Surgical castration in dogs: does the incision approach influence postoperative recovery?

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Appraisal, application and reflection

Castration in the male dog is a common surgical procedure with multiple indications including humane population control, modulation of certain undesirable behaviours (McGreevy et al., 2018), and as an intervention in the control of some health conditions caused by infectious, endocrine, testicular and epidydimal pathologies (Hamilton et al., 2014). It is conventionally taught using an incisional approach made cranial to the scrotum that avoids excessive tissue handling of the scrotal skin. Some authors have suggested that this approach, which is unique among domestic animal species, is due to a higher infection risk related to the canine scrotum resting on the ground during sitting (Wilson, 1975) or that male dogs are ‘scrotal conscious’ and prone to self-trauma (Howe, 2006). Since canine orchidectomy is widely taught and performed in companion animal practice and variations on the technique exist, evidence review is warranted to further refine a patient-centered approach for this routine procedure. In this critical appraisal of the literature, the evidence supporting the use of a scrotal incision to perform orchidectomy was evaluated against the traditional pre-scrotal approach.

Two North American studies met the inclusion criteria comparing patient outcomes after castration using the two different incisional access points. Post-operative recovery was assessed through observation of incisional swelling, haemorrhage, self-trauma, and pain. Since surgical duration is associated with incision infection risk (Eugster et al., 2004), the length of each procedure was also recorded and compared. Results from a randomised positive control multisite clinical trial conducted in 2015 found that the odds of self-trauma were reduced in dogs undergoing castration with a scrotal incision (OR: 0.51, P=0.04, 95% CI 0.27–0.97) in comparison to the positive control group, and that other complications observed were not attributable to differences in location of the skin incision (Woodruff et al., 2015). In a subsequent study by Miller et al. (2018), post-operative complications were recorded for 24 hours for 400 dogs after undergoing castration using a scrotal approach. Complications were reported as peri-incisional dermatitis in 9/400 (2.3%) dogs, as well as skin bruising in 4/400 (1.0%) dogs and incisional swelling in 1/400 (0.3%). In Britain, the reported rate of postoperative complications occurring at any time after canine castration is 10.83% (95% CI 8.51%–13.69%) (NASAN, 2021).

These two studies suggest that the risk of postoperative complications in the first 24 hours is at least no worse when a direct scrotal approach to orchidectomy is used and begin to unpick the assumption that the traditional pre-scrotal technique is safest. The protective effect of a scrotal incision against self-trauma reported by Woodruff et al. (2015) conflicts with historic assumptions related to sensitivity of the scrotal tissues. Moreover, both studies highlighted a shorter duration of surgery in dogs undergoing a scrotal castration approach. A methodology review suggested that increased surgical efficiency of direct scrotal access results from reduced time required to locate and exteriorise the gonads, as well as less time taken to close the incision, since the incision is normally left to heal by second intention or closed with tissue glue (DiGangi et al., 2016).

The preference for pre-scrotal access may be due to the cosmetic finish of a closed skin incision yielding minimal discharge, as this is generally considered to be more acceptable to pet owners since patients recover from surgery in the home. However, preventive wound management such as scrotal wrapping, adhesive dressing or a wound spray may lessen discharge (DiGangi et al., 2016), and the imperative to minimise complication risk for elective procedures in animals might one day support a shift in consensus on the most optimal access point for canine castration. Currently, however, several limitations prevent firm conclusions from being drawn from this critical appraisal of the evidence.

Only two studies met the inclusion criteria and both were conducted in the USA, where acceptance of companion animal neutering is generally very high. It is possible that patient outcomes observed in the included studies may not reflect those in other countries. Furthermore, use of multiple employees and / or private owners to observe patient recoveries as occurred in the assessed studies could have contributed to inconsistent observations. Neither study indicated that validated questionnaires or scoring systems were used in the assessment of subjective parameters, for example, the Glasgow Composite Measure Pain Scale to evaluate pain scores. Alongside inter-observer variability, differences in recovery setting (home recovery versus shelter) could also have influenced the likelihood of complication observation, since patients recovering in a home may receive more attentive care. Finally, further research is justified to evaluate postoperative complications that occur more than 24 hours after surgery, as well as trials conducted with larger sample sizes drawn from multiple sites.

This review provides support that frequently performed and routine elective procedures warrant periodic and critical review of underlying assumptions. Modern surgical techniques and perioperative care may improve outcomes of direct (scrotal) incisional approach in canine castration at least in the first 24 hours, but it remains unclear whether the advantages described in the papers reviewed would be maintained in the longer postoperative period.

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