Original Article Surgical Colic in Racing Endurance Horses G

EQUINE VETERINARY EDUCATION / AE / APRIL 2012 193

Original Article Surgical colic in racing endurance horses G. R. Alexander* and G. R. Haines Dubai Equine Hospital, Dubai, UAE.

Keywords: horse; colic; endurance racing; small intestine; volvulus

Summary and providing more in-depth information on the surgical findings, treatment and outcomes in these cases. A retrospective study was performed of horses that developed colic during endurance racing, and subsequently required surgery. Fifteen horses met the Materials and methods inclusion criteria, of which 13 (87%) had small intestinal volvulus. Nine of the 15 horses (60%) had a small intestinal A retrospective study of horses that had intestinal lesions resection and anastomosis performed. Post operative ileus, requiring surgical intervention, that developed during or particularly in those horses that had a resection performed, immediately on completion of an endurance race, was was a common complication. Eleven of the 15 (73%) performed. The patient and surgical logs were examined survived, and 4 (27%) have since raced. to identify these horses for the period from November 2004 to March 2011. All medical records that were available for Introduction those patients were then reviewed. All horses were treated for colic at the race venue, either Endurance horses may race up to 160 km in a single day, by a treatment vet or a team veterinarian. Haematology and with such prolonged exercise, they are prone to and biochemistry tests, if performed prior to referral, were 1 ‘exhausted horse syndrome’ (Foreman 1998). Colic may analysed with an i-STAT 1 . Specific tests were variable, but be a presenting sign of this syndrome, often due to a range when performed always included packed cell volume + + ++ of metabolic disarrangements and hypovolaemia. Colic (PCV), Na ,K and ionised Ca . Treatments included is typically associated with ileus, typified by reduced flunixin, butorphanol, Buscopan, xylazine, detomidine and intestinal borborygmi and possibly gastric reflux. Typically, i.v. fluids. All horses were referred because of continued horses respond to rehydration and correction of electrolyte pain. In horses where pain was marked and uncontrollable, abnormalities, along with provision of analgesia. they were transported anaesthetised. These horses had an To put post race colic into perspective, figures for the induction dose of xylazine and ketamine, followed by 2007–08 racing season were available (M.M. Misheff, repeated ‘top-ups’ of the same drugs, to maintain a light personal communication). Of 2832 starters for all types plane of anaesthesia. of races including qualifiers, 435 (15%) received some The horses were re-examined at the Dubai Equine veterinary treatment at the race venue field hospital. Hospital. Decision for surgery was made by one of the Of the treated horses, 47 (11% of treated horses, 1.7% of authors, or the hospital internist. In some cases, where the starters) had colic, and 2 of these required surgery. horse arrived anaesthetised (see below), it was taken Intestinal lesions requiring surgical intervention are straight to surgery. In all other cases, decision for surgery uncommon, but in a previous report, 5 of 25 horses was based on pain that was either nonresponsive, or only transferred from a race venue to a referral hospital temporarily responsive, to provision of analgesia. In some required surgery (Whiting 2009). The causative lesion was cases the decision was supported by continued gastric small intestinal volvulus (SIV) in every case. The aims of this reflux and/or transcutaneous ultrasonographic evidence study were to expand upon this previous observation, from of distended small intestine, possibly with thickening of the our hospital, looking at a larger population of horses intestinal wall. Xylazine and ketamine were used in induction (unless the horse arrived anaesthetised), and the horse was placed on gaseous anaesthesia with isoflurane through a *Corresponding author email: [email protected] 2 Present address: Canterbury Equine Clinic, 499 Springs Rd, Christchurch large animal ventilator system . Anaesthetic drug doses 7672, New Zealand. were very variable due to different staff and protocols in

