34th Annual Scientific Meeting proceedings

Any action before, during, or after surgery may influence success after small intestinal resection and anastomosis. Our decisions for those actions are based on current scientific knowledge and personal experience. Therefore, techniques have evolved over the years. Preoperatively, antibiotics and NSAIDs, i.e. Flunixin, are administered to all cases; alternatively, firocoxib may have similar effectiveness.¹⁰ Lidocaine CRI starts at the beginning of the anaesthesia in all small intestinal cases¹ and Polymyxin B is administered in cases with suspected increase endotoxin exposure.⁵ After localizing the strangulation, one might encounter difficulties releasing it. Placing extra fluid into the abdomen and extending the laparotomy incision may ease manipulation. Loosening the strangulation may take time and patience. When efforts are unsuccessful in a reasonable time and gentle manner, applied forces may have to be increased gradually. Fibrous bands can be severed blindly using a tenotom. In selected cases, the epiploic foramen may need to be enlarged. Digital stretching should be performed in the caudal aspect of the foramen.⁹ After release of the strangulation, the oral intestinal content needs to be evacuated. Little content can be milked into the cecum, which should be kept inside the abdomen if possible. Downside is that the endotoxin load is left in the horses, but it is technically easier and less prone to contamination. If abundant content is present, the intestine is separated from the mesentery to be evacuated through an enterotomy off the table. For this technique, an assistant securing both ends on the surgical field is important, ensuring that terminal vessels are not stretched, thus potentially forming thrombi post operatively. In any case, the serosa should be kept moist and slippery during the manipulation using ample saline or carboxymethylcellulose. Enterocentesis of the small intestine even in case of severe tympany should be avoided. Organizing the small intestine in a standardized manner, i.e. like a wheel with the ileum on the right side of the laparotomy incision and the remaining intestine following in an anticlockwise direction, helps to minimize unnecessary trauma. Some horses tend to form hematomas easily at their arcuate vessels during manipulation and gentle care is of utmost importance in those cases. Small hematomas may be left in place, but larger hematomas may warrant resection of the affected intestine. The decision about which intestinal section needs to be resected is based on published criteria³, which include colour, wall thickness, motility, and how they improve after resolution of the strangulation. Additionally, a pulse should be present within the arcuate arteries. A critical question is the length of intestine orally to the strangulation to be removed in cases with severe distention and less visible damage. Using the LigaSure for double coagulation and transection of the arcuate vessels (up to 7 mm)⁷ has significantly increased the speed of this next step if several meters are affected. The authors have observed complications using the vessel sealing device in a few cases. Alternatively, standard double ligature is a reliable technique. Before transecting the mesentery, a decision on how to close the mesenteric defect afterwards is essential. Either a suture is preplaced and a reefing technique is used² or the defect is closed in simple centrifugal manner after completion of the anastomosis. It is important to leave enough mesentery on the terminal vessels to be able to close the mesenteric defect without challenging the arteries. The authors use Penrose drains to prevent spillage of intestinal content on the oral section mainly, assuring very little constriction. To maximize the diameter of the anastomosis, the intestine is transected either in a sigmoid-shape using Mayo scissors or in a straight line at a 60° angle using a fresh scalpel blade along a Doyen (on the section to be removed) and wet sponges as cutting board. It is sometimes difficult to avoid small visible vessels within the intestinal wall at the level of the ideal large arcuate artery. The authors use hand-sewn, single layer end-to-end anastomosis in almost all cases.^4,6 After placing stay sutures, deciding on the type of suture pattern for the anastomosis dictates the next step. Advantage of an interrupted Lembert pattern is easier approximation of intestinal ends with unequal diameter. For an intestine with about 5 to 6 cm width, approx. 9-11 sutures are common for each side. This takes more time than the continuous Lembert pattern⁸, which is chosen by the authors alternatively. One should start at the mesenteric border, because of progressing edema in that location over time. Modifying the Lembert pattern, i.e. exiting the inner bite within the cut edges of the seromuscular layer helps to minimize the degree of inversion², thus further increasing the lumen size at the level of the anastomosis. The ascending colon should be emptied in cases of marked to severe filling.¹ The stomach is checked for degree of filling, because it might be helpful to lavage large amounts of solid content following the recovery, to reduce the likelihood of impaction formation orad to the anastomosis. Carboxymethylcellulose can be applied to prevent adhesion formation just before closing the abdomen in selected cases. Postoperatively, all horses receive Tinzaparin/heparin, antibiotics, NSAIDs, fluids, and electrolytes as needed. Short handwalks within 18-24 hours is initiated in selected cases. Our first choice to promote motility is lidocaine, followed by metoclopramide. Unless post-operative reflux is encountered, we offer water within the first 24 hours and start on feeding low-bulk diet or small hands of hay. If possible, we aim to have the horse within 72 hours back on full ration. 

References

1. Cohen ND, Lester GD, Sanchez LC, Merritt AM, Roussell Jr. AJ (2004) Evaluation of risk factors associated with development of postoperative ileus in horses. JAVMA 225, 1070-1078
2. Freemann DE (2019) Jejunum and Ileum. In: Auer JA, Stick JA, Kümmerle JM, Prange T Equine Surgery. Elsevier 5^th Ed., pp. 536-575
3. Freeman DE, Schaeffer DJ, Cleary OB (2014) Long-term survival in horses with strangulating obstruction of the small intestine managed without resection. EVJ 46, 711-717
4. Giusto G, Cerullo A, Gandini M (2024) Anastomotic techniques for small intestinal obstruction in horses. A scoping review. EVJ ahead of print
5. Morresey, PR and Mackay RJ (2006): Endotoxin-neutralizing activity of polymyxin B in blood after IV administration in horses. AJVR 67, 642-647
6. Nieto, JE, Dechant JE, Snyder JR (2006) Comparison of one-layer (continuous Lembert) versus two-layer (simple continuous/Cushing) hand-sewn end-to-end anastomosis in equine jejunum. Vet Surg 35, 669-673
7. Rumbaugh ML, Burba DJ, Natalini C, Hosgood G, Moore RM (2003) Evaluation of a vessel-sealing device for small intestinal resection and anastomosis in normal horses. Vet Surg 32, 574-579
8. Seitz-Cherner E, Bauck AG, Denagamage T, Freeman DE (2023) Ex vivo and in vivo evaluation of a modified interrupted Lembert pattern for small intestinal anastomoses in horses. Vet Surg 52, 407-415
9. Wanstrath MA, Bauck AG, Smith AD, Freeman DE (2023) Surgical enlargement of the epiploic foramen in horses. Vet Surg 52, 308-314
10. Ziegler AL, Freeman CK, Fogle CA, Burke MJ, Davis JL, Cook VL, Southwood LL, Blikslager AT (2019) Multicentre, blinded, randomised clinical trial comparing the use of flunixin meglumine with firocoxib in horses with small intestinal strangulating obstruction. EVJ 51, 329-335