The objective of our research was to determine the accuracy and precision of the Cavalieri principle with images obtained from magnetic resonance imaging (MRI) in estimation of the actual testicular volume in humans.

We performed volume measurements of 42 testes from 21 patients scheduled for bilateral orchiectomy for prostate cancer. We performed volume estimation measurements with ultrasonography (US), Prader's orchidometer (PrOM), and Cavalieri principle MRI (we used views in axial sagittal and planes) before orchiectomy. We measured actual testes volume with the fluid displacement technique after orchiectomy. Differences and correlations between estimated and actual volumes were evaluated. For all patients, we compared right and left testicular volumes independently with these measurements.

Mean ± SD actual testicular volume and estimated testicular volumes with US, PrOM, and Cavalieri principle using MRI axial and sagittal images were 15.3 ± 3.3 and 17.7 ± 3.0 cm³, 20.0 ± 3.5 cm³, and 16.0 ± 3.7 and 16.0 ± 3.6 cm³, respectively. Estimated and measured volumes were not different from each other. US and PrOM measured volumes were correlated with the actual volume. However, r-values with Pearson correlation test for estimated volumes measured with the Cavalieri principle with MRI were higher than US and PrOM (r-values were 0.934 and 0.961 vs 0.919 and 0.757, respectively).

The results of this study demonstrate that testicular volume measurements with the Cavalieri principle using images obtained from MRI may be considered a complementary method to traditional techniques to estimate the actual testicular volume.