place during different times of the study, and differences in 24–32); one horse was hyperglycaemic (mean 880 mg/l, the clinical state of the horse on arrival and previously range 56–137, rr 50–115); and 4 of the 5 horses had administered drugs, so will not be presented in detail. elevated PCV (mean 56%, range 44–66, rr 32–48). Two Diazepam, butorphanol and guaifenesin were additional horses had pH measured; both were alkalotic, measuring drugs commonly used for induction. Continuous infusion 7.486 and 7.558, respectively (rr 7.32–7.44). lidocaine and dobutamine were commonly used during In 4 horses, repeat haematology/biochemistry test maintenance of anaesthesia. results were available after treatment with i.v. fluids (12–40 l Small intestinal resection and anastomoses, if required, of sodium chloride with 120–240 ml calcium borogluconate, were performed by hand suturing in an interrupted given over 1–2 h), but before referral. In all 4 cases the PCV Lembert pattern, or a double layer continuous pattern was significantly reduced below the initial measured value (Freeman 2008b). (mean 37%, range 29–43), and sodium and calcium were All laparotomies were performed through ventral within normal limits. midline incisions. The laparotomy incision was closed with 2 Stage of the race at which colic occurred was variable, Vicryl3 in a simple continuous pattern. The subcutaneous as were the clinical signs at presentation to the referring tissue was closed with 2/0 Vicryl or PDS3 suture in a veterinarian. In 5 cases, gastric reflux was obtained and, continuous pattern, as was the skin. The wound was not in 5 others, distended small intestine was present on covered post operatively. All horses had an assisted rectal and/or ultrasonographic examination. In 3 horses, recovery with a head and tail rope system. distended large intestine only was palpated. Concurrent All horses had crystalline penicillin (10–12 mg/kg bwt i.v. diarrhoea was present in 3 horses. q. 6–12 h), gentamicin (4–6.6 mg/kg bwt i.v. q. 24 h), Four horses arrived anaesthetised at the hospital flunixin (1 mg/kg bwt i.v. q. 12 h) and i.v. fluids post and 3 of these went immediately to surgery. Of the operatively. Initial flow rate was approximately 5 ml/kg remaining 11 horses, heart rate was mildly to moderately bwt/h (approximately twice ‘maintenance rate’). The elevated (44–60 beats/min, rr 28–40) and distended small fluids were routinely supplemented with Ca++ and K+. intestine was more likely to be identified on rectal or Constant rate infusion of lidocaine (1.3 mg/kg bwt i.v. ultrasonographic examination, than had been noted by bolus, followed by 0.05 mg/kg bwt/min i.v.) was used in all the referring veterinarian. Decision for surgery was based horses that had resections, and additionally in cases that mostly on continued pain. had post operative ileus. Lidocaine was routinely given for Anaesthetic records were available in 12 horses. 24 h; in cases that developed post operative ileus, Anaesthesia time ranged from 50 min to 6 h with a mean of lidocaine was used until persistent gastric reflux stopped. approximately 2.7 h. The range varies markedly due to the Where possible, team veterinarians were contacted to fact that some horses were anaesthetised at the race obtain follow-up on the horses that were discharged from venue secondary to unrelenting pain. the Hospital. Thirteen of the 15 horses (87%) had small intestinal volvulus (SIV), one containing an intussusception. Eight of these 13 horses (62%) had resections, with jejuno-jejunal or Results jejuno-ileal anastomoses performed. Resection length averaged 4.1 m (range 0.9–9.1). The other 2 cases, without Fifteen horses matched the inclusion criterion. In all cases, a SIV, had thickened but not entrapped small intestine. Case case summary report, including a detailed surgical 6 had a resection performed, and Case 12 did not. Both description, was available for review. In 12 cases, complete survived. medical records from the hospital stay, which included Ten of the 13 (77%) horses with SIV survived to discharge anaesthetic records, and haematology and biochemistry from the hospital. At necropsy Cases 1 and 15 had further test results, were available. In 5 cases, laboratory results from infarction/necrosis of the jejunum; Case 15 had a resection the referring veterinarian were available. performed, and Case 1 did not. Case 2 returned to the There were 10 geldings and 5 mares (see Table 1), with hospital 8 weeks post operatively with continued colic, and an average age of 10 years (range 6–13 years), and an was subjected to euthanasia. Extensive adhesions were average weight of 374 kg (range 329–415 kg). This is fairly found on post mortem examination. The fourth fatality, representative of the racing population (Misheff et al. 2010). Case 10, was markedly endotoxaemic post operatively, Of the 5 horses that had results of haematology/ which was partially due to pleuro-pneumonia. Both the biochemistry tests available, performed soon after initial latter 2 cases had resections performed. Overall survival to presentation to the referring veterinarian, one horse was 6 months in this study was 73% (11/15). mildly hyponatraemic, 130 mmol/l (mean for the 5 horses Of the 13 horses with SIV, 7 of the 8 (88%) horses that had 138, range 130–142, reference range [rr] 132–147); all resections performed developed post operative ileus (POI), horses were normokalaemic (mean 3.3 mmol/l, range whereas only 2 of the 5 (40%) horses without resection had 2.8–3.6, rr 2.8–4.7); 3 horses were hypocalcaemic (mean POI. In 9 of the 13 horses with SIV, results of post operative 1.20 mmol/l, range 1.02–1.42, rr 1.25–1.75); 3 horses had biochemistry tests were available. Hypocalcaemia elevated total CO2 (mean 35 mmol/l, range 30–39, rr was present in Cases 3, 10 and 15. It was easily corrected in

