Anorectal Disorders

Anorectal Anatomy & Physiology - Foundation First

• Anal Canal: Length: Anatomical ~4 cm, surgical 2-3 cm.
  • Dentate (Pectinate) Line: Embryological division (endoderm/ectoderm). Columnar above, squamous below.
  • Hilton's Line: Intersphincteric groove.
• Sphincters:
  • Internal (IAS): Involuntary, smooth muscle, main resting tone.
  • External (EAS): Voluntary, striated muscle, pudendal nerve (S2-S4), squeeze.
• Blood Supply:
  • Above Dentate: Superior Rectal Artery (IMA); portal drainage.
  • Below Dentate: Inferior Rectal Artery (Internal Pudendal); systemic drainage.
• Nerve Supply:
  • Above Dentate: Autonomic (dull pain/pressure).
  • Below Dentate: Somatic (Inferior Rectal N. - sharp pain).
• Lymphatics: 📌 "Above Internal, Below Groin"
  • Above Dentate: Internal iliac nodes.
  • Below Dentate: Superficial inguinal nodes.

⭐ The dentate line dictates epithelium, neurovascular supply, lymphatic drainage, and thus pathology (e.g., internal vs. external hemorrhoids, pain perception).

Hemorrhoids & Anal Fissure - Painful Problems

Hemorrhoids: Dilated submucosal vascular cushions.

• Types: Internal (above dentate line), External (below dentate line).
• Goligher's Classification (Internal):
  • Grade I: Bleeds, no prolapse.
  • Grade II: Prolapses, reduces spontaneously.
  • Grade III: Prolapses, requires manual reduction.
  • Grade IV: Irreducible prolapse.
• Clinical Features: Painless bleeding (internal), pain (external, thrombosed internal), pruritus, prolapse.
• Management:
  • Conservative: High-fiber diet, sitz baths, adequate fluids.
  • Medical: Stool softeners, topical anesthetics/steroids.
  • Non-operative (Grades I-III): Rubber band ligation (RBL), Sclerotherapy, Infrared coagulation (IRC).
  • Surgical (Grades III-IV, failed non-op): Hemorrhoidectomy (Milligan-Morgan - open; Ferguson - closed), Stapled hemorrhoidopexy.

Anal Fissure: Linear tear/ulcer in anoderm, distal to dentate line.

• Types: Acute (<6 weeks), Chronic (>6 weeks; often with sentinel pile, hypertrophied anal papilla).
• Etiology: Hypertonic Internal Anal Sphincter (IAS), trauma from hard stools.
• Typical Location: Posterior midline (most common). Anterior midline (more common in females).
• Clinical Features: Severe tearing pain during/after defecation, bright red blood per rectum (BRBPR).
• Management:
  • Conservative: Sitz baths, stool softeners, high-fiber diet.
  • Medical: Topical 0.2% Glyceryl Trinitrate (GTN) ointment, topical 2% Diltiazem cream.
  • Surgical (Chronic, failed medical): Lateral Internal Sphincterotomy (LIS) - Gold Standard.

⭐ The most common site for an anal fissure is the posterior midline.

Anorectal Abscess & Fistula - Deep Dive Drains

Anorectal Abscess: Localized pus collection.

• Types: Perianal (most common, 60%), Ischiorectal (20%), Intersphincteric (5%), Supralevator (4%).
  • Clinical: Acute pain, swelling, fluctuance, fever.
  • Microbiology: Polymicrobial (E. coli, Bacteroides spp.).
  • Management: Prompt Incision & Drainage (I&D). Antibiotics if cellulitis/systemic signs/immunocompromised.

Fistula-in-ano: Chronic abnormal tract between anal canal epithelium and perianal skin.

• Etiology: Cryptoglandular (most common); Crohn's, TB, malignancy.
• Goodsall's Rule: Predicts tract path.
  • Anterior external opening: Straight radial tract.
  • Posterior external opening: Curved tract to posterior midline.
  • Exception: Anterior opening >3 cm from anal verge may curve posteriorly. ⭐> Goodsall's rule helps predict the track of a fistula-in-ano based on the external opening's location relative to the transverse anal line.
• Parks' Classification: (📌 Mnemonic: "ITSE" - In The Sphincter Eventually)

  Type	Description	Frequency
  Intersphincteric	Between internal & external sphincters	~70%
  Transsphincteric	Crosses both sphincters	~25%
  Suprasphincteric	Tract passes above puborectalis muscle	~5%
  Extrasphincteric	Tract passes outside sphincter complex	~1%

• Investigations: MRI (gold standard for complex/recurrent), EUA (Examination Under Anesthesia).

• Management Principles: Eradicate sepsis, heal tract, preserve sphincter function, prevent recurrence.

  • Options: FistuLOTOMY (lay open), FistuLECTOMY (excision), Seton, LIFT, VAAFT, Advancement Flaps. Choice depends on tract complexity & sphincter integrity.

Other Anorectal Conditions - Beyond the Basics

• Pilonidal Sinus: Natal cleft hair follicle blockage. Features: pain, swelling, discharge. Management: hygiene, I&D (abscess), excision (e.g., Karydakis).
• Rectal Prolapse: Types: Mucosal, Full-thickness (Procidentia). Features: concentric mucosal folds, mass, incontinence. Differentiate: hemorrhoids (radial folds). Management: conservative; surgical (e.g., Delorme, rectopexy).
• Pruritus Ani: Common causes: idiopathic, poor hygiene, infections (fungal, pinworm), skin conditions (eczema). Investigation: clinical. Management: address cause, hygiene, topical steroids (short-term).
• Anal Canal Tumors: Types: Squamous Cell Carcinoma (SCC - most common, HPV-related), adenocarcinoma, melanoma. Features: bleeding, pain, mass. Staging: TNM (brief). Management: SCC (Nigro protocol: chemoradiation), others (surgery).

  ⭐ Squamous cell carcinoma is the most common anal canal malignancy, often HPV-linked.

High‑Yield Points - ⚡ Biggest Takeaways

• Internal hemorrhoids: painless bleeding, above dentate line; Grade IV irreducible.
• Anal fissure: posterior midline most common; lateral suggests Crohn's/TB. Sentinel pile is key.
• Perianal abscess is most frequent; supralevator abscess is deep and often missed.
• Fistula-in-ano: Goodsall's rule predicts internal opening; Seton for complex types.
• Pilonidal sinus: Acquired, midline pits in natal cleft, common in hirsute individuals.
• Anal canal cancer: Squamous Cell Carcinoma (SCC) is most common, strongly HPV-associated.