Doppler indices of vascular impedance as indicators of testicular dysfunction in stallions

Does Size Matter? Testicular Volume and Its Predictive Ability of Sperm Production in Rams

Over the years, testicular volume has been used to evaluate the reproductive capacity of rams and the effects of different factors related to reproductive performance. The aim of this study was to determine the most suitable tool and formula to calculate testicular volume under field conditions to guarantee a more accurate determination of sperm production. First, testicles from 25 rams (n = 50) were measured in vivo and postmortem using calipers and ultrasonography during the breeding season (BS). The accurate testicular volume (ATV) was calculated through water displacement. In addition, the sexual status of donor rams was evaluated during a period of four years in a reproduction center, and the three most crucial groups in terms of genetic value and seminal collections were studied in the second part of this experiment: ER-NBS (Elite rams during the non-breeding season), ER-BS-S (Elite rams with a standard frequency of seminal collection), and ER-BS-O (Elite rams with a high frequency of seminal collection). The total testicular volume (TTV), testosterone (T), and total spermatozoa obtained from two consecutive ejaculates in the same day (SPERM) were measured, and the relationship between SPERM and TTV and T was analyzed to predict SPERM. Although all published formulas revealed statistically significant differences (p ≤ 0.05) from the ATV, our proposed formula (ItraULE) (Testicular volume = L × W × D × 0.61) did not show significant differences. In the second part of the study, in the ER as a model donor ram for its high genetic value and high demand from farmers, TTV and T showed strong positive correlations with SPERM (r = 0.587, p = 0.007 NBS; r = 0.684, p = 0.001 BS-S; r = 0.773, p < 0.0001 BS-O). Moreover, formulas were established to predict SPERM in these practical scenarios. In conclusion, the use of ultrasonography and a new formula adapted to rams could improve the prediction of SPERM considering crucial factors such as season and semen collection frequency.

An updated insight on testicular hemodynamics: Environmental, physiological, and technical perspectives in farm and companion animals

In all organs, control of blood flow is important but might be particularly critical for testicular functions. This is because of the very low oxygen concentration and high metabolic rate of the seminiferous tubules, the physiological temperature of the testis, and its location outside the abdominal cavity. Many factors affect the characteristics of TBF in farm and companion animals, such as environment (thermal and seasonal effects) and physiological (species, breeds, age, body weight, and sexual maturity). Thermal environment stress has detrimental effects on spermatogenesis and consequently has more serious impacts on both human and animal fertility. Numerous studies have been performed to assess TBF in different animal species including bulls, rams, bucks, alpacas, stallions, and dogs with varied results. Hence, assessment of TBF by Doppler ultrasonography is of great importance to estimate the effect of high environment temperature on testicular functions. Also, differences observed in the TBF may result from different technical aspects such as the identification of the segment of the testicular artery to be examined. In the current review, we focused on the imperative roles of TBF in various animal species. Besides, we discussed in detail various factors that could affect TBF. These factors can significantly modify the TBF and thus should be considered when establishing reference values in farm animals for better clinical diagnosis. The information provided in this review is valuable for researchers and veterinarians to help them a better understanding of testicular hemodynamics for the proper evaluation of breeding soundness examination in males.

The Use of Doppler Ultrasonography in the Examination of Testicles in Dogs

Doppler ultrasonography is method suitable for observing and measuring the blood supply of many organs. Its principle is the change in the frequency of wave blood that moves with respect to the source of the wave (probe). In a testicular examination, the use of Doppler can also be very useful for detecting abnormalities or pathological conditions. The aim is just to characterize the flow in arteria testicularis in clinically healthy dogs aged 1-5 years. Twelve dogs were included in the study, of which 6 were rough collies weighing approximately 23 kg and 6 were standard dachshunds weighing approximately 9 kg. The pulsatility index (PI) and resistance index (RI) of a.testicularis, as well as the dimensions of the testicles - height and depth, were assessed by ultrasonographic examination using the ALOKA ProSound Alpha 6 ultrasonographic device (Hitachi-Aloka, Japan). The statistical evaluation of the results shows that the differences between the averages of both measurements of PI and RI indices are highly significant, so the weight of the individual had a high effect on the measured values of PI and RI indices. The depth of the testicles was also directly related to the increasing values of PI and RI indices and to the weight of the dogs, in contrast to their height, which did not show any statistical significance in this respect. The measured values and findings may in the future also serve as a basis for determining reference values in testicular ultrasonography according to the weight of dogs, which may be beneficial in clinical status assessment, diagnosis of various pathological conditions, or predicting spermatogenesis and fertility of the individuals.

