9 Jul 2012
Laurent Findji
Job TitleLaurent Findji looks at management methods of the condition, from diagnosis using radiography through to temporary urine diversion and surgical repair
The most common lower urinary tract (LUT) trauma in cats is urethral rupture, which is most commonly iatrogenic. Bladder ruptures are also encountered and most commonly result from blunt trauma to the abdomen. LUT ruptures are best diagnosed by positive contrast radiography. Their emergency management must be directed at evaluating and correcting the metabolic disturbances resulting from the potential associated uroperitoneum, diagnosing and prioritising the treatment of any concurrent lesions and temporarily diverting urine if definitive treatment of the LUT rupture must be delayed.
Treatment of significant bladder rupture consists of surgical repair of the bladder wall, combined with placement of a means of temporary urine diversion (urethral catheter or cystostomy tube) if necessary. Whenever possible, urethral ruptures are treated conservatively by second intention healing around a retrograde urethral catheter. When this is unsuccessful, or when the urethral defect is too large, urethral repair or permanent urine diversion is performed surgically. Permanent urine diversion is achieved by urethrostomy. The technique allowing preservation of the longest portion of urethra is chosen, depending on the location of the urethral rupture – for example, perineal, transpelvic, subpubic or antepubic.
LOWER urinary tract (LUT) trauma in cats is dominated by urethral tears and ruptures, although occasional cases of bladder rupture are encountered. The most common cause of bladder rupture is blunt trauma to the abdomen, whereas the majority of urethral ruptures are iatrogenic.
Affected cats can, therefore, be presented in variable clinical conditions and with a variety of concurrent lesions (for example, pelvic fractures) and preexisting diseases (for example, postrenal failure secondary to urethral obstruction), which can mask clinical signs caused by the LUT rupture. Therefore, prompt diagnosis of LUT rupture requires a high index of suspicion, based on the patient’s history and list of concurrent lesions.
The definitive diagnosis of LUT rupture is most reliably made by contrast radiography (positive contrast cystourethrography)1 (Figures 1a to 1c and 2a, 2b), although ultrasound may also be valuable to identify bladder ruptures and evaluate associated abdominal lesions.
Depending on the location of the lesion, LUT rupture results in urine leakage into the abdomen, the retroperitoneal portion of the pelvic canal or subcutaneous tissues. The presence of free urine in the peritoneal cavity rapidly leads to peritonitis, which is only mild and does not constitute an emergency, provided the urine is sterile. On the contrary, it rapidly has significant metabolic consequences (postrenal renal failure) including dehydration, metabolic acidosis, azotaemia, hyperkalaemia, hyponatraemia, hypochloraemia and hyperphosphataemia.
The potential urgent nature of LUT trauma management therefore lies in the necessity of rapidly restoring a normal or near-normal physiology by providing a means of urine evacuation (urethral catheter, cystostomy tube, peritoneal drainage), rather than in the definitive repair of the urinary lesion.
The clinically significant metabolic disorders must be assessed and corrected by fluid therapy. When definitive treatment of the urinary tract rupture must be delayed for preoperative medical stabilisation, drainage of the uroperitoneum may be achieved by abdominocentesis or placement of an abdominal catheter or drain. Prevention of further urine leakage can be achieved by retrograde urethral catheterisation or placement of a cystostomy tube.
All these temporary procedures can be performed under local anaesthesia – combined with sedation or not – or general anaesthesia, depending on the clinical condition of the patient. When an abdominal catheter is placed it can be used to perform peritoneal dialyses for more effective medical stabilisation. Temporary cystostomy tubes can be placed either percutaneously, using purpose-designed tubes provided with an insertion system, or surgically, using Foley or de Pezzer (mushroomtipped) catheters2–6.
Urine infiltration in the subcutaneous tissues can lead to extensive tissue necrosis of the skin and subcutaneous tissues (Figures 3a, 3b). These lesions may initially resemble areas of moderate oedema and bruising and take several days to appear more severe. Reconstruction of the resulting defects can be challenging7,8 and considerably increase the cost of treatment. When such infiltration is deemed possible given the site of LUT rupture, it can, therefore, be valuable to divert urine temporarily and delay the definitive treatment of the urinary rupture until the occurrence of skin necrosis can be ruled out.
Diagnosis of uroperitoneum relies on the history, detection and analysis of the abdominal effusion. The site of leakage is then identified by contrast radiography. A bladder rupture cannot be ruled out by the bladder being palpable, urine is obtained by retrograde urethral catheterisation, normal micturitions are observed and haematuria is absent1,4.
In most cases, surgical repair of bladder ruptures is straightforward and technically easy. When required, the edges of the bladder wound are debrided and the bladder is sutured in one layer of monofilament absorbable sutures, in a continuous or interrupted pattern. As with other hollow organs, incorporation of the submucosa in all sutures is essential, but penetration of sutures in the bladder should be avoided wherever possible. It is, however, difficult if the bladder wall is not thickened and, if in doubt, it is preferable to place full-thickness sutures.
When it is deemed necessary to prevent bladder distension in the postoperative period, placement of an indwelling urethral catheter or of a cystostomy tube in a healthy portion of the bladder are options.
In my experience, a urethral catheter can be placed in a retrograde fashion without causing a urethral rupture in almost all cases of urethral obstruction in cats, provided a gentle, proper technique is used. This is in accordance with the data reported in a study of 59 cats with urethral obstruction, in which only one could not be catheterised (1.7 per cent)12.
As for bladder ruptures, spontaneous micturitions, absence of haematuria or easy retrograde urethral catheterisation, do not rule out urethral rupture, which are best diagnosed by positive contrast urethrography.
