What an anal fissure is
The anal canal is lined by a thin, very sensitive skin called the anoderm. When a hard stool, a bout of diarrhea or childbirth stretches it beyond its limit, it tears, usually in the back midline. That tear is the fissure. Because the anoderm has more pain receptors than almost any other skin, even a 1-centimeter fissure can cause pain that patients describe as "passing glass".
Fissures are classified by duration: acute when they have been present less than 6 to 8 weeks, and chronic after that, when the edges thicken, a small skin tag (sentinel pile) forms at the outer end and the white fibers of the internal sphincter become visible at the bottom.
Why it hurts so much and why it does not close
Underneath the tear lies the internal anal sphincter, a muscle you do not control. Pain makes it contract; the contracted muscle squeezes the small blood vessels that feed the back of the anal canal; without blood, the tear cannot heal; the open tear keeps hurting. This is the fissure cycle, and it is why creams that only anesthetize rarely cure a chronic fissure: they relieve the pain for an hour but do not relax the muscle.
Breaking the cycle means doing two things at once: making the stool soft so it does not re-tear the skin, and relaxing the sphincter so blood returns. That is the logic behind nitroglycerin, diltiazem and nifedipine ointments, and behind FISURIN.
Symptoms
- Sharp, cutting or burning pain during bowel movements, often continuing for minutes to hours afterwards.
- Bright red blood on the toilet paper or on the surface of the stool, usually a small amount.
- A visible crack at the anal opening, sometimes with a small skin tag.
- Spasm, a feeling of tightness, and fear of going to the bathroom.
- Itching or irritation when the fissure is healing.
Read the full symptoms page for how to tell a fissure from hemorrhoids, an abscess or an infection.
Causes and risk factors
- Constipation and hard, large stools (the most common cause).
- Repeated diarrhea.
- Childbirth: up to 1 in 10 women develop a fissure in the weeks after delivery.
- A high resting pressure of the internal sphincter, which some people have by constitution.
- Anal intercourse or insertion of objects.
- Less often: Crohn's disease, tuberculosis, HIV, syphilis, previous anal surgery or cancer. Fissures that are off the midline, multiple, or that do not heal after treatment must be examined to rule these out.
Treatment, step by step
- Soft stools. 25 to 30 g of fiber a day (psyllium works best), 2 liters of water, and a stool softener if needed. Avoid straining and avoid sitting long on the toilet.
- Sitz baths. Warm water for 10 to 15 minutes after bowel movements relaxes the sphincter and cleans the area without rubbing.
- Sphincter-relaxing cream. Topical nifedipine (0.2 to 0.3 %), diltiazem (2 %) or nitroglycerin (0.2 to 0.4 %) applied 2 to 3 times a day for 6 to 8 weeks. Nifedipine and diltiazem cause far fewer headaches than nitroglycerin. FISURIN combines nifedipine with lidocaine for pain.
- Botulinum toxin. An injection into the sphincter that relaxes it for about 3 months; used when creams fail.
- Surgery (lateral internal sphincterotomy). A 10-minute procedure that cuts a small portion of the internal sphincter; heals more than 90 % of chronic fissures, with a small risk of minor gas incontinence. Reserved for fissures that have failed medical treatment.
See the treatment comparison for details on each option.
How long it takes to heal
An acute fissure with soft stools usually closes in 2 to 6 weeks. A chronic fissure treated with a sphincter-relaxing cream closes in roughly 50 to 70 % of cases after 6 to 8 weeks; pain usually improves much earlier, in the first 1 to 2 weeks. Fissures that are still open after 8 weeks of correct treatment should be re-evaluated by a colorectal surgeon.
When to see a surgeon without delay
- Bleeding that is more than a few drops, or dark blood.
- Fever, swelling or pus (possible abscess).
- Pain that worsens instead of improving after 2 weeks of treatment.
- A fissure that is not in the midline, or more than one fissure.
- Weight loss, change in bowel habit, or age over 50 with no previous check-up.
Frequently asked questions
Can an anal fissure heal on its own?
Acute fissures often do, in 2 to 6 weeks, if the stool stays soft. Chronic fissures rarely close without a sphincter-relaxing treatment, because the muscle spasm keeps cutting off blood flow.
Is an anal fissure dangerous?
Not by itself: it is a benign tear. The danger is misdiagnosis. Bleeding and pain can also come from an abscess, an inflammatory disease or, rarely, a tumor, which is why a fissure that does not heal needs a proper examination.
Which cream is best for an anal fissure?
Creams that relax the sphincter (nifedipine, diltiazem, nitroglycerin) are the ones that heal fissures. Hemorrhoid creams with only anesthetic or steroid relieve pain briefly but do not treat the cause. FISURIN combines nifedipine with lidocaine to do both.
Does a fissure come back?
About 30 to 40 % of chronic fissures recur, almost always because constipation returns. Keeping stools soft permanently is the single most effective prevention.