TABLE 1: Cases of surgical colic in racing endurance horses

Case No. age Surgical findings and weight Pre-operative findings and treatment and treatment Outcome

1. Mare, age RV – no gastric reflux or abnormal rectal examination findings. SIV – approximately 6.7 m Had POI. Subjected to euthanasia 6 days later unknown DEH – HR 56, no gastric reflux or abnormal rectal examination findings; on US compromised, but not due to deteriorating clinical condition. 388 kg some mild DSI mixed with collapsed loops. To surgery a few hours later with resected based on PME – severe peritonitis due to segmental continued pain and increasing DSI and sedimentation on US. improvement in colour jejunal necrosis. and motility. 2. Gelding, 9 RV – no gastric reflux or abnormal rectal examination findings. SIV – 3.7 m resected and Had intermittent POI for 2 weeks but went home years 356 kg DEH – straight to surgery. JIA. after 27 days. Returned to DEH one month later and was subjected to euthanasia. PME – had extensive adhesions. 3. Gelding, 9 RV – 3 l gastric reflux, no abnormality on rectal examination. High PCV, SIV – no resection. Acidosis and hypocalcaemia immediately post years 383 kg hypocalcaemia, hyponatraemia, alkalosis initially; returned to normal after 40 l op but quickly corrected. Discharged after 10 i.v. fluids; i.v. anaesthesia for transportation. days. Raced. DEH – straight to surgery. 4. Gelding, 9 RV – normal rectal examination. SIV – no resection. Recovered quickly, discharged after 11 days. years 413 kg DEH – Tight mesenteric band on rectal examination with marked LC distension. Raced again, but was subjected to US – several loops nonmotile DSI (5 cm). To surgery a few hours later on euthanasia for a fractured humerus. continued pain. 5. Gelding, 9 RV – High PCV, alkalosis. i.v. anaesthesia for transport (approx. 3 h). SIV – 6.1 m resected and Had profuse diarrhoea Days 4–6 post op, but no years 377 kg DEH – straight to surgery. JJA. POI. Electolytes normal. Recovered, Total anaesthesia discharged after 9 days, raced again. approximately 6 h. 6. Mare, 13 RV – 19 l of gastric reflux, DSI on rectal examination. US DSI 5-6 cm. Focal proximal enteritis, Electrolytes normal. Had caecal impaction that years 339 kg DEH – HR 60. Treated as ileus for 5 days but still had gastric reflux and 3.0 m resected and JJA. resolved medically. Developed incisional intermittent colic so to surgery. Proximal end of hernia but did not have incisional infection. anastomosis was not Discharged after 23 days. Retired. healthy tissue. 7. Mare, 6 RV – i.v. anaesthesia for transport (approx. 2 h). SIV – no resection. Distal POI for 5 days. Electrolytes remained normal. years 365 kg DEH – approximately 10 l of gastric reflux was obtained when horse in lateral jejunal and Ileal Bilateral corneal ulcers treated medically. recumbency in trailer, then straight to surgery. impaction reduced Discharged after 19 days. manually. Total Retired for breeding. anaesthesia time approximately 4 h. 8. Gelding, 13 RV – LC distension on rectal examination, 4-5 l of gastric reflux. SIV – mid-jejunal. 9.1 m Had POI for 4 days. Electrolytes remained years 357 kg DEH – Painful on arrival. HR 48. DSI on rectal examination and US (4.5 cm). Small resected and JJA. normal post op. Recovered, discharged after amount of gastric reflux. To surgery 26 days. Remained in poor body condition relative to feed levels. Yet to race. 9. Gelding, 7 RV – LC distension and a small amount of gastric reflux. High PCV and LC impaction, partial POI for 3 days. Electrolytes remained normal. years 415 kg hypocalcaemia, corrected after 12 l i.v. fluids, but then mild hypokalaemia. caecal torsion. SI Resolved, discharged after 10 days.

