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How to Obtain a Stallion Testicular Biopsy Using a Spring-Loaded Split-Needle Biopsy Instrument
L.K. Pearson, J.S. Rodriguez, A...
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1. Introduction
Testicular biopsy in the stallion is an important yet underused technique in equine practice. The two major reasons that practitioners hesitate to obtain a biopsy when indicated is unfamiliarity with the technique and the risk of complications.
The primary indications for biopsy of the stallion testis are for diagnostic evaluation of azoospermia/ oligozoospermia or to histologically assess changes within testicular parenchyma detected on ultrasonography or palpation such as in the case of degeneration or neoplasia.
Stallions that are diagnosed with azoospermia often present to the veterinarian for evaluation of infertility, either because mares that were bred live cover return to estrus, or because collection via artificial vagina yields an ejaculate with no spermatozoa.1 Azoospermia must be characterized on the basis of the horse’s spermatogenic capability versus ejaculatory disorders, including retrograde ejaculation.1 Azoospermia may be due to bilateral obstruction along the length of the epididymal ducts, epididymis, ductus deferens, or ampullae.2 A thorough examination will include palpation and ultrasonography of the external and internal genitalia,3 collection by artificial vagina to determine presence of urine in the ejaculate, and assay of enzymatic activity, including alkaline phosphatase4 and serum endocrine assays. Results of these examinations will help the clinician to determine if a testicular biopsy is indicated to assess normal seminiferous tubule architecture and presence of proper germ cell differentiation.
Similarly, stallions with testicular degeneration may present for infertility, although in some cases the clinician will note soft testes with decreased dimensions on palpation. In many cases, prior breeding soundness examination results will be available for comparison of testicular length, width, and height, as well as total scrotal width, and can be used to monitor stallions over time and especially with advancing age. In some cases, however, infertility is a presenting complaint and/or previous records are not available for comparison. In these cases, testicular biopsy can provide a histologic diagnosis to the clinician of degenerative changes within the testicular parenchyma and disruption of spermatogenesis, which may have significant effects on fertility and longevity of that stallion’s breeding career.5
On the contrary, stallions with testicular neoplasia most commonly present to the veterinarian for nonpainful testicular enlargement.6,7 In these cases, ultrasonography of the affected testis may identify abnormal regions of the testicular parenchyma that may be biopsied for histologic diagnosis.8 Histological confirmation of neoplasia supports the clinician’s decision to perform hemilateral or bilateral castration and pursue other diagnostics for potential metastasis.
Several methods of testicular biopsy have been reported for use in the stallion, including fine needle aspiration, open surgical biopsy, punch biopsy, and use of a split-needle spring-loaded biopsy instrument.
The easiest and least diagnostic method to assess the testicular parenchyma is to obtain a fine needle aspirate using a small-gauge needle and syringe.9 The aspirated material is smeared on a slide and evaluated after staining with the usual cytology technique. Some authors advocate that with a trained eye, the specific stages of germ cell development can be counted from slides made from fine needle aspirates and that the percentage of each cell type can help diagnose stallions with infertility.9,10 Although this method is inexpensive and least invasive to the testis, it does not provide the diagnostician with any information about the architecture of the seminiferous tubules and may not reflect the entire cell population of the testis.
Open biopsy of the testis, also commonly referred to as a wedge or surgical biopsy, results in the highest risk of complications. The horse is placed under general anesthesia and the scrotum is aseptically prepared. An incision is made through the scrotum and a wedge biopsy of the testis is obtained.11 The scrotal incision is apposed with suture. A study on open biopsy in the stallion demonstrated transient inflammatory infiltrate and formation of granulation tissue in biopsied testes as well as transient decreases in testicular size and local areas of testicular degeneration after biopsy.11 However, these effects all resolved over time. Although the tissue obtained affords excellent histopathologic assessment of the seminiferous tubular architecture and any degenerative or neoplastic conditions present, procurement of this type of biopsy may increase the risk of hemorrhage, infection, adhesion formation, and, most significantly for breeding stallions, a negative effect on spermatogenesis that can range from decreased spermatozoa production to the production of morphologically abnormal spermatozoa or degenerative changes within the seminiferous tubules. This technique also requires general anesthesia.
Punch biopsy or biopsy using a Tru-Cut style needle is similar to the technique using a spring-loaded biopsy instrument, except that the needle or biopsy punch is introduced by hand into the testicular parenchyma, which can lead to increased rates of hemorrhage and parenchyma damage, depending on the size of the biopsy obtained.12,13 Samples are adequate for assessment of tubule architecture.
The split-needle spring-loaded biopsy instrumenta (Figure 1), first used in equine practice in 1994,14 is an inexpensive tool that has distinct advantages over other testicular biopsy methods in stallions. The 14-gauge diameter is adequate for histologic assessment of seminiferous tubule architecture without causing significant loss of parenchymal tissue and without negative effects on spermatogenesis, although one study demonstrated a transient decrease in percentage of progressively motile spermatozoa for 3 weeks after biopsy.15 However, this decrease in motility did not have detrimental effects on fertility.15 The rapid-fire mechanism of the biopsy instrument not only shortens the time to procure the biopsy but also minimizes trauma to the tissues. Additionally, the biopsy can be obtained under standing sedation without general anesthesia.16
Because many practitioners hesitate to obtain a testicular biopsy due to inexperience using the technique and because of the risk of complications, the objectives of this study were (1) to evaluate the ease of use and diagnostic validity of biopsy samples obtained with the spring-loaded split-needle biopsy instrument in the hands of novice users and (2) to assess the complication rate in stallions after testicular biopsy using a split-needle spring-loaded biopsy instrument.
2. Materials and Methods
Thirteen mixed-breed stallions ages 3 to 12 years were acquired by the Washington State University Veterinary Teaching Hospital for training veterinary students techniques in stallion handling, medicine, and surgery. [...]
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Affiliation of the authors at the time of publication
Veterinary Clinical Sciences, Washington State University, Pullman, WA 99164, USA
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