Evaluation of testicular echotexture with Ecotext as a diagnostic method of testicular dysfunction in stallions

This study aimed to assess if Ecotext, a new software for evaluation of testicular echotexture, is a good method for diagnosis of stallions with testicular dysfunction (TD). Relationships between Ecotext parameters and sperm motility and production, testicular volume, and testicular blood flow were also studied. Ecotext provides a total of six echotexture parameters: Ecotext 1 (black pixels), 2 (white pixels) and 3 (grey pixels), and another 3 parameters related to hypoechogenic areas: Ecotext tubular density (ETD), Ecotext tubular diameter (ETd), and Ecotext tubular area (ETA). Stallions (n = 33) were assessed using proven diagnostic techniques (spermiogram, B-mode and Pulse Doppler ultrasound), and subsequent analysis with Ecotext. Animals were classified as "control stallions" (n:21, acceptable semen quality), and "stallions with TD" (n:12, poor semen quality (TM < 60%, PM < 45% and total nº of sperm with PM < 2000 × 10⁶ spz), that were subdivided into "induced TD group" (immunized, anti-GnRH vaccine) and "acquired TD group". The acquired TD group showed differences in all Ecotext parameters in relation to controls (Ecotext 1:0.11 ± 0.17 vs 2.82 ± 2.52, Ecotext 2:1584.0 ± 575.8 vs 388 ± 368.2, Ecotext 3:134.2 ± 9.26; ETA: 2.14 ± 0.59 vs 5.40 ± 1.90; ETd: 65.66 ± 6.27 vs 86.93 ± 10.65 and ETD: 92.35 ± 11.24 vs 132.10 ± 16.35, p ≤ 0.001). Results suggest acquired TD stallions were suffering testicular degeneration with loss of architecture and function as all Ecotext parameters were altered in relation to controls. Induced TD horses only showed a reduction in ETD (116.2 ± 8.59 vs 132.10 ± 16.35, p ≤ 0.001), despite all sperm parameters being worse. These findings suggested immunized stallions probably only experience an acute loss of testicular functionality and parenchyma architecture is likely not affected since differences in Ecotext parameters with control stallions were not detected. ETD was the best parameter to identify animals with TD (AUC: 0.84, optimal cut-off value of 124.3 seminiferous tubules/cm²). Correlations were found between ETD and Doppler indices (PI: 0.60; RI: 0.47 p ≤ 0.001), total testicular volume (r: 0.48; p ≤ 0.05) and sperm motility (TM:0.51; and PM:0.54; p ≤ 0.001) and production (r:0.51; p ≤ 0.001). In summary, Ecotext could identify changes in testicular echotexture of stallions with TD. Results open the possibility for new research focused on establishing the relationship between Ecotext parameters and histomorphometry features in stallion testes.