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Critical review of complications between open ovariohysterectomy and ovariectomy in healthy bitches

Author Name: Vicky Nursimloo, BSc (Hons) Veterinary Nursing Science

 

Abstract

Neutering is the most frequently performed procedure in small animal practice, but surgical techniques for spaying bitches continue to vary between countries with ovariohysterectomy being the standard approach in the United States and ovariectomy used in some European countries. Research suggests that there is no difference in either intraoperative or postoperative complications between the two procedures. However, ovariectomy is proposed to be more beneficial. The more cranial incision in this procedure allows better visualisation of the ovaries, consequently reducing the risk of ovarian pedicle haemorrhage or ovarian remnant syndrome, the latter of which can potentially lead to a fatal pyometra. In addition, it could facilitate ovarian exteriorisation and ligation- surgical procedures. Final year students found these procedures the most difficult to perform, accounting for a higher complication rate recorded in studies compared to those performed by an experienced surgeon. Bodyweight, incision length, surgery and anaesthesia duration were revealed to be potential risk factors. A higher percentage of wound complications was reported in a study where surgery time exceeded 90 minutes and bitches were anaesthetised for 120 minutes or more. No significant difference in surgical time between ovariohysterectomy and ovariectomy was found, suggesting that these complications would not be increased in any procedure. However, the smaller incision length of ovariectomy could reduce wound complications. Urinary incontinence, revealed to be more evident in larger breeds, was not significantly different between ovariohysterectomy and ovariectomy. Signs of oestrus or pyometra, which was presumed to occur following ovariectomy, were also not reported in longitudinal studies, making it an alternative procedure to ovariohysterectomy if there is no uterine pathology.

 

1.0 Introduction

Elective sterilisation remains the most common surgical procedure in a veterinary practice (Goethem et al., 2006). In bitches, this can be done by ovariectomy (OVE) where only the ovaries are removed, or ovariohysterectomy (OVH) where both the uterus and the ovaries are removed. A dilemma exists as to where OVH should be performed rather than OVE, with the latter being the preferred method in The Netherlands and some European countries (Harris et al., 2013). Anecdotally, it has been presumed that leaving the uterus in situ could lead to uterine complications like pyometra (Harris et al., 2013, Goethem et al., 2006). Despite recent research, OVE remains infrequent, especially in the United States (Harris et al., 2013, Goethem et al., 2006). This review aims to evaluate whether there is a rationale for choosing either technique for neutering healthy bitches and to investigate whether there is any difference between OVH and OVE in terms of surgical complications.

 

2.0 Critical Review

2.1 Ovarian pedicle haemorrhage

According to Goethem et al. (2006), ovarian haemorrhage in OVE and OVH is likely to be clinically similar. In a veterinary teaching hospital, where OVH was performed by final year students on 142 healthy bitches, 6.3% ovarian haemorrhage was reported; 7 being from the right ovarian artery and only 2 from the left (Burrow et al., 2005). However, data for only 141 bitches were recorded and whether any bitches were excluded from the research was not specified. It is therefore possible that the percentages recorded for the type and number of complications in this study are not reliable. In Muraro and White’s (2014) report, only 1.12% bitches had significant ovarian artery haemorrhage which was lower than that reported in Burrow et al. (2005) study. However, the veterinary surgeons (VSs) who performed the procedure were all considered to have experience with the surgical technique which could consequently account for the lower percentage. In addition, Muraro and White (2014) based their findings on a sample population of 1880 bitches, which is larger than that of Burrow et al. (2005) who used only 142 bitches, and consequently makes the data more accurate.

Similarly, Harris et al. (2013) report that where canine OVH and OVE was conducted by final year veterinary students (SVs), ovarian pedicles haemorrhage was significantly higher (21.7%) than the earlier cited studies. This may have been due to a potential lack of surgical experience and practice in the students before taking part in the research. In contrast, no intraoperative complications were recorded when all the procedures were performed by one single-board certified surgeon in both Tallant et al. (2016) and Peeters and Kirpensteijn (2011) studies. Since variation of surgical technique and experience was eliminated in both reports, this prevented issues seen in other articles where several VSs performed the procedures (Mayer, 2010). However, the surgeon’s experience was not specified in Tallant et al. (2016) review and the validity of the results could be questioned due to the smaller sample size used. In addition, both studies used a vessel sealing device which could have prevented any haemorrhage.

The removal of the ovaries from the abdominal cavity and the ligation of the ovarian pedicles were found to be the most difficult surgical part of OVH or OVE for students (Harris et al., 2013, Burrow et al. 2005). Haemorrhage from the right ovarian pedicle has been shown to be more frequent due to its more cranial position in the abdomen which therefore makes it more difficult to exteriorise than the left ovary. The ability to do the incision more cranially in OVE therefore makes these procedures easier than OVH (Tallant et al., 2016, Harris et al., 2013, Burrow et al., 2005). However, in Harris et al. (2013) study, ovarian pedicle haemorrhage was unexpectedly more frequent in the OVE group, though the extent to which the incision was more cranially or caudally positioned in OVH and OVE was not mentioned. Consequently, no accurate comparison could be made between the two groups.

