Transrectal ultrasonography as a method to monitor canine prostatic size in situ: measurements following endocrine manipulation and ejaculation.

Transrectal ultrasonography was utilized to estimate canine prostatic size in situ following various experimental manipulations. By the use of dogs (n = 24) of various endocrine states, whose true prostatic weight varied from 2.28 to 73.25 g, a highly significant correlation (r = 0.99; P less than 0.0001) was obtained between actual prostate weight determined gravimetrically and that estimated by ultrasound. The relationship between these two parameters was described by the regression equation: estimated prostatic weight (g) = 1.11 x gravimetric weight (g) - 0.12. In addition, prostatic weight as estimated by ultrasound was comparable (P less than 0.10) to that estimated by direct caliper measurement. The coefficient of variation associated with repeated ultrasound measurements averaged 8.88 +/- 2.31% (mean +/- SD; n = 5). Ejaculation induced by either digital massage or pilocarpine administration (0.7 mg/kg, i.v.) had no effect on prostatic weight as estimated by ultrasound. These results demonstrate that transrectal ultrasonography can accurately estimate and detect differences in prostate size owing to various experimental manipulations without the need for surgical intervention.