Postoperative enterocutaneous fistulaTimothy A Pritts, M.D., David R Fischer, M.D., and Josef E Fischer, M.D.

Department of Surgery, University of Cincinnati College of Medicine

Introduction

Enterocutaneous fistulas may result from a wide variety of conditions and circumstances. Care of these patients can be quite challenging, frustrating, and, ultimately, rewarding. The patient with an enterocutaneous fistula presents the surgeon with a plethora of challenges, and a command of related anatomy, physiology, and metabolism is necessary to successfully meet these challenges.

Postoperative enterocutaneous fistulas, the focus of this brief review, account for approximately 80% of enterocutaneous fistulas. The remainder of enterocutaneous fistulas may occur spontaneously, as a result of tumor, irradiation, or inflammation.

Treatment of patients with postoperative enterocutaneous fistulas requires an understanding of the metabolic and anatomic derangements. In order for mortality of patients with postoperative fistulas to be minimized, nutrition, volume, and electrolyte derangements must be corrected. This must be done in addition to replacing ongoing losses in these areas. Malnutrition is easier to prevent than correct. Once established, malnutrition may be difficult to correct, especially with concomitant sepsis, but malnutrition and sepsis remain principal causes of death in patients with fistulas.

Definition and classification

In its simplest definition, a fistula is a communication between two epithelialized surfaces. Fistulas may be classified based on anatomic, physiologic, or etiologic criteria (table I). Definition of the anatomic course of a fistula is necessary as it may suggest the etiology of the fistula and aid in estimating likelihood of spontaneous closure. Knowledge of fistula anatomy is necessary to plan potential operative strategy towards closure. Physiologic classification of fistulas is based on output (in ml per day). High output fistulas (greater than 500 ml per day) are more likely to originate from the small bowel. Low output fistulas (less than 200 ml per day) are more likely to be colonic in origin. Knowledge of the underlying anatomy and physiology help the physician to anticipate and correct fluid and metabolic derangements. The etiology of the fistula may also aid in predicting spontaneous closure rates and mortality. Fistulas related to malignancy, irradiation, or inflammatory bowel disease are less likely to close spontaneously.

Table I

Classification of fistulas.

Post-operative fistulas account for 75–85% of all enterocutaneous fistulas. Although at one time most fistulas were spontaneous, this proportion has been decreasing with improved health care access. Postoperative fistula formation is most common following cancer operations, inflammatory bowel disease operations, or lysis of adhesions.

Diagnosis

In the case of enterocutaneous fistulas, the diagnosis is usually obvious, with external drainage of enteric contents. Most postoperative enterocutaneous fistulas are identified in the immediate postoperative period and follow a predictable scenario. The typical patient is 5 or 6 days postoperative, with a fever and persistent ileus. A wound abscess becomes apparent, is drained, and the patient's fever resolves. Within 24 hours, the fistula becomes obvious and enteric contents appear on the wound dressing. Once the diagnosis is made, therapy should be initiated as described below.

Treatment

The goals of therapy for patients with enterocutaneous fistulas are to correct metabolic and nutritional deficits, close the fistula, and reestablish continuity of the gastrointestinal tract. The expected treatment course can be divided into five overlapping, but sequential phases (table II).

Table II

Treatment phases.

Phase 1: Recognition and stabilization

In this initial period, the presence of an enterocutaneous fistula is established. The patient often has profound metabolic and fluid disturbances. The patient should initially be resuscitated to replace intravascular volume. Anemia, which is often present, should be corrected by transfusion. If the patient is hypoalbuminemic (less than 3 g/dl), consideration should be given to albumin administration, as this may improve bowel function. It is not uncommon for patients to also have intra-abdominal abscesses. Drainage of these abscesses should be carried out only after injection of water-soluble contrast into the abscess by the physician. These studies can yield anatomic information that is otherwise unobtainable. Computed axial tomographic scanning is also useful to evaluate the abdomen for undrained abscesses. As abscess drainage invariably leads to bacteremia, even with antibiotic coverage, central vein catheterization should be delayed until 24 hours after this procedure.

