[Calculation of prostatic volume by endorectal ultrasonography. A formula of surgical observation]

This study compares ultrasonographic prediction of prostatic volume and surgical exerese. A total of 200 prostates have been measured by the same echographist, operated upon by the same surgeon, and stratified for histology, surgical technique and weight. Adopting the general formula: Surgical volume = D1 x D2 x D3/x the surgical volume is calculated by a simplified and complete definition for a denominator giving the most accurate prediction.

a. the glands of more than 60 cc could be calculated by the classical formula of ellipsoid pi x D1 x D2 x D3/6, simplified to D1 x D2 x D3/2, with a 21% standard deviation error from the surgical volume; b. medium-sized prostates (20-60 cc) could be calculated by the formula: D1 x D2 x D3/3 with a 21% standard deviation; c. prostates smaller than 20 cc, a series which included all reoperations for remnants or recurrence, could be calculated with the same proposed formula with a 22% standard deviation, while the classical ellipsoid formula led to a 56% standard deviation error. No mathematical formula based only on three prostatic diameters is reliable to assess true parenchymal weight.