A chronic anal fissure is one that has persisted for more than eight weeks, and healing it typically requires more than the dietary changes and sitz baths that work for acute tears. The reason these fissures resist healing comes down to a self-reinforcing cycle involving the muscle that controls your anal canal. Breaking that cycle is the core of every effective treatment, from medicated ointments to surgery.
Why Chronic Fissures Don’t Heal on Their Own
The internal anal sphincter, the ring of muscle you can’t consciously control, tends to be abnormally tight in people with chronic fissures. That excessive tightness compresses the tiny blood vessels supplying the lining of the anal canal, particularly at the back (posterior midline), where blood flow is already the weakest. Researchers confirmed this by measuring both muscle pressure and blood flow simultaneously: the higher the resting pressure of the sphincter, the lower the blood supply to the tissue at the fissure site.
Without adequate blood flow, the torn tissue can’t rebuild itself. Pain from the open wound triggers further muscle spasm, which further reduces blood flow, which prevents healing. A chronic fissure often develops a deeper tear than the original injury, sometimes with small fleshy growths (sentinel piles) at its edges. Every treatment for chronic fissures, whether a cream or an operation, works by relaxing that overactive sphincter muscle so blood can reach the wound again.
Start With Conservative Measures
Even with a chronic fissure, the foundation of treatment is keeping stools soft and minimizing trauma to the area. These steps won’t always heal a chronic fissure alone, but they support every other treatment you might use.
- Fiber: A high-fiber diet or daily fiber supplements like psyllium husk make bowel movements softer and easier to pass, reducing the mechanical stress on the fissure. Aim for 25 to 35 grams of fiber per day from food and supplements combined.
- Hydration: Eight glasses of water a day helps fiber do its job and prevents hard stools.
- Sitz baths: Sitting in warm water (around 104°F or 40°C) for 15 to 20 minutes relaxes the sphincter temporarily and increases local blood flow. Three to four times a day is a common recommendation, including after bowel movements.
- Stool softeners: Over-the-counter options like docusate sodium can help if fiber alone isn’t enough.
These measures reduce pain and prevent the fissure from worsening, but for a fissure that has already become chronic, most people need pharmacological or procedural treatment to achieve full healing.
Topical Medications That Relax the Sphincter
The first-line medical treatment is a prescription ointment applied directly to the anal canal. Two types are commonly used, and they work by chemically relaxing the internal sphincter to restore blood flow.
Nitroglycerin Ointment
Topical nitroglycerin (GTN), usually at a 0.2% or 0.4% concentration, releases nitric oxide in the tissue, which relaxes smooth muscle. In a large Cochrane review, it healed about 49% of anal fissures compared to 36% with placebo. That’s a real improvement, but it means roughly half of people using it still don’t fully heal. The major drawback is headaches, which affect about 1 in 5 users and can be severe enough that people stop treatment. Dizziness is also relatively common.
Diltiazem Ointment
Topical diltiazem (typically 2%) is a calcium channel blocker that relaxes the sphincter through a different mechanism. It causes fewer headaches than nitroglycerin, which is why many clinicians now prefer it as the initial prescription. Both ointments are usually applied two to three times daily for six to eight weeks.
If one ointment doesn’t work, switching to the other is reasonable before moving to more invasive options. But if topical therapy fails after a full course, the next step is either botulinum toxin injection or surgery.
Botulinum Toxin Injection
Botulinum toxin (commonly known by the brand name Botox) temporarily paralyzes part of the internal sphincter, achieving the same goal as the ointments but more directly. A small dose, typically 20 to 30 units, is injected into the sphincter muscle during a brief office or outpatient procedure.
The overall healing rate with botulinum toxin is around 67% to 77%, depending on the study, which is better than topical nitroglycerin. A large review by NICE found a healing rate of about 56% for botulinum toxin versus 29% for placebo. Compared head-to-head with nitroglycerin ointment, botulinum toxin healed roughly 74% of fissures versus 63% with the ointment.
The effect wears off after a few months, but for many people that window is enough for the fissure to close permanently. For those whose fissure returns, a repeat injection can be tried with reasonable success. One study of 80 patients with recurrent fissures after surgery found a 74% healing rate with botulinum toxin injection, though 10% experienced temporary gas incontinence.
Surgery: Lateral Internal Sphincterotomy
When medications and injections fail, or for patients who want the highest likelihood of definitive healing, surgery is the most effective option. Lateral internal sphincterotomy (LIS) involves making a small, controlled cut in the internal sphincter to permanently reduce its resting pressure. The procedure has a healing rate around 89% to 94%, making it the gold standard.
The operation is typically done as a day procedure. Most people return to work and normal activities within one to two weeks. Full healing of the anal tissue takes about six weeks.
Incontinence Risk
The main concern with sphincterotomy is that cutting part of the sphincter could affect bowel control. Older techniques that cut a larger portion of the muscle reported incontinence rates averaging around 14%. Modern “tailored” approaches, where the cut is limited to less than 25% of the sphincter length, have dramatically reduced this risk. A large study following 287 patients over 30 years found only a 1.4% rate of minor gas incontinence and zero cases of stool incontinence. Another study of nearly 500 patients using a minimal technique reported gas incontinence in just 0.4% of cases, with no fecal incontinence at all.
Women who have had vaginal deliveries may have pre-existing sphincter thinning, so surgeons often use imaging beforehand to tailor the procedure to individual anatomy.
Sphincter-Sparing Surgery
For people at higher risk of incontinence, such as those with prior sphincter injuries or previous sphincterotomy, an anal advancement flap is an alternative. This procedure covers the fissure with a small flap of healthy tissue from nearby, without cutting the sphincter at all.
A meta-analysis comparing the two approaches found that advancement flaps produced significantly lower rates of incontinence than sphincterotomy. The healing rates and wound complication rates were statistically similar between the two procedures. This makes the flap a good option when sphincter preservation is the priority, though it is a somewhat more involved operation.
What to Do if a Fissure Comes Back
Recurrence is possible even after successful treatment. The same habits that support initial healing are your best defense against a repeat episode. Keeping stools consistently soft through fiber, adequate water intake, and stool softeners when needed is the single most important long-term strategy. Both constipation and diarrhea can reinjure the area, so the goal is regular, well-formed bowel movements.
If a fissure does return after sphincterotomy, the options include a repeat sphincterotomy on the opposite side of the canal or botulinum toxin injection. One study of 57 patients who had a second sphincterotomy on the opposite side showed a 98% healing rate with only a 4% rate of minor incontinence over more than 12 years of follow-up. This suggests that recurrence, while frustrating, is very treatable.