Nick Lagattolla
A fistula is an abnormal connection existing between two epithelial linings. The gastrointestinal tract provides much scope for the formation of a diverse variety of fistulae.
Pathology
Fistulae can arise between two different parts of the gastrointestinal tract, or between the bowel and a separate structure. An enterocutaneous fistula is an abnormal connection between the gastrointestinal tract and the skin. An end fistula arises from a segment of discontinuous gastrointestinal tract (e.g. a duodenal stump), while in a lateral fistula, the connection is with the side of an intact viscus and intestinal continuity is maintained. A simple fistula has a single tract from involved bowel to the abdominal wall, whereas a complex fistula will have multiple tracts often is associated with abscess cavities.
Fistula types The varieties most encountered are:
• Vesicocolic. • Colovaginal. • Enterocutaneous. • Gastrocolic. • Ieocolic. • Colocutaneous. • Enteroenteric. Aetiology
There are five main causes of gastrointestinal fistulae. The aetiology is important when establishing a plan of treatment.
1. latrogenic. Anastomotic leakage is a common cause of enterocutaneous fistula. This
principally arises from bowel end ischaemia, suture line tension, or construction of an anastomosis in a high-risk situation such as intraperitoneal sepsis or distal obstruction with subsequent anastomotic breakdown. Most enterocutaneous fistulae are ultimately iatrogenic in origin.
2. Gastrointestinal disease. Fistulae frequently arise secondary to sigmoid diverticular
disease, particularly colovaginal, vesicocolic and left groin colo-cutaneous fistulae. Other inflammatory causes include appendicitis presenting with chronic discharge through the right groin, Crohn’s disease (entero-enteric, entero-colic) and intestinal tuberculosis.
3. Malignancy. Colonic carcinoma causes colo-cutaneous fistulae by direct invasion of
the abdominal wall or after spontaneous perforation, abscess formation with discharge through the abdominal wall. Radical local surgical resection can be therapeutic, though this is inappropriate in patients with disseminated malignancy. Gastrocolic fistula is rare, arising as a complication of gastric carcinoma more commonly than colonic carcinoma. As a cause of fistula, malignancy is less frequently encountered than inflammatory bowel and diverticular disease.
4. Radiotherapy. Pelvic irradiation especially may lead to damage and inflammation of
small or large bowel with fistula formation.
5. Trauma. Penetrating wounds to the abdomen can cause fistulas, particularly when the
trauma results in multiple intestinal perforations with subsequent sepsis and abscess formation.
General treatment principles
Cutaneous fistulae close spontaneously in most circumstances. Approximately 60% should close within 1 month on conservative treatment. Closure will not occur if there is distal obstruction, a complex or chronic abscess cavity or direct mucocutaneous epithelial continuity. These features suggest a surgical solution is likely. Closure less readily occurs if the involved bowel is diseased or if the patient is malnourished. Internal fistulae may be asymptomatic (e.g. entero-enteric) and are unlikely to close. Colovaginal and vesicocolic fistulae require resection of the involved segment of bowel; many would advocate a stoma as opposed to primary anastomosis, though if the latter is chosen, there must be interposition of omentum between the anastomosis and the secondarily involved viscus. Other indications for surgery are failure to improve, continued metabolic or nutritional complications, or generally if the patient is not thriving.
Management of enterocutaneous fistula
These are chronic by nature, and are very debilitating for the patient. They require a team approach from medical and nutritional teams, and pharmacist, physiotherapist and stoma nurses. Initial resuscitation needs to be followed by longer-term nutritional support and detailed assessment of the pathophysiology of the fistula:
1. Fluid and electrolyte loss. A high output fistula (>500 ml/day) can lead to large fluid
and electrolyte losses with insiduous circulatory collapse from isotonic dehydration. Appropriate resuscitation needs to be guided by accurate measurement of all fluid losses. Serum levels of electrolytes need to be tested frequently until fluid balance is achieved. Thereafter twice-weekly estimations of haematological and biochemical indices should be sufficient.
2. Skin protection. Proteolytic enzymes in upper gastrointestinal secretions cause skin
excoriation and damage. Skin protection is essential around the site of a fistula. Reducing the volume of a high output fistula helps skin management and reduces fluid and electrolyte losses. This can be achieved by restricting oral intake, though
somatostatin analogues are commonly used. Other pharmacological agents (H2
antagonists, omeprazole) have been used with varying degrees of success.
3. Nutritional support. Correction of nutritional deficiencies and long-term parenteral
nutrition are often necessary for patients with proximal gastrointestinal high-output fistulae. Oral intake should be stopped, which reduces intestinal secretion and fistula output. Intravenous feeding should be commenced in any patient with an
enterocutaneous fistula other than a low output terminal ileal or colonic fistula. This rests the bowel and restores nutritional status, providing optimal conditions for spontaneous fistula closure.
4. Control of sepsis. An abscess cavity may complicate an enterocutaneous fistula and
should be suspected in the presence of persisting pain, pyrexia, tachycardia,
leucocytosis and a falling serum albumin. Confirmation and delineation of an abscess cavity is best achieved by a sinogram using gastrograffin or dilute barium. Ultrasound and CT scanning are also useful and may allow percutaneous drainage. Abscess cavities need to be drained to eliminate sepsis and convert a complex cavity into a simple tract, which can close spontaneously. Antibiotics should not be used unless there is septicaemia or surrounding cellulitis.
5. Haemorrhage. This can be life-threatening from eroded vessels within the fistula tract
or abscess cavity. Erosion of arteries occurs as a result of sepsis or the action of digestive enzymes (especially in the stomach). Treatment may require urgent resection of the fistula but arterial embolization can be considered.
Further reading
Coutsoftides T, Fazio VW. Small intestine cutaneous fistulas. Surgery and Gynecological
Obstetrics, 1979; 149:333–336.
Williams JG, Wong WD, Rothenberger DA, Goldberg SM. Recurrence of Crohn’s disease after resection. British Journal of Surgery, 1991; 78:10–19.
Related topics of interest
Crohn’s disease (p. 103); Diverticular disease (p. 116); Nutrition in the surgical patient (p. 233).