EQUINE VETERINARY EDUCATION Equine vet. Educ. (2020) 32 (8) 403-406 doi: 10.1111/eve.13047


Clinical Commentary Getting the rabbit out of the hat


R. Coomer Cotts Equine Hospital, Pembrokeshire, Wales, UK Corresponding author email: richcoomer@hotmail.com


In the accompanying paper, Rijkenhuizen and co-workers (2020) describe the presentation and subsequent successful laparoscopic surgical castration of two unusual abdominal cryptorchid horses. Both horses had hormonally active unilateral enlarged cystic intra-abdominal testicles. Their article raises important discussion points with regards to occurrence and technique when dealing with enlarged abdominal testicles and teratomas in horses. Abdominally retained testicles are infertile due to the


higher temperatures, inhibiting the development of seminiferous tubules and hence limiting spermatogenesis (Bergin et al. 1970). It is generally accepted that abdominal testes are infertile, though spermatozoa can sometimes be identified (Hobday 1914). The testicular tissue in the Tobiano horse was inactive, but it is unclear whether it was possible to differentiate temperature- and pressure-related atrophy. In the other horse a cystic teratoma was present, with no grossly visible testicular tissue. The features of this horse follow a common pattern seen in monorchid horses, whereby most other secondary structures form normally, vis-


descended testicle should be left in place regardless. Cryptorchid horses undergoing hemicastration should not occur. The authors of the accompanying article successfully


removed comparatively large structures through small incisions by first decompressing the cystic cavities via needle aspiration. This technique has been around for a while, for example Hickes (1905) aspirated 39 fluid ounces (1.15 L) from a cystic abdominal testicle to facilitate its removal. The horse described by Rijkenhuizen et al. (2020) had close similarities with that described by Cribb and Bour


403


e (2010), which also a-vis vaginal


process, ductus deferens, epididymis, proper ligament, testicular artery and vessels (e.g. Garlick 1952; Parks et al. 1989; Santschi et al. 1989; Strong et al. 1997; Brommer et al. 2011). It supports the theory that two gonads always form embryologically with subsequent loss or aberrant development occurring to the testis. The previous hemicastration of the Warmblood teratoma


horse warrants attention (Rijkenhuizen et al. 2020). The fallacious myth that castration of the descended testis in a cryptorchid horse would aid the descent of the missing testicle has no evidence to support it (Cox 1987). It probably gained traction from pony populations afflicted by delayed testicular descent, where the delayed gonad ‘appeared’ a few years after the previous one was removed, as it would have done anyway. A hormonal basis for testicular descent has been shown in man (Hagberg and Westphal 1982), leading to the recommendation for medication with hCG to stimulate descent in cryptorchid colts (Brendemuehl 2006). This may have some merit for inguinal retention and delayed descent, but the vaginal rings contract within the first few weeks, reducing the likelihood of descent of an abdominal testis (Bergin et al. 1970). A pathologically enlarged testicle would be even less likely to be able to pass the inguinal rings. Unilateral castration of a descended testicle in a cryptorchid horse could allow hormonally entire males to be mis-sold as geldings. For this reason, it could be legally construed as fraud and doing so a potential offence (Cox 1987). As well as the negative effects on the welfare of the horse, it may also increase the cost and morbidity of subsequent castration (Marshall et al. 2007), though more recent ultrasonographic methods offset this by allowing location to be determined before surgery (Schambourg et al. 2006; Coomer et al. 2016). When castrating a cryptorchid horse, the missing testicle should be removed first and if this is not possible, the


contained low viscosity liquid and was removed during standing laparoscopy. In managing decompression in this way, these authors were somewhat lucky in finding themselves presented with a liquid amenable to needle aspiration. Teratomas come in many forms and may be composed of any or all three germ layers: ectoderm, mesoderm and endoderm. Dermoid and epidermoid cysts are subtypes of benign teratoma; epidermoid cysts only contain skin, whilst dermoid cysts contain in addition, hair follicles, hair, sweat glands and their accumulated secretions. Other teratomas contain bone and cartilage (Fig 1a,b, Supplementary item 1) (Cox 1987). Teratomas in both mares and stallions are frequently cystic but because many are dermoid cysts, the contents may be of a viscous oily consistency and/or contain hair. Decompressing such cysts directly into the abdomen by tearing them open to allow the contents to drain into the peritoneum before removal was once practiced routinely with no ill effects (Hobday 1914). I recall one occasion when such a cyst wall tore during traction of what appeared, from pre-operative workup, to have been a moderately enlarged ovarian granulosa cell tumour. Liberal quantities of dark brown oily tenacious liquid admixed with hair spilled throughout the layers of the laparotomy incision (Fig 2). After lavage, no adverse effects occurred. Interested readers are directed to the beautifully illustrated descriptions of different types of testicular teratoma contained in Hobday (1914). Removing enlarged retained testicles is not as well


referenced as ovaries in horses, probably because they are encountered less frequently. The use of retrieval bags (e.g. Lloyd et al. 2007; Bont et al. 2010; Cribb and Bour


e 2010)


prevents seeding of the laparotomy surgical site, or abdomen, with tumour cells. This is a small problem because most are benign. A more tangible benefit to bags is that they provide a convenient way to provide traction without the need for hands that can slip or grasping instruments that can tear (Fig 3). Physical maceration may also be carried out inside the bag to further ease removal (Bont et al. 2010). Morcellators may reduce morbidity further by allowing removal via incisions no larger than the original laparoscopy ports (Kummer et al. 2010; Lund et al. 2014). It may be difficult to avoid peritoneal contamination if using a morcellator on a large cystic teratoma, or one containing bone. Huge testicular teratomas


© 2019 EVJ Ltd


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92