small intestine : the horse Resection and anastomosis of Current methods applicable to

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1 322 EQUINE VETERINARY JOURNAL Equine vet. J. (1986) 18(4), Resection and anastomosis of Current methods applicable to small intestine : the horse G. B. EDWARDS Royal Veterinary College, Hawkshead Lane, North Mymms, Hatfield, Hertfordshire AL9 7TA Summary lntraoperative techniques for assessing the viability of ischaemic bowel are discussed. Intravenous administration of sodium fluorescein appears useful but further investigation of the method is required. Methods of resection and anastomosis of small intestine are described and illustrated, including the use of automatic stapling instruments. Introduction THE small intestine of the horse is subject to obstruction from a variety of causes. In most cases, obstruction results in vascular occlusion which leads rapidly to irreversible tissue changes in the obstructed segment of gut. Unless the horse is referred for surgery very early in the course of the condition, resection of the compromised bowel is usually imperative. Other types of obstruction, while causing no ischaemia of bowel, require some form of bypass anastomosis, with or without resection, to restore normal flow of ingesta along the alimentary tract. Resection and anastomosis of small intestine in the horse is simplified by its long mesentery, the clearly visible blood vessels for ligation and its reasonable calibre. Which technique the individual surgeon chooses, from the variety available, depends largely on experience and personal preference. This communication describes techniques which have proved to be reliable and effective in a large number of cases at the Royal Veterinary College and at university clinics and hospitals in Europe and the USA. Evaluation of intestinal viability Assessment of the viability of ischaemic bowel is one of the most difficult problems during laparotomy. Although many cases are found to have necrotic intestine, which clearly must be removed, others have intestine of marginal viability. The surgeon has the difficult decision of whether to replace the intestine and hope that it is viable or subject the horse to potentially unnecessary resection and anastomosis. When bowel has to be resected a further dilemma is how much intestine should be removed. Frequently the demarcation between normal and abnormal intestine is far from clear, making the decision rather subjective. False interpretation of intestinal viability after correction of strangulation obstruction results in continued shock, ileus, peritonitis and, eventually, death (usually two to three days after surgical resection). Therefore, in equivocal cases, the surgeon should choose to resect some normal bowel rather than risk leaving compromised bowel in situ. Unfortunately this practice is not without complications. The risks of anastomosis failure, adhesions and stricture must not be overlooked. Furthermore, it has been observed in human patients that thelength of resected intestine is correlated directly with mortality (Ver Steeg and Borders 1979). Even recognising that this observation could be the result of added pathophysiological features associated with a greater length of infarcted bowel, it is desirable to remove a minimal amount of intestine (Sullins, Stashak and Mero 1985a). Clinical assessment of viability based on standard visual criteria (return of colour, arterial pulsation, reflex motility, refill following blanching and mucosal inspection via enterotomy) is not uniformly reliable and has been reported to be as low as 36 per cent and 50 per cent (Lee, Trainor and Kauner 1979; Papachristou 1976). White, Moore and Trim (1980) showed experimentally that, following release of jejunal ligatures applied 50 mins earlier, progressive degeneration continued even though there was gross evidence of perfusion and muscular activity. Although the intestine appeared nearly normal at 60 mins after release of the ligatures, a reversal of colour and lack of motility was seen at 120 mins. These findings explain the temporary recovery of horses, but eventual fatal outcome after correction of strangulation lesions which, during surgical operation, returned to grossly normal appearance. A number of alternative techniques, which could improve the surgeon s ability accurately to predict intestinal recovery, are being investigated. In an experimental investigation using a feline model, detection of pulsatile mural flow with a Doppler ultrasonic flow probe