13 Treatment of Obstruction Following Stress Incontinence Surgery
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Because of greater public awareness, more and more women are actively seeking treatment for stress urinary incontinence (SUI). This increase, combined with the availability of newer surgical techniques associated with less morbidity, has led to a rise in the use of surgery to treat SUI and a concomitant increase in the number of patients with postoperative voiding problems. The true incidence of voiding dysfunction and iatrogenic obstruction after SUI surgery is likely unknown and probably underestimated because of underdiagnosis, misdiagnosis, variations in definition, and underreporting. Reported rates of obstruction vary depending on the type of surgery performed (Table 13-1). Urinary obstruction requiring intervention will occur in at least 1% to 2% of patients after any SUI surgery, even when performed by an experienced surgeon.
Voiding dysfunction following SUI surgery is related to obstruction, detrusor overactivity, or impaired contractility. Iatrogenic obstruction is most commonly the result of technical factors. With sling procedures, obstruction is usually caused by excessive tension on the sling around or under the urethra. The sling can also become dislodged and displaced from the intended position, producing obstruction. During retropubic urethropexy, sutures placed medially can lead to urethral deviation or periurethral scarring resulting in obstruction. Sutures placed distally can cause kinking of the urethra with resultant obstruction and an inadequately supported bladder neck or proximal urethra, and potentially lead to continued SUI. “Hypersuspension” or overcorrection of the urethrovesical angle can also result from excessive tightening of the periurethral sutures. Vaginal prolapse that is not recognized and corrected at the time of sling surgery can also lead to obstruction via kinking or external compression. Learned voiding dysfunction with failure of external sphincter relaxation after surgery can produce functional obstruction. Finally, impaired contractility can be responsible for a relative obstruction.
Patients with iatrogenic obstruction following SUI surgery may have a variety of signs and symptoms. The most obvious are complete or partial urinary retention, the inability to void continuously, or a slow stream with or without intermittency. However, many women do not have obstructive voiding symptoms and experience mainly the storage symptoms of frequency, urgency, and urgency incontinence. It is believed by some that storage symptoms associated with obstruction develop as a result of either acquired parasympathetic denervation or alterations in cholinergic and purinergic afferent pathways. Women may also have a combination of voiding and storage symptoms. Thus, in any case of de novo voiding and/or storage symptoms, the diagnosis of obstruction should be entertained.
Transient voiding dysfunction and urinary retention are common after certain SUI surgeries (e.g., traditional procedures like pubovaginal sling). Because of this, it is difficult to determine the appropriate timing of evaluation and intervention for suspected obstruction following such SUI procedures. Traditionally evaluation was delayed for at least 3 months after surgery. This practice was based on the literature on pubovaginal sling placement, colposuspension, and needle suspension, which indicated that recurrent SUI following intervention could be minimized by waiting at least 90 days before evaluation of obstructive symptoms because spontaneous resolution of symptoms commonly takes 3 months. However, the waiting period that was advocated after these traditional procedures has largely been abandoned for retropubic, transobturator, and single-incision synthetic midurethral sling procedures. Because of the immobility and contraction of the mesh as well as in-growth of fibroblastic tissue at 1 to 2 weeks, patients with retention or severe symptoms are less likely to improve beyond this period. After retropubic and transobturator tape procedures, temporary voiding dysfunction has been reported to resolve in 25% to 66% of patients in 1 to 2 weeks and in 66% to 100% of patients by 6 weeks. Based on these data and our experience, waiting beyond 6 weeks for workup and intervention seems unwarranted. Some would also argue that because up to 66% of patients can be expected to experience resolution of their symptoms within 2 weeks, workup and possible intervention are warranted at the 2-week mark or earlier (in cases of complete inability to void) after discussion with the patient about her symptoms, level of bother, and willingness to risk possible intervention. In our practice, if a patient is unable to void spontaneously (i.e., has urinary retention) within 1 week after a retropubic or transobturator tape procedure, we will consider and discuss loosening the sling in cases in which simultaneous pelvic organ prolapse repair was not done.
