Introduction

The possibility of complications occurring with gastrointestinal (GI) surgery is a very real threat to surgeons, regardless of their level of expertise. In fact, it is amazing that the gastrointestinal tract (GIT) is able to heal at all. There is constant motion, the lumen contains fluid and there is food, bacteria and enzymes in contact with the incision at all times. The reason that the GIT is able to heal so well is that it has a profuse vasculature, rapidly regenerating epithelium and a natural defence mechanism provided by the omentum.¹

Celiotomy refers to a surgical incision into the abdominal cavity. Regardless of the reason for the procedure, general principles of abdominal surgery should be adhered to whenever an invasive exploratory celiotomy is performed. The most common approach to the abdomen is via a ventral midline incision. A ventral midline incision can extend from lateral to the xiphoid process to ventral to the pubic symphysis. The superficial epigastric vein can be clamped and ligated to improve exposure.²

The three principal sections of the GIT that will be discussed are the stomach, small intestine (SI) and large intestine (LI). Four anatomical layers form the GI tube: the mucosa, submucosa, muscularis externa and serosa. The blood supply to the GIT is provided by the mesenteric arteries which penetrate the GI wall and then split into three arteriovenous plexuses.

Dehiscence usually occurs somewhere between 72 to 96 hours after wound creation. This period is known as the "lag phase" of GIT healing and is the most critical period.³ Dehiscence leads to spillage of GI contents into the abdomen with resulting peritonitis and the consequences of this may be fatal. It can be avoided by choosing the correct size and type of suture material, catching sufficient amounts of the correct adjacent tissues and by tying careful, correct surgical knots.

The role of the omentum is vital in GIT surgery. It plays a major role in sealing GI wounds; it helps restore blood supply, controls infection and facilitates good drainage. Pedicle omental grafts are preferred over free grafts as these tend to encourage adhesion formation. Ideally omentum should be wrapped or sutured around all GI incisions prior to closure of the abdomen.⁴

Stomach

The stomach has the thickest wall of any of the sections of the GIT. It is extremely vascular and control of haemorrhage is important. Because of this rich blood supply and low bacterial numbers, most incisions into the gastric wall will heal despite the surgical technique used. The suture technique of choice is a double layer, continuous inverting pattern like the Cushing or Lembert.¹ The first layer is placed in the submucosa and the second in the seromuscular component. Absorbable suture material is advocated and suture line ulcers have been reported when nonabsorbable suture material was used.

Small Intestine

Healing of the SI occurs optimally when there is direct apposition of the layers of the intestinal wall. This allows the submucosal arteriovenous plexuses to align and reepithelialisation can occur within 3 days without compromising the diameter of the lumen. Mucosal eversion and tissue overlap retard reepithelialisation by causing mucosal ischaemia and necrosis.⁵ Further complications of this are increased inflammation, intestinal stenosis and formation of abdominal adhesions. There will also be a decrease in bursting strength and therefore an increased incidence of leakage.^3,5,6

Trimming the excess mucosa and ensuring that there is no debris on the cut edges prior to anastomosis, also decreases the chance of leakage.^5,6 Various suture patterns have been described and tested in the SI. These include simple interrupted, modified Gambee or simple continuous patterns. Crushing verses noncrushing techniques have also been described. Results are fairly similar between all of these; however, crushing techniques have been shown to cause more micro trauma and necrosis. Knots should be tied securely and should remain on the extraluminal side of the GI tube.⁷ A useful technique is to angle the needle so that the serosal surface is engaged slightly further from the edge than the mucosal suture.

