Medical Oncologist
CION Cancer Clinics
Fissure, fistula or something else: the benign causes of bleeding | CION Cancer Clinics
Most bleeding from the back passage is caused by something harmless, such as a small tear at the opening, swollen veins or an infected tunnel beside it. Cancer is a far less common cause. This page explains how a fissure, piles and a fistula usually behave, how a doctor tells them apart from a growth higher up, and which signs mean you should see someone this week rather than wait. At CION Cancer Clinics, our specialists help you judge which bowel symptoms need tests and plan screening that fits your risk.
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Medically reviewed by Dr. Naresh GunduConsultant Medical Oncologist · MBBS, DNB (Internal Medicine), DM (Medical Oncology, AIIMS) · last reviewed October 2026, next review due October 2027
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On this page
- Is bleeding from the back passage usually a fissure, a fistula or cancer?
- What does most bleeding from the back passage turn out to be?
- How does a doctor work out where the blood is coming from?
- Four things people tell us about bleeding, and what is actually true
- What this page cannot tell you
- Common questions about benign causes of bleeding
The short answer
Is bleeding from the back passage usually a fissure, a fistula or cancer?
Most bleeding from the back passage comes from the last few centimetres of the gut, and most of it has a harmless cause. A small tear at the opening, swollen veins, a tiny infected tunnel or an inflamed lining explain the great majority of cases. Cancer is on the list, but near the bottom of it for most people.
Why the pain tells you so much
A fissure hurts sharply during and after a motion, and the blood is bright red and small in amount. Piles usually do not hurt unless they clot or come out and get stuck. A fistula leaks pus or watery discharge between motions. Early colon cancer usually causes no pain at the opening at all, which is why doctors pay more attention to painless bleeding, not less.
Why a doctor still needs to look
These causes can sit side by side. A person can have piles and a polyp higher up. Only an examination, and sometimes a scope, shows where the blood is coming from.
This page does not tell you what you have. It tells you what is common, what is not, and when to stop waiting.The usual suspects
What does most bleeding from the back passage turn out to be?
Four benign conditions account for most of what doctors see. Each has a pattern, though none can be confirmed from a description alone.
Anal fissure
A small tear in the skin just inside the opening, usually from a hard stool. The pain is sharp, like passing glass, and bright red blood streaks the paper or the stool. Most heal with softer stools and warm water baths.
Usually looks like
- Pain during and after a motion
- Small amounts of bright red blood
- Often follows constipation
Piles (haemorrhoids)
Swollen veins inside or just outside the opening. They bleed bright red, often dripping into the pan, and may itch or feel like a soft lump. Blaming piles without an examination is a very common mistake.
Piles and a polyp can exist together. One does not rule out the other.Anal fistula and abscess
An abscess is a pocket of pus beside the opening that swells and throbs. A fistula is the small tunnel that can remain after it drains, leaking pus, blood or discharge between motions. Both need a surgeon, but neither is cancer.
Usually looks like
- A tender swelling or a small opening on the skin
- Discharge that stains underwear
- Comes and goes over months
An inflamed or infected lining
Gut infections, diverticular disease, ulcerative colitis and Crohn's disease can all bleed, usually with loose stools, mucus or cramping. A bleed from diverticular pouches can be sudden and heavy in an older adult, and colitis needs long-term follow-up.
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When bleeding cannot wait
Go to an emergency department today if blood is pouring or clotting into the toilet, if you feel faint, dizzy or breathless, if the stool is black and tarry, or if there is a hot, throbbing swelling beside the opening with fever. See a doctor this week if bleeding has gone on for more than two or three weeks, has come with a change in bowel habit, weight loss or new tiredness, or if you are past your mid-forties and this is the first time it has happened.
At the clinic
How does a doctor work out where the blood is coming from?
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The questions come first
Colour of the blood, whether it is on the paper, in the pan or mixed in, whether it hurts, and whether your bowel habit has changed. Be exact. Embarrassment costs more than honesty here.
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A look and a gentle finger examination
Most fissures, abscesses and external piles are visible from the outside. A gloved finger examination is quick and finds many low growths. If a fissure is too painful, the doctor treats it first and rechecks later.
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A short scope in the clinic
A proctoscope or sigmoidoscope shows the last part of the bowel and confirms internal piles. It does not see the rest of the colon.
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A colonoscopy when the story does not fit
If you are older, if the bleeding is painless or mixed into the stool, if there is anaemia (a low haemoglobin), or if bleeding carried on after treatment, a full colonoscopy is arranged so the whole colon is seen.
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Treating the benign cause
Fissures get stool softeners, creams and warm baths. Piles get banding or, less often, surgery. Fistulas need a surgeon. None of this needs an oncologist unless the scope finds something.
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Commonly believed
Four things people tell us about bleeding, and what is actually true
"It hurts, so it must be a fissure and not cancer."
