Enterocutaneous fistula

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Contents

Introduction

Enterocutaneous fistula is an abnormal communication between the bowel and skin (Enterocutaneous fistula.). It is often accompanied by intra-abdominal abscesses. Despite improvement in its management with the use of parenteral nutrition, newer antibiotics, somatostatin analogues, improved intensive care and better imaging techniques and surgical treatments, the mortality rate is still around 10%.

Enterocutaneous fistula.

Aetiology

Most cases develop following surgery for inflammatory bowel disease, cancer or lysis of adhesions. These complications usually occur in patients who are poorly prepared or who have had radiation therapy, with emergency surgery or because of poor surgical judgement. Anastomotic breakdown, sepsis and traumatic enterotomy are common predisposing factors. Malnutrition is also an important contributing factor. Less commonly, enterocutaneous fistulas develop spontaneously as part of the disease process in Crohn's disease or diverticulitis.

Some of the complications of enterocutaneous fistulas are listed in Complications of enterocutaneous fistulas.

Classification

Enterocutaneous fistulas are classified in the following manner:

  • high output: output greater than 500mLper 24 hours
  • moderate output: output between 200 and 500 mL per 24 hours
  • low output: output less than 200 mL per 24 hours.

Moderate- or high-output fistulas are usually related to the small bowel. Higher-output fistulas are more prone to electrolyte imbalance and malnutrition. The site of origin in the gastrointestinal tract is also helpful in the prediction of its outcome.

Diagnosis and medical management

In the usual setting in which fistulas develop post-operatively, the patient will have done poorly for 5 or 6 days. There is often fever and persistent ileus. A wound abscess appears and is drained.Within the next 24 hours, intestinal contents appear from the wound. By that stage, the patient is often dehydrated, anaemic and malnourished. Optimisation of the patient follows the following schema.

Nutritional support

Adequate nutritional repletion and bowel rest may allow spontaneous closure of a fistula. Unless there is prominent paralytic ileus or the fistula arises from a proximal part of the gastrointestinal tract, enteric nutritional support is encouraged because it provides some of the immunological and other hormonal functions of the gut. However, adequate caloric and nitrogen support with enteral nutrition is usually not possible for 4 or 5 days after its implementation. Supplementation with parenteral nutrition through a central venous line is helpful.

Enteric support requires the presence of approximately 120 cm of small bowel. If enteric nutrition is provided through the stomach, the osmolarity is increased first until hyperosmolarity is tolerated, followed by an increase in volume. If enteric support is provided directly into the small bowel, the volume should be increased first and then osmolarity. The small bowel does not tolerate hyperosmolar solutions well. Enteric nutritional support tends to increase fistula drainage, at least initially.

Provision of parenteral nutrition may be established as an elective procedure to provide bowel rest and maintain nutrition. Whenever possible, parenteral nutrition should be deferred until major sepsis is contained because haematogenous seeding of the central venous catheter may occur with repeated bacteraemia or septicaemia.

Management of fluid and electrolytes

The amount of fistula drainage is carefully quantified so that fluid balance is achieved. In most cases electrolytes may be adequately replaced in the parenteral nutrition solution. Occasionally, additional replacement for fluid and electrolytes may be necessary in patients with very high (>3 L per 24 hours) fistula outputs. A large amount of sodium is lost in proximal enteric fistulas. Acid-base balance must be carefully monitored in these difficult cases.

Control of fistula drainage

Bowel rest

Complete bowel rest is useful in the initial management until stabilisation and evaluation is complete, especially if there is underlying sepsis and the fistula output is high. Gradually, enteric nutrition can be initiated. The placement of a decompressive tube, either nasogastric or long gastrointestinal, should be avoided unless severe paralytic ileus or mechanical obstruction is present. The presence of an indwelling nasogastric tube for a prolonged period is not only uncomfortable for the patient but may result in pneumonia, reflux oesophagitis and serous otitis media. If long-term decompression is thought to be necessary, a gastrostomy tube is preferred.

Somatostatin

Somatostatin analogues such as sandostatin reduce fistula output, facilitate skin care and may contribute to the closure of fistulas, especially those of biliary or pancreatic origin.

H2 antagonists

These decrease gastric secretion and may prevent bleeding from gastric stress ulceration. On their own, they have little impact on fistula output.

Skin care

With higher fistula output, care of the skin surrounding the fistula is best accomplished by sump drainage of the fistula and application of various skin-protective preparations. Care is taken to avoid skin maceration, cellulitis and cutaneous necrosis. When this occurs, subsequent surgical therapy is more difficult. An enterostomal therapist should be involved with the care of these patients.

Control of sepsis

If there is clinical evidence of sepsis with swinging fever and leucocytosis, broad-spectrum antibiotics covering Gram-negative organisms and anaerobes are prescribed after preliminary work-up for sepsis (i.e. urine culture, blood culture and examination of the wound). Use of antibiotics should be judicious and guided by the cultures and sensitivity studies.

Computed tomography (CT) scans are useful in detecting closed-space infection and abscesses that are amenable to percutaneous drainage, guided by CT or ultrasonography. Uncontrolled sepsis remains the major cause of mortality in these patients. Sometimes an exploratory laparotomy may be performed to drain abscesses that are not accessible to percutaneous drainage.

General management

The process of recovery from enterocutaneous fistula may be protracted and the patient may need several operations. Because most fistulas will heal spontaneously it is important to maintain good morale from the outset. Ambulation is maintained to avoid thromboembolic complications. In less ambulant patients, compressive stockings and subcutaneous heparin prophylaxis are prescribed.

