Testicular volume measurements using Prader orchidometer versus ultrasonography in patients with infertility

To compare the accuracy of testicular volume measurements with the Prader orchidometer versus ultrasonography.

The volume of 938 testes in 469 men with infertility (mean age 35.8 years) was measured using a Prader orchidometer and by ultrasonography. The ultrasound testicular volumes were calculated using the formula length x width x height x 0.71. To compare any differences between the methods according to testicular size, the patients were divided into six groups according to the ultrasound-determined volume: less than 5, 5 to 10, 10 to 15, 15 to 20, 20 to 25, and 25 cm3 or more.

The mean volume by orchidometry and ultrasonography was 18.7 and 13.7 cm3 for the right testis and 18.0 and 12.5 cm3 for the left, respectively, and was significantly overestimated by orchidometry (P <0.0001; by 5.1 cm3 on the right and 5.5 cm3 on the left). The largest differences between methods were observed for volumes of 10 to 15 cm3 on the right and 5 to 10 cm3 on the left. The difference between the methods decreased as the ultrasound-determined volume increased (r = 0.636 on the right; r = 0.598 on the left testis). Nonetheless, the Prader orchidometric measurements showed a strong correlation with the ultrasound measurements (r = 0.707 on the right; r = 0.746 on the left).

The testicular volume estimated by Prader orchidometry correlated closely with the measurements by ultrasonography. However, the orchidometer overestimated the testicular volume, especially in small testes.