Why Is It Painful to Pass a Bowel Motion?

If you've been putting up with pain every time you go to the toilet, please know that this is one of the most common things a colorectal surgeon sees — and one of the most undertreated, simply because people feel embarrassed to bring it up. You don't have to live with it.

The most common cause by far is an anal fissure — a small tear in the lining of the back passage — which can produce pain that feels completely out of proportion to how minor it sounds. Other causes include a blood clot in a haemorrhoid, a perianal abscess, or a muscle spasm condition called levator ani syndrome. This article walks through the main causes and what can be done about each one.

What causes painful bowel motions?

Anal fissure — the most common cause

An anal fissure is a small tear in the lining of the back passage, almost always in the midline at the back (the 6 o'clock position). It produces a very recognisable pattern of pain: sharp, tearing, or burning pain at the moment of passing stool, followed by a prolonged ache or spasm lasting anywhere from 20 minutes to several hours. Many people describe it as "like passing broken glass" or "like a knife cut." It sounds dramatic — but it's exactly what a fissure feels like.

After the initial pain eases, you're often left dreading the next toilet trip. That dread leads to putting off going, which makes the stool harder, which causes more tearing — and that cycle is exactly why fissures become chronic (long-standing). A small streak of bright red blood on the toilet paper is common alongside the pain, and helps distinguish a fissure from internal haemorrhoids, which bleed without causing pain.

Thrombosed external haemorrhoid

Sometimes a blood clot forms inside one of the blood vessels at the outside of the anus — this is called a thrombosed external haemorrhoid. It causes sudden, severe pain around the anus that builds over 24–48 hours, peaks, and then slowly eases over about 7–10 days. The pain is there all the time (not just when you're on the toilet), though going to the toilet makes it worse. You'll usually be able to feel — and see — a tender, firm lump at the anal margin. This needs different management from a fissure.

Anorectal abscess

An abscess is a pocket of infection in the tissue around the anus. It causes constant, throbbing pain that's worse when you sit down or pass a bowel motion. The skin around the anus is often swollen, red, and warm — and you may have a fever. This needs urgent surgical drainage; it won't clear up with antibiotics alone. If left untreated, an abscess can develop into a more complex problem called a fistula (a tunnel between the bowel and the skin).

Levator ani syndrome and proctalgia fugax

These are two muscle-related pain conditions in the pelvic floor. Levator ani syndrome causes a dull, aching pressure deep inside the rectum (back passage), typically worse after sitting for a long time and better when you walk around. Proctalgia fugax is different — sudden, brief, intense spasms deep in the rectum, often happening at night and over just as quickly as they started. Both are diagnosed only after physical causes have been ruled out.

Anal fistula

An anal fistula is a small tunnel that forms between the inside of the back passage and the skin near the anus — usually after an abscess that didn't fully heal. It can cause intermittent pain, particularly when the opening blocks up and a new abscess starts to form. The most noticeable symptom is usually a persistent, smelly discharge from a small opening near the anus.

Inflammatory bowel disease

Crohn's disease can affect the area around the anus, causing deep ulcers, fissures that appear in unusual positions or as multiple tears, large skin tags, and complex tunnels (fistulae). If your fissure keeps coming back despite proper treatment, or appears in an unusual location, Crohn's disease is worth investigating.

Rectal prolapse

Rectal prolapse — where the inner lining of the rectum (back passage) slips down and out through the anus — can cause a feeling of incomplete emptying, mucus discharge, and pain during bowel motions. It's more common in older women and needs specialist assessment to manage properly.

