What is the workup and management of an enterocutaneous fistula?

Management of Enterocutaneous Fistula

Initial Stabilization and Resuscitation

Begin with aggressive IV fluid resuscitation using normal saline (2-4 L/day) for high-output fistulae (>500 ml/day) to prevent severe dehydration and electrolyte depletion. 1, 2

• Classify fistula by output volume immediately: low (<200 ml/day), moderate (200-500 ml/day), or high (>500 ml/day), as this determines the entire management pathway 1, 3
• Monitor and continuously replace ongoing losses with particular attention to sodium replacement (each liter of fistula fluid contains approximately 100 mmol/L sodium) 1, 2
• Restrict hypotonic/hypertonic oral fluids to <1000 ml daily in high-output fistulae, instead providing glucose-saline solution with sodium concentration ≥90 mmol/L 1, 2
• Add antimotility agents: loperamide 2-8 mg before food, occasionally with codeine phosphate for additional output reduction 1
• Consider proton pump inhibitors (omeprazole) to reduce secretory output, particularly when net output exceeds 3 liters per 24 hours 1

Sepsis Control and Abscess Management

Treat intra-abdominal abscesses with IV antibiotics and radiological drainage as first-line therapy before any other intervention. 4, 1, 2

• Never initiate anti-TNF therapy before adequate abscess drainage—this worsens sepsis and increases mortality 2
• Reserve surgical drainage only for failures of percutaneous drainage 2
• Avoid immediate surgical resection during the acute septic phase 4, 2
• Use metronidazole 400 mg three times daily and/or ciprofloxacin 500 mg twice daily for simple fistulae 2

Diagnostic Workup

Obtain MRI to define fistula anatomy—this is the preferred diagnostic tool with highest sensitivity and specificity. 1, 3

• MRI identifies fistula tract complexity, associated strictures, and presence of abscesses 1
• Assess for multiple tracts and associated stenosis, as these reduce healing rates with medical therapy and increase need for surgery 4, 3
• Determine if the fistula is associated with active Crohn's inflammation versus postoperative etiology, as this fundamentally changes treatment approach 4, 1

Nutritional Support

For proximal or high-output fistulae, provide partial or exclusive parenteral nutrition; for distal low-output fistulae, enteral nutrition is appropriate. 1, 2

• Nutritional optimization is essential before any surgical intervention, as malnutrition (BMI <20 kg/m²) is an independent risk factor for complications 2
• Continue nutritional support for minimum 5-7 days preoperatively to reduce postoperative morbidity 2
• Be vigilant for refeeding syndrome in patients with prolonged nutritional deprivation, particularly monitoring phosphate and thiamine 2
• Short-peptide-based enteral nutrition for three months achieved successful closure in 62.5% of Crohn's disease patients with enterocutaneous fistulae 1, 2

Skin and Wound Care

Protect skin from fistula output immediately to preserve peri-wound skin integrity—breakdown causes significant additional morbidity and complicates surgical planning. 2, 3

• Apply negative pressure wound therapy (NPWT/VAC) to manage output and protect surrounding skin, particularly for enteroatmospheric fistulae 2, 3
• Use "floating stoma" technique for visible fistulae: isolate the fistula with an ostomy bag, using VAC to achieve secure adhesion 3
• Create a conduit from the fistula source to the VAC canister to prevent effluent accumulation 3
• Avoid contamination with feces and urine when applying dressings; use Foley catheters, antimotility agents, and rectal tubes as needed 3

Medical Therapy Decision Algorithm

If the fistula is associated with active Crohn's inflammation (not postoperative), initiate anti-TNF therapy only after sepsis control and abscess drainage. 4, 1, 2

When to Use Medical Therapy:

• Fistulae communicating with segments of active Crohn's inflammation 4, 1
• Low-volume fistulae (<200 ml/day) without strictures or abscesses 1, 3
• Simple fistulae without multiple tracts 4, 3

When Medical Therapy Will Fail:

• Postoperative fistulae (within 30 days of surgery)—medical therapy is unlikely to help and should not delay surgical planning 1, 2
• High-output fistulae (>500 ml/day)—these require surgery as they cannot be controlled medically 1, 2, 3
• Fistulae associated with bowel stricture and/or abscess—surgery is strongly recommended 1, 2, 3
• Complex fistulae with multiple tracts—these have reduced healing rates with anti-TNF therapy 4, 3

Expected Outcomes with Anti-TNF Therapy:

• Only one-third of patients achieve fistula healing 1, 2, 3
• Half of responders experience relapse over 3 years 2
• One-third of patients treated with anti-TNF therapy develop intra-abdominal abscess, requiring careful monitoring 1

Alternative Medical Options:

• Azathioprine 1.5-2.5 mg/kg/day or mercaptopurine 0.75-1.5 mg/kg/day are potentially effective for simple fistulae 2

Surgical Management

High-output fistulae (>500 ml/day) require surgery for definitive management—plan this after completing the four-step optimization protocol. 1, 2, 3

Timing of Surgery:

• Delay surgery for 3-12 months after initial diagnosis or previous laparotomy to allow lysis of fibrous adhesions and improve outcomes 2
• Never operate immediately without completing optimization (fluid/electrolyte balance, sepsis control, nutrition, skin care)—this leads to poor outcomes and high mortality 2
• Never operate during active Crohn's inflammation without attempting medical control first 2

Surgical Indications (Absolute):

• High-output fistulae (>500 ml/day) 1, 2, 3
• Fistulae with associated bowel stricture 1, 2, 3
• Fistulae with persistent or recurrent abscess 1, 2, 3
• Postoperative fistulae that fail conservative management 1, 2
• Complex fistulae with multiple tracts that fail medical therapy 4, 3

Surgical Approach:

• Perform segmental resection of the bowel segment communicating with the fistula and restore intestinal continuity 5
• Consider temporary diverting stoma when high-dose steroids cannot be weaned before emergency surgery 2
• Stage procedures when multiple risk factors are present (sepsis, malnutrition, smoking) 2
• Enteroatmospheric fistulae require complex abdominal wall reconstruction immediately following fistula resection 5

Preoperative Optimization Checklist:

• Drain all intra-abdominal abscesses via interventional radiology 2
• Optimize nutritional status (minimum 5-7 days of support) 2
• Achieve fluid and electrolyte balance 2, 5
• Establish adequate skin protection and wound care 2, 3

Multidisciplinary Team Approach

All patients with enterocutaneous fistulae must be managed by a multidisciplinary team including gastroenterologist, surgeon, dietitian, and stoma care nurse. 1, 2

• The complexity and association with adverse outcomes including mortality (10-30% in some series) mandates coordinated care 2, 6
• Joint medical and surgical discussion is required after abscess treatment, though interval surgical resection is not always necessary 4
• Early involvement of patient and caregivers in all aspects of management is essential for successful discharge 7

Critical Pitfalls to Avoid

• Never initiate anti-TNF therapy before adequate abscess drainage 2
• Never operate immediately without completing the four-step optimization protocol 2
• Never neglect skin care—breakdown causes significant morbidity 2
• Never assume medical therapy will work for postoperative fistulae 1, 2
• Never operate during active Crohn's inflammation without attempting medical control first 2