In Brief

Article Outline

• Copyright

Intestinal fistulas are an inevitable component of surgical practice. Improvements in health care and an aging population mean that we are pushing surgical boundaries. We are now, with increased frequency, performing abdominal procedures on patients with extensive comorbidities and higher American Society of Anesthesiologists (ASA) grades. Previously, these patients might not have been considered appropriate candidates for surgical intervention. Thus, the incidence of intestinal fistula will most likely continue to remain static. Despite all our medical advances over the past 2 decades, this is a problem that still carries a significant potential for morbidity and mortality. The majority of intestinal fistulas (75% to 85%) are iatrogenic, occurring in the postoperative period following an anastomotic dehiscence. They arise following emergency abdominal surgery for intestinal obstruction, inflammatory bowel disease, or cancers. They can occur at any time, but those arising early in the postoperative course suggest a technical error and immediate surgical intervention may be necessary. Often slow postoperative progress, mild tachycardia, or a superficial skin infection may be the first manifestations of an intra-abdominal problem. Drainage of a wound abscess may be followed by the appearance of enteric contents. A smaller percentage (15% to 25%) of intestinal fistulas arise de novo from underlying Crohn's disease, malignancy, bowel ischemia, diverticular disease, or radiotherapy. They may also arise following blunt or penetrating abdominal trauma. It is an overwhelming complication for the patient and their family and provides a difficult challenge to the primary physician. The introduction of artificial nutrition and developments in intensive care has led to significant improvements in the survival rate. However, a large percentage of patients will require a prolonged hospital course with the need for repeated interventions and definitive surgery. The management of complex intestinal fistulas requires a multidisciplinary approach with varying input from radiological, surgical, nutritional, enterostomal therapy, and other personnel. If the resources are not available in the primary center, then the patient should be referred to a tertiary unit that has previous experience with an appropriate volume of these difficult cases.

It is imperative that realistic goals are discussed with the patient and their family. There are many classification systems for intestinal fistulas, which may vary depending on the origin and nature of the fistula. The anatomical, physiological, and etiological systems are commonly used in combination to provide knowledge on the associated pathophysiology and to give a prognosis on outcome. The classification systems will help in deciding the need for total parenteral nutrition (TPN), whether there is the potential that the fistula will close spontaneously, or whether surgical intervention will be required. The underlying pathology or operation from which the fistula developed will also guide the ensuing management. In the case of an enterocutaneous fistula, the color and odor of the effluent will indicate the potential site of derivation. Fistulas that are more likely to close spontaneously include those of jejunal, ileal, and colonic origin. In addition, those with an enteral defect of less than 1 cm, a nonepithelialized tract greater than 2 cm, and fistulas arising from the lateral aspect of the gastrointestinal tract, which is in continuity, are more likely to close. The time to fistula closure varies according to anatomical location, with esophageal and duodenal fistulas healing at a greater rate than fistulas of colonic and small bowel origin. Regardless, if the fistula has not closed within 6 weeks in response to conservative measures, then it is unlikely to do so without surgical intervention. If the fistula is associated with a distal obstruction, complete disruption of the bowel lumen, multiple tracts, or ongoing intra-abdominal sepsis, then it will not close spontaneously. The management of pancreatic, esophageal, or gastric fistulas generally comes under the care of surgeons specializing in upper gastrointestinal pathology in contrast to fistulas arising from the small bowel and colon, which tend to come under the care of colorectal surgeons.

The triad of sepsis, malnutrition, and electrolyte disturbance is the greatest determinant of mortality. The first step in definitive management is to ensure the eradication of underlying sepsis. In the majority of cases this can be achieved using computed tomographic- or ultrasound-guided percutaneous drainage. If the patient fails to improve then one should have a low threshold to repeat the scans plus upsize any draining catheters or insert additional ones as required. With all the radiological advances it is very rare that one will require an open surgical approach to deal with undrained sepsis. In addition, most tertiary centers will have interventional radiologists with extensive experience in the management of complex intra-abdominal collections. Patients, particularly those in whom the fistula is associated with a chronic smoldering intra-abdominal infection, may not present with the classical manifestations of infection. Instead, they may present with cachexia, jaundice, and hypoalbuminemia, often raising an index of suspicion for underlying malignancy, when, in fact, unresolved sepsis is the diagnosis. Failure to control intra-abdominal sepsis can lead to a spiral of immune suppression, problems with opportunistic infections, and the development of multiorgan failure. Inability to control sepsis is one of the indications for early operative intervention. Involvement of the infectious disease team will help guide antimicrobial therapy.

Patients with intestinal fistulas may present with a myriad of problems and symptoms. If the fistula communicates with the skin, in particular if it is associated with an open abdominal wound, then early involvement of the enterostomal therapist (ET) is critical. The digestive juices can have a very toxic effect on the skin and lead to an unmanageable wound. The ET will help with placing an appliance over the fistula, which will control the wound, reducing the excoriation to the surrounding skin, and provide a means of recording the fistulous output. At some stage patients and their caregivers may be taught how to change the appliances, providing them with independence and confidence in managing their fistula following discharge from hospital. One should also be aware that the discharge of malodorous intestinal contents onto the skin can be extremely distressing, in particular for young patients, and therefore they must be cared for with the utmost sensitivity. In a subset of patients with an open abdominal wound and associated fistula, the application of a vacuum-assisted device (VAC) may be a helpful adjunct in wound management. It works by applying a negative subatmospheric pressure, removing purulent material from the wound, and encouraging angiogenesis, which is central to wound healing. However, if there is exposed intestinal mucosa within the wound then this must be carefully isolated from the VAC device, and this requires a lot of care and expertise from the wound care team.