Investigation

After the initial 48 hours most patients will have stabilised enough to allow investigation and definition of the fistula. Radiological investigations are usually the most important step in defining the anatomy of the fistula. Collaboration between the surgeon and radiologist is important for optimal management.

Computed tomography scan

Computed tomography scan determines whether there are any drainable septic collections. Because the presence of contrast in the bowel or in the peritoneal cavity will distort CT images, whenever possible the CT scan should be done prior to other contrast examinations.

Sinography

The fistula orifice is cannulated with a small feeding tube or catheter, and the water-soluble contrast such as gastrografin is injected through the tube. The following information is sought:

  • nature of the fistulous tract
  • site of entry into the bowel
  • nature of adjacent bowel (whether strictured, damaged or inflamed)
  • intestinal continuity (whether it is a side or an end fistula).

Contrast small bowel follow-through or contrast enema

Contrast small bowel follow-through or contrast enema provides information on the underlying bowel and demonstrates the presence of intestinal obstruction distal to the fistula. The fistulas may not be visualised as clearly as in a sinogram.

Treatment

The aim of therapy is to restore intestinal continuity enabling the patient to take nutrition orally. This is best achieved by spontaneous closure. However, in complicated fistulas, this occurs only in approximately onethird of patients. The following factors are important for clinical decision making.

Fistula drainage

Usually fistula output decreases with bowel rest and total parenteral nutrition. If it does not decrease, surgery will probably be required. If the fistula output has not reduced markedly after a 4–5-week period without sepsis and with adequate nutritional support, it is unlikely that the fistula will close spontaneously.

Nature of fistula

The site of the fistula is important. Ileal and gastric fistulas are less likely to undergo spontaneous closure than lateral oesophageal, lateral duodenal and jejunal fistulas, or pancreatic and biliary fistulas (Adverse factors to spontaneous closure of fistulas).

Abnormal underlying bowel

With inflammatory bowel disease such as Crohn's disease, radiation or malignancy, the fistulas may close readily but then re-open. In these circumstances, the fistula is allowed to heal and surgery is then performed with a formal resection and end-to-end anastomosis. Fistulas occurring in association with a carcinoma should be resected whenever feasible.

General condition of the patient

In patients who are severely malnourished with significant co-morbid factors, a period of non-operative management is preferred. If severe sepsis is present, salvage procedures that include drainage of abscesses and proximal diversion, with or without resection of the phlegmon, are indicated. A macerated abdominal wall further affects the surgical outcome adversely.

In most cases, a period of bowel rest and total parenteral nutrition is indicated to restore nutritional balance and to allow for healing of the skin surrounding the fistula. With control of sepsis and restoration of nutrition, about 50% of enterocutaneous fistulas close spontaneously over a 3–6-week period. Following recent surgery and the fistulising process, dense peritoneal reaction in the form of obliterative peritonitis is commonly encountered. Thus, definitive surgery is best deferred for at least 4 months to allow resolution of this peritoneal reaction.

Operative therapy

Prevention

Because most fistulas follow surgical mishaps, the foremost principle in management is prevention. This may be accomplished by adherence to strict surgical principles in performing intestinal anastomosis and sepsis prevention.

Salvage procedures

Sometimes early surgical intervention is necessary because of uncontrolled sepsis or a high fistula output, despite the poor general condition of the patient. The surgical procedures include:

  • drainage of abscesses
  • proximal diversion of bowel
  • exteriorisation of the fistulising segment of bowel
  • resection of the phlegmonous segment of bowel without anastomosis.

Definitive surgery

Major indications for surgery are persistent drainage following 2–3 months of maximal non-operative management, significant sepsis or presence of underlying diseased bowel (Crohn's disease, malignancy, radiation). Operations for fistulas are not to be taken lightly and require meticulous planning. If a recent surgery has been performed, an interval of at least 3–4 months should elapse before the definitive surgery.

Pre-operative preparations include appropriate bowel preparation, prophylaxis for deep vein thrombosis and adequate nutritional repletion. Samples from the fistula site and wound should be cultured and sensitivities obtained to guide the antibiotic prophylaxis. Blood should be cross-matched. The stoma site should be marked pre-operatively and its possibility discussed with the patient.

The operation should be performed through an adequately healed abdominal wall in which a secure abdominal closure can be obtained. Meticulous dissection and lysis of adhesions are performed to ensure that more distal obstruction of bowel is not present. Care is taken not to cause an unnecessary enterotomy, which, if it occurs, must be repaired with care. If technically possible, the entire gastrointestinal tract is carefully examined. Pre-operative imaging studies will have indicated the site of the fistula.

There are a number of surgical options: resection and anastomosis, which is the preferred option whenever feasible (the anastomosis is performed using healthy bowel in a clean field distant from the site of sepsis); resection with exteriorisation of bowel ends if there are factors adverse to optimal anastomotic healing; and wedge excision of the fistulising segment of bowel and primary repair if the fistula is small.

Post-operative management

Post-operative paralytic ileus is often prolonged and a period of decompression with a nasogastric tube is helpful. Antibiotics are continued for 72 hours after surgery, unless otherwise indicated. Parenteral nutritional support is continued post-operatively. Reintroduction of enteric intake may be slower in patients who have not eaten for several months. A minimal caloric intake of 1500 calories is necessary before parenteral nutrition can be discontinued.

Further reading

Chamberlain RS, Kaufman HL, Danforth DN. Enterocutaneous fistula in cancer patients: etiology, management, outcome, and impact on further treatment. Am. Surg. 1998; 64: 1204-1207.

Memon AS, Siddiqui FG. Causes and management of post-operative enterocutaneous fistulas. J Coll Physicians Surg Pak. 2004 Jan;14(1):25-8.
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