Transperineal contrast-enhanced ultrasound: a rapid and reliable tool for differentiating abscesses from inflammatory masses in perianal Crohn's disease.

Diagnose anorectal abscess and fistula-in-ano clinically: a disease-specific history and physical examination assessing symptoms, relevant history, abscess and fistula location, and secondary cellulitis (1C), with digital rectal exam and anoscopy/proctoscopy as needed. Routine diagnostic imaging is NOT typically necessary (1B); reserve imaging for selected patients with occult abscess, recurrent or complex fistula, immunosuppression, or anorectal Crohn's disease (MRI sensitivity 97% vs 74% for endoanal ultrasound in complex fistula; combined accuracy approaches 100%). Treat acute anorectal abscess promptly with incision and drainage (1C), placing the incision close to the anal verge to limit subsequent tract length and preserve the sphincter complex; packing is not required and unpacked wounds gave better resolution, less pain and faster healing in randomized trials. Reserve antibiotics for abscess complicated by cellulitis, systemic signs of infection, or underlying immunosuppression (2B); routine antibiotics after uncomplicated drainage in healthy patients do not improve healing or reduce recurrence, and conversely immunosuppressed patients with low neutrophil counts and no fluctuance may initially be treated with antibiotics alone rather than drainage. Concomitant fistulotomy at the time of drainage may be performed in selected patients with a simple anal fistula (2B), balancing lower recurrence (RR 0.13 in a 479-patient meta-analysis) against a non-significant increase in continence disturbance. For simple fistula-in-ano with normal sphincter function, lay-open fistulotomy heals over 90% (1B); for low fistulas involving less than one third of the external sphincter the clinically significant incontinence risk is minimal, and marsupialization improves healing and reduces bleeding. Sphincter-preserving options: endorectal advancement flap (1B; 66% to 87% initial healing, but up to 35% mild-to-moderate incontinence) and, for transsphincteric tracts, ligation of the intersphincteric fistula tract (LIFT) (1B; 76% pooled success, 1.4% incontinence). A cutting seton may be used selectively for complex cryptoglandular fistula (2C, downgraded from 2B; reported incontinence ranges 0% to 67%). The anal fistula plug and fibrin glue are relatively ineffective (1B, upgraded from 2B; contemporary healing 50% or less). Endoscopic or laser closure techniques (VAAFT, FiLaC, OTSC) have reasonable short-term healing but unknown long-term healing and recurrence rates (2C). In Crohn's disease, where abscess and fistula arise from penetrating inflammation rather than cryptoglandular infection, management is multidisciplinary and a draining seton is typically useful and may be used for long-term disease control (1B, upgraded from 1C); Crohn's disease is a named risk factor for failure or recurrence of fistulotomy, advancement flap, LIFT, and plug.