EQUINE VETERINARY EDUCATION / AE / DECember 2008 635

Case Report Small intestinal incarceration through an omental rent in a horse G. KELMER*, T. E. C. HOLDER AND R. L. DONNELL† Department of Large Animal Clinical Sciences; and †Department of Pathobiology, The University of Tennessee College of Veterinary Medicine, 2407 River Dr., Knoxville, Tennessee 37996, USA. Keywords: horse; omentum; hernia; small intestine

Summary Case details

Intestinal incarceration in an omental rent is a rare History and clinical signs abdominal disorder in horses. A case of a horse with small intestinal incarceration in an omental rent is A 7-year-old American Saddlebred mare presented for severe described here. The report includes description of the colic of 2 days duration. At physical examination, the mare clinical presentation, surgical and post mortem findings was dehydrated and showed severe abdominal pain with an elevated heart rate and injected mucous membranes. Rectal and discusses the features unique to this case. The palpation and abdominal ultrasound revealed multiple loops clinical presentation is similar to other small intestinal of amotile small intestine consistent with strangulation strangulation lesions; however, the location of the obstruction. Nasogastric intubation yielded 12 l of net reflux. lesion is unusual and the anatomical relation to the Blood work showed leucopenia (3.9 x 109/l; reference range gastrosplenic ligament interesting. [rr] 5.4–14.3 x 109/l), mild azotaemia (creatine 20 mg/l, rr 7–18 mg/l), mild hypocalcaemia (ionised calcium Introduction 1.14 mmol/l; rr 1.16–1.42), mild haemoconcentration (packed cell volume 46%; rr 37–53%), hypoproteinaemia Small intestine incarceration through a rent in the greater (total protein 57 g/l; rr 58–85 g/l), bilirubinaemia (total omentum occurs rarely in the horse. The greater omentum bilirubin 58 mg/l; rr 8–22 mg/l), and elevated creatine kinase arises from the greater curvature of the stomach and forms at 1804 u/l (rr 93–348 u/l). Based on the level of pain and the a veil that prevents the intestines from progressing cranially presumptive small intestinal strangulation, exploratory toward the stomach. The gastrosplenic ligament, also celiotomy was recommended and the horse prepared for referred to as the lesser omentum, is a continuation of the general anaesthesia. Because of the guarded prognosis given greater omentum and connects the hilus of the spleen to the to the horse the owners considered euthanasia due to greater curvature of the stomach (Nickel et al. 1979; financial concerns but elected to pursue with surgery. Frandson et al. 2000). Small intestinal herniation through the Treatment gastrosplenic ligament is uncommon but well described (Yovich et al. 1985; Marien and Steenhaut 1998; Jenei et al. The mare was given tetanus toxoid, hypertonic saline and 2007). However, to the authors’ knowledge, herniation and preoperative medications (i.v. potassium penicillin 22,000 strangulation of small intestine through a rent in the greater iu/kg bwt q. 6 h, gentamicin sulphate at 6.6 mg/kg bwt omentum has been mentioned once but has not been q. 24 h and flunixin meglumin at 1.1 mg/kg bwt q. 12 h) and thoroughly described in the horse. The purpose of this report was anaesthetised for abdominal exploration. Polymyxin B is to provide a first clinical description of a horse with small (6000 iu/kg bwt i.v., diluted in 1 l 0.9% saline) was intestinal herniation and strangulation in a rent in the administered under anaesthesia. Multiple loops of distended, greater omentum. hyperaemic small intestine protruded immediately as the abdomen was opened. Small intestinal volvulus at the root of the mesentery was diagnosed and partially corrected. Further *Author to whom correspondence should be addressed. †Present address: Equine Department, Kansas State University, College of exploration revealed a completely devitalised segment of small Veterinary Medicine, 101 Trotter Hall, Manhattan, Kansas 66506, USA. intestine entrapped by a thin cord of nonviable tissue. Small 636 EQUINE VETERINARY EDUCATION / AE / DECember 2008