Application of ultrasound technique to evaluate the testicular function and its correlation to the sperm quality after different collection frequency in rams

The frequency of semen collection is a crucial factor to consider in the rams performance inside breeding centers workout. To evaluate this factor, ram Breeding Soundness Evaluation could include sperm quality evaluation and new predictive and non-invasive tools such as ultrasound technique. In this work, an advanced ultrasonography technology, analyzing the testicular volume, echotexture, and vascular function, was used in three different frequencies of semen collection (abstinence frequency, AF; standard frequency, SF; and intensive frequency, IF). Semen samples were cooled (15°C, 6 h) and evaluated in terms of production, motility, viability, apoptosis, and content of reactive oxygen species. Correlation coefficients were calculated between ultrasonography measurements of echotexture and blood flow and sperm quality parameters. Our results showed an increase in the testicular echotexture when the frequency of semen collection was intensified. Doppler parameters (PSV, RI, PI, TABF) increased (P ≤ 0.05) when the frequency of semen collection was intensified. The sperm motility and functionality decreased in the samples of IF (P ≤ 0.05), evidencing the frequency of semen collection's influence. Moreover, moderate positive correlations were established among echotexture and different Doppler parameters with motility parameters in SF. Furthermore, the influence of abstinence days on AI success was analyzed in a field assay. The highest fertility rates were obtained when males had two to five abstinence days. To conclude, frequency of semen collection could be influenced in terms of semen quantity and sperm quality, showing changes in parenchyma echotexture and testicular vascularization. The standard semen collection frequency was the most adequate option. In addition, ultrasonography may be a predictive tool for estimating variations in the sperm quality of donor rams subjected to different frequencies of semen collection in reproduction centers.

Advances in the ultrasound diagnosis in equine reproductive medicine: New approaches

Ultrasound technology has led to new lines of research in equine reproduction, and it has helped to greatly improve clinical diagnosis and reproductive outcomes in equine practice. This review aims to discuss the potential clinical uses and new approaches of ultrasonography in equine reproduction. Doppler modalities are usually used to evaluate the vascularization of the follicles, corpus luteum (CL), and the uterus in the mare for diagnostic purposes. Inclusion of Doppler ultrasound in artificial insemination and embryo transfer programs could improve the reproductive outcome of these techniques. Better selection of recipients based on CL functionality, early pregnancy diagnosis 7-8 days postovulation of the donor before flushing or diagnosis of mares with endometritis with pathological increases of blood flow are examples of clinical applications in the mare. In the stallion, colour Doppler ultrasound has improved the diagnostic potential of B-mode ultrasound, improving the differential diagnosis of pathologies such as testicular torsion (decrease or absence of blood flow in the cord) and orchitis (increased blood flow in the cord). The incorporation of pulsed Doppler ultrasound into the reproductive evaluation of the stallion has enabled early identification of stallions with testicular dysfunction, thus allowing administration of timely treatment and subsequent improvements of the fertility prognosis for these animals. In addition, this technique has been used in the monitoring of patients undergoing medical and surgical treatments, thus verifying their efficacy. Recently, computer-assisted pixel analysis using specific software has been performed in research work in order to semi-quantitatively evaluate the vascularization (colour and power Doppler) and echotexture of different organs. These softwares are now being developed for clinical purposes, as is the case with Ecotext, a computer program developed for the evaluation of testicular echotexture, providing information on testicular functionality.

The Relationship between the Testicular Blood Flow and the Semen Parameters of Rams during the Selected Periods of the Breeding and Non-Breeding Seasons

