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Can underlying conditions (Crohn’s disease, sexually transmitted infections, childbirth) cause or complicate anal fissures?
Executive summary
Anal fissures are most often caused by trauma from passing hard stools or straining, but multiple clinical sources say underlying medical conditions — notably Crohn’s disease and certain infections — can cause or complicate fissures, and events like vaginal childbirth and anal trauma are also implicated [1] [2] [3]. Guidelines and reviews note that fissures in atypical (lateral or multiple) locations should prompt investigation for secondary causes such as Crohn’s, STIs (including syphilis, HIV) or malignancy; management then targets both the fissure and the underlying disorder [2] [4].
1. Primary cause: hard stools and sphincter spasm — the common pathway
Major clinical summaries emphasize that the typical initiating event for an anal fissure is mechanical stretching or tearing of the anal lining from hard stools, constipation, or straining; this leads to internal sphincter spasm, reduced blood flow and a cycle that prevents healing — the pattern described as primary or “typical” fissures [1] [5].
2. Crohn’s disease: a recognized underlying cause that changes evaluation and treatment
Authoritative reviews and textbooks classify Crohn’s disease as a cause of “secondary” or atypical fissures — especially when fissures are lateral, multiple, recurrent, or otherwise atypical — and advise further workup (endoscopy/biopsy) because management must address both fissuring and the inflammatory bowel disease [2] [4] [6].
3. Sexually transmitted infections and other infections: documented contributors
Multiple clinical reviews list infectious causes and sexually transmitted infections (syphilis, HIV, herpes, chlamydia, HPV among examples) as associated with fissures or fissure-like ulcers; when infection is suspected, clinicians investigate and treat the infection as part of care [4] [7] [2].
4. Childbirth and anal trauma: obstetric contribution to fissures
Hospitals and health systems report vaginal childbirth and other local trauma (including anal intercourse or instrumentation) as risk factors for fissures; childbirth is singled out repeatedly as a precipitating event that increases fissure risk in otherwise healthy people [8] [3] [9].
5. How clinicians tell primary from secondary fissures — why location and recurrence matter
Sources emphasize a practical rule: most primary fissures occur in the midline (posterior or anterior); fissures that are lateral, multiple, chronic, or recurrent are considered “secondary” and trigger investigations for Crohn’s, infections or malignancy because those diagnoses alter management [2] [4] [6].
6. Treatment implications: treating the fissure vs treating the root cause
For primary fissures, conservative measures (fiber, stool softeners, topical relaxants, botulinum toxin, or surgical sphincterotomy if refractory) are common; for secondary fissures, the literature stresses treating the underlying condition (for example controlling Crohn’s or treating an STI) because healing and recurrence depend on addressing the root cause [1] [2] [5].
7. Evidence strength and clinical limitations — what the sources agree and where detail is limited
Clinical overviews and textbooks consistently list Crohn’s disease, infections, childbirth and anal trauma as causes or complicating factors [2] [4] [3], and they uniformly identify constipation/straining as the most common trigger [1] [5]. Available sources do not provide precise population-level risk estimates comparing each underlying condition’s absolute risk of causing fissures, nor detailed odds ratios for STIs or postpartum periods (not found in current reporting).
8. Practical takeaways for patients and clinicians
If a fissure is midline, acute and related to hard stool, standard conservative care is appropriate; if a fissure is lateral, multiple, chronic or recurrent, clinicians should investigate for Crohn’s, infections (including STIs), or malignancy and manage accordingly [1] [2] [4]. Explicitly discuss childbirth history, sexual practices, and symptoms of inflammatory bowel disease during evaluation so that secondary causes are not missed [8] [7].
Limitations: This summary relies on clinical reviews, institutional guidance and textbooks included in the search results; detailed quantitative risk data and long‑term comparative outcomes for fissures by specific underlying diagnosis are not present in the available reporting (not found in current reporting).