was found to be even less sensitive than standard clinical criteria in detecting non-viability in arterial and arterial/venous occluded segments. It was more successful in predicting irreversible damage in venous occlusions because the ischaemic injury they cause appeared to be more generalised (Wheaton, Strandberg, Hamilton and Buckley 1983). Preliminary experimental studies in the horse (Purohit, Hammond, Rossi and Pablo 1982) suggest that thermography may have a practical application in the determination of intestinal viability. Marfuggi and Greenspan (1981) described a reliable intraoperative method of predicting intestinal viability in man using a fluorescent indicator. The principle of the procedure is that sodium fluorescein injected intravenously (iv) is distributed rapidly to all perfused tissues. Intestine with a normal blood supply fluoresces under long wave ultraviolet light (Woods lamp) whereas areas with reduced circulation show less, or no, fluorescence. Sullins, Stashak and Mero (1985b) reported the results of an experimental study in horses in which two types of ischaemic lesions were created in small intestinal segments by selective ligation of vessels and intestinal wall for up to 3 h. After confirming the ischaemia by iv injection of 25 per cent sodium fluorescein (1 1 mg/kg bodyweight), the ligatures were released and 5 mins later the fluorescent patterns were recorded photographically. Observed patterns ranged from normal to patchy distribution of non-fluorescence, indicating incomplete perfusion. When re-evaluated one month later, none of the experimental segments was normal. The typical appearance included fibrosis, adhesions and thickening of the bowel, which made obstruction at some future date seem probable. It was

2 EQUINE VETERINARY JOURNAL 323 IOC ICC y$ \?A, Fig 1. Isolation and resection of ischaemic bowel. (a) Isolation of strangulated loop. (b) Ligation of mesenteric vessels and transection of intestine distal to the ischaemic bowel. (c) Evacuation of contents of ischaemic bowel. (d) Transection of intestine proximal to the ischaemic bowel. ICC Intestinal crushing clamp (Carmall). IOC Intestinal occlusal clamp (Doyen) concluded that iv injection of fluorescein could be used to indicate perfusion of intestine, but that this is not the only criterion for determining clinical outcome in cases of intestinal ischaemia. Despite uniform perfusion, damage at the cellular level can apparently be undetected. Nevertheless the technique is potentially useful to aid intraoperative assessment of intestinal viability and warrants further investigation. A physiological limit of small intestine resection has been identified in the horse (Tate, Ralston, Koch and Everitt 1983). Ponies in which 40 per cent of the small intestine had been resected maintained their pre-surgical weight, whereas those in which 60 per cent was removed lost bodyweight throughout the experimental period. These findings correlate well with clinical experience which suggests that in all but exceptional cases, 8 m is the maximum length which should be removed (B. Huskamp, unpublished data). Isolation and resection of the strangulated loop Where possible the strangulated loop of intestine (Fig la) should be isolated with bowel clamps before its release from the obstruction or immediately afterwards. Failure to do so allows highly toxic material within its lumen to reflux into healthy intestine from which it will be absorbed rapidly, causing physiological deterioration in the animal's condition. A suitable site for resection is chosen distal to the ischaemic bowel close to a major mesenteric artery. Carmalt crushing clamps are applied at an angle of 60" towards the viable intestine (Fig lb). This ensures adequate vascular distribution to the antimesenteric border and slightly increases the diameter of the intestinal lumen. Non-toxic contents are handstripped for a distance of 15 cm distal to the clamp and a rubber-shod Doyen intestinal clamp is applied with just sufficient force to prevent spillage of intestinal contents. The mesenteric vessels to the ischaemic gut are isolated and double ligated with 0 polyglycolic acid (Dexon Plus; Davies & Geck). The ends of the proximal ligatures are left long. The intestine is transected by cutting with a scalpel along the outer edge of the crushing clamps, and the mesentery by cutting between the ligatures with scissors. The distal end of the bowel to be resected can now be lifted gently over the side of the abdomen and its contents evacuated into a receptacle by removing the crushing clamp (Fig lc). This reduces the risk of rupture when a long length of grossly distended, friable