02EJLtd EVJ 2012 © DEH – HR 44, 15 l of gastric reflux. Gas distended LC and caecum on RE. US – intussusception within SIV Developed laminitis one month later and was multiple loops of moderately DSI. To surgery approx. 4 h later. (secondary?). 4.0 m retired. resected and JJA. 195 196 02EJLtd EVJ 2012 ©

TABLE 1: Continued

Case No. age Surgical findings and weight Pre-operative findings and treatment and treatment Outcome

10. Mare, 8 RV – presented at end of race with colic but also neurological signs? Some mild SIV – resected 6.4 m and Hypocalcaemia, acidosis, high PCV. Had POI. years Weight to moderate DSI on rectal and US examination. i.v. anaesthesia for JJA. In recovery had Subjected to euthanasia 30 h later for unknown transportation. brown fluid with blood deteriorating clinical condition. DEH – US only one loop moderately DSI, stomach not full. Rectal examination clots drain from Pleuro-pneumonia diagnosed on PME. normal. Allowed to recover from GA. To surgery 10 h later for recurrent pain endo-tracheal tube. and increasing DSI. 11. Gelding, 12 RV – no gastric reflux, suspected nephron-splenic entrapment on rectal SIV – no resection. Rapid recovery, electrolytes were not retested. years 393 kg examination, LC distension. Discharged after 4 days. Raced. DEH – HR 60. On rectal the colon was relatively ‘full’ but no nephron-splenic entrapment. On US several loops of marked DSI (6-8 cm). Mild alkalosis preoperatively. Electrolytes normal. To surgery shortly when failed to settle with further analgesia. 12. Mare, 10 RV – colic and diarrhoea post race. 9.1 m of distal SI including Rapid recovery, electrolytes not re-tested. years 329 kg DEH – HR 64. Multiple loops of SI had thickened wall (7.5 mm). Electrolytes ileum thickened and Discharged after 8 days with instructions for normal preoperatively. oedematous, but not long course of corticosteroid. Yet to race. entrapped. No resection.

Infiltrative disease EQUINE VETERINARY EDUCATION /AEAPRIL 2012 diagnosed. 13. Gelding, 11 RV – 7 l of gastric reflux and DSI on US. PCV and electrolytes normal, but PCV SIV – resected 3.3 m and Mild hypokalaemia the day after surgery, but years 352 kg reduced after 25 l i.v. fluids. JJA. did not persist. Had repeat laparotomy for POI DEH – HR 48, DSI on rectal examination and US. after 4 days, but stoma not revised. Had one more bout of gastric reflux post op, then fine. Discharged after 9 days. Yet to race. 14. Gelding, 13 RV – Colic and diarrhoea post race. DSI on rectal examination and US. SIV – 0.9 m resected and POI for 5 days, discharged after 11 days. Retired. years 352 kg DEH – mild pain on arrival, HR 52. Several loops of amotile DSI on US. To surgery JIA. 5 h later with continued pain, more loops of DSI, and 4 l of gastric reflux. 15. Gelding 13 RV – Colic and diarrhoea during race. DSI on rectal exam and US. High PCV, SIV – 2.4 m resected and Good for 48 h post op, but then started POI, years 413 kg hypocalcaemia. Improved, but mild hypernatraemia after 25 l of i.v. fluids. JJA. inappetance. Acidosis, hypokalaemia and DEH – Mild pain, some DSI on US, no gastric reflux. To surgery 3 h later for hypocalcaemia on several tests. Condition continued pain. deteriorated and subjected to euthanasia 10 days post op. PME – infarct of jejunum.

