Chapter 04 — Anal Fissure — Break the Pain–Spasm–Ischaemia Cycle

Purpose: diagnose fissure by gentle inspection, relax the internal sphincter medically for 6–8 weeks, protect continence when medicine fails — and never miss the atypical fissure.

🎨 INFOGRAPHIC / VISUAL BLUEPRINT — CHAPTER 04

• Chapter colour palette: Warm Amber (#B45309) header bar, Cream-Gold (#FFFBEB) panels, Deep Brown (#451A03) text.
• Hero graphic: Circular five-step cycle (hard stool → tear → pain → internal sphincter spasm → posterior midline ischaemia → non-healing) with arrows showing where each treatment acts (fibre, lidocaine, topical calcium-channel blockers or GTN, botulinum toxin, sphincterotomy), plus an “off-midline” warning badge listing Crohn’s, TB, HIV/herpes, syphilis/LGV, and cancer.
• Icon set: Broken-glass shard (pain), circular arrows (cycle), ointment tube, syringe (botulinum toxin), shield with crack (continence risk), red compass needle pointing off-midline.
• Bedside aphorism banner: “Use anatomy, not the clock. And never let topical GTN meet a PDE5 inhibitor.”

1. Recognise It on Gentle Inspection

A classic fissure is diagnosed by gently parting the buttocks while the patient bears down slightly. A DRE or anoscopy is not required for the diagnosis and is often intolerable in the acute phase.

Table 4.1 — Acute versus chronic fissure

The location rule: midline is typical — anything else must be investigated

• Typical: posterior midline (the commonest site — the posterior commissure has the poorest anodermal blood supply); anterior midline (more frequent in women, especially postpartum).

• Atypical: lateral, multiple, painless, large or deep, irregular, indurated, or non-healing. Think C-T-H-S-C: Crohn’s disease · Tuberculosis · HIV, herpes, CMV · Syphilis and chlamydia (LGV) · Cancer (anal squamous cell carcinoma, leukaemic or lymphomatous infiltration).

• Action for an atypical fissure: 🟡/🔴 urgent specialist referral for examination under anaesthesia with biopsy and cultures or PCR, colonoscopy where indicated, and a sexual-health screen. Never perform a sphincterotomy on an atypical fissure.

2. The 6–8 Week Medical Trial

Every chronic fissure persists through the same loop: hard stool → tear → pain → reflex internal-sphincter spasm → posterior midline ischaemia → non-healing. Healing requires softer stool and a relaxed internal sphincter (ASCRS 2023).

Table 4.2 — Treatment options

Uncontrolled manual anal stretch (Lord’s procedure) is obsolete because of unpredictable sphincter injury. Low resting pressure, previous obstetric sphincter injury, prior anal surgery, or IBD favour sphincter-sparing options (botulinum toxin or anocutaneous advancement flap).

Algorithm 4.1 — Anal fissure

[TEARING PAIN ON DEFECATION + BRIGHT-RED BLOOD]
 Gentle buttock separation; DRE/anoscopy only if tolerated
|
+-- ATYPICAL? lateral, multiple, painless, large, irregular,
|   indurated, non-healing, or systemic features
|     -> NO sphincterotomy
|        urgent referral: EUA + biopsy + cultures/PCR;
|        screen for Crohn's, TB, HIV, herpes, syphilis, LGV,
|        anal cancer, leukaemia (Chapters 07, 09, 11)
|
+-- TYPICAL midline fissure
    |
    +-- ACUTE (< 6 weeks)
    |     -> GREEN: fibre + fluids + stool softener,
    |        warm sitz baths, topical lidocaine;
    |        add topical diltiazem/nifedipine if severe
    |
    +-- CHRONIC (>= 6 weeks: tag, papilla, exposed fibres)
          -> GREEN: 6-8 week trial of topical CCB
             (or GTN if no PDE5 inhibitor / riociguat)
          -> not healed at 6-8 weeks -> surgical referral
             +-- normal continence and resting tone
             |     -> tailored LIS (most durable) or
             |        botulinum toxin (shared decision)
             +-- continence risk (OASIS, multiparity,
                   prior anal surgery, low tone, IBD)
                   -> botulinum toxin or advancement flap
                      (sphincter-sparing)

3. Dangerous Mimics

Table 4.3 — Fissure mimics

4. Role-Targeted Action Boxes

🚑 ER DOCTOR ACTION BOX

• Skip the traumatic DRE and anoscopy in an acute fissure. If gentle inspection shows a fresh posterior midline tear and the patient is in severe pain, treat the spasm (topical lidocaine, topical calcium-channel blocker, stool softener, oral analgesia).
• Fever, induration, or a suspected mass changes everything — this is not a simple fissure; refer the same day for examination under anaesthesia.

🩺 FAMILY MEDICINE / GP CLINIC BOX

• Teach ointment use: a pea-sized amount applied with a gloved fingertip to the anal margin twice daily for the full 6–8 weeks. “The pain usually settles within 2 weeks, but the skin needs 6–8 weeks to heal — stopping early lets the tear reopen.”
• Ask about PDE5 inhibitors (including “herbal” erection products, which may contain them) and riociguat before prescribing GTN. Prefer diltiazem when in doubt.
• Review at 6–8 weeks. Refer if not healed, or earlier if atypical.
• For a postpartum anterior fissure, ask about continence and obstetric sphincter injury before any surgical referral.

