The inability of spectral Doppler ultrasonography to identify stallions with testicular dysfunction

This retrospective study aimed to validate the usefulness of spectral Doppler ultrasonography in diagnosing testicular dysfunction in stallions. The first part of the study included a pony stallion with age-related testicular degeneration (18 - 21 yrs. old). Testicular dimensions, spectral Doppler parameters of testicular blood flow, and semen parameters were obtained numerous times from this pony over four consecutive years. While testicular volume decreased dramatically, and the stallion became azoospermic, there were no changes in any of the spectral Doppler parameters of testicular blood flow, except the TABF rate (Total Arterial Blood Flow rate). TABF rate gradually increased, most likely due to a significant decrease in testicular volume. In the second part of the study, medical records of four horse stallions (5 - 8 yrs. old) with testicular dysfunction (TDF) were reviewed and analyzed. Parameters evaluated included testicular dimensions, spectral Doppler parameters of testicular blood flow, and semen parameters. Five fertile stallions (FR) served as the reference for TDF stallions. There were no significant differences between FR and TDF stallions in any of the spectral Doppler parameters of testicular blood flow, except TABF, which was significantly higher in FR stallions than in TDF stallions (P < 0,005). This was likely caused by the larger testicular artery diameter in FR stallions. However, when individual stallions were considered, the values of the TABF overlapped between FR and TDF stallions. Based on the results of this study, we conclude that spectral Doppler ultrasonography is not always a reliable method for diagnosing testicular dysfunction in stallions.