Prior to closing the abdomen, leakage tests using sterile saline are recommended and surgeons should then also wrap the anastomosis site in omentum.⁴

Serosal patching is a technique that consists of placing the antimesenteric border of an adjacent loop of intestine over a suture line in the GIT and securing this to it with sutures. The aim of this procedure is to provide the damaged section with a fibrin seal, blood supply, support and a barrier against leakage. The use of serosal patching is recommended whenever viability is questionable or if dehiscence has already occurred. Kinking of the adjacent intestinal loops should be avoided when using this technique.^1,8

Large Intestine (Colon)

The colon demonstrates the same mechanisms of healing that occur in the stomach and SI, however, the entire process is delayed. Morbidity and mortality rates in the LI are high due to the following reasons: colonic circulation is poor, the blood supply is segmental, the population of bacteria is high and the faeces place additional mechanical strain on the incision sites.^1,8 A further disadvantage is that the omentum rarely reaches that far.⁴ The risk of early incisional dehiscence is high in the colon. Effective means of counteracting some of these problems are to eliminate faeces using enemas at least 24 hours before the procedure, use effective antibiotic protocols and practice good serosal apposition. The holding layer for the colon is also the submucosal layer and the recommended suture pattern is a simple, interrupted, appositional pattern or a modified Gambee.⁷ The sutures should be placed 3 to 4 mm apart and 2 to 3 mm from the cut edge. Using commercial end-to-end anastomosis staple guns are also an effective, but expensive technique to close colonic incisions.^1,8

Possible Complications

Dehiscence and the resulting peritonitis are extremely severe consequences to surgery of the GI system. Peritonitis is the inflammation of the peritoneum, which may be primary or secondary and infectious or noninfectious. Post-surgical peritonitis is the most common type and is typically classified as secondary and infectious.² The three main causes of dehiscence include preexisting intestinal trauma, preexisting peritonitis or hypoalbuminaemia.

Peritonitis is suspected when the abdominal effusion contains intracellular bacteria, when spontaneous extraluminal gas bubbles are present on radiographs or when the peritoneal effusion contains more than 25,000 neutrophils per microliter. The goals of treatment of peritonitis include most importantly, removing the source of the contamination, resolving the infection and restoring the normal fluid and electrolyte imbalances.^2,8 Surgery is indicated when the cause of the contamination cannot be found or when bowel rupture is suspected.

Lavage with sterile intravenous fluid is indicated in animals with diffuse peritonitis, but should be used with caution in localised cases in order to prevent dissemination of the infection. Despite aggressive therapy, the prognosis for peritonitis remains guarded and so, as in many surgical cases, prevention is better than cure.

Conclusion

The GIT will usually heal without complications provided atraumatic techniques are used, tissue viability is preserved and contamination is minimised. Adhering to basic principles and using due diligence when suturing, can result in complications being minimised and surgical success rates, improved. Postoperative monitoring of the patient can further improve success rates by picking up any potential complications as early as possible and correcting them before the animal becomes too debilitated.

References

1.  Radlinsky MG. Surgery of the digestive system. In: Fossum TW, Dewey CW, eds. Small Animal Surgery. 4th edition. St. Louis, MO: Elsevier Mosby; 2013:339–497.

2.  Fossum TW. Surgery of the abdominal cavity. In: Fossum TW, Dewey CW, eds. Small Animal Surgery. 4th edition. St. Louis, MO: Elsevier Mosby; 2013:356–385.

3.  Allen DA, Smeak DD, Schertel ER. Prevalence of small intestinal dehiscence and associated clinical factors: a retrospective study of 121 dogs. J Am Anim Hosp Assoc. 1992;28:70–76.

4.  McLackin AD, Denton DW. Omental protection of intestinal anastomosis. Am J Surg. 1973;125:134–140.

5.  Blikslagen AT, Roberts MC. Mechanisms of intestinal mucosal repair. J Am Vet Med Assoc. 1997;211:1437–1441.

6.  Coolman BR, Ehrhart N, Maretta SM. Healing of intestinal anastomoses. Comp Cont Educ Pract. 2000;22:363–371.

7.  Weisman DL, Smeak DD, Birchard SJ, et al. Comparison of a continuous suture pattern with a simple interrupted pattern for enteric closure in dogs and cats: 83 cases. J Am Vet Med Assoc. 1999;214:1507–1510.

8.  Tobias KM, Johnston SA. Digestive system. In: Veterinary Surgery Small Animal. Volume 2. St. Louis, MO: Elsevier Saunders; 2012:1425–1690.