Drainage of the fistula should be controlled. This provides accurate records of daily fistula output, simplifies fluid and electrolyte replacements, and TAP suggest whether or not the fistula is closing spontaneously, and aids wound care. The latter is especially important, as operative closure is much easier with an intact, non-indurated abdominal wall. Simply bagging the fistula can lead to closure of the tract at the skin level while enteric leakage continues, leading to abscess formation. Use of a sump catheter to control drainage is preferred. We have found that the use of a soft latex catheter, such as a Robinson nephrostomy tube, with a 14 gauge intravenous catheter inserted into the tube to serve as an air vent works well.

Care of the skin around the draining fistula is also extremely important. In addition to a mechanism of drainage collection, as described above, the integument also needs to be protected.

Several preparations are available the decrease skin maceration and breakdown, including ileostomy cement, Karaya® powder, Stomadhesive®, and glycerine. The success of surgical therapy may be improved if excoriation or superinfection of the skin surrounding the fistula tract can be prevented.

After initial stabilization and resuscitation, adequate attention must be directed to nutritional support. Many patients with enterocutaneous fistulas are hypercatabolic and have ongoing nutritional losses. Caloric requirements can be determined from the Harris-Benedict equation, with multiplication by a stress factor, or through indirect calorimetry. Both methods require correction based on patient activity. Nitrogen equilibrium should be achieved in order to restore protein synthesis. Protein requirements range from 1–1.5 grams per kilogram per day for patients with low output fistulas, to as high as 2.5 grams per kilogram per day for some patients with high output fistulas. Fluid requirements can be calculated based on body weight or body surface area and must be adjusted for pre-existing deficits and ongoing fluid losses. With the provision of adequate nutrition to previously malnourished patients, vitamins and trace elements may also be rapidly depleted and patients with high output fistulas should receive almost twice the US recommended daily allowance of water-soluble vitamins. Serum electrolyte levels, including magnesium, should be followed closely and replacements given as needed. Additional zinc supplementation may also be necessary with high output fistulas.

The route of nutrition should be carefully considered. Rates of fistula closure are slightly lower with enteral than with parenteral nutrition, but where possible, the enteral route is preferred, as it carries several real and theoretical advantages over the parenteral route. In general, at least 48 inches of bowel either proximal or distal to the fistula must be present in order to utilize this route. Even if full enteral nutritional support is not practical, a portion of the patient's nutrition should still be given by this route as advantages are probably obtained when as little as 20% of nutritional needs are given enterally. After enteral feeding is initiated, fistula output may transiently increase. If output remains elevated, the tube feeding rate should be decreased and supplemental parenteral nutrition given. In reality, at least a brief overlapping period of both parenteral and enteral nutrition is necessary in most patients as it requires five to ten days to achieve caloric and nitrogen balance by the enteral route.

Recent studies have begun to examine the role of somatostatin in the treatment of fistulas. Treatment with conservative measures alone results in the closure of between 30 and 75% of fistulas, depending on the series and selection criteria. It appears that closure rates with somatostatin treatment are similar, but that the duration of time to closure may be lessened.

Phase 2: Investigation

Following stabilization of the patient and maturation of the fistula tract, the anatomy of the fistula should be investigated radiographically. A fistulogram should be performed as a collaborative effort between the senior surgeon and a senior radiologist. An adequate fistulogram will obviate the need for other gastrointestinal tract examinations, such as a small bowel follow-through or barium enema. Several questions should be answered at this time:

1.From what region of the bowel does the fistula arise?2.Is the bowel wall defect larger than 1 cm?3.Has the bowel been completely disrupted?4.Does the fistula communicate with the bowel distally?

5.Does the fistula arise from the lateral bowel wall?6.Is there an abscess associated with the fistula, and if so, does the fistula drain into the abscess cavity?7.Is the adjacent bowel damaged, strictured, or inflamed?8.Is there a distal obstruction?9.What is the length of the fistula?

