It is consistent with the formula (pi/6)*a*b*c.
It is a rough approximation, they assume an ellipsoid shape with b=c. But it is more or less right, you only need an approximation to have clinically useful parameters like the psa density.
However, different ecography and MRI techniques give different results, in my case MRI's was bigger. The actual weight after it was removed was even greater (I hope yours will not need to be weighted that way).
Post Edited (jmadrid) : 2/19/2018 9:08:04 AM (GMT-7)