Morphological and Clinical Studies on Testicular Artery of the Stallion
Małgorzata A Pozor and Dorota Kolonko
Department of Animal Reproduction
University of Agriculture, Krakow, Poland

Introduction

            Evaluation of testicular vasculature has become an important part of clinical examination of testes in men.  New modalities of imaging techniques have become valuable in diagnosing many pathological changes of human testes by detecting even slight vascular disturbances.  Doppler color ultrasonography appears to be the most helpful of these methods in the patient with an acute scrotal disorder (Herbener 1996).  Estimation of an echostructure, blood supply vascularization and the character of vascular flow have proven very useful in distinguishing early inflammatory or neoplastic changes of the testes and epididymidis in men  (Górecka-Szyld 1999). Also, analysis of color Doppler images help to make preoperative diagnosis of a stage of varicocele and to monitor effectiveness of the surgery (Górecka-Szyld 1999).  And in addition, the values of quantitative flow indices, estimated by Doppler ultrasonography, have shown increased vascular resistance in the artery in aging men (Wielgoś et al. 1998).

            Ultrasonography of stallion testes has been used routinely in veterinary medicine in recent years. The normal echostructure and ultrasound picture of many pathological changes of stallion testes have been described (Love 1992, Love 1998, Turner 1998).  Unfortunately, there are still few papers focused on this topic and only limited review of clinical cases of stallions with early pathological changes of testes detected by ultrasonography.  Love (1992, 1998) described ultrasound images of the normal testicular artery and central vein, as well as of varicocele, torsion of spermatic cord and testicular tumors.  There are no, however, reports on ultrasound-detectable vascular changes in orchitis and epididymitis in the stallion, and on application of new modalities of ultrasonography, such as color Doppler, in evaluating external genitalia in stallions.

In order to examine peripheral vasculature of an organ, a knowledge of normal anatomy of the area is needed.  Anatomical textbooks have inadequate descriptions of testicular vasculature of various species of domestic animals, especially of the stallion.  Original papers on this topic were published mostly in the 1960’s, 1970’s and 1980’s (Jantosovicova 1969, Ippensen et al. 1972, Collin 1973, Smith 1974, Jantosovicova and Jantosovic 1983).  Therefore, there is a need to conduct new morphological studies of the testicular artery in the stallion with special attention to future clinical applications in diagnosing early pathological changes of the stallion testes using current imaging technologies.

            This paper describes our pilot study on angioarchitecture of stallion testes and normal echostructure of testicular artery in conventional ultrasonography.

Material and Methods

Isolated testes

            Seventy-two isolated stallion testes were used in this study.  Forty-six testes were retrieved from stallions by castration and the remaining 26 were isolated immediately after slaughter. The shape and all visible vascular structures of each testis were described and drawn on worksheets.  Simultaneously, preliminary classification of the testes was done in order to assign each to one of three methods used to further study angioarchitecture.

1.   Ultrasonography:       Ultrasound evaluation of isolated testes, submerged in water, was done using ultrasound Pie Medical 200 (Pie Medical Equipment B.U., The Netherlands), equipped with dual frequency linear probe 5/7,6 MHz. 

2.      Radiography:  Testes with intact tunica albuginea and testicular artery (n=11) were injected with contrast medium (barium suphuricum into the testicular artery) and radiographs were taken.

3.      Vascular cast studies:  As above, an intact testicular artery was crucial for this work. Either latex (n=2) or Dentacryl (n=3) was injected into the testicular artery.  After injecting liquid latex, each testis was submerged into 70% ethyl alcohol for 14 days.  Testes that were to be filled with Dentacryl (Spofa, Czech Republick) were injected with a mixture of the substance and diluent (1:4 ratio) and put into warm water (temp. 45-65^oC) for 8-10 hours.  Irrespective of the method of filling, the testes were then completely submerged into corrosive medium (20% NaOH) for 5-7 days.  The remaining testicular tissue was washed out with running water and the cast of testicular artery was freed and saved.

In vivo study

            Testes of 17 adult stallions of various breeds (average body weight of 590 kg) were palpated and then examined and measured using ultrasound (equipment as above).  During ultrasound evaluation the central vein of each testis was localized in the central position of the testis (half of the longitudinal axis of the testis) and its diameter  was precisely measured.  The testicular artery was visualized in the spermatic cord and then followed until it was visible.  The diameter of the testicular artery was measured in the area of the caudal pole of the testis, just under the tail of epididymis.

Results

            Only 64 of 72 isolated testes represented within-stallion pairs (32 pairs).  The remaining 8 right testes were isolated, most likely, from unilateral cryptorchids.  Based on descriptive, radiographic and cast studies we have observed a few patterns of the route of the testicular artery in stallion testes. 

1.        Single testicular artery (n=66)

In 39 testes this artery coursed along the epididymal edge of the testis as a marginal artery of the testis, making multiple zigzags on the caudal pole of the testis, continuing as a single vessel around the caudal pole, along the free edge of the testis towards the cranial pole until it penetrated the parenchyma.  Small arteries branched from the artery running along the free border on both – lateral and medial sides and penetrated the parenchyma.
         In 15 cases, a single marginal artery of the testis bifurcated at 1/3 of the way from the caudal pole to the cranial pole along the free edge of the testis.
         And in 12 cases, the marginal artery of the testis ran similarly as described above but at about 1/3 of the way along a free edge of the testis divided into multiple small arteries that penetrated the parenchyma.

2.        Double testicular artery (n=5)

In these cases the marginal artery of the testis bifurcated early, on the epididymal edge into two large arteries, one running as described above and one running on the lateral side of the testis.

