Gastrointestinal Resection and Anastomosis in Dogs
Dr. David Diamond
Gastrointestinal resection and anastomosis is the name given to any surgical procedure in which a portion of the gastrointestinal tract is excised (resected) and the remaining ends of the tract are reattached (anastomosis). Any gastrointestinal resection and anastomosis procedure can be associated with post-operative complications. The most common and serious complication is leakage at the anastomosis site. Leakage can be secondary to poor surgical technique, but is usually the result of dehiscence, or splitting open, because the edges of the reattached tract were not completely healthy and did not heal well. This complication usually occurs within the first 3 to 5 days after surgery. If dehiscence occurs, gastrointestinal contents leak into the abdomen and cause infection. This requires another emergency surgery or euthanasia.
Resection and anastomosis is most frequently done in the small intestines; however, resection and anastomosis of the stomach, colon (large intestines), or rectum is necessary with some diseases. Resection of a portion of the esophagus is less commonly performed.
Ingestion of a foreign body that subsequently becomes lodged in the small intestine is a common condition of dogs that requires resection and anastomosis. The obstruction can lead to necrosis or death of the wall of the intestine and ultimately to intestinal perforation. The entire length of damaged intestine is removed such that the two ends of the reattached intestine are healthy.
Another cause of obstruction is stricture, in which the walls of the esophagus or intestine constrict like a tightening ring, limiting the size of the lumen or opening. Stricture can be the result of previous injury by foreign objects, previous surgery, or tumors.
Intussusception is a condition in which a portion of the gastrointestinal tract advances into the intestine adjacent to it, similar to an old-fashioned telescope. If the intussusception cannot be undone, resection and anastomosis of the affected intestine may be necessary.
Torsion is the abnormal twisting of an organ that can cause disruption of its blood supply. Gastric dilatation/volvulus (GDV) is a condition where the stomach of dogs, typically large breeds, twists on itself. Depending on the duration and severity of the twist a portion of the stomach may be necrotic (unhealthy). If a large portion of stomach is severely damaged, resection and anastomosis may be necessary.
Mesenteric (intestinal) torsion is the twisting of the small intestines on its blood supply. This condition is almost always fatal; however, occasionally when surgery is done quickly a portion of the intestine may be salvageable. The necrotic (unhealthy) portion is removed and an anastomosis is performed.
Neoplasia (cancer) or benign tumors can occur in any region of the gastrointestinal tract. Fortunately the esophagus, which is difficult to operate on and is most prone to complications after surgery, is rarely involved. The stomach, small intestines, large intestines and rectum do develop tumors that may require resection and anastomosis to treat. The rectum is the portion of the colon that passes through the pelvic canal to the anus. It is accessed through an incision near the anus or under the pelvis (the floor of the pelvis must be split to access this area of the rectum).
Tumors of the stomach, small intestine and large intestine within the abdominal cavity are approached through an incision in the animal's belly. Large tumors of the stomach can be difficult to remove with "clean" margins (lack of tumor cells at the cut edge of the removed tissue). The small and large intestine are much longer and usually allow for several centimeters of unaffected tissue to be excised to maximize the chance for complete tumor removal.
Depending on the underlying condition that requires that resection and anastomosis be performed, the prognosis is variable. For benign conditions (such as foreign body obstruction, intussusception, and benign tumors) the prognosis is generally excellent. If perforation of the gastrointestinal tract has occurred due to any cause the abdominal contents are usually inflamed (peritonitis) and anastomoses may not heal well. Thus, the presence of abdominal infection generally warrants a guarded prognosis. If the blood supply to a region of the gastrointestinal tract has been compromised, such as with torsion, the patient must be monitored closely after surgery because healing may be impaired. Some neoplastic conditions carry a poor prognosis because of possible recurrence, while others may be cured with surgery.
Another serious post-operative complication is stricture at the anastomosis site. As the anastomosis heals the scar tissue can form a constrictive band around the repair. If this occurs, the opening between the reattached segments becomes too small for food and digested material to pass through. This is an unlikely occurrence after small intestinal resection and anastomosis, but is more likely after esophageal surgery.
A less common complication is "short bowel syndrome," which is the result of a majority of the small intestine being removed. The small intestines are important in absorption of nutrients from ingested food. As the ingested material moves too rapidly through the excessively short gastrointestinal tract, diarrhea and malnutrition occur. Sometimes these animals adapt over time and dietary changes may be helpful.