Testicular volume: Comparison of orchidometer and US measurements in dogs

PURPOSE: To compare the accuracy and precision of orchidometer and ultrasonographic (US) measurements of testicular volume in a canine model. MATERIALS AND METHODS: 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) × width (W) × height (H) × 0.52, L × W² × 0.52, and L × W × H × 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. RESULTS: US volume measurements demonstrated lower variability and better linear fit compared with orchidometry (R² = 0.75-0.90 vs R² = 0.14-0.38). The formula L × W × H × 0.71 had the smallest mean bias relative to true volume with use of either transducer over the entire volume range. CONCLUSION: US methods of testicular volume measurement are more accurate and precise than orchidometry. The formula L × W × H × 0.71 provides a superior estimate of testicular volume and should be used in clinical practice.