To identify the success rate of sacral nerve modulation in patients with chronic urinary retention (CUR) and voiding dysfunction (VD), identified as having primary urethral dysfunction (Fowlers syndrome).

Retrospective data was collected between January 2013 till January 2018 (5-year period) in the uro-neurology department. All the patients were diagnosed with urinary retention due to primary urethral dysfunction identified using cystometography (flow rate and post void residual measurements), urethral sphincter volume, urethral pressure profile and urethral electromyography (EMG). All patients underwent sacral nerve modulation (SNM) at the same unit under a single surgeon. This was carried out using the two-stage approach, with electrode insertion (stage 1) followed by battery insertion (stage 2) if stage one was deemed to be successful. The primary outcome measure was success rate of SNM. This was identified using improvement in quality of life as well as objectively using bladder diaries and flow rate and PVR measurements The failure rate was separated into primary failure after stage 1, true failure of the electrode and secondary failure (after insertion of the battery). Secondary complications were also identified including infection, pain, medical complications, displaced electrode.

No ethical submission was required.

A total of 388 patients were identified in this study. 369 patients were women, 17 were male and 2 were transgender. The overall success rate for SNM in patients with CUR was 85%. In male patients it was 82% whereas in women it was 86%. The overall primary failure rate was 10% and secondary failure rate was identified as 5%. The infection rate was 5%. 
29 patients (7%) were identified to have had a successful SNM but required removal of the device. Of these patients 48% required removal due to infection, 17% as due to requiring MRI imaging for other pathology, 17% due to patient request, 14% due to pain and 4% due to pregnancy.
18 patients complained of other complications but despite these felt the benefit outweighed the complications and therefore the SNM device was left in situ. Of these patients 44% complained of battery site pain, 27% complained of leg pain, 11% complained of groin pain, 6% (1 patient) suffered from a haematoma, 6% (1 patient) suffered from a DVT and 6% (1 patient) complained of toe curling.

There was significant improvement in chronic urinary retention in both male and female patients with sacral nerve modulation. The overall infection rate of 5% is an appropriate risk in this surgery.

Sacral nerve modulation has a very high success rate in patients with chronic urinary retention with voiding dysfunction and should be considered as the gold standard in treatment for these patients.