Pulse Doppler ultrasound as a tool for the diagnosis of chronic testicular dysfunction in stallions

Abstract

Testicular function is particularly susceptible to vascular insult, resulting in a negative impact on sperm production and quality of the ejaculate. A prompt diagnosis of testicular dysfunction enables implementation of appropriate treatment, hence improving fertility forecasts for stallions. The present research aims to: (1) assess if Doppler ultrasonography is a good tool to diagnose stallions with testicular dysfunction; (2) to study the relationship between Doppler parameters of the testicular artery and those of sperm quality assessed by flow cytometry and (3) to establish cut off values to differentiate fertile stallions from those with pathologies causing testicular dysfunction. A total of 10 stallions (n: 7 healthy stallions and n: 3 sub-fertile stallions) were used in this study. Two ejaculates per stallion were collected and preserved at 5°C in a commercial extender. The semen was evaluated at T0, T24 and T48h by flow cytometry. Integrity and viability of sperm (YoPro®-1/EthD-1), mitochondrial activity (MitoTracker® Deep Red FM) and the DNA fragmentation index (Sperm Chromatin Structure Assay) were assessed. Doppler parameters were measured at three different locations on the testicular artery (Supratesticular artery (SA); Capsular artery (CA) and Intratesticular artery (IA)). The Doppler parameters calculated were: Resistive Index (RI), Pulsatility Index (PI), Peak Systolic Velocity (PSV), End Diastolic Velocity (EDV), Time Average Maximum Velocity (TAMV), Total Arterial Blood Flow (TABF) and TABF rate. The capsular artery was the most reliable location to carry out spectral Doppler assessment, since blood flow parameters of this artery were most closely correlated with sperm quality parameters. Significant differences in all the Doppler parameters studied were observed between fertile and subfertile stallions (p ≤ 0.05). The principal components analysis assay determined that fertile stallions are characterized by high EDV, TAMV, TABF and TABF rate values (high vascular perfusion). In contrast, subfertile stallions tend to present high values of PI and RI (high vascular resistance). The ROC curves revealed that the best Doppler parameters to predict sperm quality in stallions were: Doppler velocities (PSV, EDV and TAMV), the diameter of the capsular artery and TABF parameters (tissue perfusion parameters). Cut off values were established using a Youden´s Index to identify fertile stallions from stallions with testicular dysfunction. Spectral Doppler ultrasound is a good predictive tool for sperm quality since correlations were determined among Doppler parameters and markers of sperm quality. Doppler ultrasonography could be a valuable diagnostic tool for use by clinical practitioners for the diagnosis of stallions with testicular dysfunction and could be a viable alternative to invasive procedures traditionally used for diagnosis of sub-fertility disorders.

Examination of jackass (Equus asinus) accessory sex glands by B‐mode ultrasound and of testicular artery blood flow by colour pulsed‐wave Doppler ultrasound: Correlations with semen production

“…As already reported in stallions (Ortiz-Rodriguez et al., 2017), bulls (Gloria et al, 2018) and dogs (Zelli, Troisi, Elad Ngonput, Cardinali, & Polisca, 2013), the values of the testicular artery blood flow variables were similar in the right and left testis. The present blood flow results are also comparable to those described in stallions (Ortiz-Rodriguez et al, 2017), bulls (Gloria et al, 2018), dogs (de Souza, Barbosa, et al, 2015 and camels (Kutzler, Tyson, Grimes, & Timm, 2011). Certainly, the RI and PI in the stallion are similar to those recorded here.…”

“…To the best of our knowledge, this is the first study to describe a correlation between sperm viability/semen concentration and Doppler‐measured testicular artery blood flow variables in the jackass. As in the dog (Zelli et al, ) and stallion (Ortiz‐Rodriguez et al, ), the strongest correlation with semen quality was recorded at the level of the CA. However, Bollwein, Scheibenzuber, Stolla, Echte, and Sieme () found no correlations at all in the stallion, perhaps because of the location used to take the Doppler measurements or the technology used.…”

“…Several authors report a correlation between testicular artery blood flow variables and semen quality in humans and certain animal species (Gloria et al, ; Ortiz‐Rodriguez et al, ; Pinggera et al, ; Zelli et al, ). To the best of our knowledge, this is the first study to describe a correlation between sperm viability/semen concentration and Doppler‐measured testicular artery blood flow variables in the jackass.…”

“…As a result, the testis survives on the edge of hypoxia (Bergh, Collin, & Lissbrant, 2001)perhaps to protect sperm DNA from the damage caused by oxygen radicals. Any disturbance in the blood flow could negatively affect spermatogenesis and therefore fertility (Ortiz-Rodriguez et al, 2017).…”

“…Research into the genetics and reproduction of the donkey has increased over the last 20 years, but if this is to help us preserve endangered breeds or increase fertility in farming systems, a deeper understanding will be required. Ultrasound imaging can provide useful information on the male genital tract and can be used to detect abnormalities (Segabinazzi et al, 2018), including accessory glands affection or testicular dysfunction and subfertility disorders (Ortiz-Rodriguez et al, 2017). Indeed, it is routinely used to monitor the reproductive status of many species (Kahn, 1994;Ortega-Ferrusola, Gracia-Calvo, Ezquerra, & Pena, 2014).…”