A urethral rupture can be total (urethral disjunction) or partial, and it can be difficult to differentiate between the two without surgical exploration. However, since, in most cases, the rupture is iatrogenic, it is most commonly partial. Three therapeutic options exist:
• temporary urine diversion in hope of second intention healing of the urethra;
• permanent urine diversion by urethrostomy; and
• surgical primary repair.
The latter is most often considered for the treatment of complete urethral rupture. However, in such cases, it is common for a portion of the urethra to be severely damaged or necrosed, which makes bridging the gap for anastomosis impossible. In all cases, the small size of the feline urethra renders its primary repair technically challenging and fraught with complications.
Consequently, a urethrostomy may be preferred. When a urethral anastomosis (ureteroureterostomy) is performed, an indwelling urethral catheter bridging the anastomosis – acting as a stent and a means of urine diversion – is placed and left there for five to seven days to support wound healing. It can be combined with a temporary cystostomy tube.
The urethra heals rapidly and small urethral defects, which remain spanned by at least a strip of mucosa, are reported to epithelialise in seven days13. However, urine contact with the wound slows its healing, induces fibrosis and increases long-term risks of urethral stenosis14. Therefore, when the urethra is left to heal by second intention, it is important to divert urine by placing an indwelling urethral catheter, a cystostomy tube, or both. In a study comparing these methods of urine diversion, no differences in urethral healing were found15.
In the case of urethral rupture, if retrograde placement of an indwelling urethral catheter is possible, a conservative treatment is indicated in first intention – the indwelling catheter serving as a guide and support for second intention healing. The urethra is most likely to heal by second intention when its rupture is partial, but it may do so after complete rupture10.
If a urethral catheter cannot be placed in a simple retrograde fashion, it may be possible to place one surgically: a cystotomy is performed and normograde placement of a urethral catheter is attempted. If it is successful, the tip of the normograde catheter coming out of the penis is cut and it is linked to another catheter with a cut tip by placing a long stylet or a suture through both catheters. The two catheters then form a “train” of catheters.
The normograde catheter is carefully pulled back cranially while the retrograde catheter is pushed cranially and guided through the urethral rupture site by the normograde catheter. The cystotomy wound is closed routinely and the retrograde catheter left in situ. This approach has led to satisfactory healing of urethral rupture (n = 10) in one study10, and 80 per cent of these cases did not show any related complication.
No data exists to indicate the optimal amount of time the catheter must be left in the urethra. It is sensible to leave it in situ as little as possible, as its presence increases the risk of urinary tract infection (UTI) and post-healing stenosis. Five to 14 days should provide enough time for the urethra to heal10 although longer minimum durations (more than three weeks) have previously been advocated13,16.
When urine leakage around the urethral catheter is observed or feared, the urethral catheter can be combined with a cystostomy tube to achieve more complete urine diversion and minimise the interference of urine with urethral wound healing.
When the urethral rupture is not amenable to conservative treatment, does not heal, or a post-healing stenosis develops, a permanent urine diversion by urethrostomy should be considered. A ure throstomy may also be chosen in the face of a complete urethral rupture when primary repair is not contemplated.
Several urethrostomy types can be considered:
• perineal;
• transpelvic19;
• subpubic; and
• antepubic (prepubic).
As a rule, the urethral portion cranial to the urethrostomy site should be left as long as possible to minimise the likelihood of postoperative complications. Therefore, whenever possible, a standard perineal urethrostomy (PU) is performed. If the length of urethra proximal to the rupture is insufficient to perform a perineal urethrostomy, a transpelvic or subpubic urethrostomy can be performed. Lastly, if the urethral rupture is close to the bladder neck, an antepubic cystotomy may remain the only option.
The surgical technique for performing a PU is described elsewhere13,20–22. Reported short-term complications of this procedure include haemorrhage, subcutaneous urine leakage, wound dehiscence and urinary incontinence. Potential long-term complications include UTIs, urethral stricture and urinary incontinence.
Provided a proper surgical technique is used, short-term complications are rare and mostly consist of mild haemorrhage and temporary imperfect urinary continence. Longterm complications almost exclusively comprise UTIs. In one retrospective study of urethral stoma stricture requiring surgical revision after PU, all strictures resulted from technical errors23.
To avoid complications, the surgeon must be attentive to several key points. The urethra must first be opened up to the bulbourethral glands. Failure to do so was found to be the most common reason for urethral stoma stricture23. Second, tension on the mucocutaneous anastomosis must be kept to a minimum, as it favours stricture. This is achieved by completely freeing the penis from its ventral pelvic attachment by a combination of blunt and sharp dissection, so the penis can be clearly pulled caudally.
However, dorsally to the penis, dissection is not extended cranially (proximally) to the bulbourethral glands to decrease the risk of postoperative incontinence. In addition, placement of tension-relieving sutures between peri-penile structures (bulbourethral glands and ischiocavernous muscles) and surrounding tissues (proximal aspect of the caudal femoral muscles, subcutaneous tissues) helps keep the mucocutaneous anastomosis free of the tension resulting from the caudal traction on the penis.
Thirdly, the mucocutaneous apposition must be precise. If not, urine may infiltrate the surrounding tissues – at best promoting scarring stenosis and, at worse, leading to extensive necrosis of perineal and inguinal tissues. Lastly, the postoperative use of an Elizabethan collar is important to prevent selfmutilation, which is a reported cause of complications.
Should these principles and atraumatic proper technique be adhered to, PU is a straightforward procedure associated with few complications and a fair prognosis.
When the site of urethral rupture is located too cranially to allow performance of a PU, a subpubic or antepubic urethrostomy must be performed. It is important to preserve as much urethra as possible. Therefore, it may be necessary to approach the intrapelvic urethra by pubic or ischiopubic osteotomy (Figures 4a to 4f).
Laurent Findji
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