EQUINE VETERINARY EDUCATION / AE / MARCH 2016
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a) b)
Fig 3: Example image of an inguinal testis obtained using an 8– 13 MHz linear probe.
to predict the location of missing left or right testes for the purposes of surgical planning. Cryptorchids have been classified into 3 groups within the
literature: inguinal, incomplete and complete abdominal (Cox et al. 1979). If both the testis and the epididymis are found within the abdomen, the horse is a complete abdominal cryptorchid. If the tail of the epididymis enters the inguinal canal, leaving the testis and remnants of epididymis within the abdomen, the horse is an incomplete abdominal cryptorchid. This made no difference to surgical approach used because the testis was inside the abdomen regardless, therefore no attempt was made to distinguish incomplete and complete abdominal retention in this series. The significance of this type of retention rests solely with inexperienced surgeons who may inadvertently remove the epididymis mistaking it for an atrophied testis. Two false positives occurred in this series, both 2-year-old
horses, in which an incomplete abdominally retained testis was retrieved. One explanation for these false positive horses was that the epididymis was misidentified as a testis on ultrasound. The epididymis is clearly much smaller than a testis, but it shares many of the same characteristic features of structure and appearance. Routine size measurement of the structure may alleviate this error and improve sensitivity further. Another explanation could be that a testis lying very close or over the deep inguinal ring could be visualised inguinally and erroneously labelled as inguinal. The only other possibility is that the testis retracted internally through one or both inguinal rings during hoisting in dorsal recumbency. To minimise time and cost, both false positive horses in this study underwent the transinguinal abdominal cryptorchidectomy method described by Turner and McIlwraith (1989) rather than recover to undergo flank laparoscopy. Having an alternative surgical method available proved helpful in these horses. Other general anaesthetic techniques that have been described include parainguinal laparotomy (Wilson and Reinertson 1987), paramedian laparotomy (Lowe and Higginbotham 1969), suprapubic paramedian laparotomy (Cox et al. 1975) and by laparoscopy with the horse insufflated in Trendelenburg position (Fischer and Vachon 1998; Cribb et al. 2015). Two false negatives out of 84 inguinal cases occurred; this appears to have occurred through failing to visualise the
Fig 4: (a,b) Longitudinal ultrasound image taken in the same region (a), showing an abdominally retained testis deep to the body wall. Corresponding laparoscopic image (b) in the same horse. Visualising abdominal testes is unreliable in these authors’ experience.
inguinal testis. Possibly the pressure of the probe temporarily displaced this testis out of view, or it was just not visualised despite being present. In one case, it was possible to retract this testis into the abdomen laparoscopically without further enlargement of the deep inguinal ring. In the other, it was not possible to retract the testis, therefore the mesorchium was transected laparoscopically and the testis subsequently removed under general anaesthesia. Besides the inguinal percutaneous ultrasound, other diagnostic examinations may help localising the missing testis. Rectal palpation has been a useful technique to determine location of abdominal testes, being utilised in 395 of 604 cases, 65% (Hartman et al. 2015). Perhaps unsurprisingly, these authors found a statistically significant beneficial effect of increasing operator experience, with trainee surgeons being correct in 71% of patients and faculty surgeons in 94%. Rectal palpation of the internal inguinal ring may be dangerous in some young horses and impossible in ponies, but whenever possible it can provide useful information about presence and size of the internal inguinal ring and whether or not a ductus deferens is going into the inguinal canal. If an internal inguinal ring is not palpable at the cryptorchid side, it is highly likely that the testis is intra-abdominal.
© 2015 EVJ Ltd
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