The study aimed to conduct advanced semen evaluation tests during routine ram examination periods in the breeding and non-breeding seasons and to investigate their correlation with the dynamics of testicular blood flow. Semen was collected from eighteen rams, and pulse wave Doppler examination before (BBS), during (BS), and after the breeding season (ABS). Routine and advanced semen analysis, including computer-assisted sperm analysis (CASA), sperm chromatin dispersion test (SCD), and motile sperm organelle morphology examination (MSOME), were conducted. In Doppler ultrasonography, the peak systolic velocity (PSV), end-diastolic velocity (EDV), resistive index (RI), and pulsatility index (PI) were calculated. In BS period, high sperm concentration (p < 0.0001) and total sperm number/ejaculate (p = 0.008) were noted. During the BBS period, a low percentage of forwarding motility (p = 0.017) and high sperm abnormalities (p = 0.005) were found. Also during this period, both SCD and MSOME revealed high sperm DNA fragmentation (p < 0.0001) and signs of vacuolization (Grade II-IV, p < 0.05). The advanced features of higher sperm abnormalities (Grade IV of MSOME) correlated with an increase RI (ρє <0.60;0.61>) and PI (ρє <0.46;0.52>), whereas the basic percentage of sperm abnormalities correlated with the EDV (ρє <0.44;0.73>) value. One may conclude that the current preliminary study requires further research concerning the monthly examination of a ram to provide full yearly characteristics of the relation between advanced semen evaluation tests and the dynamics of testicular blood flow.

Advances in applications of color Doppler ultrasonography in the andrological assessment of domestic animals: A review

Compared to human cases, potential applications of Doppler imaging technology in farm animals' practice are still limited and are mostly concerned with females. Testicular blood perfusion (TBP) is the pathway through which all nutrients, oxygen, and regulatory agents pass through to the testis. TBP is crucial to the testis function because of the high metabolic rate and very low concentration of oxygen in the seminiferous tubules, which constitute about 70%-80% of the testicular mass. Color Doppler ultrasonography is one of the recent non-invasive technologies, which plays a vital role in the assessment of blood flow to the testis in various animal species. In the past 20 years, a significant number of studies have highlighted the importance of assessments of TBP using color Doppler ultrasonography to illustrate its potential uses for breeding soundness examination, diagnosis, and monitoring of infertility problems in farm animals. This review was aimed at providing, for the first time, updated knowledge on the potential clinical uses of color Doppler ultrasonography for the assessment of TBP in domestic animals. Additionally, a few essential details on the relationship between TBP and male fertility are discussed in this review. Furthermore, a number of caveats relating to the use of color Doppler ultrasonography are discussed, which collectively appear to constrain its routine, on-farm application for breeding soundness assessments, at least at the present. The new perspectives related to animal reproduction that researchers claim to do in further investigations are also discussed.

Pulse-wave Doppler pulsatility and resistive indexes of the testicular artery increase in canine testis with abnormal spermatogenesis

Pulse-wave Doppler (PWD) ultrasonography of the testicular artery was recently used to compare parameters in fertile and infertile males, or males with normal and abnormal semen quality, while no studies verified the concomitant histological feature of the testis. The experimental hypothesis of the present study was that the blood flow parameters measured by PWD at different levels of the testicular artery reflect sperm attributes evaluated on spermatozoa collected from the tail of the epididymis and testicular histological characteristics. Pulse-wave Doppler parameters were recorded on both testes from 16 dogs of unknown fertility. After routine castration, epididymal spermatozoa were collected and evaluated for sperm total and progressive motility, membrane integrity, and sperm morphology. Testes were submitted to histological and immunohistochemical evaluations to quantify microscopic attributes and connective tissue and vascular area extent, respectively. The findings showed that the increased PWD indexes were suggestive of testicular histological alteration since negative correlations were found between pulsatility index and resistive index, measured in the marginal testicular artery, and histological attributes such as the seminiferous epithelial thickness (R = -0.528, P = 0.016 and R = -0.554, P = 0.005, respectively) and the tubular area/total area ratio (R = -0.494, P = 0.024 and R = -0.563, P = 0.004, respectively). Some histological characteristics, such as tubular diameter, seminiferous epithelium thickness, and the tubular area/total area ratio of the testis are correlated with the percentage of primary abnormalities (R = -0.874, P = 0.001, and R = -0.847, P = 0.001, and R = - 0.865, P = 0.001, respectively). In testes with increased sperm primary abnormalities, higher pulsatility index was found compared with testes with normal spermatogenesis in supratesticular artery (1.07 ± 0.06 vs 0.82 ± 0.23, P < 0.05), marginal artery (0.73 ± 0.04 vs 0.61 ± 0.07, P < 0.05), and intratesticular artery (0.67 ± 0.03 vs 0.43 ± 0.1, P < 0.05). Similarly, the resistive index was found significantly higher in the same vessel tracts in testes with abnormal and normal spermatogenesis (0.62 ± 0.02, 0.53 ± 0.02, and 0.46 ± 0.02 vs 0.51 ± 0.06, 0.44 ± 0.04, and 0.32 ± 0.06, respectively; P < 0.05). Our data demonstrated for the first time the relationship between PWD indexes and the contextual testicular architecture, suggesting that the pulsatility and resistive indexes could be an effective tool in andrology. In light of different histological alterations in the testis, caution is warranted in the definition of thresholds for normal and abnormal testicular blood flow indexes.

