Gastrocolic Fistula

Gastrocolic fistula is an abnormal communication between the stomach and the colon, usually the transverse colon. It is rare, and the cause differs by era. Historically peptic ulcer disease and benign gastric ulcer were common, and today malignancy and surgery lead.

Causes

• Gastric adenocarcinoma invading the transverse colon (and the reverse, colon carcinoma invading the stomach)
• Lymphoma of the stomach or colon (often after chemotherapy-induced tumor necrosis)
• Marginal ulcer after gastrojejunostomy, which forms a gastrojejunocolic fistula
• Crohn disease
• Percutaneous endoscopic gastrostomy tube misplacement through the colon
• Radiotherapy, trauma, pancreatic disease, tuberculosis and NSAID-related peptic ulcer

Pathophysiology: colonic bacteria contaminate the stomach and the upper gut, with fecal reflux causing diarrhea with undigested food (lientery), malabsorption and malnutrition. Gastric acid and food reach the colon and cause diarrhea. Complications: sepsis, severe malnutrition, hemorrhage, peritonitis and bacterial overgrowth.

• Diarrhea shortly after meals with undigested food in the stool, weight loss and malnutrition
• Fecal vomiting, foul-smelling belching and halitosis
• Epigastric pain, anorexia, abdominal distension and upper gastrointestinal bleeding
• Signs of the underlying cause: epigastric mass, lymphadenopathy, cachexia
• Red flags: sepsis, peritonitis, significant hemorrhage and severe dehydration with electrolyte disturbance

1. Barium enema is the most sensitive test (about 90%): reflux of contrast into the stomach and small bowel. Use water-soluble contrast if perforation is suspected.
2. Upper gastrointestinal endoscopy shows the fistula opening with fecal material and permits biopsy.
3. CT of the abdomen with oral and intravenous contrast: gas in the stomach and colon with a track, a mass, thickened wall and local invasion, and staging for cancer.
4. Colonoscopy with biopsy.
5. Laboratory tests: full blood count, albumin, prealbumin, electrolytes, magnesium, phosphate, vitamin B12, iron studies, and H. pylori testing in benign ulcer disease.

Differentials: gastroenteritis, malabsorption, bacterial overgrowth, gastric outlet obstruction, chronic pancreatitis, short bowel syndrome.

1. Resuscitation and optimization: correct dehydration and electrolytes (potassium, magnesium, phosphate), treat sepsis with piperacillin-tazobactam 4.5 g IV every 6 hours, and give nutritional support. Use parenteral nutrition (at 25 to 30 kcal/kg a day with 1.2 to 1.5 g/kg of protein) or enteral feeding distal to the fistula for 2 to 4 weeks before surgery in malnourished patients.
2. Acid suppression: omeprazole 40 mg IV or orally twice daily. Treat H. pylori with omeprazole 20 mg, clarithromycin 500 mg and amoxicillin 1 g, all orally twice daily for 14 days, or bismuth quadruple therapy where resistance is high.
3. Definitive surgery (most fistulas need operation):
   • Malignant: one-stage en bloc resection of the involved stomach and colon with adequate margins and lymphadenectomy, and primary anastomoses where feasible. Oncologic therapy follows.
   • Benign peptic or marginal ulcer: resection of the fistula with partial gastrectomy and colonic segment, with vagotomy as indicated and reconstruction by Roux-en-Y.
   • Staged approach for unstable or malnourished patients: a diverting colostomy or proximal colonic diversion first, then definitive resection after 6 to 8 weeks.
   • Percutaneous gastrostomy fistula: removal of the tube, bowel rest and observation for spontaneous closure in a stable patient.
   • Crohn disease: infliximab 5 mg/kg IV at weeks 0, 2 and 6, then every 8 weeks, with azathioprine 2 to 2.5 mg/kg orally daily. Surgery for failure.
4. Perioperative prophylaxis: cefazolin 2 g IV with metronidazole 500 mg IV before incision, and enoxaparin 40 mg SC daily for 7 to 28 days (28 days if cancer).
5. Complications: anastomotic leak (5 to 15%), sepsis, recurrence of the fistula and malnutrition.

Follow-up at 2 weeks, 6 weeks and 3 months, with nutritional review. Counsel on adherence to acid suppression and on stopping NSAIDs.