Anal Fissure

First half of ASCRS Ch12 (second chapter of Part II, "Anorectal Disease"). No population studies establish exact incidence, but anal fissures are common and a frequent driver of anorectal consultation due to pain severity and QoL impact.

Definition, presentation, and etiology

A linear tear of the anal mucosa, usually extending from the dentate line to the anal verge. Chief complaints: anal pain and bleeding with defecation. Acute fissures are symptomatic <6 weeks; chronic fissures persist >6 weeks, with persistently high internal sphincter (IAS) tone driving chronicity and causing pain even after local anesthetic. Chronic fissures show indurated edges, visible sphincter muscle at the base, a proximal hypertrophic papilla, and a distal sentinel tag.

Location: 90% posterior midline. Anterior midline fissures are more common in women (10–25%) than men (1–8%); concomitant anterior+posterior fissures occur in 3%. Atypical fissures (lateral location, broad base, skin changes) should raise concern for inflammatory bowel disease (see Crohn's cross-link below), tuberculosis, HIV, or syphilis — biopsy-directed treatment of the causative organism/disease is indicated rather than standard fissure management.

Only 13% of patients with fissuring disease report constipation, despite constipation/hard stools being the commonly assumed culprit (anoderm trauma from hard stool or high-frequency diarrhea).

Obstetric fissures: 11% of chronic fissures are associated with difficult or instrumented deliveries, most common anterior midline. Notably, these are not associated with increased sphincter tone but with normal or even low pressures — an etiologically distinct subgroup from the high-tone majority, with direct treatment implications (see Local Advancement Flaps below).

Pathophysiology

Two converging mechanisms are implicated:

Nitric oxide synthase (NOS) deficiency: internal sphincter biopsies from chronic-fissure patients show little/no NOS compared to abdominoperineal-resection control specimens, implying a loss of the normal NOS-mediated relaxation signal.
Ischemia: postmortem angiography shows anoderm perfusion (via the inferior rectal arteries, which traverse the internal sphincter) is inversely related to internal sphincter pressure — high sphincter tone directly causes low anodermal perfusion, framing a chronic fissure as a nonhealing ischemic ulcer. Cadaver studies additionally show a relative paucity of arterioles specifically in the posterior midline, explaining the strong positional predilection.

Medical/pharmacologic treatment

First-line for all acute fissures and initial management of chronic fissures.

Topical agents / conservative care: stool softeners, psyllium/fiber, sitz baths, topical lidocaine gel. Conservative management alone heals 16–31% of acute and chronic fissures; lidocaine does not increase healing rates over placebo but provides symptomatic pain relief; fiber maintenance therapy reduces recurrence.
Topical nitrates (isosorbide dinitrate, glyceryl trinitrate): heal ~50% of chronic fissures (13.5% absolute improvement over placebo per a Cochrane review of 77 studies/5031 patients: 48% vs. 35%), but recurrence is high (~50% of nitrate-healed fissures recur) and side effects (primarily headache) limit contemporary use.
Topical calcium channel blockers (nifedipine, diltiazem): healing close to 90% of chronic fissures in some series; a double-blind multicenter RCT found nifedipine healed 95% of acute fissures within 21 days vs. 50% for hydrocortisone/lidocaine control, with a 30% resting-pressure reduction confirmed manometrically. Equivalent efficacy to nitrates with fewer side effects per Cochrane — considered first-line for chronic fissures. Cure rates are higher with three-times-daily dosing over a 3-month course.
Botulinum toxin (Botox) injection — second-line, used when topical therapy fails. Healing rates 27–96% across a wide dosing range (20–100+ IU, varied injection sites). Advantage over nitrates/CCBs: no frequent application schedule, no similar side-effect profile. Disadvantages: one meta-analysis found no significant advantage over nitrate application or placebo; a separate meta-analysis comparing Botox to sphincterotomy found lower healing rates but also lower incontinence rates with Botox — the expected efficacy/morbidity trade-off between medical and surgical management. Most common side effect: temporary incontinence (particularly to flatus), up to 18% of patients.
Across medical therapies overall: nitrates are marginally more efficacious than placebo; Botox and CCBs are roughly equivalent to nitrates in efficacy but with fewer side effects. No medical therapy arm compares favorably to surgical treatment on healing rate — but all carry a lower permanent-incontinence risk than surgery.

