Objective
To evaluate the effect of a transrectal probe on the opening of internal urethral sphincter.

Method
Twenty-five patients with a neurogenic bladder dysfunction were included in this study. For the transrectal ultrasonography (TRUS), a transrectal probe was inserted into the rectum before the bladder was filled. Internal urethral sphincter opening was investigated during the filling and voiding phases. The bladder was emptied and the probe was introduced intrarectally after the bladder filling for the investigation of internal urethral sphincter opening. Twelve subjects underwent an additional cystometry for the recording of maximal intravesical pressure with and without transrectal probe.

Results
There was no significant difference in the sensitivity of TRUS for the opening of internal urethral sphincter with insertion of the probe before or after the bladder filling. There was no significant change of the maximal intravesical pressure with or without the probe in the rectum.

Conclusion
The results demonstrate that transrectal probe for TRUS does not cause a reflex effect on the opening of internal urethral sphincter.