The use of biotechnology in livestock production has allowed qualitative and quantitative genetic improvements. Ultrasonography is the use of sound reflection technology and is reportedly safer and more effective in soft tissues. It provides information about size, shape, and location of structures and also provides information about the soft-tissue architecture of the structure or organ being examined. Ultrasonography makes a distinction between solid and fluid-filled structures and provides internal details of such structures. It is easily accessible and does not cause deleterious effects. It is based on soft-tissue density and reflection of sound waves where highly reflective structures are termed hyper-echoic and low reflections are referred to as hypo-echoic1. Ultrasound imaging has been widely used in reproductive clinical examinations. It is a rapid and non-invasive technique that assists clinicians to complete diagnosis and may lead to early detection of disorders of the testes and related structures2, and it has been used to evaluate testicular function in domestic animals3. Several authors who have worked on testicular evaluation using ultrasonography are documented in different species of large animals which includes cattle4, camel5, sheep6, Alpine goats7 and dogs8. Although ultrasonography has been utilized to determine the breeding soundness of bucks9, proper identification of the parts of the testes have not been done in WAD goats. The WAD buck is a small ruminant endowed with great breeding potential9. The aim of this study is to establish the normal anatomy of the testes of WAD bucks using ultrasonography.
2. Materials and Methods
This study was carried out at University of Ibadan Large animal clinic ward 2, Veterinary Teaching Hospital, University of Ibadan, Oyo state, Nigeria. Five matured and clinically healthy West Africa dwarf bucks aged about one and half years with an average weight of 15±0.5Kg were selected for the project. The bucks were acclimatized for a period of two weeks and fed with grasses, commercial concentrates, water and mineral salt ad libitum.
Body weight was taken daily during the course of the experiment using a bathroom scale (Camry®) as described10.
During selection and prior imaging in this study, animals were subjected to physical examination in order to detect possible diseases that could interfere with their reproductive potential. The examination included a general clinical evaluation (inspection of body condition and presence of hereditary defects and functionality of the nervous, respiratory, circulatory, digestive and musculoskeletal systems) and morphological evaluation of the genitalia (inspection and palpation of the scrotum, testes, epididymides, spermatic cords, prepuce and penis). The animals were declared healthy and free of any clinical manifestation.
Testicular ultrasonography was done by restraining animals by holding the hind limbs spread apart allowing the scrotal sac to dangle free of any encumbrance. The scrotal sac was not shaved because it is covered by a thin layer of hair which did not interfere with the procedure. The scrotal sac was thoroughly cleaned with tissue paper before ultrasound gel was applied generously covering the entire scrotal surface. A Draminski portable 5MHz ultrasound machine was used. The ultrasound gel was also applied on the probe covering the entire surface and then pressed gently on the surface of the testes held in the scrotal sac. The images were captured from the monitor and stored on an electronic device. Testicular ultrasound protocol for the bucks involved viewing the longitudinal, sagittal and transverse planes for both testes in each of the animals.
The ultrasound images showed the skin of the scrotum and sub-scrotal structures, as a single hyperechoic band A surrounding the scrotal content. The testicular parenchyma was homogeneous and moderately hypoechoic B (see Figure 1).
Figure 1. Ultrasonography of WAD buck testes in transverse plane. A shows the scrotal wall and subscrotal structures. B shows the testicular parenchyma made up of seminiferous tubules. F is the hypoechoic intertesticular area.
The mediastinum testis is the highly echogenic (hyperechoic) band C within the testes. The whole breadth (D-E) of the right and left testes was seen on the transverse plane and A shows the hyperechoic area indicating the scrotal wall of the right testis (figure 2). The hypo-echoic area between the right and left testicle F is the inter-testicular septum while the wide linear hyperechoic structure in the central axis of the testes (C) represents the mediastinum testis. The hypoechoic lower border represents the epididymis. The sagittal plane allowed a view of blood vessels and spermatic cord at the upper border (see Figure 3- A) and the hyperechoic mediastinum testis C and scrotal wall D, as well as the anechoic epididymis, G. All the animals evaluated in this study presented no testicular abnormalities.