The exteriorisation of ovaries and the ovarian pedicles ligation were also shown to be more difficult in bitches with a higher bodyweight due to their large amount of abdominal fat obstructing access to the ovaries (Muraro and White, 2014, Harris et al., 2013, Burrow et al., 2005). Bodyweight was significantly associated with incidence of complications in Muraro and White (2014) review. However, bodyweight could have potentially been associated with any type of complications and not just ovarian haemorrhage, therefore making it hard to draw reliable conclusions. Since obese dogs were more difficult to ovariohysterectomise, Peeters and Kirpensteijn (2011) recorded the body condition score (BCS) of each bitch preoperatively, to allow a more accurate consideration of obesity than bodyweight. No significant influence of BCS was found for any variables. However, further research would need to be conducted to investigate the relationship between the amount of intra-abdominal fat and BCS. In a study where laparoscopic OVE was performed, a subjective measurement of ovarian ligament fat scores based on a previous study was recorded (Dupré et al., 2009). A higher amount of fat was found to increase the surgical time. This method can therefore be carried out in future studies to highlight any differences between OVE and OVH on different variables which may be related to the procedure.

 

2.2 Ovarian remnant syndrome and pyometra

Ovarian remnant syndrome (ORS) occurs when any remaining ovarian tissue continues to function following OVH or OVE, giving rise to pyometra or stump pyometra (Muraro and White, 2014). A previous study, where ORS was present in the 35% of bitches that had stump pyometra supports this (Okkens et al., 1981). In Muraro and White (2014) study, ORS was reported in two ovariohysterectomised bitches that developed pseudopregnancy one year postoperatively after examination. According to the author, this could have been due to poor visualisation of the ovarian pedicles or accidental loss of ovarian tissue in the abdomen. Similarly, in Okkens et al. (1981) report, 41 right remnants of ovarian tissue were removed compared to 22 on the left. It can therefore be suggested that OVE might reduce the risk for ORS compared to OVH, due to having a more cranial incision and consequently allowing better visualisation of the ovaries. It can also be concluded from the above studies that ORS can be due to surgical error rather than the neutering procedure.

It was presumed that OVH was the method of choice over OVE for neutering bitches to prevent occurrence of pyometra or stump pyometra (Goethem et al., 2006). However, in both Burrow et al. (2005) and Okkens et al. (1997) studies, no signs of pyometra were recorded in the 54 and 69 bitches that were ovariectomized 2 years and 8 to 11 years earlier respectively. Furthermore, where laparoscopic ovariectomy was performed on 125 bitches, no signs of postoperative oestrus or pyometra were recorded (Corriveau et al., 2017). The large sample population used, the long follow-up period and the consistency in these various studies give strong evidence that ovariectomy does not increase the chance of these complications if the ovaries are fully removed and if no uterine pathology is found at time of surgery.

 

2.3 Wound complications

According to Goethem et al. (2006), wound complications could be incidental to any sterilisation procedure, but since a smaller incision is made in OVE, these complications should be lowered. In a research where 40 healthy bitches were randomly and equally assigned to undergo OVE or OVH by an experienced VS, no significant differences for total wound scores between each group were found at any time. These were evaluated by four SVs for 24 hours who were unaware of the surgical procedure performed (Peeters and Kirpensteijn, 2011). In the same research, the incision lengths in the OVH group were significantly increased. Since age, bodyweight and BCS did not differ between groups, this suggested that an accurate comparison could be made, and results obtained were more likely to be reliable. Nevertheless, even if the students were trained to assess the wound adequately, interobserver variability remained a potential source of bias in this study. In addition, the different wound scores obtained in each group were not mentioned. In Burrow et al. (2005) report, 12 bitches exhibited wound complications postoperatively; 5 with both wound inflammation and discharge and 7 with wound inflammation only. Among these dogs, 83.3% were anaesthetised for 120 minutes or more and had a surgery time that exceeded 90 minutes. Bitches that had postoperative wound complications had a significantly longer total surgery time and total anaesthesia time than those who did not. Furthermore, bodyweight was also found to be positively correlated with total surgery time. This research was therefore useful to indicate that duration of surgery or anaesthesia and bodyweight could be potential risk factors in developing wound complications. The bitches were also considered to be healthy based on their history and clinical examination, making the method reliable in evaluating complications. However, four bitches had mild pyoderma ventrally and were given antibiotics. They were not excluded from the study and could have introduced biased results, though none of them had any complications. Consequently, it could be concluded that they did not interfere with any wound complication results although it was possible that the use of antibiotics, even if it was ethically appropriate, could have prevented any wound complications from occurring. Other factors such as lack of surgical experience, patient interference and poor wound management at home or the maintenance of the theatre and surgical instruments could have also potentially increased the wound complication development rate. 1.2% of the bitches that had incisional swelling, pain and redness (with or without discharge) were not wearing an Elizabethan collar. This could have potentially increased the incidence of wound complications rather than the actual technique used. Furthermore, the 0.21% incisional hernia reported were potentially due to improper surgical technique. In another study, 3.9% of wound complications were recorded where none of the bitches were anaesthetised for more than 120 minutes (Muraro and White, 2014). Consequently, this could explain the reduced rate recorded although the surgical expertise of the VS could also have decreased the complication rate as a result of the lower anaesthesia time. In addition, anaesthesia time was significantly associated with incidence of complications. In Tallant et al. (2016) report, surgery duration was significantly greater in OVH than OVE whereas no significant difference was found between the two groups in a previous report (Peeters and Kirpensteijn, 2011). The latter article may be more reliable than Tallant et al. (2016) study, as its findings were based on a larger sample size and no difference in age, bodyweight and BCS was detected between OVE and OVH. In another review, no difference in surgical time was also discovered between the two procedures when performed by SVs (Harris et al., 2013). In addition, age and bodyweight did not differ between groups, enabling an accurate comparison and suggesting that neither procedures would increase the risk of wound complications based on surgical time.

