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.