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Fig 1: Interrupted horizontal mattress colopexy performed with elevation of left body wall.
seromuscular layer of the stomach and an incision through the peritoneum and transversus abdominus muscle. The incisions are then sutured together. An incision in the seromuscular layer of the equine colon appears to be unnecessary and would likely be risky in a compromised colon. Based on the success of laparoscopic colopexy in horses, in which the peritoneum is not incised, a body wall or peritoneal incision is not crucial to the success of the colopexy adhesion, although we are not aware of any clinical retrospective studies of laparoscopic colopexy (Trostle et al. 1998). The authors of this commentary do not routinely make a body wall incision or dissection of the subcutaneous space in their left paramedian colopexy procedures (Fig 1), which has not resulted in any instances of dehiscence, to our knowledge. This procedure has led to mature adhesions confirmed on necropsy in cases subjected to euthanasia for reasons unrelated to colopexy dehiscence (Fig 2). A variety of suture materials and suture patterns have
been described for equine colopexy. An experimental colopexy technique using surgical gut suture did not result in long-term adhesions between the right and left colons, whereas the technique using polypropylene suture resulted in colopexy adhesions that remained at one year (Markel et al. 1986). Polypropylene suture was also used in the report by Hance and Embertson (1992), and nylon suture has been
described for use in laparoscopic colopexy, mainly due to the needle size which allows penetration through the body wall (Trostle et al. 1998; Wilson 2012). The use of braided absorbable suture (polyglycolic acid and polyglactin 910) has been described more recently with the technique of incorporating the lateral free band in the celiotomy incision closure (Hunt and Spirito 1995; Broyles et al. 2018). Absorbable and nonabsorbable suture have been reported for bovine omentopexy (Fubini et al. 1992; Baird et al. 2017). Incorporation of the visceral wall in the surgical fixation appears to mitigate risk of future left displaced abomasum (LDA) in cattle, with recurrence of LDA in 14% of cows with omentopexies versus 0% of cows with pyloro-omentopexies (Baird et al. 2017). To the authors’ knowledge, catastrophic incisional
dehiscence of the celiotomy incision has not been reported with colopexy at either ventral midline or left paramedian sites. This lack of body wall failure may lend support to the theory that the most common cause of colopexy dehiscence is failure at the seromuscular layer of the colon, similar to the mode of failure of gastropexies in dogs. Ex vivo biomechanical analysis of gastropexy techniques has been performed in canine cadavers (Imhoff et al. 2015; Culp et al. 2016). The primary mode of failure with axial tension to failure was gastric seromuscular tissue tearing at the gastropexy site. Pilot data from our laboratory demonstrated that failure of an equine ex vivo colopexy construct occurred most commonly with pull-though at the colonic band, which lends support to the recommendation for adequate bites of the lateral band (Fig 3). The effect of suture pattern and needle/suture size on colopexy strength has not been evaluated but may play a role in the strength of the colopexy and quality of the adhesion. Based on the large retrospective studies out of central
Kentucky, a colopexy technique incorporating the ventral midline or left paramedian celiotomy incision is an effective prevention of large colon volvulus and displacement in Thoroughbred broodmares. There is limited information about outcomes in sport horses. Authors of retrospective studies of diverse populations of horses with large colon volvulus propose large colon resection to prevent future volvulus (Driscoll et al. 2008; Pezzanite and Hackett 2017), a procedure more technically difficult and requiring a lengthier surgical time than colopexy. A case report by Markel et al. (1988b) documents three horses that returned to athletic work after colopexy surgery without complications, and show horses having received colopexy at the authors’ institution are currently in athletic work. Further work must be done to evaluate what restrictions, if any, should be safely recommended for return to performance following colopexy. An additional factor in the decision to perform colopexy versus resection is the duration of volvulus and severity of compromise to the colon, with colon resection preferred for compromised colons. Horses with frequent, chronic colic referable to the large colon may also benefit from large colon resection, although colic episodes have also been reported after large colon resection (Driscoll et al. 2008; Pezzanite and Hackett 2017). Current published data are not sufficient to recommend a
Fig 2: Post-mortem image of colon to body wall adhesions 24 months after colopexy.
standardised colopexy technique. The authors in the accompanying case series chose to repeat the colopexy procedure in horses with repeat colon volvulus after dehiscence, with successful outcomes. The authors could
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