 

2.4 Urinary Incontinence

Urinary incontinence is frequently observed following sterilisation in bitches and involves the involuntary passing of urine (Goethem et al., 2006). In Murraro and White (2014) study, 1.9% of the ovariohysterectomised bitches had at least one experience of urinary incontinence postoperatively, either while sleeping or during recumbency within the four weeks of hospitalisation monitoring. However, no diagnostic tests were performed due to financial restrictions. Consequently, it cannot be ascertained that the incontinence recorded was due to the surgery. In a previous study where the long-term effect of OVE and OVH was compared in bitches by sending questionnaires to 264 owners, 3.7% and 4.4% developed urinary incontinence 0.5 to 8 years and 9 to 10 years later respectively (Okkens et al., 1997). It is therefore possible that Muraro and White (2014) study was underpowered in recording the rate of incontinence as the bitches could have become incontinent after the four weeks. Similarly, in Burrow et al. (2005) review, no urinary incontinence was reported in bitches who were followed up for up to 2 years, but they could have developed it afterwards. In Okkens et al. (1997) study, complete data analysis was available from only 135 owners. Consequently, it could also be possible that incontinent bitches were present among the missed data. The study also had to rely on owners’ answers which could have introduced bias into the results. Of the 15 incontinent bitches, 80% weighed more than 20kg. This report was therefore useful to support that larger breeds are at higher risk of developing urinary incontinence. Incidence of urogenital problems were also not significantly different between OVH and OVE during the 8 to 11 years period. However, in both Muraro and White (2014) and Okkens et al. (1997) reports, no clear history of previous urinary tract problems was taken, potentially giving invalid results. In Corriveau et al. (2017) study, where laparoscopic OVE and laparoscopic-assisted OVH was compared, preoperative urinary tract abnormalities (urinary tract infections, calculi, or incontinence) was associated with postoperative incontinence using multivariable analysis. Among the 8 bitches who were 9 years old or more before the first appearance of urinary incontinence, 87.5% had polydipsia and polyuria. There was therefore a possibility that urinary incontinence could have been due to other diseases unrelated to the neutering procedure. Future studies, where a complete history of urinary tract disorder is available, will need to be conducted to determine whether urinary incontinence is truly related to OVH or OVE, highlighting if there are any differences between the two procedures.

 

3.0 Conclusion

No differences between OVE and OVH were found in terms of intraoperative or postoperative complications. However, OVE seems to have more potential benefits in reducing the risks of ovarian pedicle haemorrhage or ORS due to its more cranial incision which consequently allows better visualisation of the ovaries. Surgical experience also played a significant role in reducing these complications when compared with SVs. We could conclude that surgical training and practice should be encouraged to decrease the risk of these complications occurring. Bodyweight, incision length, and time of both surgery and anaesthesia, were also potential risk factors in increasing the complication rate. Although surgical time for OVH was found to be greater in some studies, other work found no significant difference between OVH and OVE, suggesting that neither procedure increases the incidence of wound complications. However, in this same study, a smaller incision length was recorded for OVE which could have potentially lowered the rate of wound complications. With reference to long-term complications, no difference was found in the occurrence of urinary incontinence between the two groups although those studies were underpowered in assessing long-term urological problems. Signs of oestrus or pyometra were also not reported in longitudinal studies where a large sample of healthy bitches were reviewed where the ovaries were removed between 2 years and 14 years earlier. This supports that OVE does not increase the chance of these complications developing if the ovaries are completely removed and if no uterine pathology is found at time of surgery. Consequently, OVE could be the procedure of choice for neutering healthy bitches.

 

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