Testicular Volume Measurement: Comparison of Prader Orchidometer, Calliper and Ultrasound Estimates with Actual Volume Obtained by Water Displacement.

Abstract

Introduction: The volume of the testis, mainly made up of seminiferous tubules, is a reflection of spermatogenesis. The accurate measurement of the testicular volume is therefore critical in the evaluation of testicular function. Aim is to compare the volumes obtained by Prader orchidometer, calliper and ultrasound with actual volume in humans.

Materials and methods: One hundred testicles from 50 men with advanced prostate cancer were recruited into the study over a 12-month period. Testicular volume was estimated in vivo using Prader orchidometer, calliper, ultrasound scan and in vitro after orchidectomy by water displacement.

Statistical analysis used: Statistical analysis used paired t test, Pearson correlation coefficient and simple linear regression analysis.

Results: The age of the patients ranged from 55 to 82 years (mean 71.66 ± 6.5). The mean testicular volumes were 16.13 ± 4.5, 9.07 ± 3.5 and 13.48 ± 4.3mL for Prader orchidometer, calliper and ultrasound (Lambert formula), respectively. The mean volume from water displacement was 15.08 ± 4.3 mL. The Prader orchidometer most appropriately estimates the actual volume, (P = 0.657). Calliper significantly underestimated the actual volume. Ultrasound estimation by Lambert formula showed no significant mean difference from the actual volume (P = 0.362). In addition, the orchidometer and Lambert ultrasound formula showed excellent positive correlation with the actual volume (r = 0.931, P < 0.001) and (r = 0.869, P < 0.001), respectively.

Conclusions: Prader orchidometer provides an accurate and rapid assessment of testicular volume; it is, therefore, useful in clinical practice. Calliper does not give an accurate assessment of testicular volume. Of the three ultrasound formulae, Lambert formula is the best in providing a near accurate testicular volume measurement.