Key: RV = referring veterinarian; DEH = Dubai Equine Hospital; US = ultrasonographic examination; HR = heart rate (beats/min); SI = small intestine; DSI = distended small intestine; LC = large colon; post op = post operatively; SIV = small intestinal volvulus; JJA = jejunojejunal anastomosis; JIA = jejunoileal anastomosis; PME = post mortem examination; POI = post operative ileus. EQUINE VETERINARY EDUCATION / AE / APRIL 2012 197

Case 3, but not in the others, which had other serious malrotation (lack of full normal rotation of the bowel complications. Hypokalaemia was present in Cases 13 during organogenesis) is often a predisposing cause. and 15. It was easily corrected in Case 13, but persisted Primary volvulus, occurring in an otherwise healthy intermittently in Case 15. abdomen, has been associated with ingestion of bulky, Of the 11 surviving horses in this case series, 3 (27%) high fibre diets and is predominated by adult men (Parkes have raced successfully, 3 (27%) are in training at the time 1997; Ghebrat 1998). Experimentally, sections of bowel of publication, 4 (36%) were retired for reasons unrelated and mesentery, or latex models of the same, curl into a to the colic surgery, and one (9%) was subjected to helical shape as they become distended. This is simply to euthanasia for a humeral fracture at a race. accommodate greater elongation at the antimesenteric border relative to the mesenteric border (Perry 1983). In one study, in which almost all the patients were Discussion middle-aged farmers, common features included not being overweight, having strong abdominal muscles and The predominant lesion (87%) in this group of horses volvulus occurring during or immediately after prolonged following prolonged strenuous exercise was SIV. Detailed heavy exercise. It was proposed that a fat-free abdomen reports from a retrospective study involving 115 horses with allowed greater intestinal movement (Vaez-Zadeh et al. SIV have been published (Stephen et al. 2004a,b). The 1969). reports were comprehensive but, unsurprisingly, activity at Human marathon runners are susceptible to ischaemic the time of development of clinical signs was not included. colitis, thought to be due to preferential shunting of blood Several studies have reported on activity levels associated from the gastrointestinal tract to skeletal muscle, and with colic, but findings have been variable. Factors exacerbated by dehydration. It is generally reversible, but associated with increased risk of colic have included in a very small percentage of sufferers, can be severe a recent change in level of activity (Cohen et al. 1995; enough to cause necrosis and perforation, requiring Hillyer et al. 2002), participation in showing activities surgery (King and Avery 2011). It is possible that volvulus is (Kaneene et al. 1997) and higher levels of athletic activity initiated by the movement of the racing horse over a long (Tinker et al. 1997; Hillyer et al. 2001). distance, in small intestine on a fat-free mesentery. Small intestinal volvulus in horses has been described as Under-perfusion, increased sympathetic stimulation and, in being caused by a hypermotile segment of intestine some cases, electrolyte abnormalities, may interfere with feeding into an amotile segment, and the resulting stop in normal peristalsis. forward peristalsis causing the intestine to twist (Rooney Decision for surgery was generally based on continued 1965). Racing endurance horses often develop ileus, part of pain. Small intestinal distension was not palpable on rectal a spectrum of clinical signs associated with hypovolaemia, examination of all horses, at least initially, and in some and electrolyte and acid-base disturbances (Whiting cases only large intestinal distension could be palpated. 2009). The most common laboratory abnormality in the Increasing small intestinal distension over time was a 5 horses sampled at the time of initial presentation was common finding, and typically presented as increased elevated PCV. In reality, as endurance horses have low loops of mild to moderate distension. Only in Case 11 was resting PCV values anyway, as a training adaptation marked small intestinal distension noted. Ultrasonography (Carlson 1979; McKeever et al. 1987), it is likely that the PCV is used routinely for examination of horses with abdominal was significantly raised from baseline in all 5 horses. pain at our hospital; in these cases increased wall Hypocalcaemia affected 3 of the 5 horses. This thickness was not noted on any cases with volvulus. electrolyte abnormality is common in our population of Abdominocentesis is not used routinely, but may be used racing horses eliminated for metabolic reasons, although if excess free fluid is detected ultrasonographically. False the majority of eliminated horses are normocalcaemic negative peritoneal fluid analysis, in the presence of (unpublished data on file, Dubai Equine Hospital). severe bowel disease, has been noted previously (White The underlying circumstances resulting in volvulus in the 1990), due to fluid compartmentalisation. Both current cases presented in this study were undetermined. The authors have independently seen cases of colic where authors do not believe that generalised small intestinal peritoneal fluid analysis has been normal, but a decision distension secondary to ileus is the primary cause of for surgery was made based on other criteria, and found volvulus in these horses. Insensible losses incurred during bowel that had already ruptured. endurance racing are profound. It is unlikely that a horse Another confusing variable in the decision for surgery is could sequester large volumes of fluid into the intestinal that occasionally some horses with marked metabolic tract and simultaneously race. Additionally, small intestinal derangements post race may appear to have abdominal distension was found in only 5 horses on initial presentation. pain. This so-called ‘false colic’ is most likely to be seen in In man, SIV is uncommon in Western countries, but horses with a combination of rhabdomyolysis and acute more common in Africa and Asia (Iwuagwu and Deans renal failure, and is differentiated from gastrointestinal pain 1999). Secondary volvulus is the more common type in on other clinical signs and biochemistry. Neurological signs Western countries and, in children and young adults, may also confuse the diagnosis (see below).