For a patient with suspected obstruction, the workup should include a focused history taking, physical examination, and measurement of postvoid residual. The workup may include uroflowmetry, cystourethroscopy, and urodynamic testing in selected cases. Key points to address in the history taking are the patient’s preoperative voiding status and symptoms, and the temporal relationship of new symptoms to the SUI surgery. The type of procedure and relative risk of obstruction associated with that procedure should be considered and the risk of obstruction determined. If the patient is straining to void, she should be instructed to stop this behavior, because SUI surgeries are designed to stop the flow of urine with abdominal straining. Physical examination should focus on determining the angulation of the urethra and detecting any signs that it may be kinked or hypersuspended. However, most patients will not appear to be overcorrected after a midurethral sling procedure. Patients should be examined for prolapse, urethral hypermobility, and recurrent stress incontinence. Cystourethroscopy may be performed to rule out the presence of any sling material in the urethra or bladder as well as to evaluate for any scarring, narrowing, occlusion, kinking, or deviation. Urodynamic evaluation can be performed if there is doubt regarding the diagnosis based on the history, physical examination, and noninvasive testing (measurement of urine flow and postvoid residual). Unfortunately, no universally accepted urodynamic criteria exist for bladder outlet obstruction. A finding of classic high-pressure, low-flow voiding dynamics confirms the diagnosis, but this is not always present even with significant obstruction because of the differing voiding dynamics in women and men. For patients with complete or significant retention who emptied normally before surgery, urodynamic testing is of minimal diagnostic benefit, and often the results do not affect treatment. The usefulness of urodynamic testing for patients with retention is limited and should not be used to exclude patients from an intervention, even if detrusor contraction or high-pressure, low-flow voiding dynamics are absent. For patients with predominately de novo storage symptoms who have normal emptying, urodynamic testing can help identify or rule out obstruction. Videourodynamic testing is preferable to standard urodynamic testing because it allows the site of obstruction to be identified by fluoroscopy regardless of pressure-flow dynamics.
In women with postoperative urinary retention following synthetic midurethral sling procedures, some surgeons advocate early intervention within 7 to 14 days after surgery. After placement of synthetic midurethral slings (retropubic, transobturator, and single-incision slings) the vast majority of patients should be able to void spontaneously within 72 hours. Early sling loosening can be performed in a minimally invasive procedure under local anesthesia in the office setting or operating room. Early sling loosening is recommended only for women who are dependent on catheterization to empty the bladder.
The described procedure can be performed in the office if the patient is cooperative. However, if the patient is anxious or unwilling, it can be done in the operating room with intravenous sedation and local anesthesia. It is best to perform the procedure within 10 to 14 days of surgery, because after this time tissue ingrowth may prevent loosening. In such a case we recommend cutting the sling in the midline.
Transvaginal sling incision can be used for traditional pubovaginal slings (autologous, xenograft, or allograft) as well as synthetic midurethral slings. Sling incision is the treatment of choice for treatment of obstruction caused by a pubovaginal sling or synthetic midurethral sling in the nonacute setting.
3. The sling should be identified and isolated. It may be encased in scar or may be under significant tension and difficult to identify. Careful dissection is required to identify the sling. A cystoscope or sound may be placed into the urethra with upward retraction to expose the sling by isolating the axis of tension and indention on the urethra. Some biological slings may not be identified because of autolysis. In such cases the surgeon may proceed to urethrolysis. All synthetic slings must be definitively identified.
3. Careful dissection is performed to isolate the sling. Injury to the urethra can be avoided by beginning the dissection distally to identify normal urethra and then proceeding proximally to identify and isolate the sling. It should be kept in mind that when there is no urethral erosion, in most cases the sling will be superficial to the periurethral fascia.