1. Relevant anatomy and examination
   • Anal canal, sphincters, ischioanal fossa, perianal skin
   • Digital rectal examination, anoscopy/proctoscopy
   • Red flags: sepsis, immunosuppression, Crohn disease, malignancy
2. Perianal abscess
   • Types: perianal, ischioanal, intersphincteric, supralevator
   • Presentation, incision and drainage, antibiotics, complications
3. Fistula-in-ano
   • Cryptoglandular mechanism
   • Parks classification
   • MRI pelvis, EUA, seton, fistulotomy, sphincter-preserving operations
4. Anal fissure
   • Acute vs chronic
   • Primary versus secondary fissure
   • Medical treatment and lateral internal sphincterotomy
5. Hemorrhoids
   • Internal versus external, grading, conservative care, office procedures, hemorrhoidectomy
6. Pilonidal disease
   • Acute abscess and chronic sinus management
7. Pruritus ani and dermatologic lesions
   • Hygiene-related irritation, infections, inflammatory skin disease, contact dermatitis
8. Sexually transmitted and infectious lesions
   • Condyloma, herpes, syphilis, HIV-associated disease
9. Crohn-related perianal disease
   • Fistula, abscess, skin tags, strictures and multidisciplinary care
10. Cancer and other serious pathology
    • Anal cancer, perianal Paget disease, melanoma
    • When biopsy or urgent referral is needed
11. Postoperative care and common complications
    • Pain control, stool regulation, wound care, continence risk, recurrence

Perianal conditions: high-yield overview

The one mechanism to remember

Essential examination

1. Inspect at rest and on straining: swelling, discharge, scar, external opening, fissure, hemorrhoidal prolapse, skin lesion.
2. Palpate gently for tenderness, fluctuance, induration and a tract.
3. Perform digital rectal examination only if tolerable. Do not force it in severe fissure or acute abscess.
4. Anoscopy/proctoscopy identifies internal hemorrhoids, fissure, proctitis, mass, and possible internal fistula opening.
5. For recurrent/complex fistula, Crohn disease, supralevator disease, or unclear anatomy: MRI pelvis is the preferred mapping study.

Core topics for detailed surgery-rotation study

1. Perianal abscess and fistula-in-ano
2. Anal fissure
3. Hemorrhoids
4. Pilonidal sinus disease
5. Pruritus ani, infections and dermatologic disease
6. Crohn-related perianal disease
7. Anal and perianal malignancy
8. Examination, investigations, operations and postoperative care

Rotation-level takeaways

• Abscess = source control. Drainage is the main treatment. Antibiotics do not substitute for drainage.
• Fistula treatment balances cure and continence. A simple low tract may undergo fistulotomy; complex/high fistulas often need a seton or sphincter-preserving procedure.
• Posterior midline fissure is typical. Lateral fissures, multiple fissures, painless ulcers, or atypical lesions require investigation for Crohn disease, infection, TB, HIV-related disease, or malignancy.
• Do not label all rectal bleeding “hemorrhoids.” Consider cancer, inflammatory bowel disease, fissure, proctitis and diverticular/colonic sources where appropriate.
• Continence preservation matters. Before cutting sphincter in fistula or fissure surgery, consider sex, obstetric injury, baseline continence, prior anorectal operations, and fistula anatomy.
• Red flags: systemic toxicity, rapidly progressive pain or necrosis, diabetes/immunosuppression, recurrent abscess, Crohn features, unexplained weight loss, anemia, mass, persistent ulcer, and change in bowel habit.

High-yield perianal surgery notes

1. First, distinguish the presentations

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2. Essential anatomy

Dentate line

• Above dentate line: visceral innervation, mucosal covering, relatively insensitive to pain.
  • Internal hemorrhoids occur here.
  • Rubber-band ligation is performed here.
• Below dentate line: somatic innervation, anoderm/skin, very pain-sensitive.
  • External hemorrhoids and thrombosis occur here.

Anal sphincters

• Internal anal sphincter: involuntary smooth muscle. Hypertonicity/spasm drives the pain-ischemia cycle in chronic fissure.
• External anal sphincter: voluntary striated muscle. Damage risks fecal incontinence.
• In fistula surgery, the goal is simple: eradicate sepsis without unnecessarily dividing sphincter.