Fig 1: Necropsy examination demonstrating diffused Fig 3: Post mortem examination depicting the origin of the hyperaemia of the small intestine with haemorrhagic strangulating tissue strand at the greater omentum. The white mesentery. The photograph was taken following correction of arrow illustrates the defect in the greater omentum, while on a volvulus of the small intestine at the root of the mesentery. the right the devitalised portion of the jejunum is noted. intestinal incarceration in the gastrosplenic ligament was necrotised portion of the jejunum had passed through a rent suspected as the primary lesion at that point. Part of the in the omentum. The small intestinal volvulus was probably strangulating tissue was ligated and resected deep within the secondary to the omental incarceration. The adjacent abdomen, allowing the nonviable intestinal segment to be gastrosplenic ligament was completely intact, viable and not partially exteriorised. Due to the guarded prognosis, combined involved in the lesion. with the owner’s financial limitations, euthanasia was elected and performed. Discussion Necropsy revealed partial volvulus of the small intestine at the root of the mesentery. The vast majority of the small The omentum is a thin veil of connective tissue, with multiple intestine was hyperaemic with mesenteric vascular congestion small vessels, that receives blood supply from gastroepiploic and multifocal to coalescing haemorrhage of the surrounding arteries. In the horse, the omentum is composed of the mesentery (Fig 1). These findings were indicative of greater and lesser omentum. The greater omentum is generalised vascular embarrassment of the small intestine. A attached to the greater curvature of the stomach and well-demarcated 130 cm segment of distal jejunum was connects to the dorsal aspect of the stomach to form the completely black and friable (Fig 2). This portion appeared omental bursa. The lesser omentum connects the stomach to entirely necrotic and was still entangled by a thin string of the spleen and is more commonly referred to as the black-green connective tissue that was connected to the gastrosplenic ligament. greater curvature of the stomach (Fig 3). Further separation Incarceration of small intestine through a rent in the and visualisation of the involved tissues demonstrated that the gastrosplenic ligament is an uncommon, although well string of tissue was part of the greater omentum and that the described, cause for small intestinal strangulation in the horse (Marien and Steenhaut 1998). In all reported cases the intestines were displaced in a caudal to cranial direction and the ileum was involved in nearly 50% of the horses (Yovich et al. 1985; Marien and Steenhaut 1998; Jenei et al. 2007). The intestine typically lies craniolateral to the spleen, and adjacent and lateral to the stomach (Yovich et al. 1985). Although no recurrences have been reported, in some cases the ventral part of the ligament was transected in order to prevent reincarceration (Marien and Steenhaut 1998). In 3 reports including 26 horses with small intestinal incarceration in the gastrosplenic ligament, the intestines were nonviable necessitating resection or euthanasia (Yovich et al. 1985; Marien and Steenhaut 1998; Jenei et al. 2007). In contrast, it is interesting that in 2 horses with a gastrosplenic incarceration we recently encountered no intestinal resection was needed and Fig 2: Post mortem examination demonstrating a well reduction resulted in a successful outcome. As with all intestinal demarcated, devitalised segment of jejunum accompanied by strangulation the time from occurrence to surgical reduction has the causative, previously strangulating tissue strand. a major impact on the need for resection and the outcome. EQUINE VETERINARY EDUCATION / AE / DECember 2008 637

