Principles of GI surgery (Proceedings)
Gastrointestinal surgery is performed very commonly in small animal for biopsy, removal of a foreign body, upper gastrointestinal bleeding, resection of a necrotic segment of intestine, resection of necrotic portion of the stomach, and resection of a neoplasia. Approximately 10% of dogs with gastric dilatation volvulus have a devitalized gastric wall requiring gastrectomy . Ischemic injury occurs most commonly in the fundic area along the greater curvature. Upper gastrointestinal bleeding results from chronic renal and liver disease, mast cell tumor, gastrin producing neoplasia of the pancreas, gastric neoplasia and non steroidal anti-inflammatory drugs. Gastrotomy, gastrectomy, enterotomy, and enterectomy are the procedures routinely performed. General principles common to all of these procedures have to be followed.
Gastrointestinal surgery is considered as a clean-contaminated surgery. Therefore antibiotics are required during the procedures. Most common bacteria encountered during gastrointestinal surgery are: Escherichia coli, Enterococcus spp, Streptococcus, Staphylococccus aureus, proteus, and Bacteroides fragilis. In the stomach the bacteria population is more limited than in the rest of the intestine because of the acid environment. In the colon the population of anaerobic bacteria is elevated. Before surgery the patient is placed on prophylactic intravenous antibiotic. For the surgery of the stomach, ampicillin or first generation cephalosporin (20 mg/kg IV every 60 min) can be used. For the rest of the intestine, second generation antibiotics are preferable because they a have a broad sprectrum against gram + and -. Cefoxitin (20 mg / kg IV every 90 min) is the antibiotic of choice. A combination of ampicillin enrofloxacin can be used also. Antibiotics are interrupted at the end of the procedure unless the animal has peritonitis. The animals need to be watch closely for signs of infection.Assessment of viability
No objective criteria exist to evaluate the gastric wall viability. Absence of peristaltic wave, pale greenish to gray serosal color, thin gastric wall, and lack of bleeding after partial thickness incision are signs of gastric wall devitalisation.
Viability is assessed by coloration of the serosa, peristalsism, pulse in the jejunal arteries, and utilization of intravenous fluorescein. Fluorescein at the dose of 15 mg/kg is injected intravenously. Fluorescein emits a gold green fluorescence when exposed to ultraviolet light. Viable intestine has a smooth uniform green gold fluorescence. Hyperemic intestine has a brighter color than normal. Non viable intestine has patchy fluorescence or no fluorescence. The fluorescence can also be located around blood vessel.
Choice of suture material and needles
A wide range of suture materials has been used during gastrointestinal surgery. It is recommended to use synthetic absorbable monofilament suture materials. Synthetic sutures are stronger sutures than gut and more resistant to infection. Synthetic absorbable sutures are absorbed primarily by hydrolysis, which is more predictable than enzymatic digestion. Monofilament cannot harbor bacteria and do not have a wick effect like braided suture therefore they are resistant to infection. Polydioxanone (PDS), polyglyconate (Maxon), or Glycomer 631 (Biosyn) size 4.0 or 3.0 are the recommended sutures for gastrointestinal surgery. A taper needle is recommended for placement sutures in the stomach wall and the intestine.
Every effort should be made to prevent contamination of the abdominal cavity during gastrointestinal surgery. The stomach or the loop of intestine are "packed off" the rest of the abdominal cavity. Layers of moist laparotomy sponges are used. Intestinal content is moved away for the surgical site with gentle manipulation and atraumatic clamps are placed to prevent the intestinal content to come back. Stay sutures are placed in the stomach to elevate the stomach wall and prevent spillage of stomach content into the peritoneal cavity.
After completion of the surgery, the peritoneal cavity is lavaged with warm sterile saline solution to removed gastrointestinal spillage and blood clots. Usually 1 liter of saline is used for a 10 kg dog. The entire fluid is eliminated with surgical suction to get the peritoneal cavity as dry as possible.
Gloves and instruments are then changed. New surgical towels are placed on the edges of the laparotomy. The abdominal cavity is then closed routinely.