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Article of the week: Prolonged SNM testing effective despite bacteria presence

Every week the Editor-in-Chief selects the Article of the Week from the current issue of BJUI. The abstract is reproduced below and you can click on the button to read the full article, which is freely available to all readers for at least 30 days from the time of this post.

In addition to the article itself, there is an accompanying editorial written by a prominent member of the urological community. This blog is intended to provoke comment and discussion and we invite you to use the comment tools at the bottom of each post to join the conversation.

If you only have time to read one article this week, it should be this one.

Prolonged percutaneous SNM testing does not cause infection-related explanation

Bastian Amend, Jens Bedke, Mahmoud Khalil, Arnulf Stenzl and Karl-Dietrich Sievert

Department of Urology, Eberhard Karls University Tuebingen, Tuebingen, Germany

OBJECTIVE

• To evaluate the impact of prolonged stage 1 testing on bacterial electrode colonization, infection and treatment success.

MATERIALS AND METHODS

• In all, 21 patients who underwent sacral neuromodulation (SNM) for periods 1 month were prospectively evaluated; nine patients had overactive bladder syndrome (OAB), 10 had urinary retention, two had faecal incontinence (FI), and 13 had diabetes and overweight/obesity.

• After stage 1 testing electrode extension leads were microbiologically analysed to assess bacterial colonization.

• The primary measurements were pre- and post-SNM treatment comparisons based on patient-agreed criteria using an increased 70% minimum improvement rate; secondary measurements were bacterial colonization and impact of infection.

RESULTS

• The mean stage 1 evaluation period was 52.3 days; 16 patients (76%) progressed to stage 2, and five patients were explanted due to inadequate improvement (<70%).

• There was bacterial colonization in 42.9% of patients and 38.2% of extension leads.

• Stage 2 patients showed no infection or wound-healing disorders at a mean follow-up of 33.9 months.

• The success rate for stage 2 implantation treatment was 94%.

CONCLUSIONS

• There are few studies in the literature evaluating SNM testing periods vs the risk of clinically relevant implant infection rates. The present study shows that prolonged testing could potentially enhance treatment efficacy without infection-related explantations of the chronic implant, despite the identification of bacteria.

• SNM-implanted patients with diabetes mellitus or obesity should be followed closely.

• Clinicians might consider using prolonged testing under everyday conditions.

• Prolonged SNM stage 1 testing is a very effective minimally invasive treatment option to evaluate pelvic-related dysfunction.

 

Read Previous Articles of the Week

Editorial: What is the optimal length of time for SNM testing?

The authors are to be commended for their unique investigation of an extended stage 1 SNM test period. To our knowledge, no other series has included a minimum 4-week duration and microbiologic testing. Optimal duration for the test phase has not been elucidated and initial responses are likely compounded by a short-term placebo effect that may dissipate after time. Knowledge of when maximal improvement occurs would define a population of true responders and reduce implant failure rates. This series shows the feasibility of an extended test phase in a small cohort, but does not identify the optimal length of time for testing.

One must question how many responders are in the 2- to -4 week interval and if such patients would do as well with earlier implantation. Current testing with permanent leads and externalized hardware is cumbersome and not always convenient for activities of daily living, especially showering. Furthermore, knowing the sampling interval used by the authors to assess response and the time at which the majority of patients reached the established implant criteria could clarify the time needed for maximal response. In this small cohort, however, the difference would fail to show significance.

As the authors note, a low stage 2 failure rate is important in an era with rising concern over health care expenditure, but it generates questions on what to do for responders
who have symptomatic improvement >50% but <70%. Do we risk not helping an individual who has 50% improvement in order to reduce stage 2 failures, and how do we justify making this quality-of-life decision? The low stage 2 failure rate in this study may have resulted from the strict criteria for stage 1 success, specifically a 70% or greater response, and not necessarily the prolonged test phase.

Notably, there were no infections in this series despite an extended stage 1 test phase. This is considerably lower than the 5–7% infection rate reported in the literature (UrologyEur Urol). Perhaps the degree of hygiene and antibiotic regimen contributed to the lack of infectious complications, but concern remains that such results are not generalizable. Infectious events not captured in this series may become evident with a larger sample size and surely the rate will be greater than zero. Granted, the results of this study add to our knowledge of SNM, it is not conclusive that the outcomes can be applied to the population at large, and further evidence from randomized trials are needed to identify the balance between benefits and risks associated with an extended test phase.

Brian K. Marks and Sandip P. Vasavada
Center for Female Urology and Reconstructive Pelvic Surgery, Glickman Urological and Kidney Institute, Cleveland Clinic, Cleveland, OH, USA

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