Cryptoglandular theory

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3. Anorectal abscess

Definition and pathology

Types of abscess

Clinical features

• Constant severe throbbing pain, not just pain while passing stool
• Tender erythematous swelling if superficial
• Fever, malaise, leukocytosis may occur
• Deep abscess may cause urinary retention, pelvic pain, or pain on DRE without external swelling

Examination

• Inspect and gently palpate.
• DRE can identify deep tenderness/fluctuance but may be intolerable.
• If the clinical diagnosis is obvious superficial abscess, imaging should not delay drainage.
• Consider imaging, usually MRI pelvis or CT in acute settings, if abscess is occult, recurrent, complex, supralevator, associated with Crohn disease, or the patient is immunosuppressed.

Management

Main treatment: incision and drainage

• Prompt adequate drainage is the treatment.
• Incision is placed close to the anal verge when possible, minimizing the length of a future fistula tract.
• Break loculations, ensure adequate drainage, and send culture selectively rather than routinely.
• An examination under anesthesia is often appropriate for deep, recurrent, complex, or unclear disease.

Antibiotics: when?

• Cellulitis
• Systemic sepsis
• Immunosuppression
• Neutropenia
• Diabetes or other high-risk host factors
• Selected valvular/cardiac indications according to local guidance

Important complications

• Fistula-in-ano
• Recurrence or missed deep abscess
• Sepsis
• Fournier gangrene/necrotizing infection, especially in diabetes or immunosuppression

Viva line

A perianal abscess is treated by urgent incision and drainage. Antibiotics alone are inadequate because the infection is a closed pus collection.

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4. Fistula-in-ano

Definition

Typical history

• Previous abscess, often drained
• Cyclical pain/swelling followed by spontaneous purulent discharge and relief
• Persistent external opening with discharge, staining, or pruritus
• Recurrent abscess in the same site

Goodsall rule

• External opening anterior to transverse anal line: usually a straight radial tract to the nearest internal opening.
• Posterior external opening: often curves to the posterior midline internal opening.
• Exception: an anterior external opening more than 3 cm from the anal verge may follow a curved tract to the posterior midline.

Parks classification

Simple versus complex fistula

• Low intersphincteric or low transsphincteric tract
• Minimal external sphincter involved
• No Crohn disease, radiation, malignancy, or significant continence risk

• High tract or substantial external sphincter involvement
• Multiple tracts, horseshoe extension
• Recurrent disease
• Female anterior tract
• Crohn disease, radiation, malignancy
• Baseline incontinence, prior sphincter injury, or obstetric injury

Investigations

• Clinical examination and proctoscopy/anoscopy
• MRI pelvis is preferred for complex/recurrent fistula, Crohn disease, suspected deep sepsis, or uncertain anatomy.
• Endoanal ultrasound is another option where available.
• Colonoscopy if symptoms suggest Crohn disease or another colonic pathology.

Management principles

1. Drain sepsis first

2. Fistulotomy

• Lay open the tract.
• Best for simple low fistulas in patients with good sphincter function.
• High cure rate, but inappropriate division of sphincter can cause incontinence.

3. Seton

• Loose/draining seton: maintains drainage and controls sepsis, particularly for complex fistulas or Crohn disease.
• Cutting seton: gradually divides tissue. Used selectively because of continence concerns.

4. Sphincter-preserving options

• LIFT: ligation of intersphincteric fistula tract
• Endorectal advancement flap
• Selected minimally invasive/endoscopic/laser approaches, although long-term recurrence data are less certain

Crohn disease warning

• Multiple or complex fistulas
• Recurrent abscesses
• Large edematous skin tags
• Fissures off the midline
• Diarrhea, abdominal pain, weight loss, or extraintestinal disease

Viva line

In fistula surgery, the priority is not just tract cure. It is cure with preservation of continence.

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5. Anal fissure

Definition

Typical presentation

• Severe sharp pain during defecation, classically “razor blade” or “passing glass”
• Pain can persist for minutes to hours afterward due to internal sphincter spasm
• Small-volume bright-red blood on toilet paper or stool
• Constipation due to fear of defecation

Acute versus chronic

Site

• Posterior midline: about 75%, classic location
• Anterior midline: more common in women
• Lateral/off-midline, multiple, painless, or atypical fissure: investigate for Crohn disease, TB, HIV, syphilis, herpes, leukemia, or malignancy. Sabiston Textbook of Surgery, p. 2160.

Pathophysiology: the fissure cycle

Examination

• Diagnosis is often clinical.
• Gentle separation of buttocks may reveal the tear or sentinel tag.
• Avoid a painful DRE/anoscopy in clear acute fissure. It can worsen spasm and pain.
• Consider examination under anesthesia and biopsy if atypical, nonhealing, suspicious, or diagnosis is unclear.

