Perianal Crohn Disease

Perianal Crohn disease includes abscesses, fistulas, fissures, ulcers, stenosis and destructive anorectal inflammation caused by transmural Crohn disease.

Complex fistulating disease requires coordinated control of both perianal sepsis and luminal inflammation.

Closing a fistula while leaving an undrained abscess behind can precipitate severe sepsis.

Patients may have recurrent perianal abscesses, multiple draining fistulas, deep fissures, skin tags, ulceration and pain.

Crohn fissures may be lateral, multiple and less painful than primary hypertonic fissures.

Severe rectal inflammation substantially lowers the chance of successful fistula closure.

Pelvic MRI: define fistula tracts and occult abscesses.

Perform examination under anaesthesia when drainage or seton placement is required.

Assess the rectum endoscopically because active proctitis materially affects surgical options.

Drain every clinically significant abscess before starting or escalating major immunosuppressive fistula therapy.

For complex fistulas, establish drainage with a loose seton before definitive medical or surgical closure. Chronic seton drainage alone should not be considered definitive treatment except for palliation.

Antibiotics can control acute perianal sepsis but do not reliably close Crohn fistulas by themselves.

A practical short course when infection is present is:

Ciprofloxacin 500 mg orally twice daily

with or without

Metronidazole 500 mg orally two to three times daily, depending on severity and microbiology.

For established complex fistulating disease after sepsis control:

Infliximab 5 mg/kg IV at weeks 0, 2 and 6, then every 8 weeks is a major first line biologic strategy.

A simple low fistula in a patient without proctitis and with good continence can occasionally undergo fistulotomy.

Avoid fistulotomy through substantial sphincter in complex disease.

After luminal disease control, suitable fistulas can undergo LIFT or advancement flap closure.

Avoid cutting setons because of sphincter injury and incontinence risk.

Severe refractory anorectal disease with uncontrollable sepsis, destructive proctitis or intolerable symptoms may require faecal diversion or proctectomy.