Feline testicular ultrasonogram differentiates pre vs. postpubertal and normal vs. disrupted spermatogenesis

The aims of this study were: to ultrasonograhically describe and compare testicular parenchyma echogenicity and heterogeneity using digital image analysis in: I) prepubertal (PREP), peripubertal (PERI) and mature (MAT) cats; II) Normal and abnormal mature felids. Secondary, the relationships between histomorphological and ultrasonographic attributes of the testes were also determined. I) Fourteen, PREP, PERI and MAT male cats were ultrasonographically examined and then castrated. II) Seven adult cats were ultrasonographically examined before and after a GnRH antagonist administration and then castrated. All the testes were grossly and histomorphometrically assessed. In the frozen digital images of the longitudinal ultrasound sections, 3 regions of interest (ROI, 1 mm2) were selected. Within each ROI the echogenicity and the heterogeneity of the testicular parenchyma were digitally analyzed. In experiment I, testicular volume (0.15 ± 0.0 vs. 0.49 ± 0.1 vs. 1.65 ± 0.1; P < 0.01) and gonadosomatic index (0.04 ± 0.0 vs. 0.05 ± 0.0 vs. 0.08 ± 0.0; P < 0.01), echogenicity (56.54 ± 0.75 vs. 81.87 ± 5.88 vs.94.67 ± 3.62; P < 0.01) and heterogeneity (10.2420 ± 1.3740 vs.13.65 ± 0.65 vs. 14.67 ± 1.49; P < 0.01) augmented throughout PRE, PERI, and MAT. In experiment II, testicular volume (1.00 ± 0.09 vs. 0.85 ± 0.09; P < 0.05), echogenicity (87.74 ± 1.53 vs. 83.32 ± 1.54; P 0.01) but not heterogeneity (14.09 ± 0.26 vs. 14.19 ± 0.29; P > 0.05) decreased in the post GnRH antagonist abnormal testes. For both experiments, testicular volume, seminiferous tubular diameter, percentage of spermatids as the most mature cell type, and luminal/intertubular ratio were highly correlated (P < 0.01) with their echotextural attributes. Computer-assisted image analysis of B mode ultrasonogram appears as a good indicator of pubertal development and mild alterations of spermatogenesis in felids.