Treatment

Acute fissure

• Fiber, fluids, stool-softening regimen as appropriate
• Avoid straining
• Warm sitz baths
• Simple analgesia and topical local anesthetic if needed

Chronic fissure: pharmacologic “chemical sphincterotomy”

1. Topical calcium-channel blocker
   • Diltiazem or nifedipine, commonly preferred due to fewer headaches
2. Topical nitrate
   • Glyceryl trinitrate/nitroglycerin
   • Effective but headache often limits adherence
3. Botulinum toxin injection
   • Temporary internal sphincter relaxation
   • Consider when topical treatment fails or when avoiding surgical sphincter division

Surgery: lateral internal sphincterotomy, LIS

• Divides part of the internal anal sphincter laterally.
• Most effective treatment for selected chronic fissures refractory to conservative/medical treatment.
• Provides excellent healing and rapid pain relief.

• Baseline fecal incontinence
• Previous obstetric anal sphincter injury
• Known sphincter injury
• Prior anorectal surgery
• Inflammatory bowel disease or other high-risk contexts

Viva line

Chronic fissure is maintained by internal sphincter hypertonia and local ischemia; treatment breaks this cycle by ensuring soft stool and reducing sphincter tone.

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6. Hemorrhoids

Definition

Internal versus external

Grading of internal hemorrhoids

Symptoms

• Painless bright-red bleeding with defecation
• Prolapse
• Mucus discharge, soiling, pruritus
• Discomfort rather than severe pain

Examination

• Inspect at rest and with strain.
• DRE to exclude mass and assess other pathology.
• Anoscopy is key for diagnosis and grade assessment.
• Consider colonoscopy/endoscopy for selected patients with rectal bleeding, especially if bleeding source is uncertain or red flags are present.

Treatment ladder

1. Conservative treatment

• Increase dietary fiber and fluid intake
• Avoid straining and prolonged time on the toilet
• Treat constipation/diarrhea
• Toilet habit education
• Short-term symptom relief with topical agents may help, but they do not correct prolapse

2. Office procedures

• Most common and generally most effective office treatment.
• Band is placed above dentate line.
• Band causes ischemic necrosis/scarring and mucosal fixation, reducing prolapse.
• Do not band too low, because it causes severe pain.
• Complications: pain, delayed bleeding, urinary retention; pelvic sepsis is rare but dangerous.

• Injection sclerotherapy
• Infrared coagulation

3. Surgery

• Most appropriate for:
  • Symptomatic grade III-IV disease with substantial external component
  • Mixed hemorrhoids
  • Failure of office therapy
• Effective but associated with postoperative pain, urinary retention, bleeding, anal stenosis, and rarely continence issues.

• May reduce pain but can have recurrent prolapse.

• Treats prolapsing internal hemorrhoids by mucosal resection/fixation above the dentate line.
• Not generally for external disease and may have recurrence or uncommon serious complications.

Thrombosed external hemorrhoid

• Acute tender, blue-purple perianal nodule due to clot in external hemorrhoidal tissue.
• If severe pain and early presentation, often within about 48-72 hours, excision/evacuation can give rapid relief.
• Later or milder disease: analgesia, sitz baths, stool regulation, and observation are reasonable.
• The key point: it is below the dentate line, so any procedure needs adequate anesthesia. Pfenninger and Fowler's Procedures for Primary Care, p. 2160.

Viva line

Internal hemorrhoids bleed and prolapse but are usually painless. Pain suggests thrombosis, fissure, abscess, strangulation, or another diagnosis.

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7. Rapid comparison for exams and ward rounds

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8. Red flags requiring senior/colorectal review

• Fever, tachycardia, sepsis, urinary retention, rapidly worsening pain
• Diabetes, severe immunosuppression, neutropenia
• Crepitus, skin necrosis, severe pain out of proportion: consider Fournier gangrene
• Recurrent/deep abscess or multiple external openings
• Suspected Crohn disease
• Lateral, multiple, ulcerated, indurated, painless, or nonhealing fissure
• Anal mass, unexplained anemia, weight loss, altered bowel habit, or persistent rectal bleeding
• Baseline continence problem before LIS or fistula surgery

One-minute memory summary

• Abscess: pus under pressure. Drain it.
• Fistula: chronic tract after abscess. Map it, then protect sphincter.
• Fissure: painful tear plus internal sphincter spasm. Soft stool plus sphincter relaxation.
• Hemorrhoids: painless bleeding/prolapse from anal cushions. Fiber first, band selected internal disease, operate advanced/mixed disease.