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Published on: April 25, 2017
The Long-Term Effects of Sacral Neuromodulation on Urodynamic Parameters in Female Patients With Functional
Ross Stephens1, Sachin Malde1, Arun Sahai1
1Guy's and St Thomas' NHS Foundation Trust, London, UK.
Introduction:
Sacral neuromodulation (SNM) is used to treat women with dysfunctional voiding (DV), including those with high-pressure, low-flow (HP-LF) voiding. In this subgroup, persistent elevated voiding pressures raise concerns about long-term bladder and upper tract deterioration. Conventional urodynamic measures such as Pdet.Qmax and Qmax reflect only a single point in the voiding cycle and do not capture the full detrusor workload. The area under the pressure-flow curve (AUC) offers a more comprehensive metric of cumulative voiding pressure.
Aim:
To assess whether long-term SNM reduces AUC in women with HP-LF due to DV, and how this compares to changes in standard urodynamic parameters.
Methods:
Seven women with DV and HP-LF underwent urodynamics before and after SNM. Inclusion criteria included female patients with prolonged or irregular flow rates on urodynamics, high voiding pressures (BOOIf > 18) and either radiological evidence of dynamic mid-urethral narrowing or elevated mid-urethral closure pressure for age. Outcomes included AUC, AUC/VV (normalised to voided volume), and standard voiding/storage metrics. Symptom change was assessed via PGIC score.
Results:
Median age was 42. Median follow-up was 986 days. PGIC scores ranged 4-7 (median 6). Median (IQR) AUC decreased from 3548 (2540-6228) to 2998 (1714-4605) cmH₂O·s (p = 0.297) and AUC/VV from 20 (10-47) to 17 (3-21) cmH₂O·s·mL⁻¹ (p = 0.688). Median (IQR) Pdet.max decreased by from 54 (49-66) to 44 (40-59) cmH₂O (p = 0.047). No other pressure or flow parameters demonstrated a statistically detectable change.
Conclusion:
Long-term SNM improves symptoms in women with HP-LF voiding but does not significantly reduce cumulative detrusor pressure. These patients may remain at risk of bladder dysfunction and warrant continued follow-up.