Operative treatment

Anal dilation — historic interest only; a 2011 Cochrane review of 7 RCTs found it less effective than sphincterotomy with higher incontinence rates (OR 4.03, 95% CI 2.04–7.46).
Pneumatic balloon dilation — a more controlled modern variant (40mm-diameter/60mm-long balloon, 10mm protruding, inflated to 20 psi for 6 min). One study found fissure-healing rates of 83.3% (pneumatic dilation) vs. 92% (LIS), but at 24-month follow-up, incontinence was 0% with pneumatic dilation vs. 16% with LIS (P<0.0001) despite similar manometric pressure reductions — suggesting a real advantage on the efficacy/continence trade-off worth further study, not yet practice-changing given it's a single study.
Lateral internal sphincterotomy (LIS) — the gold standard for chronic fissures, with multiple RCTs showing superior symptom resolution vs. conservative medical management. Healing rates 88–100%; incontinence rates 8–30% (transient in most, <2 months, but prolonged >2 months in 3–7% — see Fecal Incontinence for this mechanism in context of iatrogenic sphincter-defect incontinence generally). Traditional LIS (sphincterotomy to the dentate line) has lower recurrence but higher permanent-incontinence risk than "tailored" sphincterotomy (divided only to the apex of the fissure) — tailored sphincterotomy is now the preferred approach, preserving more sphincter and lowering incontinence while maintaining similar/only slightly lower healing rates. Repeat LIS on the contralateral side is an option for recurrent fissures (one series: 57 patients, 12.5±4.2-year follow-up, 98% healing, 4% minor incontinence to flatus/seepage).
Technique: open (incision exposing the intersphincteric groove, IAS divided to fissure height under direct vision) vs. closed (blind submucosal division via a narrow-bladed scalpel through the intersphincteric groove) — a Cochrane review found no difference in fissure persistence or incontinence between techniques.
LIS may be considered first-line surgical treatment (bypassing a medical-therapy trial) in patients without prior obstetric injury, IBD, prior anorectal surgery, or sphincter weakness — i.e., patients with chronic fissures and no underlying continence risk.
Local advancement flaps — first-line surgical treatment specifically for fissures associated with normal or low anal pressure — most often the obstetric/postpartum subgroup above. Typically anocutaneous flaps (dermal V-Y or house flap). One RCT (Giordano et al.) found a 98% healing rate independent of anal tonicity, no recurrence/incontinence at 6 months, but a 6% rate of new-site fissure formation. Can be combined with sphincterotomy or Botox to simultaneously address the nonhealing wound and any underlying hypertonicity: a randomized study (50 LIS / 50 V-Y flap / 50 combined) found 1-year healing rates of 84% (LIS), 48% (V-Y flap alone), 94% (combined) and recurrence rates of 4%, 22%, 2% respectively (p=0.001/0.01) — combined therapy outperformed either alone.
Fissurotomy and fissurectomy — not standard treatment options. Fissurotomy (incising/dividing the chronic subcutaneous tract, left open to heal secondarily) had 98% symptom resolution in one 109-patient series. Fissurectomy (excision of the chronic wound ± sentinel pile) is associated with higher recurrence (3%) and incontinence (6%) than sphincterotomy in a Cochrane review (OR 8.07 favoring sphincterotomy over fissurectomy for treatment failure) — one included study concluded fissurectomy is not a procedure of choice for this reason. Combining fissurectomy with isosorbide dinitrate cream or Botox has shown better results (100% healing without recurrence in small series) than fissurectomy alone.

