Doppler assessment of testicular arterial blood flow in stallions: influence of age and 180° spermatic cord torsion.

Objective Summary

• This study evaluated how age and 180° spermatic cord torsion affect testicular arterial blood flow in stallions using Doppler ultrasonography.
• The researchers measured blood flow parameters in normal and torsed testes to understand changes in testicular hemodynamics associated with aging and torsion.

Introduction and Background

• Doppler ultrasonography is a non-invasive imaging technique that provides detailed information on blood flow dynamics within organs, including the testes.
• While widely used in human and small animal medicine, its application in equine reproductive health (andrology) has been limited due to a lack of comprehensive data and reference values.
• Testicular arterial blood flow is critical for maintaining testicular function and fertility, making it important to understand how factors like age and spermatic cord torsion affect it.

Aims of the Study

• To characterize the normal patterns of testicular arterial blood flow in stallions of different age groups.
• To examine how a 180° spermatic cord torsion influences these blood flow patterns.
• To establish Doppler ultrasonographic reference values that can support diagnosis and treatment monitoring in equine testicular disorders.

Methods

• Subjects: 48 Mangalarga Marchador stallions were examined.
• Group Division:
  • Normal testes: divided by age into young (YN, n=10), adult (AN, n=10), and senior (SN, n=10) groups.
  • Torsion group: stallions with 180° spermatic cord torsion classified as young torsion (YT, n=10) and adult torsion (AT, n=8).
• Measurements:
  • Used spectral Doppler ultrasonography to evaluate blood flow in two segments of the testicular artery:
    • Supratesticular artery (Supra)
    • Capsular artery (Cap)
  • Parameters recorded included:
    • Resistance index (RI) – measures resistance within the vessel
    • Pulsatility index (PI) – reflects blood flow pulsatility
    • Peak systolic velocity (PSV) – highest blood flow velocity during systole
    • End-diastolic velocity (EDV) – blood flow velocity at the end of diastole
    • Time-averaged maximum velocity (TAMV) – averaged maximum velocity over time
• Statistical analysis:
  • Linear mixed-effects models were used to analyze the effects of torsion, age group, and side (left vs. right) on Doppler parameters.
  • Pearson’s correlation coefficients assessed relationships between different variables.

Key Findings

• Age-related differences:
  • Senior stallions showed higher peak systolic velocity (PSV) in the supratesticular artery compared to young stallions (P = 0.041), indicating altered arterial blood flow with aging.
  • The pulsatility index (PI) was higher in the left testis of senior stallions compared to the right testis in young and adult stallions (P < 0.001), suggesting left-right differences in blood flow in older animals.
• Effects of torsion in young stallions:
  • Testes with 180° torsion had a significantly lower resistance index (RI) in the supratesticular artery compared to normal testes (P < 0.001), indicating increased arterial blood flow resistance changes due to torsion.
• Effects of torsion in adult stallions:
  • The contralateral (untorsed) testis in stallioned with torsion exhibited a lower end-diastolic velocity (EDV) than normal adult testes (P < 0.001), suggesting that torsion affects blood flow even in the unaffected testis.
• Regional differences:
  • Across all groups and ages, resistance index (RI), pulsatility index (PI), and peak systolic velocity (PSV) decreased moving from the supratesticular (Supra) artery to the capsular (Cap) artery.
  • End-diastolic velocity (EDV) increased from the supratesticular to the capsular artery, reflecting physiological changes in vascular resistance along the artery’s path.

Conclusions

• Testicular blood perfusion declines with age in stallions, as evidenced by variations in Doppler blood flow parameters.
• Stallions with spermatic cord torsion show altered blood flow dynamics not only in the affected testis but also in the contralateral testis, highlighting systemic or compensatory vascular responses.
• The study provides important Doppler ultrasonographic reference data for stallions, aiding the diagnosis and management of testicular pathologies involving vascular disturbances.
• Doppler ultrasonography is validated as an effective, non-invasive tool for monitoring testicular hemodynamics and assessing the impact of both physiological (age) and pathological (torsion) changes in equine andrology.