3 324 EQUINE VETERINARY JOURNAL Fig 2. Interrupted Lembert suture. s Serosa; musc Muscularis layers; srn Submucosa: rn Mucosa intestine is being resected. Removal of the proximal isolation clamp allows some decompression of the distended proximal bowel. The long-ended mesenteric ligatures are tied together in sequence, thus considerably reducing the size of the hole in the mesentery. A suitable site for resection proximal to the ischaemic bowel is identified and clamped with crushing and rubber-shod clamps as described previously. If necessary, any additional mesenteric vessels are ligated before the intestine is transected (Fig Id). \,..--- Anastomosis techniques for small intestine End-to-end anastomosis Open end-to-end anastomosis using one of a number of inversion suture patterns is still one of the most commonly employed methods of intestinal anastomosis in the horse, but other methods have been evaluated both experimentally and clinically. End-to-end anastomoses can be classified into three types: single or double-layer inverting sutures which may be interrupted or continuous (eg, Lembert, Connell or Cushing); single-layer everting sutures; and single-layer approximating sutures (eg, simple interrupted crushing type and Gambee sutures). Fig 3. Connell suture Single or double-layer inverting sutures. - The technique favoured by the author is a single layer closure using interrupted Lembert sutures of 2/0 polyglycolic acid (Fig 2). The open ends of the intestine are held together with their mesenteric borders

4 EQUINE VETERINARY JOURNAL 325 Fig 4. Garnbee suture. s Serosa; rnusc Muscularis layers; srn Submucosa; m Mucosa slightly offset. Stay sutures at the mesenteric and antimesenteric borders help to keep the edges under tension and ensure that the two open ends of the bowel have comparable diameters. Closure using 2/0 polyglycolic acid suture material on an atraumatic needle is commenced midway between the mesenteric and antimesenteric borders on the dorsal surface and continued on either side. Each suture is inserted 5 mm from the cut edge and penetrates the tough submucosal layer. Once the mesenteric and antimesenteric borders have been reached the intestine is rotated through 180" and the posterior wall is closed in the same way. Approximately 20 sutures are required in all. To ensure that the anastomosis is leakproof particular care is required in placing the sutures at the mesenteric border. Providing all the sutures are properly placed a reinforcing layer is not required and the size of the diaphragm is minimal. The Connell suture (Fig 3) is a satisfactory alternative. It has the advantage of being quicker to perform and although, in theory, a continuous suture placed parallel to the cut edge will tend to compromise the vascular supply to a greater degree than interrupted sutures placed perpendicular to the edge, in practice this does not appear to be a problem. This technique is performed using a single strand of 2/0 polyglycolic acid suture material with an atraumatic needle at each end or two strands, each with a needle, tied securely together. The posterior wall is closed first. Commencing midway between the mesenteric and antimesenteric borders the two ends of the intestine are sutured together with a horizontal mattress suture which is tied with the knot lying within the lumen of the intestine. The closure is then continued in the form of a continuous mattress suture to each border using each needle in turn. Care is taken to ensure that the needles penetrate the whole thickness of the wall, including the serosa which has a tendency to retract. On reaching the antimesenteric and mesenteric borders, the respective needle is brought through to the serosal surface. With the two segments of the intestine rotated slightly towards each other, closure is completed using a Connell suture. The two sutures eventually meet midway along the dorsal wall where they are tied together. A reinforcing layer is not required. Single layer everting techniques. - Experimental studies have shown that when this technique is adopted adhesions and strictures become evident after the immediate postoperative period as the scar tissue matures. These are attributed to the inflammatory reaction, resulting from exposure of the tissue edges and contamination from the exposed mucosa (Reinertson 1976). The technique is not advocated for use in the horse. Gambee suture.