Post operative ileus was the most common major pain, unresponsive to analgesia, is an indication for complication, and affected 9 of the 15 (60%) horses in this surgery. The prognosis for survival is good, even after series. POI has been identified as placing horses at higher lengthy anaesthetic times. Prognosis to race again is poor risk for nonsurvival (Morton and Blikslager 2002; Mair and to fair, but it is possible for an endurance horse to train Smith 2005; Torfs et al. 2009). Many of the horses in this study and compete successfully after extensive small intestinal had risk factors for development of POI such as small resection. intestinal resection (Torfs et al. 2009), age >10 years, anaesthesia >2.5 h duration, surgery >2 h duration (Roussel Authors’ declaration of interest et al. 2001) and long length intestinal resections (Holcombe et al. 2009). The exact aetiology of POI remains No conflicts of interest have been declared. elusive and is controversial. Some authors favour a primarily inflammatory cause (Little et al. 2005), whereas others Manufacturers’ addresses suspect it is mainly mechanical (Freeman 2008a). In our series, there were no consistent electrolyte abnormalities 1Abbott Point of Care Inc., East Windsor, New Jersey, USA. that may have contributed to POI. 2Mallard Medical Inc., Redding, California, USA. Treatment of post operative ileus is highly variable. The 3Ethicon, Somerville, New Jersey, USA. surgeon must attempt to assess the potential mechanical reasons for lack of progressive motility vs. those related References to functional causes. Many surgeons advocate early re-exploration of the abdomen in the face of ileus. In these Carlson, G.P. (1979) Physiologic responses to endurance exercise. instances the surgeon is looking for segments of bowel that Proc. Am. Ass. equine Practnrs. 25, 459-468. have failed to survive despite initial evaluation, poorly Cohen, N.D., Matejka, P.L., Honnas, C.M. and Hooper, R.N. (1995) Case-control study of the association between various functioning anastamoses, obstructing haematomas, or management factors and development of colic in horses. J. Am. early fibrinous adhesions with kinking of the bowel. In this vet. med. Ass. 206, 667-673. study, only Case 13 had repeat laparotomy for continued Foreman, J.H. (1998) The exhausted horse syndrome. Vet. Clin. N. Am.: gastric reflux. The stoma was not revised, and the horse Equine Pract. 14, 205-219. had only one episode of gastric reflux after the second Freeman, D.E. (2008a) Post operative ileus (POI): Another perspective. surgery. In hindsight, repeat laparotomy was performed Equine vet. J. 40, 297-298. too early. Freeman, D.E. (2008b) Small intestinal resection and anastomosis. In: The In all cases in which resection was performed, an Equine Acute Abdomen, Eds: N.A. White, J.N. Moore and T.S. Mair, end-to-end anastomosis was performed. Despite tension Teton NewMedia, Jackson, Wyoming. pp 521-538. with stay sutures by an assistant, neither author routinely