PURPOSE: Transrectal ultrasonography is known to be an effective tool for the determination of prostatic volume. But the irregularity of shape and the limitation of reliability by intra-observer and inter-observer bias may influence over the results. I would like to represent several factors for the error of transrectal ultrasonographic measurement of prostatic volume. MATERIALS AND METHODS: Errors for transrectal ultrasonographic volume determination of the prostate, based on the principle of HWL(Height x Width x Length x pi/6) are presented. Some artificial prostatic models were made and compared between the real volumes and calculated results. The intra-observer error was determined in 39 cases by repeated measurements. The inter-observer error was also determined in 32 cases by repeated measurements of different observer. RESULTS: There were significant discrepancies between real volumes and calculated results and the range of error by shape was -19?38%. The ranges of intra-observer and inter-observer errors with 95% confidence interval were -7.4?6.1% and 2.7?9.9%. CONCLUSIONS: Errors by several factors should be considered for the clinical application of measured prostatic volume by ultrasonography irrespective of its statistical validity and reliability.
Bias (Epidemiology) ; Prostate ; Reproducibility of Results ; Ultrasonography*