- The Gambee suture pattern (Fig 4), which is similar to the end-to-end crushing suture pattern, results in near normal lumen diameter and is a safe and effective method of anastomosis. The needle is passed from the serosa through all layers into the lumen. It is then directed from the lumen through the submucosa, crosses the incision, passes through the submucosa and mucosa and enters the lumen. The suture is then reintroduced through the entire thickness of the wall to emerge on the serosal surface of the bowel. The suture is tied firmly so that the tissue compresses on itself. Although it takes longer to perform than a simple interrupted pattern, the Gambee suture is a useful technique in equine intestinal surgery. When evaluated experimentally in horses it caused minimal adhesion formation and stricture (Vaughan 1972; Reinertson 1976). Closure of the mesentery After the anastomosis has been checked for patency and leakage, the remaining gap from the stump of the mesentery to the mesenteric border of the intestine is closed with a continuous suture. In order to prevent adhesion formation to the extensive stump of mesentery, in which some necrotic tissue remains distal to the ligature after resection of long length of bowel, Huskamp (1982) advises enveloping it in two folds of mesentery, one drawn from either side. The intestinal segment and its mesentery is rinsed clean of all blood and fibrin using warm polyionic solution containing antibiotic before being carefully replaced in the abdomen. Anastomosis of intestinal segments of varying diameters Dilation of the proximal segment necessitates joining intestine of unequal diameters. The problems can be overcome by using an angled incision if the discrepancy is minimal (Fig 5a) or a tapering technique if the discrepancy is great (Fig 5b). However, chronic obstruction of the small intestine owing to progressive constriction of its lumen by neoplasia, or adhesions, results in gross hypertrophy of the proximal bowel which can only be overcome satisfactorily by side-to-side anastomosis. Side-to-side anastomosis Side-to-side anastomosis (Fig 6) is used routinely by some surgeons for all jejunal anastomoses. It is also employed for jejuno- and ileocaecostomy, gastrojejunostomy, for bypassing obstructions and anastomosing adjoining segments of large bowel. When joining two segments of small intestine, each open end is closed with a double inversion suture, eg, Parker Kerr oversew (Fig 7). The two ends of intestine are laid alongside one another so that they are isoperistaltic and overlap for approximately 10

5 326 EQUINE VETERINARY JOURNAL Fig 5. Methods of end-to-end anasfomosis of twosegments of differing diameters. (a) Oblique incision of narrow segmenf. (b) Tapering technique cm. They are united just dorsal to the antimesenteric border by a continuous over-and-over serosal suture. A longitudinal incision 9 cm long is made into the lumen of both segments close to the suture line but not so close as to prevent insertion of the Connell suture. Particular attention is paid to continuing the incisions as close to the blind ends as possible. Failure to do so can result in a blind pouch developing in the proximal segment leading to stasis, obstruction, necrosis and peritonitis. The lumina of the bowel are united using a Connell suture. When this has been completed, the over-and-over serosal suture which forms the reinforcing layer is returned to its origin and tied. The overlapped mesentery is sutured with a row of interrupted sutures along each free edge. The size of the opening is checked using thumb and index finger. Postoperative complications are rare but some horses develop obstruction a few years later, because of dilation at the site of anastomosis, and require further resection (Huskamp 1982). Resection of the ileum The ileum is commonly involved in obstructive colic from a wide variety of causes. Although a ventral midline incision permits adequate exposure of the proximal ileum, the terminal portion is inaccessible making treatment of obstructions by resection and end-to-end anastomosis very difficult, if not impossible. Because of its lack of collateral blood supply, the \ 3 n J Fig 6. Side-to-side anastomosis \ J