Atypical fissures

Most commonly seen in Crohn's disease and sexually transmitted diseases.

Crohn's disease — per this chapter, Crohn's fissures usually present as deep, painful ulcerations, treated with Crohn's medical therapies; surgery is rarely used given a perceived risk of poor wound healing, perianal deformity, and incontinence. Optimal medical management may resolve more than half of cases. This directly conflicts with Crohn Disease's existing Sabiston-sourced characterization of Crohn's fissures as "usually lateral, relatively painless, large, and indolent" — flagged explicitly as an unresolved discrepancy between the two textbook sources rather than silently reconciled; painful vs. painless is not a matter of framing/emphasis, it's a directly contradictory clinical description. Multidisciplinary care is emphasized for anorectal Crohn's pathology generally.

Update (2026-08-25): ASCRS Ch47 - Anorectal Crohn's Disease — now ingested — describes atypical CD fissures/cavitating ulcers as causing "pain, bleeding, and, occasionally, pruritus," siding with this chapter's "painful" characterization rather than the Sabiston-sourced "relatively painless" one (now 2-against-1 across the wiki's sources). Still not treated as resolved given the direct contradiction remains unexplained, consistent with this wiki's discrepancy-flagging convention. - STI-related — HIV-related fissures are most common among STI etiologies; may present as deep broad-based ulcers or typical-appearing fissures, and are not associated with internal sphincter hypertonicity (a mechanistic distinction from ordinary fissures). Short-term treatment: surgical debridement and intralesional steroid injection; long-term symptom control depends on optimizing antiretroviral therapy. See Anorectal Sexually Transmitted Infections for this wiki's fuller HIV-anal-ulcer content (typically tender, necrotic, exudative, off-midline, associated with a hypotonic sphincter — internal sphincterotomy not advised unless clearly distinguished from ulcerating disease).

Conclusion

Anal fissures are common and usually treatable conservatively. Long-standing (>6 week) fissures should get topical calcium channel blockers plus sitz baths/fiber as first-line; Botox is added when medical management fails. LIS is the standard surgical treatment for chronic fissures with hypertonic sphincters, and may be first-line surgery in patients without continence risk factors. Advancement flaps are the option for symptomatic chronic fissures with hypotonicity or compromised continence.

Anal Stenosis — a fissure can be the cause or result of stenosis; several of that page's reconstructive flap techniques (V-Y, diamond, house) are shared or adapted from this page's advancement-flap approach.
Fecal Incontinence — LIS/dilation as iatrogenic causes of sphincter-defect incontinence.
Crohn Disease — atypical/Crohn's fissures; see the flagged pain-characterization discrepancy above.
Pediatric Colorectal Disorders — pediatric-specific epidemiology (anterior-midline predominance in females), GTN trial data, and the sphincter-surgery caution specific to small children.
Hemorrhoids — shares anoderm/sphincter anatomy and several of the same reconstructive flap techniques when treating post-hemorrhoidectomy complications.
Pruritus Ani — fissures are listed among the anorectal-disorder causes of anal pruritus in that page's differential.
Anorectal Sexually Transmitted Infections — fuller content on HIV-related anal ulcers/fissures.

Open items / gaps

~~The Crohn's-fissure pain-characterization discrepancy (above) is unresolved between this chapter and the existing Sabiston-sourced Crohn Disease content — worth revisiting when ASCRS Ch47 ("Anorectal Crohn's Disease," a dedicated chapter) is ingested.~~ Partially addressed (2026-08-25) — Ch47 is now ingested and sides with this page's "painful" characterization (see the Update note above); the underlying Sabiston-vs-everyone-else contradiction is still not resolved, just now better-evidenced as likely wrong.
Pneumatic balloon dilation vs. LIS continence outcomes are based on a single study — worth updating if a larger comparative trial is published.

Colorectal LLM Wiki