Symptoms — distinguishing the causes

A few patterns can help point to what's causing your pain — though a proper diagnosis always needs an examination:

• Sharp pain during and after going to the toilet, with a small blood streak on the paper → most likely an anal fissure
• Constant throbbing pain with a visible, tender lump near the anus → thrombosed external haemorrhoid or abscess
• Pain, fever, and swelling but no obvious lump → anorectal abscess deeper in the tissue — needs urgent review
• Aching pressure or fullness after sitting for a while, no structural cause found → levator ani syndrome
• Persistent smelly discharge from a small opening near the anus, with intermittent pain → anal fistula
• Fissure in an unusual position, or multiple fissures, that aren't healing → worth investigating for Crohn's disease

Causes of anal fissures specifically

Most fissures start with a hard, large, or very fast-moving stool that over-stretches the lining of the back passage. The reason they stay open and become chronic is a self-reinforcing cycle: the tear causes the internal sphincter muscle to go into spasm, which squeezes the blood vessels in that area and reduces blood flow. Without good blood flow, the tissue can't heal — and every bowel motion re-injures the same spot. Breaking that cycle is what treatment is all about.

Things that put you at higher risk of developing a fissure include:

• Constipation and hard stools (the most common cause)
• Diarrhoea — frequent, urgent bowel motions can also tear the lining
• Childbirth — front-facing fissures are more common in women after delivery
• Inflammatory bowel disease, particularly Crohn's disease
• Naturally high resting pressure in the sphincter muscle (some people are simply built this way)

When to worry

• Fever, swelling, or warmth around the anus — this may be an abscess that needs urgent drainage
• Sudden, severe pain that's stopping you from sitting comfortably — could be an abscess or blood clot
• Pain that isn't getting better after 2–3 weeks of treatment
• A fissure in an unusual location, or more than one fissure — worth being checked for Crohn's disease
• Any change in your usual bowel habit, unexplained weight loss, or blood mixed through the stool (not just on the paper)
• Persistent smelly discharge from a small opening near the anus — this could be a fistula

Treatment options

First-line: Stool softening and dietary measures

The first and most important step for any fissure is making your stools soft and easy to pass, so each toilet trip causes as little disruption as possible to the healing area. A high-fibre diet (aim for 25–35g per day), plenty of water, and a stool softener such as lactulose or macrogol all help. Warm sitz baths (sitting in a few centimetres of warm water) after each bowel motion relax the sphincter spasm and give real pain relief. Most new fissures heal within 4–6 weeks with these measures alone.

Topical relaxant creams

For fissures that have been around longer (chronic fissures), a cream that relaxes the sphincter muscle is usually added. Topical diltiazem 2% is the most widely used in Australia — applied twice daily to the inside of the back passage. Glyceryl trinitrate (GTN) 0.2% is also effective but causes headaches in up to half of people who use it, which makes it harder to stick with. Both take 6–10 weeks to work properly, and around 65–80% of fissures heal with consistent use.

Botulinum toxin (Botox) injection

If cream hasn't worked, the next step is a Botox injection into the sphincter muscle. This temporarily relaxes the muscle — usually for 3–4 months — which reduces the pressure inside the back passage and allows blood flow and healing to return to normal. It's a short procedure done under light anaesthesia, not a major operation. About 75–80% of fissures heal with Botox. A small number of people notice some temporary minor leakage while the Botox is active, but this is nearly always short-lived.

Lateral internal sphincterotomy (LIS)

If cream and Botox haven't been enough, a small surgical procedure called a lateral internal sphincterotomy (LIS) is the most effective option. A surgeon carefully divides a small portion of the internal sphincter muscle under a general anaesthetic — it's a day procedure, meaning you go home the same day. Pain relief is often dramatic within just a few days, and over 90% of fissures heal completely. The main consideration is a small risk (around 5%) of some temporary difficulty controlling wind or liquid stool; more significant continence issues are uncommon with modern technique.

When surgery is needed

Surgery (LIS) is recommended when a fissure hasn't healed after a proper trial of topical cream and at least one round of Botox. How quickly you reach that point depends on how much pain you're in, your age, and whether you have any pre-existing concerns about bowel control. For most people, the non-surgical options are tried first — and many fissures never need surgery. But if you've already been through cream and Botox without enough improvement, LIS is a highly effective and well-established solution.

If you have a perianal abscess, that's a different situation — it needs urgent surgical drainage and shouldn't wait for an elective appointment.

Frequently asked questions