structural (anatomic) or functional causes, as outlined below.
Urinary incontinence and anatomic abnormalities
The most frequent cause of urinary incontinence due to anatomic abnormalities in young dogs and cats is called ectopic ureter. In animals with this anatomic abnormality, the ureter (the connecting tube that allows urine to flow from kidneys to bladder) does not end in the bladder but in any other part of the uro-genital apparatus (urethra, vagina, vulva). The ectopic ureter may affect one or both ureters. Both figures depict cases of bilateral ectopic ureter, either with CT (on the left) or with radiograph and contrast medium (on the right); arrows show the dilated and ectopic ureters.
Because of the anatomical defect, the urine, which is produced by the kidney, does not fill the bladder and is involuntarily lost out of the body.
Often in these cases, in addition to urinary incontinence, hydronephrosis and hydroureters (dilation of the kidney and ureter, respectively) are documented. Furthermore, hydronephrosis and hydroureters frequently predispose to bacterial infections of the urinary tract. Bacterial infections can be dangerous and may lead to death. In dogs the most predisposed breeds are Labrador Retriever, Golden Retriever, Siberian Husky, West Highland White Terrier and English Bulldog.
Intramural ectopic ureter
The ectopic ureter is intramural in more than 90% of cases. In the intramural form the ureter crosses the bladder and urethral wall to end into the urethra, vagina or vulva. Treatment of the ectopic ureter is surgical and the aim is to bring back the ureteral end to its correct position, the bladder. Besides traditional surgery (neoureterostomy and neoureterocystostomy), recently a mini-invasive technique based on laser surgery (laser diode) has been developed to be performed under endoscopic guidance. After cystoscopic identification of the ureteral ends, the laser surgery fiber is inserted in the working channel of the endoscope and the anatomic abnormality is corrected. In almost all cases treatment is performed immediately following diagnosis.
(A: endoscopic diagnosis of ectopic ureter (the arrow shows the abnormal opening of the ureter in the urethra). B: use of laser surgery to treat the ectopic ureter (the arrow shows the laser surgery correcting the abnormal ureter). C: opening of the ureter after treatment with laser surgery (the arrow shows the normal ureteral opening in the bladder).
The advantage of the laser surgery technique consists in its limited invasiveness and in the procedural velocity, with fast post-operative recovery periods. Indeed, treatment with laser surgery is performed in day hospital and, usually, from the day after the patient is again in good clinical conditions.
Extramural ectopic ureter
In case of extramural ectopic ureter the ureter entirely bypasses the bladder to end in an abnormal position. This form of anatomic abnormality is infrequent and its correction is only possible by means of traditional surgery.
Ectopic ureter and additional anatomic abnormalities
Sometimes the ectopic ureter is accompanied by other anatomic abnormalities. In the female, for instance, paramesonephric septal remnant and the vestibulovaginal stenosis are often concurrently present (figure on the left; arrow shows the stenosis). These abnormalities can be corrected with laser surgery under endoscopic guidance. Moreover, malformations of the kidney (figure on the right; renal agenesia) or of the external genitals can also be present.
Urinary incontinence and sexual hormones
In some dogs the lack of sexual hormones (estrogens) due to neutering causes loss of urethral tone and, in particular, of the bladder neck, which is important to "close the door" to urine flowing out of the body. Normally, the bladder neck remains contracted during bladder filling and is relaxed only during micturition. In pathologic conditions, the tone decreases (the door opens) and urine involuntarily flows out. To treat the disorder two paths can be followed: one is based on hormonal treatment, to equilibrate the hormonal decrease and normalize the muscular tone; the other is surgical, to recreate an obstacle to urine flowing out of the body. For this last purpose several techniques have been proposed; among them the most used are urethroplasty with bulking agents and the artificial urethral sphincter.
Urethroplasty with bulking agents
In case of urethroplasty with bulking agents, using the mini-invasive endoscopic approach it is possible to inject collagen in the context of the urethral wall (in 3 points) in order to effectively reduce the urethral lumen but allowing normal micturition.
A: endoscopy of the urethra (the arrow shows the distended urethra). B: urethroplasty with bulking agents (the arrow shows the site for injecting the bulking agent in the urethral tissue). C: urethra after injection of the bulking agent (the arrow shows that the urethra is less distended).
The advantage of urethroplasty with bulking agents is represented by the fact that it is a mini-invasive procedure. The most important disadvantage is that the injected substances tend to reabsorb during time and, therefore, it may be necessary to repeat the treatment. In recent times a polymer that is much less reabsorbed than collagen has been introduced. This substance can be used as an alternative to collagen.
Artificial urethral sphincter
The artificial urethral sphincter is a device (balloon) that is surgically positioned around the urethra and is connected to a small subcutaneous reservoir. The device causes external compression of the urethra. By means of the reservoir the surgeon can, from the outside, regulate the pressure of the balloon, modifying the degree of urethral narrowing. After 15 days from surgical implantation, necessary to give time to the body to "accept" the foreign body, the artificial urethral sphincter can be inflated (the procedure is performed under sedation) until the most appropriate degree of narrowing is reached to maintain continence and, at the same time, to allow micturition.
A: artificial urethral sphincter (the arrow shows the balloon that surrounds the urethra). B: urethral endoscopy with deflated artificial urethral sphincter (the arrow shows the distended urethra). C: urethra with inflated artificial urethral sphincter (the arrow shows the urethra, almost entirely closed).
In some cases, to achieve the best degree of narrowing, more post-surgical inflations are required. The advantage of the artificial urethral sphincter is that, in general, once the device has been implanted it works for the entire dog's life. The disadvantage is represented by the fact that its positioning requires surgical intervention.
Lastly, in female dogs that have been neutered by means of ovariohysterectomy (removal of the ovaries and uterus) it is possible to observe bladder dislocation. The bladder may dislocate caudally, in the pelvic canal, because the bladder is not mechanically sustained by the uterus. This dislocation causes the so called pelvic bladder and may lead to urinary incontinence because the bladder neck is located in a region where the abdominal pressure is limited. Abdominal pressure is necessary to keep normal urinary continence. Correct positioning of the bladder can be easily ascertained during the diagnostic workup. The treatment of choice is represented by colposuspension, urethropexy and cystourethropexy.
Urinary incontinence and neurological diseases
Incomplete or lack of bladder voiding may be one clinical sign of a neurological disease. Affected animals have neurogenic urinary incontinence. Involuntary urine loss is often secondary to excessive filling of the bladder in these cases.
Indeed, in normal conditions, the bladder contracts when the urine volume reaches the necessary threshold to stimulate pressure receptors which are present on the bladder walls. The pressure stimulus "travels" across peripheral nerves, spine and brain. Therefore, a disease that affects any of these neurological structures can cause a defect in voiding of the bladder and neurogenic urinary incontinence. In such cases it is important to identify the neurological disease that leads to incontinence. Resolution of the bladder problem relies on solving the underlying neurological disease.
If treatment is not curative with regard to the cause of neurogenic urinary incontinence, the animal may be managed as above described for the hormonal urinary incontinence.
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