The continence surgery for neurogenic bladder is challenging for urologists. As neurogenic stress urinary incontinence (NSUI) is usually accompanied by detrusor dysfunction and intrinsic sphincter deficiency, midurethral sling which is known to be treatment of choice for non-neurogenic stress incontinence may not result in satisfactory outcome for NSUI patients. In addition, for NSUI patients, restoration of the continence with anatomically supporting sling may result in high pressure reservoir dangerous to upper urinary tract. Possible newly developed detrusor overactivity following midurethral sling may aggravate the increase of intravesical pressure. Nevertheless, little literature is available on the change of bladder compliance after midurethral sling in NSUI patients [1][2][3]. Hereby we have performed study to evaluate the change of urodynamic parameters after midurethral sling for female NSUI.

Female patients who received retropubic midurethral sling for NSUI from March 2008 to October 2017 at a tertiary referral center were retrospectively reviewed. The urodynamic studies were conducted according to the “Good Urodynamic Practice” suggested by the International Continence Society (ICS). Patients were positioned in the supine or semi-seated position. Warm physiologic saline solution was infused through a No. 6-Fr double lumen catheter at median filling rate of 20-30ml/min. Abdominal pressure was measured using No. 8Fr rectal balloon catheter. Urodynamic parameters were determined according to the terminology standardized by the ICS. Paired comparison of urodynamic parameters, before and after midurethral sling, were performed using Wilcoxon Signed Rank test (SPSS ver. 23).

Eighteen female patients received retropubic midurethral sling for NSUI. Out of them, 10 patients with urodynamic data, both before and after midurethral sling, were included in assessment. Median patient age at midurethral sling was 53.6 (35.8~74.2) years. Causative diseases were multiple system atrophy (2), spinal dysraphism (1), spinal cord injury (3), spinal stenosis (1), spinal cord tumor (1), cerebrovascular accident (1) and systemic lupus erythematosus (1). Median bladder compliance was 64.6(11.1~270.5) ml/CmH2O, median maximum cystometric capacity was 497.5(103~716) ml, before midurethral sling. All the patients proved to have NSUI by preoperative urodynamic study. Eight patients (80%) had mixed urinary incontinence before surgery. Nine patients received readjustable mesh sling, one patient received autologous rectus fascial sling. For one patients with bladder compliance less than 20 ml/CmH2O, synchronous augmentation ileocystoplasty was performed. During the median follow up period of 45.7(11.6~120.7) months, there was no significant surgical complication including mesh erosion, and 4 patients needed sling readjustment.
At the latest follow up, 5(50%) patients showed surgical success without NSUI, 5(50%) had improved but still persistent NSUI. Out of 5 patients with NSUI, 4(40%) had mixed urinary incontinence. Six patients (60%) relied on assisted bladder emptying. Except for one patient with augmentation ileocystoplasty, 9 patients were included in paired assessment of urodynamic parameters before and after midurethral sling. In success group, without postoperative NSUI, bladder compliance has increased from median 64.6 (34.8~219.5) ml/CmH2O to median 94.3(54.5~179.0) ml/CmH2O (P=1.000), maximum cystometric capacity has increased from median 522 (254~664) ml to median 584(537~600) ml (P=0.465). On the other hand, in failure group with persistent NSUI, bladder compliance has significantly decreased from median 76.1(25.8~238.7) ml/CmH2O to median 27.5(19.6~154.5) ml/CmH2O (P=0.043), and maximum cystometric capacity has also decreased from median 492 (103~716) ml to median 459 (87~618) ml (P=0.500) without statistical significance. The lowest postoperative bladder compliance was 19.6 ml/CmH2O, and all the other patients’ bladder compliance was more than 20 ml/CmH2O.

Although bladder compliance has decreased significantly in persistent NSUI group, maximum cystometric capacity has not changed significantly. With this result, we could infer that the decreased bladder compliance is not associated with under-filled state of bladder, caused by persistent urinary incontinence. Although, it is not known which cause is the leading factor, we could observe aggravation of bladder compliance in persistent NSUI group.

Contrary to general concern that restoration of continence may result in high pressure bladder and consecutive poor bladder compliance, patient with persistent NSUI showed significant decrease in bladder compliance. Therefore follow up urodynamic investigation might be provided for all the patients with neurogenic bladder regardless of presence of NSUI.

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