Assessing the effectiveness of different urinary catheters in emptying the bladder: an application of transvaginal ultrasound.

The effectiveness of different types of urinary catheters in completely draining the bladder has not been tested. Transvaginal ultrasound, which is able to measure bladder volumes in women from 2 to 175 ml, provides a means of measuring any fluid volume remaining in the bladder following catheter drainage. Using transvaginal ultrasound, the post-catheterisation bladder volumes were measured in 26 female patients; 14 underwent urethral catheterisation using either a 14F short plastic female catheter or a Foley catheter of the same size (balloon not inflated); 12 had an indwelling 12F suprapublic catheter following bladder neck surgery. The mean post-catheterisation bladder volumes after using the short plastic female and Foley catheters were less than 1 ml and 77 ml respectively. A short plastic catheter should be used in women to collect the residual urine volume by urethral catheterisation. A Foley catheter is relatively ineffective in this task. A 12F suprapubic catheter was found to drain the bladder relatively well. The mean post-catheterisation bladder volume was 35 ml. Prior to removing a suprapubic catheter post-operatively, it is recommended that the residual urine volume (measured using the suprapubic catheter) be checked by measuring the post-catheterisation bladder volume (using either a short plastic catheter or transvaginal ultrasound).