Determination of prostate gland volume by transrectal ultrasound: correlation with radical prostatectomy specimens.

Seventy six patients underwent transrectal ultrasound examination of the prostate prior to radical prostatectomy. All radical specimens were weighed and measured when freshly excised. Corresponding measurements calculated using transrectal ultrasound dimensions were retrospectively compared with those of the freshly excised glands. Estimation of gland volume by ultrasound measurement, utilizing the prolate ellipse formula [Width x Height x Length) x 0.70 was applied to a control group of 19 patients, and a close correlation (r = 0.77) between ultrasound estimated volume and actual weight was shown. A modified prolate ellipse formula, using the factor of 0.70, appears to be a more reliable means of estimating gland volume with transrectal ultrasound than the original formula [Width x Height x Length) x 0.523).