The answers to these questions are important, as they assist in identifying fistulas with anatomic features that are less likely to close spontaneously, including those arising from the stomach, ileum, or jejunum at the ligament of Treitz, those with a tract length less than 2 cm in length, with wall defects larger than 1 cm, with complete disruption of the bowel wall, with poor quality of adjacent bowel, or those associated with the presence of a large abscess cavity.

Phase 3: Decision

During this phase, an approach is devised to reach the goal of fistula closure and reestablishment of gastrointestinal continuity. Although spontaneous closure is the ideal outcome, this may occur in only about one third of patients with complicated fistulas. In addition to the anatomic characteristics discussed above, unfavorable factors related to fistula closure include poor nutritional status, presence of sepsis, active Crohn's disease, active malignancy, presence of a foreign body, epithelialization of the fistula tract, and a serum transferrin less than 200 milligrams per deciliter. The expected time period for spontaneous closure, if it is to occur at all, varies with the anatomic location of the fistula. Fistulas from the esophagus and duodenum are expected to heal in two to four weeks. Colonic fistulas may heal in 30 to 40 days. Small bowel fistulas may take at least 40 to 60 days.

If uncontrolled sepsis is present at any point, urgent abscess drainage or resection of a phlegmon should be carried out, preferably with restoration of intestinal continuity at that time. Likewise, patients with solid organ transplants should also have relatively brief periods of non-operative management due to immunosuppression and impaired wound healing. Otherwise, a period of nutritional support and trial of spontaneous closure may allow the patient's abdominal skin to heal as well as improve the patient's nutritional status and overall condition prior to operation.

Phase 4: Definitive therapy

If the anatomic features of the fistula preclude spontaneous closure or an anatomically favorable fistula has not closed in the expected time frame (4–5 weeks of sepsis free adequate parenteral nutrition), the patient should be prepared for operative closure. Ideally, with meticulous skin care and control of fistula drainage, the abdominal wall will be healthy, enhancing the opportunity for secure abdominal closure. The patient is prepared for operation in the standard fashion, with intraluminal antibiotics and mechanical bowel preparation. Discontinuation of enteral nutrition prior to operation may decrease abdominal distension and aid in abdominal closure.

Entering the abdomen through a new incision is preferred if possible. Dissection to free the bowel from the ligament of Treitz to the rectum is then carried out. The bowel should be freed from all adhesions to ensure that there is no obstruction. This usually requires extensive dissection, meticulous technique, and, not infrequently, a great deal of time. The highest closure

and lowest complication rates may be obtained by resection of the involved section of bowel with end-to-end anastomosis. Other procedures should be performed only if this is not possible. Enteral access for the postoperative period should be established, either through a gastrostomy, which can also be used for gastric decompression, a feeding jejunostomy, or preferably both.

One circumstance in which resection and end-to-end anastomosis should not be performed is the patient with a duodenal fistula. Satisfactory closure of these fistulas can be achieved with a bypass procedure, such as gastrojejunuostomy.

At the end of the operation, secure abdominal wall closure should be obtained. If the abdominal wall has been compromised, such as with partial destruction by sepsis, a plastic surgeon should be consulted to assist closure, and flaps may be necessary.

Phase 5: Healing

In the postoperative period, it is necessary to ensure that the patient continues to receive full nutritional support. Adequate protein and calories must be provided to maximize healing and minimize complications. Although enteral nutrition may be attempted early in the post-operative course, it is nearly impossible to meet the patient's entire nutritional demand by this route. Thus, postoperative care will most likely include parenteral and enteral supplementation in an overlapping manner.

After fistula closure, whether by spontaneous or surgical means, the patient will need to resume oral intake. This my be especially difficult in an individual who has had little or no oral intake for 4 to 6 weeks or more, and enlisting the assistance of a dietician and the patient's family is often helpful. Weaning enteral and parenteral nutritional supplementation and switching to nocturnal tube feeds may help to increase appetite.

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References

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