6 EQUINE VETERINARY JOURNAL 321 f Fig 7. Closure of small intestinal stump by Parker-Kerr method of oversewing a clamp. (a) Cushing suture laid over a clamp. (b) Clamp withdrawn as traction is applied to both ends of the suture. (c) Continuous Lembert suture used as an oversew and tied at the origin of the first layer (b) (C) Fig 8. Resection of ileum and jejunocaecal anastomosis as viewed by the surgeon positioned on the left side of the horse. The caecum has been exteriorised and reflected caudally. (a) Transection of ileum. (b) Transection of jejunum. (c) Site of jejunocaecostomy. A Dorsal band o f caecum; B Medial band; C Ileocaecal fold; D Level of abdominal wall

7 328 EQUINE VETERINARY JOURNAL ileum is more susceptible to vascular interference than is the jejunum. Death may result from loss of motility following reduction of an intussusception or resection of a length of diseased ileum, even though there may be no evidence of devitalisation. Ileocaecal and jejunocaecal anastomoses, whereby the natural ileocaecal junction is bypassed, have proved very successful in overcoming these problems (Mason, Johnston, Wallace and Christie 1970; Donawick, Christie and Stewart 1971 ; Huskamp 1973; Owen et al 1975). A right-angled clamp is applied as low down the ileum as possible. After the contents have been stripped proximally for 20 cm an intestinal crushing clamp is applied and the ileum is transected just distal to this clamp (Fig 8a). Oedema and friability of its wall frequently makes closure of the distal ileal stump difficult. After it has been rendered watertight by a row of preplaced inversion sutures or, if it is too friable to invert, simple interrupted sutures, the right angled clamp is removed. This facilitates accurate inversion of the stump by a second row of inversion sutures. When the distal end of the strangulated loop is close to the ileocaecal junction, its inaccessibility makes it impossible to avoid leaving potentially necrotic ileum in situ. Huskamp (1982) advises that it be intussuscepted into the caecum using a continuous inverting Cushing suture. Alternatively a layer of greater omentum can be sutured over the stump to minimise the risk of peritonitis and adhesions. Jejunocaecal anastomosis A suitable site for resection of jejunum proximal to the ischaemic bowel is identified, clamped and transected (Fig 8b). Continuity is restored by closing the distal jejunal segment with a double row of inversion sutures and anastomosing it side-toside to the caecum at the junction of its dorsal and middle thirds. The jejunum is placed between the dorsal and medial bands of the caecum with its closed end pointing towards the base of the caecum. Marking the proposed sites of the 8 to locm long incisions into the jejunum and caecum, by incising the serosal layer only, facilitates accurate placement of the anchoring over-and-over serosal suture (Fig 8c). The anastomosis is continued as previously described for side-toside anastomosis. The mesenteric defect is closed by suturing the cut edge of the jejunal mesentery to that of the ileum and to the ileocaecal fold (Fig 9). It is important to create a large enough communication between the ileum and caecum to ensure the free flow of ingesta and reduce the risk of impaction in the early postoperative period. Experience has shown that 10 weeks later the stoma has decreased considerably in size leaving an opening which does not impede the passage of ingesta yet prevents significant reflux. A modification of this technique, in which the ileum is anastomosed side-to-side to the caecum (Fig 10) without resection, can be used to bypass non-strangulating obstructions of the terminal ileum caused by hypertrophy or ileal-ileal intussusceptions (Edwards 1981). The technique is now used extensively in cases of ileal impaction because a number of horses develop impaction following simple reduction without enterotomy (D. Allen, personal communication). Duodenocaecostomy Huskamp (1985) has described a technique for anastomosis of duodenum to caecum for the treatment of severe cases of anterior enteritis (gastroduodenojejunitis) which do not respond to gastric decompression and fluid therapy. The site for anastomosis is approached by removing the last rib on the right side of the abdomen. Access is somewhat restricted and, in order to minimise the risk of contamination of the peritoneal cavity with ingesta, the anastomosis is performed using a technique in which the mucosal layers are not incised until the anastomosis has been almost completed (Fig 11). The proposed site for the anastomosis is marked by incising the serosa of both duodenum and caecum which are then united with an over-and-over serosal suture. The incisions, 2 to 3 cm long, are extended down to, but not through, the mucosa. The posterior wall of the anastomosis is formed using a Connell suture. A