What is an anal fissure?

DEAR DOCTOR K:

I’ve had pain and some bleeding during bowel movements. My doctor says it’s an anal fissure. What is that, and what’s the best way to treat it?

DEAR READER:

An anal fissure is a rip in the lining of the anal canal. It usually results from trauma, such as passing hard stool. It causes severe pain, often accompanied by a small amount of blood. Pain from anal fissures often is confused with pain from hemorrhoids.

Anal fissures are common and can easily become chronic. After the lining of the anal canal is torn for the first time, bowel movements re-injure the area. Underneath the lining of the anal canal is a circular muscle, called the sphincter. When it relaxes completely, we have a bowel movement. Most of the time, of course, it’s not relaxed: It’s either clamped down enough or clamped down more than it needs to be.

When the lining of the anal canal is torn, the sphincter muscle beneath the tear goes into spasm, pulling the edges of the tear apart. A cycle of spasm and pain further damages the tissue and prevents healing.

Since most of the patients I see with anal fissures are men, I consulted with my colleague, Dr. Celeste Robb-Nicholson, editor-in-chief of the Harvard Women’s Health Watch, to ask about advice for women. She told me the advice for women is the same as my advice for men.

It’s important to relax the anal sphincter and keep stools soft and regular. The mainstay of therapy is added fiber in the diet. Fruits and vegetables are good sources. So are fiber supplements such as psyllium (like Metamucil), methylcellulose (like Citrucel), or the more recently available tasteless fiber powders that dissolve in liquids (like Benefiber). Plenty of fluid is also important. If fiber and fluid don’t do the trick, try an over-the-counter stool softener.

To help relax the sphincter and relieve pain, take a warm sitz bath after bowel movements. Vaseline (petroleum jelly) may also ease your symptoms.

Medications can help. Topical nitroglycerin promotes healing by increasing blood flow to the area and reducing pressure in the anal sphincter. A 0.4 percent nitroglycerin ointment (Rectiv) is available by prescription. Headaches are a common side effect, but they generally subside within 30 minutes.

Injections of botulinum toxin (yes, that’s Botox) into the sphincter muscle heal some fissures. They ease debilitating spasms and pain. Botulinum toxin is more effective than topical nitroglycerin. But because botulinum injections are invasive, it’s best to try nitroglycerin first. (I’ll bet you never imagined that Botox could be a treatment for a pain in the butt!)

If these measures fail, surgery is an option. Sphincterotomy is a procedure in which a tiny nick is cut in the internal anal sphincter. This relaxes the sphincter and relieves pain. The procedure generally prevents anal fissures from recurring. However, it carries a risk of fecal incontinence. In my experience, patients rarely need surgery; simpler treatments work just fine.