Strangulation of small intestine in an omental rent is a rare Small intestinal incarceration through a rent in the greater gastrointestinal lesion in man (Versaci et al. 1999; Li et al. omentum should be considered as a differential diagnosis for 2005). An emergency celiotomy can be life saving and, if small intestinal strangulation. In addition to preventing performed early, reduction is sufficient and no intestinal adhesions, omentectomy may prevent omental herniation and resection is necessary (Li et al. 2005). incarceration. Adhesions after small intestinal surgery are a major life threatening complication in the horse (Freeman et al. 2000; References Mair and Smith 2005a). The survival rate of horses suffering from colic due to adhesions is low (Parker et al. 1989; van den Butson, R.J., England, G.C. and Blackmore, C.A. (1996) Omento- omental adhesion around the uterine horn as a cause of recurrent Boom and van der Velden 2001; Mair and Smith 2005a). Thus colic in a mare. Vet. Rec. 139, 571-572. prevention of adhesions is an important consideration in Frandson, R.D., Wilke, W.L. and Fails, A.D. (2000) Anatomy of the abdominal surgery. Adhesion prevention strategies include digestive system. In: Anatomy and Physiology of Farm Animals, adherence to the Halsted principles of surgery, use of surface 6th edn., Eds: R.D. Frandson, W.L. Wilkes and A.D. Fails, Lippincott barriers and lubricants such as carboxy-methyl-cellulose Williams & Wilkins, Philadelphia. pp 306-325. (CMC), peritoneal lavage and systemic medications such as Freeman, D.E., Hammock, P., Baker, G.J., Goetz, T., Foreman, J.H., antibiotics, heparin, DMSO and NSAIDs (Mueller et al. 1995; Schaeffer, D.J., Richter, R.A., Inoue, O. and Magid, J.H. (2000) Hague et al. 1998; Nieto et al. 2003; Sullins et al. 2004). Colic Short- and long-term survival and prevalence of postoperative ileus after small intestinal surgery in the horse. Equine vet. J., Suppl. due to adhesions involving the omentum have been reported 32, 42-45. (Norrie and Heistand 1975; Butson et al. 1996), and removal Gayle, J.M., Blikslager, A.T. and Bowman, K.F. (2000) Mesenteric rents of the majority of the greater omentum (omentectomy) has as a source of small intestinal strangulation in horses: 15 cases been previously described and recently demonstrated as an (1990-1997). J. Am. vet. med. Ass. 216, 1446-1449. effective measure in preventing clinically significant adhesions Gayle, J.M., Macharg, M.A. and Smallwood, J.E. (2001) Strangulating following exploratory celiotomy (Kuebelbeck et al. 1998; Mair obstruction caused by intestinal herniation through the proximal and Smith 2005a). Aside from its role in adhesion prevention, aspect of the coecocolic fold in 9 horses. Vet. Surg. 30, 40-43. the omentectomy may carry an additional benefit of Hague, B.A., Honnas, C.M., Berridge, B.R. and Easter, J.L. (1998) Evaluation of postoperative peritoneal lavage in standing horses preventing omental herniation and strangulation. for prevention of experimentally induced abdominal adhesions. Rents in the intestine mesentery can lead to small Vet. Surg. 27, 122-126. intestinal incarceration and strangulation (Gayle et al. 2000). Jenei, T.M., Garcia-Lopez, J.M., Provost, P.J. and Kirker-Head, C.A. Repair of these lesions can be complicated due to an inability (2007) Surgical management of small intestinal incarceration to access the rent for closure, haemorrhage from mesenteric through the gastrosplenic ligament: 14 cases (1994-2006). J. Am. vessels, and difficulty in reducing the entrapped intestine vet. med. Ass. 231, 1221-1224. (Gayle et al. 2000). Small intestinal incarceration occurs Kuebelbeck, K.L., Slone, D.E. and May, K.A. (1998) Effect of through rents in the caecocolic fold as well (Gayle et al. omentectomy on adhesion formation in horses. Vet. Surg. 27, 132-137. 2001). Small intestinal incarceration in an omental defect is Li, J.C., Chu, D.W., Lee, D.W. and Chan, A.C. (2005) Small-bowel identical in nature to these incarcerating lesions. In a recent intestinal obstruction caused by an unusual internal hernia. Asian retrospective study describing 224 horses with small intestinal J. Surg. 28, 62-64. strangulation, 2 horses were reported to suffer from small Mair, T.S. and Smith, L.J. (2005a) Survival and complication rates in intestinal herniation through the greater omentum in a 300 horses undergoing surgical treatment of colic. Part 4: Early caudal to cranial direction (van den Boom and van der Velden (acute) relaparotomy. Equine vet. J. 37, 315-318. 2001). In both cases the intestine was nonviable, Mair, T.S. and Smith, L.J. (2005b) Survival and complication rates in necessitating resection but both horses survived until 300 horses undergoing surgical treatment of colic. Part 2: Short- term complications. Equine vet. J. 37, 303-309. discharge (R. van den Boom, personal communication). The mare in this report arrived at the hospital after Marien, T. and Steenhaut, M. (1998) Incarceration of small intestine through a rent in the gastrosplenic ligament in five horses. Equine showing signs of abdominal discomfort for about 48 h and vet. Educ. 10, 187-190. was suffering from advanced ischaemic necrosis of the Moore, J.N. and Morris, D.D. (1992) Endotoxemia and septicemia in intestine due to prolonged strangulation. Advanced intestinal horses: experimental and clinical correlates. J. Am. vet. med. Ass. damage leads to endotoxaemia due to increased intestinal 200, 1903-1914. permeability and absorption of lipopolysaccharide into the Mueller, P.O., Hunt, R.J., Allen, D., Parks, A.H. and Hay, W.P. (1995) systemic circulation (Moore and Morris 1992). Endotoxaemia Intraperitoneal use of sodium carboxymethylcellulose in horses causes rapid deterioration of the horse’s cardiovascular status undergoing exploratory celiotomy. Vet. Surg. 24, 112-117. and significantly decreases its prognosis for survival (Mair and Nickel, R., Schummer, A. and Seiferle, E. (1979) Alimentary canal of the Smith 2005b). Early referral has greatly contributed to the horse. In: The Viscera of Domestic Mammals, Eds: R. Nickel, A. Schummer and W.O. Sack, Springer-Verlag, New York. pp 183-185. increased survival rates reported for horses undergoing Nieto, J.E., Snyder, J.R., Vatistas, N.J., Spier, S.J. and van Hoogmoed, surgery for small intestinal strangulation (Freeman et al. 2000). L. (2003) Use of an active intra-abdominal drain in 67 horses. Vet. Earlier referral cannot be overemphasised as a crucial mean to Surg. 32, 1-7. continue and improve survival of horses undergoing Norrie, R.D. and Heistand, D.L. (1975) Chronic colic due to an omental emergency abdominal surgery. adhesion in a mare. J. Am. vet. med. Ass. 167, 54-55. Continued on page 672 672 EQUINE VETERINARY EDUCATION / AE / DECember 2008

Continued from page 637

Parker, J.E., Fubini, S.L. and Todhunter, R.J. (1989) Retrospective of the small intestine in horses: a review of 224 cases. Vet. Q. evaluation of repeat celiotomy in 53 horses with acute 23, 109-115. gastrointestinal disease. Vet. Surg. 18, 424-431. Versaci, A., Rossitto, M., Pante, S., Lepore, V., Genovese, A. and Sullins, K.E., White, N.A., Lundin, C.S., Dabareiner, R. and Gaulin, G. Ciccolo, A. (1999) A case of strangulated trans-omentum hernia. (2004) Prevention of ischaemia-induced small intestinal adhesions G. Chir. 20, 487-489. in foals. Equine vet. J. 36, 370-375. Yovich, J.V., Stashak, T.S. and Bertone, A.L. (1985) Incarceration of van den Boom, R. and van der Velden, M.A. (2001) Short-and long- small intestine through rents in the gastrosplenic ligament in the term evaluation of surgical treatment of strangulating obstructions horse. Vet. Surg. 14, 303-306.