Urethral sphincter volumes in women with obstructed voiding and abnormal sphincter electromyographic activity

OBJECTIVE: To investigate the role of transrectal ultrasonography (TRUS) of the female urethral sphincter and to compare sphincter volumes in controls and women with obstructed voiding associated with abnormal myotonic-like electromyographic (EMG) activity in the urethral sphincter. PATIENTS AND METHODS: Fourteen women patients (mean age 29 +/- 3.2 years) with symptoms of urinary outlet obstruction underwent videocystometrography (VCMG), urethral sphincter EMG and TRUS. Their sphincter volumes were compared with those obtained from 20 age-matched control patients with other urodynamic diagnoses or normal urodynamics. RESULTS: In every patient the urethral sphincter was identified as an ovoid, hypoechoic structure distal to the bladder outlet. The mean volume of the sphincter in those patients with abnormal EMG activity (3.05 +/- 0.23 cm3) was significantly greater than that in the control group (1.30 +/- 0.09 cm3; P < 0.001). CONCLUSION: TRUS provided a useful method of imaging the urethral sphincter in women. The results suggest that there was an increase in the volume of the urethral sphincter in females with obstructed voiding, providing collateral evidence that the abnormal EMG activity is a significant factor in the pathophysiology of the disorder.