In bitches, is ovariectomy/ ovariohysterectomy by laparoscopy less painful post-operatively than by midline open laparotomy?

Imagine this clinical scenario: you are discussing the benefits of spaying a client’s young French Bulldog bitch in the near future. The client enquires about a keyhole approach, as your practice started performing laparoscopic spays last year. Her previous practice did not offer the technique, as the veterinary surgeons had many years of great success with small incisions. The client would like to know whether her dog would be in less pain following a laparoscopy, so you decide to explore the evidence.

The evidence

Seven studies were critically appraised; three were blinded randomised controlled trials, two were non-blinded randomised controlled trials and two were non-blinded non-randomised controlled trials.

Dalmolin et al. (2020) used three pain scoring systems: the visual analogue scale (VAS), the University of Melbourne Pain Scale (UMPS) and the short-form Glasgow Composite Measure Pain Scale (CMPS-SF). However, they only had low to moderate agreement between them. There was no significant difference in pain scores between groups at any point using VAS. The only significant differences in pain scores (at 6 hours using UMPS, and 36 and 48 hours using CMPS-SF) between groups showed the laparoscopic group to be more comfortable. There were, however, individual time points on each of the pain scoring systems where pain scores were lower for the laparotomy group. A significantly faster return to voluntary feeding was noted for the laparoscopy group which has previously been suggested as a sign of reduced post-operative pain (Sarrau et al., 2007). Unlike the other studies, ongoing pain medication was provided throughout the recovery period which would reduce differences in pain scores between groups.

Coutinho et al. (2018) found that the intensity of post-operative pain was lower for the laparoscopic-assisted ovariohysterectomy group at most time points… but this was not statistically significant

Coutinho et al. (2018) found that the intensity of post-operative pain was lower for the laparoscopic-assisted ovariohysterectomy group at most time points, measured using VAS and UMPS, but this was not statistically significant. Significantly faster return to eating (and in greater proportion) was found in the laparoscopy group, but this behaviour is not captured by any pain scoring system.

Vasiljević et al. (2015) showed that dogs operated on by laparotomy had much higher pain scores than those in the laparoscopic group. However, this may be a result of the reported slower recovery from general anaesthesia in the laparotomy group. The strength of evidence from this study is weak, due to a lack of recording of group characteristics and poor standardisation, as additional analgesia was used for all patients in the laparotomy group but not the laparoscopic group.

Freeman et al. (2010) found that the mean laparoscopic group pain scores were equal to or lower than the laparotomy group at all post-operative time points, and higher nociceptive thresholds were identified at 4 and 12 hours post-operatively. A combination of UMPS and nociceptive threshold testing was used but was performed by two observers, creating inter-observer bias.

Devitt et al. (2005) found that pain scores and requirement for rescue analgesia… were significantly higher in the dogs neutered by laparotomy

Devitt et al. (2005) found that pain scores and requirement for rescue analgesia (as well as neuroendocrine markers for some time points) were significantly higher in the dogs neutered by laparotomy. Limitations include that the study was underpowered, and the pain scoring system was adapted from a system validated for use in human paediatric patients, not dogs, so the strength of evidence is weak.

Hancock et al. (2005) found significantly lower pain scores and higher nociceptive thresholds in dogs operated on by laparoscopy. Dogs were housed for 96 hours prior to surgery to limit the effects of stress on post-operative behaviour changes and pain scores. Although three different surgeons were responsible for intervention, block randomisation ensured that no surgeon performed an unequal number of surgeries in each group. A multidimensional composite pain scale (UMPS) was combined with an objective nociceptive threshold measurement technique and assessed by a single (blinded) observer, removing inter-observer bias. The strength of evidence could have been increased by larger group sizes, as only 16 dogs were studied.

Davidson et al. (2004) reported that mean pain scores (UMPS) were significantly lower for the laparoscopy group compared to open surgery. However, the study has many limitations

Davidson et al. (2004) reported that mean pain scores (UMPS) were significantly lower for the laparoscopy group compared to open surgery. However, the study has many limitations: there was no standardisation of anaesthetic protocol or surgical team between groups, the technique used was not applicable in general practice, and although the same surgeon was responsible for laparoscopic surgery, multiple veterinary students (who are likely to have poorer tissue handling) performed open surgery, increasing bias in favour of laparoscopic techniques.

Conclusion

Despite the widely held belief that laparoscopic surgery is associated with less post-operative pain, the available veterinary literature only provides weak evidence to support this in bitches undergoing ovariectomy/ovariohysterectomy. There are many uncontrolled variables to consider across the underpowered studies here including surgeon number (and experience), the choice of perioperative analgesia, method of pain scoring and the laparoscopic technique. While they supported the use of laparoscopy (to varying degrees) over traditional laparotomy for causing less post-operative pain, small patient numbers and the large variability between studies (and in some cases, groups) were significant constraints to the strength of evidence. Future well-powered controlled clinical trials would be beneficial.