length of thin braided nylon, which will subsequently be used to cut through the mucosal layers, is introduced into the lumen of the caecum using a large curved needle starting at the cranial end of the incision and emerging at the caudal end. The same procedure is carried out in reverse on the duodenal side. The anterior wall of the anastomosis is formed by continuing the Connell suture to its origin where it is left untied. Continuity between the caecum and duodenum is now achieved by pulling alternatively in saw-like fashion on the two ends of the nylon suture. The duodenocaecostomy is completed by tying the Connell suture and returning the over-and-over serosal reinforcing suture to its origin. The same technique can be used for jejuno- or ileocaecostomy. Fig 9. Jejunocaecal anastomosis completed Fig 10. Ileocaecal anastomosis without resection

8 EQUINE VETERINARY JOURNAL 329 (7 A u Fig 11. Technique of side-to-side anastomosis using braided nylon to incise the mucosal layers. After Huskamp (1985) Automatic mechanical stapling techniques Since intestinal stapling was introduced in Russia in the late 1950s, the techniques and instruments have been refined to the point that stapling is used almost routinely in human soft tissue surgery. They have been developed for intestinal anastomosis in order to reduce surgery time and thereby increase the chances of survival of critically-ill patients. The very fine stainless steel staples which close to form a perfect B preserve the blood supply to the tissues involved in the anastomosis and therefore avoid ischaemia. Stainless steel, which is one of the most inert materials, is far less reactive than available suture materials. Mechanical staplers are supplied by the United States Surgical Corporation and have been used in equine gastrointestinal surgery. TA 90 (thoraco-abdominal) stapler With one motion, this instrument inserts 33 staples in a double staggered row 91.5 mm long. The staples are produced in two sizes, 3.5 mm and 4.8 mm. For equine work it is recommended that the 4.8 mm cartridge should be used and its applications include the following. Closure of intestine during resection.- The length to be resected can be removed after applying the TA 90 instrument across the intestine at each end of the devitalised gut. As the instrument does not cut automatically this must subsequently be performed with a scalpel. A side-to-side anastomosis is then carried out using manual or automatic stapling techniques. End-to-end anastomosis of small intestine utilising an everting triangulation technique (Fig I2).- The two ends of the bowel are opposed and triangulated using three traction sutures. The anastomosis is performed with three applications of the TA 90 and completed by excising the free margin of tissue which protrudes through the jaws of the instrument. The full thickness of both intestinal walls is held with tissue forceps when the instrument is applied and care is taken to ensure that the lines of Fig 12. End-to-end eversion using a TA 90 automatic stapler staples overlap at the corners of the triangle. Although Gideon (1975) has reported excellent results, Sullins et al(1985b), using the same technique, encountered numerous adhesions, stricture and delayed healing at the site. They concluded that the time saved did not justify the risk of these adverse postoperative sequelae which they attributed to eversion of the intestine rather than the use of staples. Unfortunately, instruments currently available for inverting end-to-end anastomosis in man are not large enough to use in the horse. The use of staples should be avoided if the tissues are oedematous or thickened because of the risk of disruption and leakage. Unfortunately, this precludes their use for closure of an oedematous distal ileal stump - a difficult procedure which would be made considerably easier by the use of the TA 90. Gastrointestinal anastomosis instrument This instrument inserts 52 staples arranged in two double staggered rows 53 mm long and 3.5 mm apart. A knife blade cuts between them creating a side-to-side anastomosis. Its use is gaining popularity for jejuno- and ileocaecostomy and gastrojejunostomy in the horse. For jejunocaecostomy (Fig 13) the jejunum is positioned between the dorsal and medial bands of the caecum as described for the manual technique. A small incision is made into each segment of the gut and when a limb of the instrument has been inserted into each lumen it is fired. It is then withdrawn and the openings closed with sutures. Experience has shown that a single application of the gastrointestinal instrument does not ensure a large enough stoma in the horse and it is necessary to use two instruments to produce an anastomosis similar in size to that created using conventional hand-sewn techniques. MacLean (1985) advises that the line of staples should be supported by stay sutures at each end of the incision to minimise the risk of disruption. Ligating dividing stapling instrument This instrument, which is used for ligating mesenteric vessels, applies wire ligatures 1 cm apart and cuts between them. It holds