Ghebrat, K. (1998) Trend of small intestinal volvulus in north-western establishes a stoma size as described by Freeman (2008b). Ethiopia. East Afr. med. J. 75, 549-552. In most cases, the healthy small intestinal ends contract, Hillyer, M.H., Taylor, F.G.R. and French, N.P. (2001) A cross-sectional study of colic in horses on Thoroughbred training premises in the British Isles and are not flaccid with large luminal diameters. in 1997. Equine vet. J. 33, 380-385. In Cases 1 and 15, the cause of gastric reflux was Hillyer, M.H., Taylor, F.G.R., Proudman, C.J., Edwards, G.B., Smith, J.E. and mechanical as, on post mortem examination, residual French, N.P. (2002) Case control study to identify risk factors for jejunum had become necrotic. This was the main cause of simple colonic obstruction and distension colic in horses. Equine vet. death in our series, and is presumably due to the vascular J. 34, 455-463. compromise caused by the original volvulus, with the Holcombe, S.J., Rodriguez, K.M., Haupt, J.L., Campbell, J.O., Chaney, further negative effects of endotoxaemia. K.P., Sparks, H.D. and Hauptman, J.G. (2009) Prevalence and risk factors for postoperative ileus after small intestinal surgery in two In hindsight, Case 10 should have gone immediately to hundred and thirty three horses. Vet. Surg. 38, 368-372. surgery, as the mare arrived at the hospital anaesthetised. Iwuagwu, O. and Deans, G.T. (1999) Small bowel volvulus: A review. J. R. Unfortunately there was confusion over the original Coll. Surg. Edinb. 44, 150-155. presenting signs, and the mare was recovered from the first Kaneene, J.B., Miller, R., Ross, W.A., Gallagher, K., Marteniuk, J. and anaesthesia for transportation, for neurological assessment. Rook, J. (1997) Risk factors for colic in the Michigan (USA) equine It is likely that the large volume of ketamine given had population. Prev. vet. Med. 30, 23-36. pronounced analgesic effects, as the mare did not show King, D.R. and Avery, L. (2011) Marathon-induced colitis. J. Surg. Radiol. abdominal pain for many hours, despite the presence of 2, 1-110. a SIV. Little, D., Tomlinson, J.E. and Blikslager, A.T. (2005) Post operative In summary, clinicians should be aware of the neutrophilic inflammation in equine small intestine after manipulation and ischaemia. Equine vet. J. 37, 329-335. possibility of surgical lesions being present in endurance horses during and immediately after racing. Distinguishing Mair, T.S. and Smith, L.J. (2005) Survival and complication rates in 300 horses undergoing surgical treatment of colic. Part 2: Short term a surgical lesion from ileus combined with other metabolic complications. Equine vet. J. 37, 303-309. disturbances is not always straightforward but, as with all McKeever, K.H., Schurg, W.A., Jarrett, S.H. and Convertino, V.A. (1987) colic cases, serial examinations may be required, during Endurance training-induced hypervolaemia in the horse. Med. Sci. which time the horse should receive i.v. fluids. Continued Sports Exerc. 19, 21-27.