Accuracy of residual urine measurement in men: comparison between real-time ultrasonography and catheterization.

PURPOSE: The practical value of ultrasonography as a rapid means to determine accurately residual urine volume was assessed.

MATERIALS AND

METHODS

Transverse and sagittal bladder diameters, as well as areas from longitudinal and transverse images, were measured with real-time ultrasonography in 324 men immediately after voiding. Calculated bladder volumes using measured diameters and areas for each of 11 formulas in the literature were compared to the corresponding measured total residual urine volumes.

RESULTS

The lower limit of ultrasonographic visualization of urine in the bladder was approximately 48 ml. No correlation existed between ultrasound calculated bladder volumes and measured residual urine for any of the 11 formulas.

CONCLUSIONS

Ultrasonography cannot rapidly measure bladder volumes accurately to date. Catheterization remains the most accurate method of assessing post-void residuals but in many cases it may not be the best approach to patient care.