9 330 EQUINE VETERINARY JOURNAL / Fig 13. Jejunocaecal anastomosis using a gastrointestinal anastomosis au fomatic stapler 15 sets of staples and is powered by a carbon dioxide cartridge. However, it may be inadequate for the large thrombosed vessels associated with a length of strangulated intestine. Another disadvantage is that a large gap in the mesentery cannot be closed, as described previously, by tying together individual mesenteric ligatures. It is likely that the use of automated stapling equipment in gastrointestinal surgery in the horse will increase in the future. It is simple to use and the time required to perform an anastomosis can be reduced by 50 to 75 per cent compared to conventional suturing techniques (MacLean 1985; Sullins et al 1985b). However the considerable cost of each cartridge of staples may be prohibitive in all but valuable animals. References Donawick, W. J., Christie, B. E. and Stewart, J. V. (1971) Resection of diseased ileum in the horse. J. Am. vet. med. Ass. 159, Edwards, G. B. (1981)Obstructionoftheileurnin thehorse: areport of 27 clinical cases. Equine vet. J. 13, Gideon, L. A. (1975) Staple sutures for bowel surgery in the horse. Proc. 21st ann. Con. Am. Ass. equine Pract. pp Huskamp, B. (1973) Ileum-resection und jejunocaecostomie beim pferd. Bed. Munch. tierarzte Wschr. 86, Huskamp, B. (1982) The diagnosis and treatment of acute abdominal conditions in the horse : the various types and frequency as seen at the animal hospital in Hochmoor. Proc. equine Colic Res. Symp. University of Georgia, Athens, Georgia. pp Huskamp, B. (1985) Diagnosis of gastroduodenojejunitis and its surgical treatment by a temporary duodenocaecostomy. Equine vet. J. 17, Lee, B. Y., Trainor, F. S. and Kauner, D. (1979) Intraoperative assessment of intestinal viability with Doppler ultrasound. Surg. Gynec. Obsfef. 149, MacLean, A. A. (1985) Surgery of the colicpalient. Refresher Course on Equine Gastroenterology. Proc. No th February. University of Sydney. pp Marfuggi, R. A. and Greenspan, M. (1981) Reliable intraoperative predictions of intestinal viability using a fluorescent indicator. Surg. Gynec. Obstet. 152, Mason, T. A., Johnston, D. E., Wallace, G. E. and Christie, B. A. (1970) Laparotomy in equine colic - a report of 13 clinical cases. Ausf. vet. J. 46, Owen, R. ap. R., Physick-Sheard, P. W., Hilbert, B. J., Horney, F. D. and Butler, D. G. (1975) Jejuno- or ileocaecal anastomosis performed in seven horses exhibiting colic. Can. vef. J. 16, Papachristou, D. (1976) Prediction of intestinal viability by intraarterial dye injection; a simple test. Am. J. Surg. 132, Purohit, R. C., Hammond, L. C., Rossi, A. and Pablo, L. S. (1982) Use of thermography to determine intestinal viability. Proc. equine colic Res. Symp. Universify of Georgia, Athens, Georgia. pp Reinertson, E. L. (1976) Comparison of three techniques for intestinal anastomosis in equidae. J. Am. vet. med. Ass. 169, Sullins, K. E., Stashak, K. S. and Mero, K. N. (198Sa) Evaluation of fluorescein dye as an indicator of small intestinal viability in the horse. J. Am. vet. med. Ass. 186, Sullins, K. E., Stashak, T. S. and Mero, K. N. (1985b) Evaluation of intestinal staples for end-to-end anastomosis of the small intestine in the horse. Vef. Surg. 14, Tate, L. P., Ralston, S. L., Koch,C. M.andEveritt, J. I. (1983)Effects of extensive resection of the small intestine in the pony. Am. J. vet. Res. 44, Vaughan, J. T. (1972) Surgical management of abdominal crisis in the horse. J. Am. vet. med. Ass. 161, Ver Steeg, K. G. amd Borders, C. W. (1979) Gangrene of the bowel. Surg. North Am. 59, Wheaton, L. G., Strandberg, J. D., Hamilton, S. R. and Buckley, G. B. (1983) A comparison of three techniques for intraoperative prediction of small intestinal injury. J. Am. Anim. Hosp. Ass. 19, White, N. A., Moore, J. N. andtrim, C. M. (1980) Mucosal alterations in experimentally induced small intestinal strangulation obstruction in ponies. Am. J. vet. Res. 41,