Pulse wave Doppler ultrasound of testicular arteries and their relationship with semen characteristics in healthy bulls

BACKGROUND

Semen evaluation is used to estimate the testicular function. In bulls, the spermatozoa present in the ejaculate are the result of a process that begun more than 2 mo earlier, bequeathing a delayed depiction of the actual function of the testis. Since testis vascularization might be critical for the gonad function, selected pulse wave Doppler ultrasound parameters were assessed in this study, for instance the peak systolic velocity, the end diastolic velocity and the resistive index of the testicular artery along the spermatic cord, the marginal portion of the testicular artery and the intratesticular branches of the testicular artery both in healthy adult and young bulls. Correlations between these parameters and characteristics of semen that was collected numerous times, before and after the Doppler ultrasound examination.

RESULTS

The peak systolic velocity and the end diastolic velocity measured in the testicular artery along the spermatic cord (supratesticular artery - SA) were variable among the bulls and within individual bulls, likely due to the convoluted course of the vessel. The resistive index was found highly repeatable in the same bull. A reduction in the resistive index was found between the supratesticular artery and the marginal portion of the testicular artery (P < 0.01), and between the marginal portion of the testicular artery and the intratesticular branches of the testicular artery (P < 0.05). No differences were recorded for the pulse wave Doppler ultrasound parameters in young bulls compared with adults. A significant correlation was found between the resistive index of the marginal portion of the testicular artery and total sperm in the ejaculate (r = 0.516, P < 0.05), the immature sperm (r = 0.462, P < 0.05), the teratoid sperm (r = 0.375, P < 0.05), and the "Dag defect" sperm (r = 0.389, P < 0.05). Similarly, the resistive index of the intratesticular branches of the testicular artery were found correlated with the total sperm number in the ejaculate (r = 0.568, P < 0.05), the immature sperm (r = 0.523, P < 0.05), the teratoid sperm (r = 0.418, P < 0.05), and the "Dag defect" sperm (r = 0.341, P < 0.05).

CONCLUSIONS

The data presented in this study suggest that the resistive index, measured at the marginal portion of the testicular artery, could be an easy-to-perform parameter to evaluate the spermatogenesis quality in young bulls and normal adults.

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

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.

Testicular perfusion after standing laparoscopic peritoneal flap hernioplasty in stallions

Acquired inguinal herniation is a very common condition in stallions, usually leading to unilateral or bilateral castration to prevent future recurrence. Recently, several surgical techniques such as the standing laparoscopic peritoneal flap hernioplasty (SLPFH) have been developed to avoid herniation recurrence and also preserve the breeding activity of high economic value stallions. However, studies on SLPFH lack more comprehensive and systematic data about reproductive-related adverse effects and outcomes. The aim of this study was to evaluate whether SLPFH of the internal inguinal rings produces changes in the testicular blood flow in a 1-year follow-up. For that purpose, six healthy stallions were used and testicular blood flow was assessed before, 3, 6, and 12 months (T0, T3, T6, and T12) after the procedure. Blood flow was evaluated ultrasonographically, using the pulsed-wave color Doppler mode. Peak systolic velocity, end-diastolic velocity, the time-averaged maximum velocity, and the derived indexes (resistive index) and pulsatility index) of the testicular artery were measured in two localizations: in the spermatic cord and on the caudal epididymal edge of the testicle. On the spermatic cord, the peak systolic velocity of the testicular artery increased significantly at T12. However, on the epididymal edge location of the artery, the pulsatility and resistive indexes were decreased at T12 (P < 0.05). This pattern of blood flow was related to a hyperemic process. Furthermore, SLPFH might have compressed the spermatic cord, causing a slight occlusion of the testicular artery and triggering a compensatory hyperemia to compensate the deficit of blood flow that supplies the testes. The SLPFH of the internal inguinal ring affected the testicular perfusion in stallions in a 1 year follow-up, although there was no effect on sperm production during this time. The spectral Doppler ultrasound is a useful tool to asses the testicular perfusion after reproductive surgical procedure and provides information which anticipates vascular supply compromise of the stallion testicles.