Electrical stimulation of the urethra evokes bladder contractions in a woman with spinal cord injury

Abstract

Objective: Electrical stimulation of pudendal urethral afferents generates coordinated micturition in animals and bladder contractions in men after spinal cord injury (SCI), but there is no evidence of an analogous excitatory urethra-spinal-bladder reflex in women. The objective of this study was to determine whether electrical stimulation of the urethra could evoke bladder contractions in a woman with SCI.

Case report: A 38-year-old woman with a C6 ASIA A SCI who managed her bladder with clean intermittent catheterization and oxybutynin demonstrated neurogenic detrusor overactivity on urodynamics. Oxybutynin was discontinued 2 days prior to urodynamic testing with a custom 12F balloon catheter mounted with ring-shaped electrodes located in the bladder neck, mid urethra, and distal urethra. The inflated balloon was placed against the bladder neck to stabilize the catheter electrodes in place along the urethra. However, the balloon limited emptying during contractions. Urodynamics were performed at a filling rate of 25 mL/minute until a distention-evoked bladder contraction was observed. The urethra was stimulated over a range of bladder volumes and stimulus parameters to determine whether electrical stimulation could evoke a bladder contraction.

Findings: Electrical stimulation via urethral electrodes evoked bladder contractions that were dependent on bladder volume (>70% capacity) and the intensity of stimulation.

Conclusions: This is the first report of an excitatory urethra-spinal-bladder reflex in a woman with SCI. Future studies will determine whether this reflex can produce bladder emptying.

Figure 1

Detrusor pressure in response to electrical stimulation (bar) of the urethra. Electrical stimulation of the distal urethra at 35 mA, 20 Hz, evoked a bladder contraction, which generated some voiding, but the bladder neck was occluded by a Foley balloon and the voided volume was not recorded. Bladder volume prior to stimulation was approximately 90% of the volume threshold for distention-evoked contractions (V_th). Peak detrusor pressure increase evoked by stimulation was approximately 70 cmH₂O.

Figure 2

Detrusor pressure in response to urethral stimulation at different bladder volumes. Electrical stimulation of the distal urethra did not evoke a bladder contraction when the bladder was filled to 50% of V_th (A), but stimulation did evoke a contraction when the bladder was filled to 70% of V_th (B). Stimulus amplitude was 22 mA and frequency was 20 Hz. Bladder contraction generated some voiding, but the voided volume was not recorded. Peak detrusor pressure increase evoked by stimulation was approximately 75 cmH₂O.

Figure 3

Detrusor pressure in response to urethral stimulation at different stimulus amplitudes. Electrical stimulation of the midurethra at 12 mA did not evoke a bladder contraction (A), but stimulation at 15 mA evoked a substantial increase in detrusor pressure (B). Bladder contraction generated some voiding, but the volume voided was not recorded. Bladder volume was 70% of V_th at the beginning of each stimulation trial, and stimulation frequency was 20 Hz. Peak detrusor pressure increase evoked by stimulation was approximately 85 cmH₂O.