Figure 2. Ultrasonography of WAD buck testes showing the width of the testes (D-E). C shows the hyperechoic mediastinum testis.
Figure 3. Ultrasonography of WAD buck testes in longitudinal plane showing the blood vessels and spermatic cord A, hyperechoic mediastinum testis C, hyperechoic scrotal wall D and the anechoic epididymis G.
Figure 4. Ultrasonography of left WAD testis. Mediastinum testis M, tail of the epididymis T and scrotal wall W are shown.
Figure 5. Ultrasonography of Wad testes. The variable echogenicity of the region between the mediastinum testis and the scrotal wall is demonstrated. Compare with figure 4.
The homogenously hypoechoic testicular parenchyma demonstrated on the transverse plane is asserted11 to be the testicular echogenicity presentation which is linked to the level of differentiation of Sertoli cells, the high proportion of seminiferous tubules in the parenchyma as well as the increased diameter of the seminiferous tubules at maturity.
Ultrasonography is a non-invasive technique allowing the study of changes in reproductive organs12. Pugh et al.,13 described canine testis as having a coarse medium echo pattern whereas the normal testicular ultrasound of WAD bucks in this study revealed a discrete homogenous moderately echogenic pattern. Kealy et al.,14 describes a normal canine testis ultrasound as a dense, homogeneous, fine echotexture comparable to the spleen with a hyperechoic capsule. Their report further describes a central hyperechoic line that represents the mediastinum testis and epididymis is identified as a slightly less echoic, coarse echo-textured structure lying dorsal to the testis. This is very similar to what is observed in this study but is different from what Raji et al.,9 reported. The observation of a homogenous, medium-echoic testicular parenchyma and a hyperechoic mediastinum testis in this study aligns with the observation of Dascanio15 who reported similar findings in the testis of Llama and alpaca using ultrasonography. The seminiferous tubules were homogenously hypoechoic with a bright hyperechoic mediastinum testis (Figure 2). Testicular echo-texture of the WAD buck goats were similar to those reported in fertile bulls16, rams12, camels5 and Alpine goats7. The tail appeared as a moderately hypoechoic to anechoic structure which is similar to descriptions by 13Pugh et al., who evaluated the testis in dogs.
Ultrasonography has shown high usefulness in its ability to go beyond distinguishing lesions which are extra-testicular and testicular to even determining cystic and solid lesions, it also goes further to identify individual lesions, thereby making diagnosis more definite17. 18Lacasta et al., used ultrasonography to diagnose a unilateral scrotal hernia, varicoele and sperm granuloma in a ram by identifying a hyperechoic covering of the left testis thought to be omental fat within the hernia sac and non-echogenic tortuous areas were diagnosed as varicocele which were confirmed at post-mortem. 19Carazo et al, using ultrasonography demonstrated changes over time in testicular parenchyma and linked the changes with the photoperiod in goats and allowing its use in predicting of sexual maturity.
Dascanio15 recommends that a 5Mhz Ultrasound machine will suffice to evaluate the testes while a 7.5 Mhz machine will only be required to demonstrate subtle ultrasonographic lesions. A study carried out in Nigeria9 reports use of a 7.5 Mhz machine but this study used a 5Mhz ultrasound machine.
The lack of resources to demonstrate normal anatomy also reported by other authors like 19Carazo et al; 20Cruz and Freitas, has led to difficulty with recognizing some of the ultrasonographic lesions seen in this breed and others breeds and species. The labeled parts of the testes aid in identifying a normal ultrasonographic study. This will enhance clinical assessment of the testes in this highly prolific specie and the value of ultrasonography as a clinical imaging technique in evaluating the testes was demonstrated. In conclusion, ultrasonography is a valuable imaging tool that can be utilized in clinical assessments of reproductive potential of WAD bucks ante mortem in a bid to select fertile animals in a breeding program.