Accuracy of Prader orchidometer in measuring testicular volume

Background: Seminiferous tubules comprise 80-90% of testicular mass. Thus, the testicular volume is believed to be an index of spermatogenesis. Therefore, accurate testicular volume is one way to assess testicular function. Objective: To determine the accuracy of Prader orchidometer for measuring the testicular volume by comparing the resultant measurement with the actual testicular volume in humans. Materials and Methods: The testicular volumes of 121 testes from 62 patients with prostate cancer (mean age 72.74 9.38 years) were measured using Prader orchidometer before therapeutic bilateral orchidectomy. The actual testicular volumes were then determined by water displacement of the testis. Results: The mean testicular volume of the 121 testes was 10.60 3.5 ml and13.26 5.2 ml for water displacement and Prader orchidometer measurements, respectively. A strong correlation was found between the actual testicular volume and volumes obtained by Prader orchidometer (r 0.926, P 0.0001). The Prader orchidometer however, over-estimated the mean actual testicular volume by 2.66 2.37 ml (25.10%). Conclusion: The result of this study has shown that measuring the testicular volume by Prader orchidometer overestimates the actual testicular volume.