Pre‑operative Management of Perianal Fistula in Hospitalized Patients

Immediate Assessment and Diagnostic Workup

• All hospitalized patients with a perianal fistula should undergo prompt multimodal assessment that includes examination under anesthesia (EUA) by an experienced colorectal surgeon and pelvic MRI, followed by seton placement, nutritional optimization, and disease‑specific medical therapy. 1
• EUA performed by an experienced colorectal surgeon identifies fistulous tracts, sinuses, and abscesses with ≈ 90 % sensitivity, providing essential anatomic detail for planning. 2
• Detection of proctitis during EUA markedly worsens surgical outcomes (odds ratio 2.85; 95 % CI 1.65‑4.89) and reduces fistula‑healing rates; therefore it must be documented. 1
• Pelvic MRI is recommended as the standard imaging modality to delineate fistula anatomy, uncover indolent abscesses missed on EUA, and create a baseline for postoperative monitoring. 2

Initial Surgical Intervention

• A draining seton should be placed immediately after assessment to control sepsis, maintain a patent tract, and allow inflammation to settle before definitive repair. 3
• All identifiable abscess collections must be adequately drained prior to initiating any medical therapy; uncontrolled sepsis compromises subsequent treatment efficacy. 4

Nutritional Optimization

• Systematic malnutrition screening using validated tools and a comprehensive nutritional assessment is mandatory for every patient scheduled for perianal surgery. 1
• Nutritional support—whether oral supplements, enteral feeding, or parenteral nutrition—should be provided as needed to correct deficits before operative intervention. 2
• In severely undernourished patients, exclusive enteral nutrition for at least 2 weeks preoperatively reduces postoperative septic complications (4 % vs 25 %; p = 0.04). 1
• Total parenteral nutrition is reserved for patients who cannot tolerate the enteral route or who require emergency surgery. 4

Medical Management of Crohn’s‑Related Fistulas

• Complex perianal Crohn’s fistulas: Initiate anti‑TNF therapy (infliximab preferred) combined with an immunomodulator after adequate surgical drainage. 4
• Add combination antibiotic therapy with ciprofloxacin + metronidazole to improve short‑term outcomes in this subgroup. 4
• Target high anti‑TNF trough levels to maximize therapeutic response. 3
• Steroid management: Wean systemic steroids at least 4 weeks before surgery to lower postoperative complication rates. 4
• Immunomodulator management: Discontinue immunomodulators that are used alongside anti‑TNF agents as early as possible before surgery, as they increase the risk of intra‑abdominal sepsis. 4

Antibiotic Therapy

• Routine prophylactic antibiotics are not recommended unless there is documented superinfection, intra‑abdominal abscess, or systemic sepsis. 4
• When antibiotics are indicated, employ broad‑spectrum agents covering Gram‑negative aerobic/facultative bacilli, Gram‑positive streptococci, and obligate anaerobes. 4
• Duration of therapy should be guided by clinical improvement and biochemical response (e.g., decreasing C‑reactive protein). 4

Supportive Care

• Provide adequate intravenous fluid resuscitation for all patients presenting with acute perianal symptoms. 4
• Initiate venous thromboembolism prophylaxis with low‑molecular‑weight heparin immediately, given the heightened thrombotic risk in inflammatory bowel disease. 4
• Correct electrolyte disturbances and anemia before proceeding to definitive surgery. 4

Multidisciplinary Planning

• Gastroenterology and colorectal surgery teams should be involved from the moment of admission to ensure coordinated care. 3
• Early initiation of advanced therapies (e.g., anti‑TNF agents) is associated with improved outcomes and should be pursued promptly. 1
• The definitive surgical strategy must be individualized based on fistula complexity, presence of proctitis, and patient‑centered goals after initial drainage and medical optimization. 3

Critical Pitfalls to Avoid

• Definitive surgical repair must never be attempted before achieving adequate drainage and sepsis control. 3
• Failure to assess for proctitis can dramatically lower healing rates and may contraindicate certain procedures; thorough evaluation is essential. 1
• Continuing immunosuppressive therapy (steroids or immunomodulators) close to the operative date increases septic complications and should be avoided. 4
• Relying solely on EUA or imaging is insufficient; a combined multimodal approach improves diagnostic accuracy by detecting indolent abscesses that might be missed on a single modality. 2

Treatment of Perianal Fistulas

Classification and Diagnosis

• The American Gastroenterological Association classifies perianal fistulas as simple or complex, with simple fistulas being low intersphincteric or trans-sphincteric fistulas with a single external opening, and complex fistulas being high intersphincteric, high trans-sphincteric, extrasphincteric, or suprasphincteric fistulas 5, 6
• Imaging with MRI or endoanal ultrasound is used to define fistula anatomy, and endoscopy is performed to assess for active rectal disease, which affects treatment decisions 5, 7

Treatment Algorithm

• The European Crohn’s and Colitis Organisation recommends initial seton placement followed by medical therapy, preferably anti-TNF agents, as the standard of care for most cases of perianal fistulas 8, 9
• For simple perianal fistulas, first-line medical treatment includes metronidazole and/or ciprofloxacin, with second-line treatment being azathioprine or mercaptopurine, and third-line treatment being infliximab 10, 11, 12
• For complex perianal fistulas, first-line medical treatment includes anti-TNF therapy, preferably infliximab, combined with immunomodulators, with adjunctive therapy including antibiotics such as metronidazole and ciprofloxacin 8, 9, 7

Surgical Options

• For simple fistulas, fistulotomy has the highest success rate, while for complex fistulas, non-cutting setons, advancement flaps, and ligation of intersphincteric fistula tract (LIFT) are considered, depending on fistula characteristics 8, 9, 6, 7
• For rectovaginal fistulas, medical therapy is used to control active luminal disease, followed by surgical repair with transanal or transvaginal advancement flaps only after endoscopic healing of rectosigmoid mucosa 13, 14

Management of Refractory Cases

• For refractory cases, hyperbaric oxygen therapy and fecal diversion are considered, with proctectomy being a last resort for severe disease with irreversible perineal destruction 8, 9, 7, 13, 14
• Maintenance therapy with immunomodulators is considered after initial response to prevent recurrence 7, 14

Important Considerations

• Clinical closure does not equal MRI closure, with a high risk of recurrence without complete fibrotic tract on MRI 8, 9
• Active luminal disease should be treated concurrently, as perianal fistulas are often associated with active disease elsewhere 5, 6
• Monitoring for development of malignancy in chronic perianal fistula tracts is recommended 5, 6

Management of Perianal Fistulas

Diagnosis and Treatment Approach

• Examination under anesthesia should include assessment of the rectal mucosa, as the presence of proctitis is associated with lower rates of fistula healing, according to the American Gastroenterological Association 15
• Commonly performed procedures for perianal Crohn's disease include removal of draining seton (70.7%), fistulotomy (57.1%), advancement flap (38.9%), fistula plug (36.4%), and LIFT procedure (31.8%) 15
• Video-assisted anal fistula treatment (VAAFT) combined with advancement flap has shown 82% success rate at 9 months in complex fistulizing Crohn's disease 15
• Careful preparation of the fistula track with curettage to destroy epithelial tissue and ligation of the internal opening should be considered as standard treatment 15
• Expanded allogeneic adipose-derived stem cells have shown promise for treatment-refractory complex perianal fistulizing Crohn's disease 15