A 32-year-old woman presents with severe pain during and after defecation for the past 3 weeks. She reports bright red bleeding on toilet paper and describes the pain as sharp and burning, lasting for 1–2 hours after bowel movements. On external examination, a visible tear is seen in the posterior midline of the anal verge. Digital rectal examination is deferred due to severe pain. She denies fever, purulent discharge, or constitutional symptoms. What is the most likely diagnosis?

Explanation

## Diagnosis: Acute Anal Fissure ### Clinical Presentation **Key Point:** Anal fissure presents with the classic triad of severe pain during/after defecation, visible tear at the anal verge, and bright red bleeding on toilet paper. ### Distinguishing Features | Feature | Acute Fissure | Chronic Fissure | Hemorrhoids | Fistula | |---------|---------------|-----------------|-------------|----------| | **Pain timing** | During & after defecation | Chronic, persistent | Usually painless | Variable | | **Visible finding** | Linear tear at verge | Tear + sentinel pile + skin tag | Internal/external hemorrhoids | Opening(s) with discharge | | **Bleeding** | Bright red, on paper | Bright red | Bright red, may drip | Purulent drainage | | **Duration** | < 6 weeks | > 6 weeks | Variable | Chronic, recurrent | | **Fever/systemic signs** | Absent | Absent | Absent | May be present | ### Pathophysiology 1. Trauma from hard stool or diarrhea → mucosal tear 2. Severe pain → internal anal sphincter spasm → ischemia 3. Ischemia → delayed healing and chronicity (if untreated) ### Location **High-Yield:** ~90% of fissures occur in the **posterior midline** (as in this case); 10% anterior. Fissures at lateral margins or multiple locations suggest **Crohn disease** or **syphilis**. ### Management Algorithm ```mermaid flowchart TD A["Acute anal fissure<br/>< 6 weeks"]:::outcome --> B{"Conservative<br/>treatment response?"}:::decision B -->|"Yes<br/>4-6 weeks"| C["Stool softeners<br/>Sitz baths<br/>Topical anesthetics"]:::action B -->|"No or<br/>Chronic"| D{"Failed medical<br/>management?"}:::decision D -->|"Yes"| E["Botulinum toxin<br/>or<br/>Lateral internal<br/>sphincterotomy"]:::action C --> F["Healing"]:::outcome E --> F ``` ### Clinical Pearl **Clinical Pearl:** The severe pain in acute fissure is disproportionate to the size of the lesion — it is driven by internal anal sphincter spasm and ischemia, not just the tear itself. This explains why pain relief is the primary therapeutic goal. ### Why DRE Was Deferred The examiner correctly deferred digital rectal examination due to severe pain; forcing the examination may worsen spasm and delay healing. In acute fissure, diagnosis is clinical and visual. [cite:Sabiston Textbook of Surgery Ch 28]