3.        Triple testicular artery (1)

Only one testis had three, equivalent arteries, one running similarly as a single marginal artery, and two additional ones, running from the epididymal edge on the lateral side of the testis.
         It is worth mentioning that all testes with a single marginal artery were oval shaped while all testes with one or two lateral arteries were pear shaped with a part of a testis bulging on the lateral side where additional arteries were running.
         Ultrasonography of isolated testes did not yield meaningful results.  In a few cases echogenic blood clots were visualized in the area of a central vein and irregularly throughout the parenchyma, possibly due to hemorrhagic changes after injecting local anesthetic before castration.
         In live animals, the central vein was visible on ultrasound in all cases, with a mean diameter of 2.8 mm (1.9 – 5.4 mm).  A marginal artery in the area of a caudal pole of the testis was visualized in 18 testes (12 animals).  We were unable to visualize this artery in 6 stallions, and in the remaining 6 cases the artery was visualized in only one testis.  In three cases we detected a presence of an additional, lateral artery running on a lateral side of the testis (double testicular artery).  And in one case, both testes had double marginal arteries of the testis.  All testes with double arteries were pear shaped.  The mean diameter of the left marginal artery was 3.3 mm (2.5 – 4.2 mm) and of the right marginal artery was 3.8 mm (2.7 – 5.3 mm).  Diameters of the lateral arteries were: 3.3, 3.3, 4.6 and 5.3 mm.

Discussion

Our study confirmed the presence of a few different patterns of the route of the testicular artery of the stallion.  Collin (1973) was the first author to describe lateral arteries running on the side of stallion testes.  Smith pointed out the importance of the possibility of damaging this artery when taking biopsy specimens if the operator is not aware of this anatomical eventuality (1974).  We have shown that the testes with lateral testicular arteries are pear shaped, and that ultrasonography may help in detecting this additional vessel and in defining its route.

Conventional ultrasound is being used in evaluation of some scrotal disorders in stallions.  It helps in diagnosis of testicular tumors, cysts, epididymal blockage, torsion of spermatic cord, varicocele and hydrocele (Love 1992, 1998; Turner 1998).  We have evaluated a stallion with an ultrasonographically detectable increase in vascularization of the caudal pole of one testis.  This stallion had palpable changes of this testis and epididymis.  He was also showing signs of pain when the epididymis was palpated and just prior to ejaculation.  Chronic epididymitis was suspected in this stallion.  Unfortunately, there were no additional imaging techniques available at that time that could have helped in confirming our preliminary diagnosis. 

Conventional ultrasound and color Doppler ultrasound of testes are the methods of choice in evaluating causes of infertility in men.  Images and blood flow indices of normal human testes have been described.  Now there are many new papers published each year on applications of these techniques in detecting very slight pathological changes.  There are no such studies done on stallion testes.  It seems that there is a need to describe color Doppler ultrasound images and to define normal values of quantitative flow indices for stallion testes as an introduction of this diagnostic modality to stallion andrology clinic. 

Our cast models seem to be very useful in training an operator in normal anatomy of testicular vasculature, especially in various patterns of the testicular artery route.  The study, described above, is preliminary work towards further investigations on new applications of imaging techniques in evaluating testicular vasculature of stallion testes.

References

1.        Collin B 1973. La vascularisation  artérielle du testicule chez le cheval. Anatomia, Histologia, Embryologia 2: 46-53.

2.        Górecka-Szyld B 1999.  Ocena wartości dopplerowskiego badania ultrasonograficznego w kolorze w diagnostyce najczęściej występujących chorób worka mosznowego. Annales Academiae Medicinalis Stetin 45: 227-237.

3.        Herbener TE 1996. Ultrasound in the assessment of the acute scrotum. Journal of Clinical Ultrasound 24: 405-421.

4.        Ippensen E, Klug-Simon Ch, Klug E 1972.  Der verlauf der blutgefäße vom hoden des pferdes im hinblick auf eine biopsiemöglichkeit. Zuchthygiene  7: 35-45.

5.        Jantošovičová J 1969. To the question of anastomoses of the arteries of ram, boar and stallion testis and epididymis.  Folia Veterinaria XIII (2): 21-26.

6.        Jantošovičová J, Jantošovič J  1983. Topographisch-anatomische Angaben über die A.testicularis, A.ductus deferentis und A.cremasterica beim Hengst. Gegenbaurs Morph Jahrb, Leipzig 129 (4), 467-482.

7.        Kim ED, Lipshultz LI 1996. Role of ultrasound in the assessment of male infertility. Journal of Clinical Ultrasound 24: 437-453.

8.        Love CC 1992. Ultrasonographic evaluation of the testis, epididymis, and spermatic cord of the stallion. In TL Blanchard and DD Varner(Eds) Stallion Management, Veterinary Clinics of North America: Equine Practice 8 (1): 167-182.

9.        Love CC, Varner DD 1998. Ultrasonography of the scrotal contents and penis of the stallion, In NW Rantanen and AO McKinnon, Equine Diagnostic Ultrasonography, Williams & Wilkins, Philadelphia, 253 – 269.

10.     Smith JA 1974.  Biopsy and the testicular artery of the horse. Equine Veterinary Journal 6(2): 81-83.

11.     Turner RM  1998. Ultrasonography of the reproductive tract of the stallion.  In V Reef (Ed), Equine Diagnostic Ultrasound,  WB Saunders, Philadelphia,   446-479. 

12.     Wielgoś M, Bablok L, Frącki ST, Marianowski L 1998.  Dopplerowska ocena przepływów naczyniowych w tętnicy jądrowej u mężczyzn w wieku dojrzałym. Ginekologia Polska 69(6): 537-540.

Acknowledgements

This work was supported by the State Committee for Scientific Research of Poland.