EQUINE VETERINARY EDUCATION Equine vet. Educ. (2020) 32 (8) 431-436 doi: 10.1111/eve.13074
Original Article
Clinical findings in 10 horses diagnosed with monorchidism following exploratory laparotomy or standing laparoscopic surgery P. E. Clements†* , R. P. C. Coomer†
†Cotts Farm Equine Hospital Ltd, Narberth, Pembrokeshire, UK; ‡M€ alaren H€
Grove Veterinary Surgery, Newbury, Berkshire; and ¶Bell Equine Veterinary Clinic, Maidstone, Kent, UK *Corresponding author email:
pclements@rvc.ac.uk
Keywords: horse; monorchid; cryptorchid; laparoscopy; exploratory laparotomy
Summary Monorchidism describes the complete absence of one testis and is rare in horses. This study reports the clinical findings in 10 horses diagnosed as monorchids by standing laparoscopy or exploratory laparotomy. Hospital records for all horses undergoing cryptorchidectomy (2000–2016) in four centres were reviewed from which horses diagnosed with
monorchidism were identified. Surgery was by either standing flank laparoscopy or an inguinal exploration and subsequent exploratory laparotomy under general anaesthesia. Ten horses were diagnosed as monorchids, five by laparoscopy (one bilateral laparoscopy) and five by laparotomy. Nine horses had a normally descended scrotal testicle, which was also removed at surgery. The right testicle was absent in three horses, and the left testicle was absent in seven horses. Anatomical findings were recorded in each case; the vaginal process was present in all horses, ductus deferens and epididymis were present in 80% of horses and the ligament of the tail of the epididymis and testicular vessels were present in 50% of horses. Laparoscopy allowed easy identification of spermatic structures enabling a prompt diagnosis of monorchidism. In conclusion, when monorchidism occurs, most other associated spermatic structures are likely to be present. A diagnosis of true monorchidism is reliant on hormonal testing and absence of testicular tissue on histopathology and so some of these horses may strictly be somewhere on the spectrum of testicular degeneration. This information is particularly useful in the surgical situation when it is not clear whether the testicle is present or not.
Introduction
Monorchidism is the term used to describe the complete absence of one testis and is rare in horses (Cox 1987). There are a limited number of previously published single case reports (Garlick 1952; Koppang 1957; Adams 1964; Johnson et al. 1976; Petrizzi et al. 2004) and small case series of horses diagnosed with monorchidism after exploratory surgery using various laparotomy approaches (Parks et al. 1989; Santschi et al. 1989). These studies however predate the use of laparoscopy. The advantages of laparoscopy have been well published in the literature over the last 20 years (Hendrickson 2001), which includes assisting in the diagnosis of a monorchid or an anomalous abdominal cryptorchid (Kelmer et al. 2006; Smith and Perkins 2009; Brommer et al. 2011). Monorchidism can be due to agenesis, but most are attributed to testicular degeneration (Parks et al. 1989; Santschi et al. 1989; Kelmer et al. 2006; Rakestraw 2006).
There is evidence that testicular ischaemia may accompany cryptorchidism in the horse (Gardner et al. 2017) and so progression of testicular ischaemia could lead to complete testicular necrosis and a monorchid appearance. The presence of remnants of testicular tissue has been given the term anomalous abdominal cryptorchid (Brommer et al. 2011). A comprehensive recording of the presence or absence
of spermatic structures from a series of monorchid horses is lacking. There are three attachments of the spermatic tissues: the testicular vessels from the aorta, the vas deferens leading to the bladder and the ligament of the tail of the epididymis running to the apex of the vaginal process. Understanding which spermatic structures are present in these horses would be useful clinically particularly during surgery when it may be unclear whether a testicle is present or not. Identification of anatomical structures also aids attempts to locate an undescended testicle if present (Ortved et al. 2014). The aim of this study was to report the clinical findings in 10 horses diagnosed as monorchids by laparoscopy or laparotomy.
Materials and methods
The hospital records for all horses undergoing cryptorchid castration between 2000 and 2016 in four centres were reviewed retrospectively, from which horses diagnosed with monorchidism were identified.
Inclusion criteria Horses presenting as cryptorchids based on a known history of no previous surgery and surgical findings consistent with monorchidism were included in this study. During surgery, the three attachments of the spermatic tissues were identified as well as an absence of testicular tissue on the one side. Information obtained from the records included signalment, pre-surgery evaluation, surgical technique, structures identified at surgery, post-operative complications and results of hormone assays and histopathology. Pre-surgical evaluation involved external palpation in all
horses, with additional percutaneous inguinal ultrasonography in five, as described by Coomer et al. (2016). Rectal palpation was not performed in any horse. All horses received perioperative antibiotics (intramuscular procaine penicillin 22,000 iu/kg bwt) administered 60 min prior to the first skin incision. Surgery was performed in each horse by one of four
board-certified equine surgeons using two methods: either laparoscopy under standing sedation (Kummer 2012) or exploration via an inguinal approach made directly over the
© 2019 EVJ Ltd
, S. A. McKane†, D. Gorvy‡, B. Bladon§ and T. Mair¶ astklinik, Sigtuna, Sweden; §Donnington
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