Sacral Neuromodulation (SNM) is a treatment modality for patients with refractory overactive bladder (OAB) symptoms and voiding dysfunction (VD). SNM is performed in two stages, with the initial test phase being performed as a percutaneous nerve evaluation (PNE) or an advanced tined lead evaluation (ATLE). Traditionally, PNEs are done without the use of fluoroscopy but instead via surface anatomical landmarking. The International Continence Society (ICS) Standardisation document suggests that the conversion rate from a PNE to a permanent implant is 44-52% and is based on surface anatomy marking. This is considerably less than their suggested 80% following ATLE. There is limited research evaluating the average success rate of PNE with fluoroscopy and therefore this study reviewed the data from a single implant center who routinely use fluoroscopy determine PNE conversion rates.

A retrospective review of PNEs performed between September 2018 and September 2022 was conducted. During this two-year period, 212 patients underwent PNE with fluoroscopy for indications of voiding disfunction (VD), detrusor overactivity (DO), nocturnal enuresis and bladder pain syndrome. The rate of permanent implant after ≥50% improvement in symptoms assessed on a bladder diary was analysed along with continued symptom control at 2 – 42 months of follow-up.

64% (n=136) of patients experienced a more than 50% improvement in symptoms which is higher than the previously reported success rate of 44-52% (figure 1), without the use of fluoroscopy. Of these 136 patients, 115 have already been implanted and the remaining 21 are awaiting a full implant date. 
Success rate was established through self-reported outcome measures which included the International Consultation on Incontinence Questionnaires for lower urinary tract symptoms (ICIQ-LUTS) and quality of life (ICIQ-QoL), as well as an ICIQ bladder diary.
The successful group was evaluated based on patient diagnosis (figure 2) with the highest continued success rate being observed in patients with mixed symptoms. Specifically, DO and VD with 100% of patients (n=8) still experiencing a ≥50% improvement at least 2 months post implant. 
Of the 76 (36%) unsuccessful  PNE patients, the most common diagnosis was detrusor overactivity incontinence (DOI) in 26 patients (27%), followed by VD (24%) and DO (21%). These findings suggest that DO, DOI, and VD are common diagnoses among patients with unsuccessful PNE procedures, and this mimics published data that SNM works in about 70-75% of cases.

The two main criticisms of PNE have been wire migration and not inserting the PNE test lead in the same position of the final implant. Based on our data, fluoroscopy has significantly increased the success rate of conversion from PNE to full SNM implant by allowing the PNE lead to be inserted in a similar position to the full implant lead while reducing pressures on theatre waiting lists and reducing costs of having unsuccessful tests. ATLE need to be inserted under sedation in the operating room and has to either be removed or have a full implant within four weeks which may not be possible and adds pressures to theatres in some healthcare systems. While the PNE can be removed in the outpatient setting with a planned insertion of the full implant at a later date. With careful taping of the PNE lead, we have not had wire migrations unless accidentally pulled by the patient

PNE with fluoroscopy guidance is a viable test option for patients with DO or VD allowing an acceptable conversion rate without the need for an ATLE. It can be performed in the outpatient setting under local anaesthetic only and therefore has the benefit of not requiring theatre space or being as vulnerable to surgical cancellations. This study shows a higher than reported success rate with the addition of fluoroscopy, and this may have important financial, and patient centered implications including reducing waiting lists and pressures on operating lists.