What pre‑operative management should be provided for an inpatient with a perianal fistula?

Pre-operative Management of Perianal Fistula in Hospitalized Patients

All inpatients with perianal fistula require immediate multimodal assessment with examination under anesthesia (EUA) by an experienced colorectal surgeon combined with pelvic MRI, followed by seton placement for drainage control, nutritional optimization, and initiation of medical therapy based on fistula complexity and presence of Crohn's disease. 1

Immediate Assessment and Diagnostic Workup

Clinical Evaluation

• Perform examination under anesthesia (EUA) by an experienced colorectal surgeon to classify the fistula (90% sensitivity for identifying tracts, sinuses, and abscesses), assess rectal mucosa for proctitis, and drain any collections 1
• Assess for proctitis during EUA, as its presence is associated with significantly poorer surgical outcomes (OR=2.85,95% CI 1.65-4.89) and lower fistula healing rates 1, 2
• Order pelvic MRI as standard imaging to define fistula anatomy, identify indolent abscesses that may be missed at EUA, and establish baseline for follow-up 1
• Perform endoscopy to evaluate for active rectal disease, as this affects treatment decisions and surgical planning 2

Initial Surgical Intervention

• Place a draining seton immediately to control sepsis, create a patent tract, and allow tissue inflammation to settle before definitive treatment 1, 2, 3
• Drain all abscess collections adequately before considering any medical therapy, as uncontrolled sepsis will compromise all subsequent treatments 1

Nutritional Optimization

Malnutrition screening and correction is mandatory for all patients requiring surgery for perianal disease. 1

• Screen for malnutrition using validated tools and perform comprehensive nutritional assessment 1
• Provide nutritional support (oral supplements, enteral nutrition, or parenteral nutrition) as required to correct deficiencies 1
• Consider exclusive enteral nutrition (EEN) for at least 2 weeks preoperatively in severely undernourished patients, as this reduces postoperative septic complications (4% vs 25%, p=0.04) 1
• Reserve total parenteral nutrition (TPN) for patients unable to tolerate enteral route or when emergency surgery is needed 1

Medical Management

For Crohn's Disease-Related Fistulas

Complex Perianal Crohn's Fistulas:

• Initiate anti-TNF therapy (infliximab preferred) combined with immunomodulators as first-line medical treatment after adequate surgical drainage 1, 2
• Add combination antibiotic therapy with ciprofloxacin and metronidazole to improve short-term outcomes 1, 2
• Aim for high anti-TNF trough levels to optimize response 1

Simple Perianal Crohn's Fistulas:

• Start with metronidazole and/or ciprofloxacin as first-line therapy 2
• Consider azathioprine or mercaptopurine as second-line treatment 2

Medication Adjustments

• Wean steroids preoperatively (ideally 4 weeks before surgery) to decrease postoperative complications 1
• Stop immunomodulators associated with anti-TNF agents as soon as possible before surgery, as these are risk factors for intra-abdominal sepsis 1

Antibiotic Therapy

• Do NOT routinely administer antibiotics unless there is documented superinfection, intra-abdominal abscess, or sepsis 1
• When antibiotics are indicated, provide broad-spectrum coverage against Gram-negative aerobic/facultative bacilli, Gram-positive streptococci, and obligate anaerobic bacilli 1
• Duration depends on clinical and biochemical response (monitor CRP levels) 1

Supportive Care

• Administer adequate intravenous fluid resuscitation for all patients presenting with acute symptoms 1
• Provide venous thromboembolism prophylaxis with low-molecular-weight heparin immediately, as IBD patients have high thrombotic risk 1
• Correct electrolyte abnormalities and anemia before surgery 1

Multidisciplinary Planning

• Involve gastroenterology and colorectal surgery from admission for coordinated care 1
• Initiate early advanced therapies promptly, as this is associated with favorable outcomes 1
• Plan definitive surgical approach based on fistula complexity, presence of proctitis, and patient goals after initial drainage and medical optimization 1, 2

Critical Pitfalls to Avoid

• Never attempt definitive surgical repair without adequate drainage and sepsis control first 1, 3
• Do not overlook proctitis assessment, as this dramatically affects healing rates and may contraindicate certain procedures 1, 2
• Avoid continuing immunosuppression close to surgery, as preoperative immunomodulators with anti-TNF and steroids increase septic complications 1
• Do not rely solely on EUA or imaging alone—multimodal assessment increases diagnostic accuracy as indolent abscesses may be missed at EUA 1