When dealing with sepsis and instituting wound care one must also be cognizant that the patient's nutritional needs are being met. Ideally if the gastrointestinal tract is in continuity and there is no distal obstruction then it should be used. The presence of an enterocutaneous fistula is not a contraindication to enteral nutrition unless it leads to an extremely high output and difficulties with wound management. The patient's clinical appearance and markers such as albumin, prealbumin, and transferrin will help in determining nutritional status. The addition of supplements to the diet will often provide the patient with a large number of calories despite minimal oral intake. Some patients may have a mucus fistula, which is in continuity with an adequate amount of distal small bowel and colon. In this scenario they can receive their enteral nutrition down the efferent bowel limb (fistuloclysis), thereby maintaining gut integrity while reducing the potential for bacterial translocation and diversion colitis. In a percentage of patients with complex intestinal fistula, TPN may be required from the initial presentation. This includes patients with proximal high-output fistula and refractory electrolyte derangements, those with gastrointestinal discontinuity, and significant underlying pathology such as malignancy, inflammatory bowel disease, or cancer. This will require the insertion of a peripherally inserted central catheter (PICC) or a Hickman line, which may have to be left in situ for several months. This carries the inherent risk of line infection and an added burden to patient care. Nonetheless, TPN should allow their basal and increased nutritional needs to be met until definitive surgical intervention can be safely instituted. The role of octreotide in patients with intestinal fistula is controversial. It works by decreasing gastrointestinal secretions, hormone production, and gut motility. It is usually used in conjunction with TPN and may be added as a supplement. The overall consensus is that in a percentage of patients it will reduce the time to fistula closure, reduce the fistulous output, and thereby may aid in wound management. If it works then the beneficial effects are generally seen within 48 to 72 hours. However, for small bowel and colonic fistulas, the general belief is that it will not help in the closure of a fistula that would not have responded to conservative management in the first instance.

The next step in the management algorithm is to define the underlying anatomy. This may require a combination of radiologic and endoscopic investigations. In spontaneously occurring fistulas one generally requires a pathological diagnosis before proceeding with intervention. With colovesical or colovaginal fistulas and a presumptive diagnosis of diverticular disease, the purpose of investigations is to confirm the diagnosis and exclude any associated Crohn's disease or malignancy. Indeed, in elderly patients with significant comorbidities some fistulas may be best managed conservatively. In fistulas arising in the postoperative period, the underlying cause may be clinically apparent and few investigations may be required. A fistulogram may provide valuable information about the underlying fistula, but should only be considered once the fistula tract has matured.

If the fistula persists beyond 6 weeks then one may have to contemplate surgical intervention. Intra-abdominal adhesions achieve their maximum density from the tenth postoperative day to the sixth week. Any surgical intervention within this time frame carries a considerable risk for enterotomies and additional fistulas. We would advise delaying any surgery for a minimum of 6 months until the underlying inflammatory response has resolved, the patient's nutritional status has returned to baseline, and metabolic derangements have resolved. By this stage the adhesions will have softened, but if the inflammatory insult resulting from the primary surgery is extensive then any surgery may have to be delayed for 12 months. The surgical success rate is 80%. Resection of the fistula site and associated diseased bowel is associated with a better outcome than repair of the defect. The omission or formation of a stoma at the time of definitive surgery is generally not a prognostic indicator but should be considered if mandated by patient factors or intraoperative circumstances. If reconstruction of the abdominal wall is required, then aim to use native tissues, since the insertion of a biological mesh carries an increased risk of fistula recurrence. If a mesh is required then most authors advocate the use of more inert materials such as Permacol or Alloderm. An appropriate amount of time should be allocated to these cases since the lysis of adhesions may take several hours until the area of relevant pathology is isolated. The greatest risk of enterotomies is at the time of peritoneal entry and this should be done at a site removed from the previous scar. If the adhesions are extremely dense, hydrodissection may aid progress. In extremely difficult cases where one runs the risk of multiple enterotomies, bleeding, and bowel loss, then it may be prudent not to proceed and to have an exit strategy. The patient should be warned preoperatively about this potential scenario and the need for a proximal stoma.

Complex intestinal fistulas, the majority of which are iatrogenic, can be extremely difficult to manage. They manifest with a myriad of problems and require extensive multidisciplinary input. Although we describe the general principles of management, each case is unique and must be dealt with according to the underlying pathology and patient circumstances. Advances in nutritional support and radiological care mean one may delay surgical intervention in the majority of cases. This allows the initial inflammatory cascade to resolve and makes the ensuing surgery easier. If the fistula does not close spontaneously then surgical intervention can be planned electively at a time when the patient's condition is optimized. We recommend that complex cases are best managed in a tertiary unit with the full complement of appropriate resources.