rate but I would be happier if the injury incidence had beencalculated against the number of catheterizations.

I am unsure whether the pre-intervention and post-inter-vention populations were identical. Although the mean ageswere virtually identical, the mean ages of those who wereinjured were less so. Also, the pre-intervention group in-cluded patients in whom catheterization would have beenexpected to be more difficult, such as 7 with BPH and 1 withprostate cancer. However, the differences are significant andthe post-intervention injury occurred in the operating room,where the intervention was not applied. The study empha-sizes the importance of proper technique.

J. G. CallearyDepartment of Urology

Southmead HospitalBristol, United Kingdom

REPLY BY AUTHORS

While it is true that basing the incidence of injury on thenumber of catheters inserted during the study period wouldhave provided a fine measure of risk, our method of usingthe total number of male admissions is an equally acceptableapproach. The first method estimates the risk of injury dur-ing any particular catheterization, whereas the secondmethod estimates the risk of injury to any particular patientduring hospital stay.

In addition, the characteristics of the injured patients donot necessarily reflect the characteristics of the at risk pop-ulation (all male inpatients older than 18 years). Thus, theseobservations would not bias the results nor influence theefficacy of the intervention in the at risk population. More-over, the sample sizes are too small to draw any meaningfulconclusions regarding disease prevalence in injured pa-tients.

INCIDENCE AND PREVENTION OF IATROGENIC URETHRAL INJURIES2258