The accuracy of transrectal ultrasound prostate volume estimation: clinical correlations

Sonographic estimates of prostate volume have been applied to the diagnosis and management of prostate cancer. However, we have observed wide variation between transrectal sonographic estimates of prostate volume (TRUS-V) and the corresponding volumes of unfixed radical prostatectomy specimens (P-V). Because TRUS-V may influence the management of men with prostate disease, the relationship between TRUS-V and P-V was characterized for 100 consecutive men undergoing a radical retropubic prostatectomy (RRP). For the entire cohort, TRUS-V (35.9 +/- 16.9 mL) underestimated P-V (45.4 +/- 22.9 mL, p < .01). Mean signed percentage error between TRUS-V and P-V was -16 +/- 32%. The relationship of TRUS-V to P-V was volume dependent (p < .001). For volumes (P-V) < 30 mL, TRUS-V overestimated P-V. For volumes (P-V) > 30 mL. TRUS-V increasingly underestimated P-V. In summary, transrectal ultrasound estimates of prostate volumes differ significantly from the volume of unfixed RRP specimens. The direction and magnitude of TRUS-V error is volume dependent. Applied clinically, treatment paradigms employing prostate-volume-dependent management algorithms derived from nonuniform methods of volume estimation may not accurately reflect volume nomograms derived from uniform methods of measurement, and thus alter patient management.