Perianal Disease
Benign and malignant anorectal conditions — hemorrhoids, fissure, abscess/fistula, pilonidal disease, and anal cancer — organized around the dentate line.
High-Yield Points
- The dentate line is the key landmark. Above = columnar/transitional, internal hemorrhoid plexus, insensate (visceral), drains to internal iliac/IMA nodes. Below = squamous, external plexus, sensate (somatic, inferior rectal nerve), drains to inguinal nodes.
- Internal hemorrhoids (above dentate) → painless bright-red bleeding ± prolapse. Grading: I bulges/bleeds, II prolapses + reduces spontaneously, III needs manual reduction, IV irreducible.
- Hemorrhoid management: all grades start with fiber, stool softeners, fluids, sitz baths. Failed conservative → rubber band ligation (grades I–III; superior to sclerotherapy/IR coagulation). Grade IV → excisional hemorrhoidectomy. Never band external hemorrhoids (painful).
- Thrombosed external hemorrhoid = acute, exquisitely painful bluish nodule at the verge. Within ~48–72 h → excise (elliptical, under local). After ~72 h → conservative (pain already resolving).
- Anal fissure = anoderm tear distal to dentate, classically posterior midline (ischemic watershed); severe pain with defecation + blood on tissue. Medical first: fiber, sitz baths, topical nitroglycerin/diltiazem (relax internal sphincter); Botox = best nonoperative healing. Refractory → lateral internal sphincterotomy. Off-midline/recurrent/multiple fissure → suspect Crohn/IBD — do NOT operate.
- Anorectal abscess (95% cryptoglandular, from infected anal glands at the dentate) → incision & drainage. Below levators (perianal/intersphincteric/ischiorectal) → drain through perianal skin; supralevator → transrectal. Ischiorectal can track to a horseshoe abscess (modified Hanley). Antibiotics only if cellulitis, diabetes, immunosuppression, or prosthetic hardware. ~50% develop a fistula afterward.
- Fistula-in-ano (chronic drainage after abscess). Goodsall's rule: anterior external opening (within 3 cm) → straight/radial tract; posterior opening → curved to posterior midline; anterior >3 cm = exception (also tracks to posterior midline). Tx balances eradicating sepsis vs continence — fistulotomy for low/simple tracts, seton/LIFT/advancement flap for high tracts; liberal seton, avoid fistulotomy in Crohn.
- Pilonidal disease — infected ingrown hair in the natal cleft, young hirsute men. Acute abscess → I&D OFF the midline (midline heals poorly) + hair removal. Chronic/recurrent → excision (rhomboid flap favored).
- Anal cancer: anal canal (above dentate) = squamous cell (HPV/HIV/XRT) → Nigro protocol (5-FU + mitomycin C) chemoradiation first-line, ~80% cure; APR = salvage for failure. Anal margin SCC (below dentate, better prognosis) → WLE if small. Spread of canal cancer → internal iliac; margin cancer → inguinal nodes.
Key Tables / Differentials
| Feature | Internal hemorrhoid | External hemorrhoid | Anal fissure |
|---|---|---|---|
| Location | Above dentate | Below dentate | Below dentate (post. midline) |
| Pain | Painless (insensate) | Painful if thrombosed | Severe with defecation |
| Bleeding | Painless bright red | With thrombosis | Streak on tissue |
| First-line Tx | Fiber → band (I–III) | Conservative; excise if acute thrombosis | Fiber/sitz/nitroglycerin |
| Hemorrhoid grade | Definition | Management |
|---|---|---|
| I | Bleeds, no prolapse | Conservative → band/sclerose |
| II | Prolapse, reduces spontaneously | Conservative → band |
| III | Prolapse, manual reduction | Conservative → band; hemorrhoidectomy if fails |
| IV | Irreducible | Surgical hemorrhoidectomy |
Board Pearls
- Painless rectal bleeding + prolapse reducing manually → grade III internal hemorrhoid.
- Posterior-midline tear, sentinel pile, severe pain → anal fissure; lateral location → think Crohn.
- Fluctuant tender perianal mass → abscess → drain (antibiotics alone fail).
- Recurrent drainage after a drained abscess → fistula-in-ano → apply Goodsall.
- HIV/HPV + anal canal mass, biopsy SCC → Nigro chemoradiation, not upfront APR.
- Fecal incontinence most common cause = obstetric injury; lateral internal sphincterotomy's worst complication = incontinence.
Classic Vignette Triggers
- "Painless bright-red blood coating stool" → internal hemorrhoid.
- "Acute exquisite anal pain, bluish lump at the verge, 1 day" → thrombosed external hemorrhoid → excise.
- "Tearing pain with defecation, blood on the paper, posterior tear" → anal fissure.
- "Ingrown hair, fluctuant swelling in the natal cleft" → pilonidal abscess → off-midline I&D.
- "Anterior fistula opening 1.5 cm out" → straight radial tract (Goodsall).
- "Immunosuppressed patient, anal canal squamous carcinoma" → Nigro protocol.