Professor, University of Bristol, Department of Clinical Veterinary Science, Langford, Bristol, UK
Colposuspension is indicated for the treatment of urinary incontinence due to urethral sphincter mechanism incompetence in bitches. Urethral sphincter mechanism incompetence is mainly a problem of large breeds of dog. Urine leakage occurs predominantly during recumbency, probably since intravesical pressure rises when a bitch's position changes from standing to recumbency. A number of factors contribute to urine leakage in bitches with urethral sphincter mechanism incompetence. As well as body size and breed, these include poor urethral tone, ovariohysterectomy/ovariectomy, a shorter urethral length than normal (both physical and functional, allowing for body size) and a bladder neck located more caudally than normal. Colposuspension is intended to correct the position of the bladder neck (although it may also have a beneficial effect on urethral urodynamic parameters). If urethral tone is adequate, the position of the bladder neck does not matter but in animals with urethral sphincter mechanism incompetence, a caudally-positioned bladder neck may be sufficient to tip the balance in favour of urine leakage, since increased external pressures on the bladder are not counteracted by similar pressures on the urethra.
Accurate diagnosis is essential. It is insufficient to assume that a spayed, incontinent bitch is suffering from urethral sphincter mechanism incompetence without performing adequate diagnostic investigations to eliminate other possible diagnoses. These should include contrast radiography, laboratory examinations and, if available, urodynamics.
Surgery on juvenile bitches with congenital urethral sphincter mechanism incompetence should be deferred until after the bitch's first or second oestrus period. The oestrus periods may result in improvement in urinary continence control and more than half of affected juvenile bitches will become continent after their first oestrus.
In adult bitches, the pros and cons of surgery versus management with drugs (alpha-adrenergics, oestrogens) should be discussed with the owners first. Oestrogens should not be used for long-term control in entire (especially juvenile) bitches because of possible adverse feed-back effects on the pituitary gland. In some juveniles, these effects may be sufficient to prevent the bitch ever having a normal oestrus period. In our clinic, colposuspension cures 53% of cases and improves most of the remainder but does nothing for 10%. The author's approach is to treat younger (less than 8 years of age) adult bitches surgically in the first instance in the hope that prolonged use of drugs such as oestrogens and alpha-adrenergics can be avoided. Colposuspension is performed on older bitches in which drug therapy has failed to control urinary incontinence.
The technique involves loosening the attachments of the lower urogenital tract to the pelvis (through a caudal mid-line laparotomy) by breaking down the pubovesical peritoneal fold and blunt finger dissection. The vagina is then stretched cranially and attached, usually using two 0 monofilament polyamide sutures (each side), to the prepubic tendon on each side of the urethra. This cranial stretching of the vagina results in cranial movement of the urethra and bladder, relocating the bladder neck to an intra-abdominal position.
Post-surgical complications are few. Since the surgery involves vaginal stimulation and some trauma to intrapelvic fascia, some animals are stimulated to strain, usually immediately after recovery from the general anaesthetic. This can be controlled by the administration of appropriate analgesics pre-, peri- and post-operatively. Rarely, some bitches find the first defaecation after surgery to be uncomfortable if the faeces are firm and bulky. This can be controlled with stool softeners.
Dysuria may occur immediately post-operatively. This is rare (less than 3% of cases in the author's experiences). It may be due to vaginal stimulation by the surgery leading to suppression of the micturition reflex and/or reflex dyssynergia. Clinical observations and the response to diazepam suggest that reflex voluntary dyssynergia is the most likely cause of dysuria after colposuspension. It appears to be exacerbated by recent oestrogen therapy and so any oestrogen therapy should cease at least one month pre-operatively. Voluntary dyssynergia usually responds within a few days to diazepam at a dose of 0.2 mk/kg by mouth two or three times daily. An indwelling urinary catheter can be used for a few days if necessary in the minority of animals which are unable to urinate at all. A further potential cause of dysuria is compression of the urethra against the pubis by the vagina. Care should be taken during surgery to avoid placement of vaginal sutures too close to the urethra.
Bitches which are allowed to be very active after colposuspension may tear the sutures from the vagina. This is more likely to happen if they are allowed to run and jump and owners should be advised of the necessity for restricting the exercise of their animals to walks on the lead only for one month after surgery.
Hymen formation and accumulation of vaginal secretions causing dysuria and/or dyschezia is an extremely rare, longer-term complication of colposuspension. It is due to breakdown of a pre-existing vestibulovaginal stricture during the operation and subsequent healing of apposing raw areas of vagina to form a barrier across the vaginal lumen.
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