🏥 ER & WARD NURSE CARE AND SBAR BOX

• Document by anatomy, never by the clock. Chart “posterior midline” or “anterior midline” — the same fissure acquires different clock numbers in lithotomy, prone, and left lateral positions.
• GTN counselling: first doses may cause headache or light-headedness; apply while sitting or lying, and use simple analgesia for headache.

💊 CROSS-SPECIALTY PRESCRIBING TRAP

• Topical GTN plus PDE5 inhibitors (sildenafil, vardenafil, tadalafil, avanafil) or riociguat can cause profound hypotension and syncope. Do not use GTN within 24 hours of sildenafil or vardenafil, or 48 hours of tadalafil. Topical diltiazem or nifedipine avoids this interaction.

⛔ NEVER DO THIS

• Never perform or request a sphincterotomy for an atypical fissure, or in active Crohn’s disease.
• Never prescribe GTN without asking about PDE5 inhibitors and riociguat.
• Never force a DRE or anoscope through acute fissure spasm.
• Never request a manual anal stretch.

📝 COMMON DOCUMENTATION ERROR

• Clock-face notation (“fissure at 6 o’clock”) without position — use anterior or posterior midline, or left or right lateral.
• “Fissure” without acute or chronic features (tag, papilla, exposed fibres) and without stating whether it is typical or atypical.
• Surgical referral without baseline continence, obstetric history, and previous anal surgery.

📨 REFERRAL URGENCY BOX

The Patient in Front of You — Chapter 04 Mini-Case

🧑‍⚕️ THE PATIENT IN FRONT OF YOU

A 29-year-old man presents with 4 weeks of “razor-blade” pain on defecation. Gentle inspection shows two ragged, relatively painless ulcers on the left and right lateral walls of the anal canal, with oedematous, violaceous skin tags. He reports 6 months of intermittent loose stools and 4 kg of unintentional weight loss.

Step 1 Spot the red-flag location. Lateral, multiple, relatively painless ulcers with oedematous tags are atypical — not idiopathic fissures.

Step 2 Build the differential (C-T-H-S-C). Perianal Crohn’s disease is most likely; also consider syphilis, herpes, HIV, TB, and anal cancer.

Step 3 Investigate. Faecal calprotectin, full blood count, CRP, ferritin, stool studies, HIV and syphilis serology, and rectal NAAT/HSV PCR as indicated.

Step 4 Refer and protect. Urgent gastroenterology and colorectal referral for ileocolonoscopy, pelvic MRI if fistulising disease is suspected, and examination under anaesthesia with biopsy. No sphincterotomy.

Board-Style Question — Chapter 04

A 34-year-old woman (three vaginal deliveries, a third-degree obstetric tear 4 years ago, occasional flatus incontinence) has a chronic anterior midline fissure that has not healed after 8 weeks of topical diltiazem 2% and fibre. Resting tone is normal to low. Which next step best balances healing and continence?

• A. Lateral internal sphincterotomy extended to the dentate line
• B. Botulinum toxin injection (or an anocutaneous advancement flap)
• C. Manual four-finger anal stretch under general anaesthesia
• D. Repeat topical GTN 0.4% combined with oral sildenafil

Answer and explanation

• ❌ A Extended sphincterotomy in a patient with prior sphincter injury and existing flatus incontinence risks permanent incontinence; even when LIS is appropriate it is tailored to the fissure apex.
• ✅ B Correct. With prior obstetric sphincter injury, an anterior fissure, existing incontinence symptoms, and low-normal tone, sphincter-sparing options — botulinum toxin or an anocutaneous advancement flap — are preferred (ASCRS 2023).
• ❌ C Manual anal stretch causes uncontrolled sphincter tearing and is obsolete.
• ❌ D Nitrates and PDE5 inhibitors must never be combined because of severe hypotension.

Ten-Item Rapid Revision Checklist — Chapter 04

• 01 I diagnose fissure by gentle inspection without forcing a DRE.
• 02 I distinguish acute (< 6 weeks) from chronic (sentinel tag, papilla, exposed fibres).
• 03 I recognise atypical fissures and apply C-T-H-S-C.
• 04 I start fibre, fluids, sitz baths, and topical lidocaine for every fissure.
• 05 I use topical diltiazem or nifedipine as preferred first-line therapy for 6–8 weeks.
• 06 I ask about PDE5 inhibitors and riociguat before prescribing GTN.
• 07 I teach correct ointment application and duration.
• 08 I review at 6–8 weeks and refer non-healing fissures.
• 09 I document continence and obstetric history in every surgical referral.
• 10 I record location anatomically, never by clock face.

Five Most Dangerous Mistakes — Chapter 04

1. ⚠️ Referring an atypical fissure for sphincterotomy and missing Crohn’s disease, infection, or cancer.
2. ⚠️ Combining GTN with a PDE5 inhibitor.
3. ⚠️ Stopping topical therapy after 2 weeks because pain has improved.
4. ⚠️ Recommending sphincterotomy in a woman with prior obstetric sphincter injury without considering sphincter-sparing options.
5. ⚠️ Calling an indurated, non-healing anal ulcer a “chronic fissure” for months.

Suggested Figure and Table Captions for the Medical Illustrator — Chapter 04

• Figure 4.1. The pain–spasm–ischaemia cycle with treatment targets.
• Figure 4.2. Chronic fissure triad: sentinel tag, hypertrophied papilla, exposed internal-sphincter fibres.
• Figure 4.3. Typical (posterior and anterior midline) versus atypical (lateral, multiple) fissure locations.
• Table 4.1. Acute versus chronic fissure.
• Table 4.2. Treatment options and verdicts.
• Table 4.3. Fissure mimics.
• Algorithm 4.1. Anal fissure.