Quick answer. An anal fissure is a small tear in the lining of the anus that causes sharp pain and bright red bleeding when you pass stool. Most heal with more fibre, fluids and stool softeners, but significant or persistent rectal bleeding always needs a doctor to exclude other causes.
An anal fissure is a small tear in the delicate lining of the anus, and despite its size it can cause surprisingly sharp pain. In Singapore it is a common reason people see a GP or gastroenterologist, often after noticing bright red blood when wiping. The classic story is a tearing or knife-like pain when passing a hard stool, followed by a burning ache.
This guide explains what an anal fissure is, why it happens, how it is diagnosed and treated, and how it differs from haemorrhoids. Importantly, it covers the red flags that mean rectal bleeding should never simply be assumed to be a harmless fissure. This is general information and does not replace a doctor’s assessment.
At a glance
| Feature | Anal fissure | Haemorrhoids |
|---|---|---|
| Main symptom | Sharp, tearing pain on passing stool | Often painless lump or itching |
| Bleeding | Bright red, small amount on stool or paper | Bright red, on paper or in the bowl |
| Cause | Tear in anal lining | Swollen blood vessels |
| Pain pattern | Worst during and after passing stool | Usually mild unless thrombosed |
| First-line care | Fibre, fluids, stool softeners, creams | Fibre, fluids, topical treatments, banding |
What is an anal fissure?
An anal fissure is a small split or tear in the skin-like lining of the anal canal, usually caused when a hard or large stool stretches the area. Once a fissure forms, the surrounding muscle can go into spasm, which both worsens the pain and reduces blood flow, making the tear slower to heal.
Anal fissures are common and affect people of all ages, including young children and otherwise healthy adults. Most are short-lived (acute) and settle within a few weeks. A fissure that lasts longer than about six weeks is called chronic and may need additional treatment.
Symptoms & signs
The symptoms of an anal fissure are usually distinctive:
- A sharp, tearing or knife-like pain when passing stool
- A burning or aching pain that can last for minutes to hours afterwards
- Bright red blood on the stool, on the toilet paper or in the bowl
- Itching or irritation around the anus
- A small visible tear or skin tag near the fissure in longer-standing cases
The pain is often severe enough that people start to dread or avoid passing stool, which can worsen constipation and create a vicious cycle.
Causes & risk factors
Anything that puts pressure on or stretches the anal lining can cause a fissure. The most common cause is passing hard stools due to constipation. Other contributing factors include:
- Constipation and straining (the leading cause)
- Persistent diarrhoea
- A low-fibre diet and not drinking enough fluids
- Childbirth
- Tight or overly tense anal sphincter muscles
- Less commonly, inflammatory bowel disease or infections
How it's diagnosed
A doctor can usually diagnose an anal fissure from your description of sharp pain and bright red bleeding, together with a gentle examination of the area. Because the area is tender, the examination is done carefully, and a full internal examination may be deferred until the fissure is less painful.
If bleeding is heavier or persistent, if you are older, or if there are other warning features, your doctor may recommend further tests such as a proctoscopy, sigmoidoscopy or colonoscopy. This is to make sure the bleeding is not coming from another source, including haemorrhoids, inflammatory bowel disease or, in older adults, bowel cancer.
Treatment options
Most acute fissures heal with simple measures aimed at keeping stools soft and easing muscle spasm:
- Diet: more fibre, plenty of fluids, and avoiding straining
- Stool softeners or laxatives: to make passing stool less traumatic
- Warm sitz baths: soaking the area to relax the muscle and ease pain
- Prescription creams: such as glyceryl trinitrate or a calcium-channel blocker ointment to relax the sphincter and improve healing
For chronic fissures that do not heal, a doctor may suggest botulinum toxin injection to relax the muscle or, in selected cases, a minor surgical procedure (such as lateral internal sphincterotomy). Surgery is usually reserved for fissures that fail to respond to other treatments.
When to see a doctor & which specialist
See a doctor if your symptoms do not improve within a week or two of self-care, or if the pain is severe. Do not assume rectal bleeding is simply a fissure. Significant or persistent rectal bleeding always needs medical assessment to exclude other causes, including bowel cancer. See a doctor promptly if you have:
- Bleeding that is heavy, persistent or recurrent
- Dark or black stools, or blood mixed through the stool
- A change in bowel habit, unexplained weight loss or fatigue
- Bleeding for the first time over the age of 40 to 50
- Fever, pus or spreading redness suggesting infection
If you have very heavy rectal bleeding, feel faint, or have severe worsening pain with fever, call 995 or go to A&E. For ongoing or unexplained bleeding and persistent fissures, see a gastroenterologist in Singapore.
Self-care and prevention at home
Because most fissures are caused by hard stools and straining, the most useful day-to-day steps focus on keeping stools soft and bowel movements comfortable.
- Build up dietary fibre gradually with wholegrains, fruit, vegetables and legumes, and increase it slowly to avoid wind and bloating.
- Drink enough fluids through the day, which matters in Singapore’s warm climate.
- Do not delay or rush when you feel the urge to open your bowels, and avoid prolonged sitting and straining on the toilet.
- Use warm sitz baths (sitting in a few inches of warm water) for several minutes a couple of times a day to relax the muscle and ease pain.
- Keep the area clean and dry, and pat rather than rub after washing.
Breaking the cycle of pain and constipation is the key to healing, so address the constipation as well as the fissure itself.
Common questions
How can I tell a fissure from haemorrhoids?
A fissure typically causes a sharp, tearing pain when passing stool, while haemorrhoids are more often a painless lump, itch or bleeding. The two can occur together, so a doctor’s examination is the surest way to know.
Will a fissure heal on its own?
Most acute fissures heal within a few weeks with softer stools, fibre, fluids and sitz baths. Persistent or recurring fissures may need prescription creams or, occasionally, a minor procedure.
Is it normal to be afraid to pass stool?
Dreading the pain is common, but avoiding bowel movements tends to make stools harder and the problem worse. Keeping stools soft makes passing them far less painful.
Related guides
- Best Gastroenterology Clinics in Singapore — our editorial shortlist
- gastroenterology clinics directory
- Pregnancy test
- Cystoscopy
- Zika virus
- Shin splints
- Ingrown toenail
Sources
- NHS – Anal fissure
- Mayo Clinic – Anal fissure
- SingHealth – Colorectal conditions
- HealthHub Singapore – Diseases and conditions
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