EQUINE VETERINARY EDUCATION / AE / AUGUST 2020


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a)


b)


Fig 3: a) Laparoscopic view of the ductus deferens crossing the suspensory ligament of the bladder (arrow). b) The tail of the epididymis within the abdomen – this is significant because the tail of the epididymis descends before the testis.


* E


Fig 4: Horse 4: This spermatic tissue was removed via unilateral standing laparoscopy. A large normal epididymis (E) in the region of the deep inguinal ring but no testicle was evident. Further gross examination of the resected tissue showed an oval nubbin of beige tissue around 5 3 5 3 8 mm in the position a testicle should have been relative to the epididymis (*). This tissue was not sent for histopathology.


normal scrotal testicle (Mason et al. 2005). However, a reduction in surgical site infections has been shown when combining a laparoscopic and conventional castration technique to remove the descended testis in abdominal cryptorchids (Rijkenhuizen and van der Harst 2017). Three different hormonal assays were used in this study,


most commonly the hCG stimulation test. Historically both hCG stimulation tests and measurement of serum oestrone sulphate concentrations have been shown to be accurate (Cox et al. 1986) but there is more recent evidence to suggest preferred testing for functional testicular tissue in cryptorchids by measuring serum anti-M€


ullerian hormone (Ball


et al. 2008; Claes et al. 2013; Parker 2016). An accurate diagnosis is important because of the behavioural differences between geldings and horses with functional testicular tissue. Hormone assays would have confirmed either the presence or absence of residual testicular tissue in the four horses for which results were not available. It has been stated that a diagnosis of monorchidism can


only be made after surgical exploration, removal of the normal testis and hormonal testing (Searle et al. 1999). The


Fig 5: Horse 1: Spermatic tissue resected for histopathology. The presumed atrophic testis is marked with the arrow. Histopathology confirmed complete absence of testicular tissue.


retrospective collection of data for our study meant that it was not possible to follow the inclusion criteria set out by Searle et al. (1999) as post-operative hormone testing had not always been performed. The diagnosis in these horses was based primarily on surgical findings, but with additional information provided by inguinal percutaneous ultrasound, which has been shown to be an accurate diagnostic tool for locating inguinal cryptorchid testes (Coomer et al. 2016). Identifying the three spermatic tissue attachments (Parks et al. 1989), as well as an absence of testicular tissue at surgery supported the diagnosis of monorchidism. In conclusion, systematic exploratory surgery requires


good knowledge of anatomy to ensure that monorchidism is identified. Understanding the possible variations in appearance of the associated spermatic structures in monorchid horses is clinically useful particularly during surgery when a testicle cannot be found. Laparoscopy assists with the easy identification of the spermatic structures and the absence of testicle enabling a prompt diagnosis at surgery whilst hormonal assays and histopathology are useful post-operatively to confirm the complete absence of testicular tissue. Histopathology may also provide additional evidence for implicating ischaemic injury as the cause of acquired monorchidism in horses and may allow us to more accurately differentiate between true monorchids and anomalous abdominal cryptorchids.


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