Patient guide
BUILD NOTE: this page was expanded for the refresh. Dr Chen’s original text is preserved in the first two sections. The added clinical detail and all cited figures have NOT yet been read by him and must be confirmed before the domain cutover.
An anal fissure is a common and debilitating condition that can cause pain, discomfort and disability far exceeding what might be expected from the size of the lesion. The pain, frequently described as “cutting” in nature, usually occurs during the passage of stools and can continue even after defecation. This is usually accompanied by a little fresh bleeding.
The tear itself is small and sits in the lining just inside the anal opening,1 an area that is highly sensitive. An injury this small can cause pain out of proportion to its size.
An anal fissure represents an ulcer near the anal verge and is believed to be caused by the passage of hard stools tearing the lining of the anus. Less commonly, severe diarrhoea can do the same.
What keeps a fissure from healing is a cycle rather than the original injury. The tear causes pain, the pain causes the internal sphincter to go into spasm, and that spasm reduces blood flow to the very area that needs to heal. Treatment is aimed at relaxing the sphincter, not at the tear itself.
Between 80 and 90% of fissures sit in the posterior midline, 5 to 10% in the anterior midline, and only 2 to 5% elsewhere.1 These two midlines are the weakest points of the anal canal, where the skin is bound more tightly to the muscle beneath.1 A fissure that sits away from the midline may be a sign of something more serious.
An acute fissure is a fresh, superficial tear. One that fails to heal after four weeks is considered chronic.1
A chronic fissure looks different on examination. Rather than a clean split, it has developed secondary changes:
An acute fissure will often resolve with stool softeners and warm soaks alone. A chronic one usually will not, and continuing the same measures for months is rarely the right answer.
The classic description is a searing or tearing pain with each bowel movement, accompanied by bright red bleeding.1 People commonly report that:
Pain is also the single most useful feature for telling a fissure apart from piles. Bleeding from internal piles is usually painless. Sharp pain with bowel movement may be indicative of a fissure.
A fissure is usually diagnosed by history and gentle examination. A full internal examination is often too painful at the first visit and is not always necessary to make the diagnosis.
A full colonoscopy is recommended for anyone over 50 with rectal bleeding.1 A fissure is a reasonable explanation for bleeding, but it does not rule out other causes.
A fissure sitting outside the two midlines is unusual. In that situation a biopsy is usually taken, to exclude Crohn’s disease, ulcerative colitis, tuberculosis, HIV and cancer.1
Traditionally a minor operation was the treatment of choice, but non-invasive medical treatment has shown promising results and gained widespread acceptance. Treatment now works up in three steps: simple measures to soften the stool, then an ointment to relax the sphincter, and surgery only if those fail.
The aim is softer stools and a relaxed sphincter. Up to half of fissures heal on these measures alone:1
Where conservative measures are not enough, a topical agent is added to reduce sphincter pressure and improve blood flow to the fissure.
| Treatment | What it does | Main side effect |
|---|---|---|
| Glyceryl trinitrate 0.2% | Improves local blood flow and reduces internal sphincter pressure1 | Headaches in 20 to 30% of patients, typically around 30 minutes after application; not to be used with sildenafil1 |
| Diltiazem 2% | Healing rates of 65 to 95% have been reported1 | Fewer headaches, though there is limited data comparing it against placebo1 |
| Botulinum toxin injection | A chemical sphincterotomy lasting two to three months, with failure rates of 20%1 | Incontinence to flatus in 10% and to stools in 5%, both temporary1 |
Botulinum toxin is a single injection rather than an ointment applied three times a day for weeks. Keeping to the ointment routine is a common reason treatment appears to fail.
Lateral internal sphincterotomy is the standard operation for a chronic fissure that has failed to respond to conservative treatments. A small part of the internal sphincter is divided through a small incision placed to the side rather than in the midline, which permanently reduces the spasm and allows the fissure to heal.
It succeeds in over 90% of cases, with symptoms settling in two to three weeks.1 The main risk is to bowel control. Around 40% notice some difficulty controlling wind or stool in the first week, falling to about 5% with mild difficulty controlling wind at one month. Quality of life is consistently good in the long term.1
Anyone who has had previous surgery in the area, and women who have had several children, are advised to have further assessment first. This is usually anal manometry or an endoanal ultrasound, which check how well the sphincter is working.1 For a fissure that keeps returning, an advancement flap or a fissurectomy combined with botulinum toxin or topical treatment are further options.1
More on fissure and fistula surgery →
See a doctor if anal pain on passing stools has lasted more than a couple of weeks, if it is severe enough that you are avoiding the toilet, or if it keeps coming back after resolving. A fissure that has been present for over a month is unlikely to resolve on diet alone.
See a doctor sooner if bleeding is heavy, if it is mixed into the stool rather than on the paper, if there is a change in bowel habit or unexplained weight loss, or if you are 50 or older and have never been screened for colorectal cancer.
No, although the two are often confused because both can cause bleeding. The distinguishing feature is pain. A fissure causes a sharp, searing or tearing pain with each bowel movement, while bleeding from internal piles is usually painless. The two can also occur together, which is one reason examination matters.
Many acute fissures resolve within a few weeks once stools are softened and the sphincter spasm is relieved. Up to half heal on those measures alone.1 A fissure that has not healed after four weeks is considered chronic and usually needs more than diet and warm soaks.1
Most people do not. Surgery is considered when a fissure has failed a proper course of medical treatment or keeps returning. The main operation is lateral internal sphincterotomy, which succeeds in over 90% of cases, with symptoms settling in two to three weeks.1
The fissure itself does not, but the operation that divides part of the internal sphincter carries a risk. Around 40% notice some difficulty in the first week after lateral internal sphincterotomy, falling to about 5% with mild difficulty controlling wind at one month.1 Surgery is not the first step, and botulinum toxin is offered as a lower-risk alternative.
It could. A fissure is a common and benign cause of bright rectal bleeding, but it is not the only one. A full colonoscopy is recommended for anyone over 50 with rectal bleeding.1 A fissure in an unusual position also needs further assessment, since it can point to Crohn’s disease, tuberculosis or other conditions.1
BUILD NOTE: every figure on this page carries a numbered citation to NUH, fetched and checked on 22 September 2026. These are NUH’s published rates, not this clinic’s outcomes, and the page says so in each sentence. The healing and continence figures for sphincterotomy vary between published series, so Dr Chen should confirm he is comfortable quoting them before cutover.
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