Anal fissure

What is anal fissure?

An anal fissure is a small tear in the lining of the anal canal that causes sharp pain and a little bright red blood with bowel movements. It most often sits at the back of the anus. Spasm of the internal sphincter muscle reduces blood flow to the tear, which is why some fissures heal slowly.

A fissure is a narrow split in the skin-like lining of the anal canal. Repeated stretching and spasm of the internal muscle reduce blood flow, which is why a fissure can become chronic. Examination usually confirms it, and further tests are arranged if the cause is unclear or the fissure is in an unusual position.

What causes anal fissure?

Anal fissures are caused by trauma to the lining of the anus, most often from a hard or bulky stool. Frequent loose stools, childbirth and a tight internal sphincter muscle can also cause them. Less often the cause is inflammatory bowel disease or another condition, so fissures in unusual positions are investigated.

• Hard or bulky stools and constipation
• A bout of frequent loose stools
• Straining during childbirth
• Tight internal anal sphincter spasm
• Less commonly, inflammatory bowel disease or other conditions

What are the symptoms?

The main symptom of an anal fissure is sharp, tearing pain during a bowel movement that can last from minutes to hours afterwards. Many people also see bright red blood on the toilet paper or the stool surface. Between bowel movements the area is often comfortable, and some people fear going to the toilet.

• Sharp tearing pain during a bowel movement
• Pain that may continue for minutes or hours afterwards
• Bright red blood on the paper or the surface of the stool
• A visible narrow tear near the anal opening
• Itching or irritation as it starts to heal

When should I see a colorectal surgeon?

An anal fissure that is no better after about a week of home care, or keeps returning, needs review by a colorectal surgeon. Seek prompt care for heavy bleeding, dark blood mixed through the stool, fever, weight loss, persistent diarrhoea or a tear in an unusual position.

The warning signs below need prompt attention.

• Heavy bleeding or dark blood mixed through the stool
• A fissure that is not at the usual position
• Weight loss, fever, or persistent diarrhoea
• More than one tear or widespread ulceration

How is it diagnosed?

An anal fissure is diagnosed by discussing your symptoms and gently examining the anal area, where the tear is usually visible. A colonoscopy or further tests are arranged only when inflammatory bowel disease or another cause is suspected, or when the tear is in an unusual position.

• History of the pain and bowel habit
• Gentle examination of the area
• Digital examination or a small scope when tolerated
• Colonoscopy if inflammatory bowel disease or another cause is suspected

How is anal fissure treated?

Most acute anal fissures heal with soft stools from fibre, fluids and stool softeners, plus warm baths and prescribed creams that relax the sphincter. A fissure lasting beyond about six to eight weeks is chronic. Botulinum toxin injection or a minor sphincter operation is considered when these measures fail.

• More fibre, fluids, and exercise to keep stools soft
• Stool softeners and avoiding straining
• Warm sitz baths to relax the muscle
• Prescription creams applied to the area
• Botulinum toxin injection for selected chronic cases
• A minor sphincter operation when other measures fail

What are the risks and complications?

Creams for anal fissure can cause headaches, light-headedness or skin irritation. A fissure can return, especially with constipation. A sphincter operation can cause leakage of wind or stool, which may persist. Your own risk depends on your existing bowel control, earlier childbirth injury or anal surgery, and the technique, and Dr Wong discusses it with you before any procedure.

• Headaches or light-headedness from some creams
• Skin irritation around the anus
• The fissure returning, especially with constipation
• Leakage of wind or stool after a sphincter operation, which may persist; the risk depends on existing bowel control, earlier childbirth injury or anal surgery, and the technique used