The enigma of post operative recurrent colic: Challenges with diagnosis and management

Recurrent colic is a frustrating problem to manage in horses, particularly following abdominal surgery for gastrointestinal disease. Possible causes of post operative recurrent colic are shown in Table 1. Colic was the most frequently reported shortand long-term complication following abdominal surgery, with 30–35% of horses having at least one episode of colic following hospital discharge (Proudman et al. 2002; Mair and Smith 2005). Importantly, most signs of colic occurred within the first 100 days of surgery and only 5% of horses had more than 3 colic episodes (Proudman et al. 2002). While at an initial glance these numbers may be somewhat of a deterrent to recommending colic surgery, it is important to recognise that 95% of horses had either none or only one episode of colic after surgery! Reasons for post operative recurrent colic should be identified so that every effort toward prevention is made. The role of recurrent colic prior to the episode requiring surgery also needs consideration when evaluating horses with signs of colic following surgery and deciding on a management strategy. Reasons for post operative recurrent colic are different for horses with small vs. large intestinal lesions. Horses with small intestinal lesions, particularly necessitating resection and anastomosis, reportedly had a higher occurrence of colic after surgery than horses with large intestinal lesions (Mair and Smith 2005). Intra-abdominal adhesion formation was an important reason for recurrent colic following small intestinal surgery (Mair and Smith 2005). Some of the factors associated with colic and adhesion formation included packed cell volume, total plasma protein, serosanguinous peritoneal fluid, resection and anastomosis, and the development of post operative ileus and the need for repeat laparotomy (Mair and Smith 2005; Proudman et al. 2005). Most of these factors are a reflection of lesion severity and the extent of cardiovascular compromise emphasising the importance of early referral and surgical intervention not only in the prevention of short-term but also long-term complications including problems with adhesion formation and recurrent colic. On the other hand, gas colic and recurrence of colonic displacement or volvulus is the most common cause of post operative recurrent colic for horses with large colon disease. Recurrence rates for nephrosplenic entrapment of the colon were most recently reported to be 8% (Hardy et al. 2000) and 15% for right dorsal colon displacement and volvulus (Hance and Embertson 1992). Horses with right dorsal displacement of the large colon were significantly more likely to experience recurrent episodes of colic requiring veterinary intervention post operatively (42%) compared to other types of displacement, particularly nephrosplenic entrapment (8%) (Smith and Mair 2010). Reasons for this disparity are unknown. Surprisingly, there was only one horse in the latter study that had recurrent episodes of colic prior to the one necessitating surgery. In another study, horses that had experienced signs of colic prior to the episode necessitating surgery for large colon displacement or volvulus had a higher occurrence of colic post operatively compared to horses with no prior history of colic (Southwood 2006). These findings suggested that there may be management factors or underlying motility disorders associated with colic in some of these patients. Motility disorders may be associated with reduced myenteric plexus and neuron density. Schusser and White (1997) found that horses with chronic colonic obstruction (>24 h duration) or with previous obstruction had significantly lower neuron density than normal horses in the pelvic flexure. Myenteric plexus and neuron density in horses with strangulating large colon volvulus was significantly less than normal and horses with colon strangulation that survived had significantly greater neuron density than horses with colon strangulation that died. Horses with chronic recurrent caecal impactions also had lower linear neuron densities compared to normal horses (Schusser et al. 2000). While findings suggest an association between lower neuron and myenteric plexus density and colonic or caecal *Corresponding author email: samhart@vet.upenn.edu 408 EQUINE VETERINARY EDUCATION Equine vet. Educ. (2010) 22 (8) 408-411 doi: 10.1111/j.2042-3292.2010.00087.x