This original retrospective study was to assess the changes in urodynamic parameters in NB patients with or without vesicoureteral reflux (VUR) who underwent sacral neuromodulation (SNM).

We retrospectively reviewed the records of 19 patients with neurogenic lower urinary tract dysfunction (NLUTD) who underwent SNM at our center from July 2018 to July 2019. Clinical data and video-urodynamic parameters were collected. The inclusion criteria: a clear history of neurogenic disease; video urodynamic examination showed DO or low bladder compliance with or without VUR; ineffective or intolerable for anticholinergic drugs; not willing to accept botox injection or augmentation cystoplasty. The patients with complete spinal cord injury or wheelchair use were excluded. The test results were evaluated through a urodynamic evaluation. The criteria used to implant the sacral neuromodulator was that the safe bladder volume was enough for intermittent catheterization. If the test was positive at the end of test phase, an implant (InterStim Model 3058; Medtronic, Inc., Minneapolis, MN, USA) was implanted.

Between 7/2018 and 7/2019, 19 patients (11 women and 8 men), mean age 32±14.1 years, received test stimulation for treating NLUTD. Neurological diseases included spina bifida(9 patients), incomplete spinal cord injury(4 patients), encephalomyelitis(3 patients), pelvic surgery(2 patients), spinal cord surgery(1 patient). The mean time between the onset of the underlying neurological disease and the test was 8.8±8.10 years. All the patients had low bladder compliance and/or DO with or without VUR in storage period and no voluntary detrusor contraction in voiding period. Preoperative urodynamic evaluation data was in table 1. These patents all needed the Credé maneuver, Valsalva maneuver, or triggered reflex voiding during the voiding phase or indwelling catheter before the testing phase. All patients were operated on by the same experienced urologist.
The mean test duration was 24±8.2 days. The urodynamic evaluation at the end of the testing phase showed a significant increase in the mean maximum cystometric capacity (136.3±118.2 vs. 216.5±137.8 ml, P=0.0071) and compliance (8.7±8.5 vs. 18.3+16.5 ml/H2O, P=0.016), as well as a decrease in the maximum intravesical pressure (57.0±39.2 vs. 36.6±31.2 H2O, P=0.0064).
Eight of 19 patients had DO revealed by urodynamic evaluations at baseline. At the end of the testing phase, the DO in 4 patients disappeared according to urodynamic re-evaluations. In the remaining 4 patients, the volume of first uninhibited detrusor contraction and maximum detrusor pressure during uninhibited detrusor contraction all improved (92.5±33.8 vs. 153.0±64.5ml; 100.8±32.7 vs. 77.3±36.1 H2O), although there was no significant difference (P>0.05). In the voiding phase, none of the patients had detrusor contraction.
Before the testing phase, 12 of 38 ureter units (10 patients) had VUR. According to urodynamic re-evaluations at the end of the testing phase, the VUR in 3 of 12 ureter units disappeared. The grade of VUR or the volume before VUR improved in 8 ureter units, and the remaining 1 did not change significantly (table 2). 
Implantation was performed in 16 cases. Three patients (patients 6, 7, and 8 in table 2) did not undergo implantation of the stimulator. After permanent implantation, all patients needed intermittent catheterization to empty the bladder in order to avoid damage to the upper urinary tract because VUR or detrusor underactivity still existed. In addition to SNM, 10 of the 16 patients also took anticholinergic drugs in the follow-up treatment. The remaining three patients, who did not have permanent implants, underwent augmentation cystoplasty with or without nonrefluxing ureteral reimplantation, as well as intermittent catheterization

In some neurogenic bladder (NB) patients, detrusor overactivity (DO) and poor compliance may lead to a high intravesical pressure during urine storage. This high pressure will result in vesicoureteral reflux (VUR), hydronephrosis and even renal failure. 
In the treatment of NB with SNM, clinicians pay more attention to the improvement of clinical symptoms[1]. However, as a very important parameter in the management of patients with NLUTD, the pressure of the detrusor during the filling period is rarely used to evaluate the success of SNM treatment.
In this study, SNM not only improved the mean maximum cystometric capacity , compliance and the maximum intravesical pressure but also cured or reduced VUR. Because SNM can play a positive role in the filling period and improve the function of urine storage, it can protect the UUT or improve the damaged UUT. 
An implant was performed in 16 cases after the testing phase. According to the results of urodynamic examination, SNM improves the storage function but does not significantly improve the voiding function of the bladder. The patient is still unable to urinate autonomously. Therefore, there is still a risk imposed on the UUT[2]. To protect the UUT, these patients still rely on intermittent catheterization to empty the bladder after permanent implantation.

This retrospective study indicates that SNM can improve the urinary storage function of the bladder in appropriate patients with NLUTD. For patients with VUR, SNM can cure or reduce VUR by improving DO and bladder compliance.

Chen G and Liao L: Sacral neuromodulation for neurogenic bladder and bowel dysfunction with multiple symptoms secondary to spinal cord disease. Spinal Cord 2014;53:204.
Amarenco G , Samer Sheikh Ismaël, Chesnel C et al: Diagnosis and clinical evaluation of neurogenic bladder. European journal of physical and rehabilitation medicine 2017;53:975.