The weight of the prostate gland is an excellent surrogate for gland volume.

AIMS: Prostate gland volume is generally assessed by transrectal ultrasound examination or magnetic resonance imaging at the time of prostatic biopsy or pre-brachytherapy planning. The volume is most commonly measured using the formula, prostate volume = height x width x length x pi/6, which is derived considering the gland as ellipsoid. There are conflicting data regarding the accuracy of this method, with most studies comparing this calculated volume with that measured radiologically using planimetry with summation of sequential area measurements. The aim was to determine the relationship between prostate gland volume and weight. METHODS AND
RESULTS: The accuracy of prostate gland volume calculated from three-dimensional measurements of the gland in 20 radical prostatectomy specimens relative to the true gland volume determined using water displacement was prospectively evaluated. Since volume measurement by water displacement is not practical in routine practice, the relationship between prostate weight and volume was also evaluated. Our findings indicate that the calculated gland volume consistently underestimates the true volume. The volume of the prostate gland (in cm(3)) very closely correlates with its weight (in g).
CONCLUSIONS: The weight of the prostate gland (without the seminal vesicles) is an excellent surrogate for prostate volume. The prostate gland in radical prostatectomy specimens should be weighed after transecting the seminal vesicles at the base.