Anal Fissure

What an anal fissure is

The anal canal is lined with sensitive skin (anoderm) and surrounded by two rings of muscle: the external sphincter, which you control, and the internal sphincter, which works automatically. A fissure is a split in the lining, usually 1 cm (0.4 in) or less, most often at the back (posterior midline) of the anus. About 1 in 10 fissures in women occur at the front.

The tear exposes nerve endings and triggers spasm of the internal sphincter. The spasm causes more pain and reduces blood flow to the area, which slows healing. This cycle of tear, spasm, poor blood flow explains why some fissures become chronic.

Symptoms

• Sharp, tearing or burning pain during and after bowel movements, often described as "passing glass"
• Pain lasting minutes to a few hours afterward, sometimes a deep ache from muscle spasm
• Bright red blood on the toilet paper or streaked on the stool, usually a small amount
• A visible tear or crack at the anal opening
• A small skin tag (sentinel pile) next to a chronic fissure
• Itching or irritation
• Fear of bowel movements, which leads to holding stool and makes constipation worse

Acute vs chronic anal fissure

Anal fissure vs hemorrhoids

Both can occur together.

Causes and risk factors

• Constipation and hard stools, the most common cause. See chronic constipation.
• Straining during bowel movements.
• Chronic diarrhea.
• Childbirth, often causing fissures at the front.
• Anal intercourse or insertion of objects.
• High resting anal sphincter tone.
• Infants: fissures are very common in babies and toddlers, usually from hard stools, and are a frequent cause of blood in a baby's diaper.

Atypical fissures

Fissures at the sides, multiple fissures, large or painless fissures, or those that will not heal may be linked to Crohn's disease, HIV, tuberculosis, syphilis, herpes or, rarely, anal cancer. These need further investigation.

Diagnosis

A doctor usually diagnoses a fissure by gently parting the buttocks and looking at the anus. A finger examination or scope is often avoided at first because it is very painful, and is done later or under anesthesia if needed.

Colonoscopy or sigmoidoscopy may be recommended if you are over 45, the bleeding does not fit a fissure, you have changes in bowel habit or weight loss, or the fissure is atypical.

Treatment

Step 1: Home care (first-line for all)

• Fiber: 25 to 35 g a day from fruit, vegetables, whole grains, or a supplement such as psyllium.
• Fluids: drink enough to keep stools soft.
• Stool softener or osmotic laxative such as polyethylene glycol, following the label.
• Warm sitz baths: sit in a few inches of warm water for 10 to 15 minutes, 2 to 3 times a day and after bowel movements. This relaxes the sphincter.
• Don't strain or delay: go when you feel the urge, and limit time on the toilet.
• Pain relief: acetaminophen (paracetamol) or ibuprofen as labeled, and a numbing ointment such as lidocaine for short-term use.
• Clean gently with water or unscented wipes.

About half of acute fissures heal with these measures alone.

Step 2: Prescription ointments

These relax the internal sphincter and improve blood flow:

• Nitroglycerin (glyceryl trinitrate) ointment: effective, but headaches are common.
• Calcium channel blocker ointments (diltiazem or nifedipine): similar effectiveness with fewer headaches.

They are applied to the anus usually twice a day for 6 to 8 weeks.

Step 3: Botulinum toxin (Botox) injection

Injected into the internal sphincter to relax it for about 2 to 3 months, allowing the fissure to heal. Healing rates are good, but fissures can recur. Temporary mild incontinence of gas occurs in a small number of people.

Step 4: Surgery

Lateral internal sphincterotomy cuts a small part of the internal sphincter to permanently reduce spasm. It heals over 90% of chronic fissures and is a short outpatient operation. There is a small risk of minor incontinence, mainly of gas, so it is usually reserved for fissures that do not respond to medical treatment. Fissurectomy or an advancement flap are alternatives in some cases.

Complications

• Chronic fissure
• Recurrence, especially if constipation returns
• Rarely, anal fistula or perianal abscess

Prevention

Keep stools soft with fiber and fluids, avoid straining, treat diarrhea promptly, and keep the area clean and dry.

Frequently asked questions

What does an anal fissure feel like?

An anal fissure causes a sharp, tearing or burning pain when you pass a stool, often described as passing broken glass. A throbbing ache can last minutes to hours afterward. You may see bright red blood on the toilet paper and feel a small crack or bump at the anus.

How long does an anal fissure take to heal?

Most acute fissures heal within 2 to 6 weeks with softer stools, fiber, fluids and warm baths. Fissures lasting longer than 6 to 8 weeks are considered chronic and often need prescription ointments, Botox injections or minor surgery.

Can an anal fissure heal on its own?

Yes. Many acute fissures heal on their own when constipation is corrected and stools stay soft. Keeping up fiber, fluids and stool softeners prevents re-tearing. Chronic fissures are less likely to heal without treatment that relaxes the anal sphincter.

Is it a fissure or hemorrhoids?

Fissures typically cause sharp pain with bowel movements and small amounts of blood on the paper. Internal hemorrhoids usually bleed without pain, and external ones cause swelling and itching. A doctor can tell them apart with a quick external examination.

When does an anal fissure need surgery?

Surgery is considered for chronic fissures that have not healed after 6 to 8 weeks of ointment treatment, or that keep returning. Lateral internal sphincterotomy heals over 90% of chronic fissures. Botox is an option for those who want to avoid or delay surgery.