Testicular volume: comparison of orchidometer and US measurements in dogs.

Abstract

To compare the accuracy and precision of orchidometer and ultrasonographic (US) measurements of testicular volume in a canine model. Volume measurements of 18 canine testes were obtained by using Prader and Rochester orchidometers. Testes were scanned with two linear-array US transducers with imaging frequencies of 6-13 MHz and 5-10 MHz. For each transducer, testicular volumes were calculated by using three formulas: length (L) x width (W) x height (H) x 0.52, L x W(2) x 0.52, and L x W x H x 0.71. Testes were weighed following bilateral orchiectomies. True testicular volume was determined by using the formula volume = weight/density. Paired t tests were used to assess whether mean measurement biases differed significantly from zero. The relationship between true and measured volume was evaluated with a linear regression model. US volume measurements demonstrated lower variability and better linear fit compared with orchidometry (R(2) = 0.75-0.90 vs R(2) = 0.14-0.38). The formula L x W x H x 0.71 had the smallest mean bias relative to true volume with use of either transducer over the entire volume range. US methods of testicular volume measurement are more accurate and precise than orchidometry. The formula L x W x H x 0.71 provides a superior estimate of testicular volume and should be used in clinical practice.