Anorectal Disease
Core concepts
Master anatomy of the anal canal: dentate line, internal and external sphincters, and the cryptoglandular origin of abscess and fistula. Know the Parks classification of fistulas and the role of examination under anesthesia, seton placement, and fistulotomy only when sphincter preservation allows. Hemorrhoids: internal versus external, grading, and treatment ladder from fiber to rubber banding to surgical hemorrhoidectomy. Fissure management (laxatives, topical agents, botulinum, lateral internal sphincterotomy) and the risk of incontinence. Understand pilonidal disease and perianal hidradenitis.
Traps
Questions test whether you avoid fistulotomy for high transsphincteric or anterior female fistulas. Another trap: confusing thrombosed external hemorrhoid (excise acutely) with prolapsed internal hemorrhoid. Watch for the pitfall of treating anorectal abscess with antibiotics alone instead of drainage.
Worked example
A 35-year-old with an intersphincteric fistula and normal continence: fistulotomy is appropriate because the tract crosses little sphincter muscle. Rule of thumb: drain every abscess; lay open only low tracts; use setons for high tracts to preserve continence.