Pain at the opening does point strongly to a fissure or an abscess, and that is reassuring. But a fissure can sit beside something else, and a low rectal or anal growth can also hurt. Pain changes the likely cause. It does not close the question.
"The pharmacist gave me a piles cream and it stopped, so it was piles."
Bleeding from a polyp or an early tumour also comes and goes. A cream cannot tell you what stopped the bleeding. If it returns, or was never examined, the cause is still unknown.
"A fistula that keeps discharging will turn into cancer."
An ordinary fistula does not become colon cancer. A fistula left discharging for many years can, very rarely, develop a cancer in its track, and a fistula with Crohn's disease needs specialist care. The common problem is simply that it never heals untreated.
"I am too young for this to be anything serious."
Most bleeding in young adults is a fissure or piles. Colon cancer is, however, being found more often in people under fifty than it was, and it is usually caught late because nobody examined them. Age lowers the odds. It does not remove them.
Being straight with you
What this page cannot tell you
It cannot tell you whether your bleeding is a fissure, a fistula, piles or something higher up. Those look alike on a description and different on an examination. If you have been bleeding and nobody has looked, that is the next step, not another search.
Who this page is not for
If you already have ulcerative colitis or Crohn's disease, take the bleeding back to the team that manages it. If your doctor found a growth in the rectum or at the anus, read our rectal cancer or anal cancer pages, because those are treated differently from colon cancer.
What CION can and cannot do here
Fissures, piles and fistulas are treated by general and colorectal surgeons, not by a cancer clinic. CION helps when bleeding has a worrying pattern: our doctors arrange a colonoscopy through a diagnostic partner, read the report with you and, if a growth is found, take the case to the tumour board. See piles versus colon cancer and bright red versus dark blood for more.
If you are unsure whether your bleeding needs a scope, call the helpline and describe it. Someone will tell you honestly.Questions we are asked
Common questions about benign causes of bleeding
How can I tell a fissure from piles at home?
A fissure hurts sharply with each motion and bleeds a little, bright red, on the paper. Piles usually bleed without much pain, sometimes dripping into the pan. The pattern helps, but only an examination confirms it, and the two can occur together.
Does a fissure heal on its own?
Many do within a few weeks, once stools are kept soft with fluids, fibre and sometimes a laxative. A fissure that keeps tearing open for months becomes chronic and may need a prescribed cream, an injection or a minor operation from a surgeon.
What is the difference between an abscess and a fistula?
An abscess is a collection of pus beside the opening that swells, throbs and often causes fever. A fistula is the small tunnel that can remain after it drains, leaking from a tiny hole in the skin. An abscess needs draining promptly; a fistula needs planned surgery.
Can a fissure or fistula turn into colon cancer?
No. Neither becomes colon cancer, which starts higher up, usually from a polyp in the lining. A fistula neglected for many years can very rarely develop a cancer in its track, which is one more reason to have it treated.
The bleeding is painless. Is that worse?
Painless bleeding is most often internal piles, so it is no reason to panic. Doctors do take it more seriously, because growths in the bowel usually do not hurt. Painless bleeding mixed into the stool, or with a change in bowel habit, should be examined this week.
Which doctor should I see for bleeding from the back passage?
Start with a family doctor or a general surgeon, who can examine the area and treat a fissure, piles or an abscess. If the bleeding seems to come from higher up, they will refer you for a colonoscopy. An oncologist is needed only if that finds a growth.
Can I have piles and a polyp at the same time?
Yes, and it is common, because piles are so widespread. Finding piles explains why someone bleeds, but does not prove nothing else is bleeding. That is why a doctor who finds piles in an older adult, or with other symptoms, still asks for a colonoscopy.
I am too embarrassed to be examined. What are my options?
Ask for a doctor of the same sex, bring a relative into the room, or say at the start that you are nervous. The examination is short and routine for the doctor. Embarrassment is a common reason bleeding is left for months, and the cost of waiting is far higher.
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Dr. C. Raghavendra Reddy
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MBBS (AIIMS), MS (Surgery) (AIIMS), DNB (Surgical Oncology), MRCS (Edinburgh)
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Sources
- NHS — Anal fissure
- NHS — Anal fistula
- NHS — Bleeding from the bottom (rectal bleeding)
- NIDDK (NIH) — Hemorrhoids
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
Keep reading
Related pages
Piles vs colon cancer: how doctors tell them apartThe examination and tests that separate the twoBlood only on the toilet paperWhat the most common pattern of bleeding usually meansBright red vs dark blood in stoolWhat the colour says about where the blood comes fromWhen bowel symptoms are an emergencyThe signs that mean hospital today, not an appointment
Talk to us
Bleeding that has not settled, and nobody has examined you?
Tell us how long it has gone on and what has been tried. A CION doctor can tell you honestly whether a colonoscopy makes sense, and arrange it through a diagnostic partner if it does. One helpline serves every CION centre.