The use and mechanism of anal sphincter stretch in the reflex bladder

Acute anal stretch inhibits NMDA-dependent pelvic-urethra reflex potentiation via spinal GABAergic inhibition in anesthetized rats

The impact of acute anal stretch on the pelvic-urethra reflex potentiation was examined in urethane-anesthetized rats by recording the external urethra sphincter electromyogram activity evoked by the pelvic afferent stimulation. Test stimulation (1 stimulation/30 s) evoked a baseline reflex activity with a single action potential that was abolished by gallamine (5 mg/kg iv). On the other hand, the repetitive stimulation (1 stimulation/1 s) induced spinal reflex potentiation (SRP) that was attenuated by intrathecal 6-cyano-7-nitroquinoxaline-2,4-dione (a glutamatergic α-amino-3-hydroxy-5-methyl-4-isoxazoleproprionat receptor antagonist, 100 μM, 10 μl) and d-2-amino-5-phosphonovalerate [a glutamatergic N-methyl-d-aspartate (NMDA) antagonist, 100 μM, 10 μl]. Acute anal stretch using a mosquito clamp with a distance of 4 mm exhibited no effect, whereas distances of 8 mm attenuated and 12 mm abolished the repetitive stimulation-induced SRP. Intrathecal NMDA (100 μM, 10 μl) reversed the abolition on SRP caused by anal stretch. On the other hand, pretreated bicuculline [γ-aminobutyric acid (GABA) A receptor antagonist, 100 μM, 10 μl] but not hydroxysaclofen (GABAB receptor antagonist) counteracted the abolition on the repetitive stimulation-induced SRP caused by the anal stretch. All of the results suggested that anal stretch may be used as an adjunct to assist voiding dysfunction in patients with overactive urethra sphincter and that GABAergic neurotransmission is important in the neural mechanisms underlying external urethra sphincter activity inhibited by anal stretch.

Urodynamic responses to anal stretch in patients with detrusor sphincter dyssynergia

OBJECTIVE

To evaluate the urodynamic responses to anal stretch in patients with detrusor sphincter dyssynergia (DSD).

DESIGN

Descriptive study.

SETTING

Rehabilitation hospital affiliated with a medical university.

PARTICIPANTS

Patients (N=36) with suprasacral spinal cord injury who had DSD confirmed on cystometrography.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Detrusor pressure, urethral pressure, and summated electromyogram of external urethral sphincter on cystometrography.

RESULTS

The urodynamic responses to anal stretch were evaluated in the first half (time 1, 1-15s) and the second half (time 2, 16-30s) of the evaluation time period. The activity of external urethral sphincter was reduced significantly in both times 1 and 2 (P<0.5). The medians of reduction percentages were 33% and 35% for times 1 and 2, respectively. The change of detrusor pressure was not significant in either time 1 or time 2.

CONCLUSIONS

Anal stretch can reduce the activity of external urethral sphincter without significant change in detrusor pressure.

Conservative treatment of the neuropathic bladder in spinal cord injured patients

Different conservative treatment modalities for the lower urinary tract dysfunction in patients with spinal cord lesion are reviewed. Conservative treatment is still the mainstay of the urological management in these patients. Growing experience has changed the classical approach. Spontaneous voiding with and without triggered voiding and/or bladder expression has proven to be less safe except in well defined patients with regular urological follow-up. Nowadays, intermittent catheterisation and self catheterisation with and without bladder relaxants are accepted as the methods of choice. Condom catheters are still needed if incontinence persists, while penile clamps have no place in the treatment of patients with spinal cord lesions. Long-term indwelling catheters should be avoided. External electrical stimulation can be used to correct the neurogenic dysfunction by neuromodulation and/or to induce a direct therapeutic response in the lower urinary tract.

Surface electrodes in perineal electromyography

In 40 elderly male patients undergoing multiple urodynamic evaluations, surface electrodes were used for recording electromyographic (EMG) activity of pelvic sphincter muscles; placement site was the external anal sphincter. The measured wave form was displayed as an analog plot. Different types of surface electrodes were evaluated in selected patients. The EMG wave form measurements varied with the type of surface electrode used and placement of the electrode. Surface electrodes for external anal sphincter EMG resulting in optimum signal response require a small metallic recording surface with an adhesive that will secure the electrode to the skin, proper anatomic placement of the electrode, appropriate preparation of the skin surface at the site of application of the electrode, and capabilities for oscilloscope monitoring of the sphincter EMG signal wave form. If properly used, surface electrodes result in a signal amplitude and frequency that approach the quality of concentric needle electrodes.