Colonoscopy for rectal symptoms

Published 13 March 2026 ·Last reviewed 13 March 2026 by the editorial team ·How we create our content

At a glance

A colonoscopy is an examination of the inside of the large bowel (colon) and rectum using a flexible camera. It is one of the most important diagnostic tools in gastroenterology and colorectal medicine, but not every rectal symptom requires one.

This guide helps you understand when a colonoscopy might be recommended, what it involves, and what it can tell you.

When it might be needed

A colonoscopy is commonly recommended when:

  • Rectal bleeding is persistent, unexplained, or associated with other concerning symptoms
  • Change in bowel habits lasting more than four weeks, particularly in people over 40
  • Unexplained weight loss combined with bowel symptoms
  • Family history of colorectal cancer or polyps, warranting screening
  • Iron deficiency anaemia without a clear cause
  • Abnormal results from other tests (such as a faecal immunochemical test or CT scan)
  • Surveillance for people with inflammatory bowel disease or a history of polyps
  • Age-related screening — screening programmes vary by country

When it probably is not needed

Not every rectal symptom warrants a colonoscopy:

  • Bright red rectal bleeding in a young person with an obvious fissure or hemorrhoid
  • Symptoms clearly explained by a known condition (such as IBS) that has been previously assessed
  • Temporary changes in bowel habits related to an obvious cause (dietary change, stress, medication)

Your doctor will assess whether the symptoms, your age, and your risk factors point toward colonoscopy or whether a simpler assessment is appropriate.

What the procedure involves

Preparation

The bowel needs to be clean for the camera to see clearly. This involves:

  • Dietary changes — a low-residue diet for one to two days before the procedure
  • Bowel preparation solution — a drink that clears the bowel. People describe this as the least pleasant part of the entire process. It causes frequent watery bowel movements
  • Timing — the preparation is taken the evening before and/or the morning of the procedure

The procedure

  1. You change into a hospital gown
  2. An intravenous line is placed for sedation (if chosen)
  3. You lie on your side
  4. The colonoscope (a flexible tube with a camera) is gently inserted through the anus
  5. Air or carbon dioxide is used to inflate the bowel slightly for better visibility
  6. The camera is advanced through the entire colon
  7. The lining is examined carefully as the camera is withdrawn
  8. If polyps are found, they can usually be removed during the procedure
  9. Biopsies may be taken from any abnormal-looking areas

After the procedure

  • You rest in a recovery area while sedation wears off
  • You may experience some bloating or mild cramping from the air used during the procedure
  • You can usually eat and drink soon after
  • You need someone to take you home if you had sedation
  • You should not drive or make important decisions for the rest of the day
  • Most people feel normal by the following day

What it can find

A colonoscopy provides direct visualisation and the ability to take tissue samples:

  • Hemorrhoids — particularly internal hemorrhoids
  • Polyps — small growths that can be precancerous. Removing them during colonoscopy is preventive
  • Inflammatory bowel disease — Crohn’s disease and ulcerative colitis
  • Diverticular disease — small pouches in the bowel wall
  • Colorectal cancer — early detection through colonoscopy significantly improves outcomes
  • Normal findings — which is the most common result, and provides reassurance

The anxiety factor

Many people feel anxious about having a colonoscopy. Common concerns:

  • The preparation — unpleasant but manageable. Staying close to a toilet and having entertainment helps
  • The procedure — sedation makes it comfortable for most people
  • The results — the waiting can be stressful. Many results are discussed immediately after the procedure; biopsy results take longer
  • Embarrassment — colonoscopy teams do this many times a day. The procedure is routine for them, and patient dignity is maintained throughout

The consistent feedback from people who have had a colonoscopy: it was much less bad than they expected, and the reassurance (or the clarity of finding something treatable) was worth it.

The key message

A colonoscopy is recommended when rectal symptoms need investigation that cannot be achieved through examination alone. It is a safe, effective diagnostic tool that provides direct answers. If your doctor recommends one, it is because the information it provides is important for your care — either to identify a cause or to provide reassurance that nothing concerning is present.

Common questions

Will I need a colonoscopy for rectal bleeding?

Not always. Many cases of rectal bleeding — particularly bright red blood in younger people with an obvious cause like hemorrhoids or a fissure — can be assessed without colonoscopy. However, your doctor may recommend one if the bleeding is persistent, unexplained, associated with other symptoms, or if you are over 40 to 50 and have not had a recent examination of the bowel.

Is a colonoscopy painful?

Most colonoscopies are done with sedation, which makes the procedure comfortable for most people. Some describe mild cramping or pressure during the examination. The bowel preparation beforehand — drinking a solution to clear the bowel — is usually described as more unpleasant than the procedure itself.

How long does a colonoscopy take?

The procedure itself typically takes 20 to 45 minutes. With preparation time, recovery from sedation, and post-procedure observations, you should expect to be at the unit for two to four hours in total. You will need someone to take you home if you have had sedation.

What can a colonoscopy find?

A colonoscopy allows direct visualisation of the lining of the large bowel and rectum. It can identify hemorrhoids, polyps, inflammatory bowel disease, diverticular disease, and colorectal cancer. It also allows biopsies to be taken and polyps to be removed during the same procedure.

When to seek care Heavy bleeding or feeling faint? Get emergency help now. Emergency: 911

Not sure how urgent it is? Get help today.

  1. Emergency

    Heavy bleeding, black tarry stools, feeling faint, severe pain or trouble breathing.

    Call 911 or go to the ER.

  2. Today

    Fever, pain getting worse, a hot swollen lump, or trouble passing urine.

    Call your doctor or go to urgent care.

  3. Soon

    Bleeding or bowel changes nobody has checked, or anything lasting 3 weeks.

    Book a doctor’s appointment.

Feeling overwhelmed? Call or text 988, any time.

See all the signs

For this topic, get medical advice if you notice:

  • Rectal bleeding — always worth getting checked
  • Unexplained weight loss
  • Persistent change in bowel habits lasting more than 4 weeks
  • Family history of colorectal cancer

Recording how you feel is not the same as being checked. These are the signs that need a doctor’s attention.

Call 911 or go to the emergency room now if you have:

  • bleeding that will not stop, a lot of blood (the toilet water turns red, or you pass large clots), or any bleeding with feeling faint or dizzy
  • fainting, a racing heart or trouble breathing
  • confusion or slurred speech, extreme shivering, no urine in a day, or blotchy skin
  • sudden severe belly pain, or a swollen, hard belly with vomiting or not passing stool or gas
  • you cannot pass urine at all, or your bladder feels full and painful and you can’t empty it
  • redness, swelling or severe pain spreading quickly around your anus, genitals or groin, especially with a fever or feeling very ill
  • a fever with a painful swelling near your anus if you have diabetes or a weakened immune system (for example, from chemotherapy or transplant medicines)
  • black, tarry stools

Call your doctor or go to urgent care today (or the ER if you can’t be seen today) if you have:

  • a temperature of 100.4°F (38°C) or higher, chills, vomiting, or feeling generally unwell
  • pain that is getting worse over days, or severe pain that stops you sitting or sleeping
  • a hot, swollen or very tender lump near your anus or at the top of the crease between your buttocks, or foul-smelling discharge
  • trouble urinating
  • bleeding that is getting heavier or more frequent, or blood mixed into your stool
  • feeling much more tired than usual, looking pale, or getting out of breath more easily than you used to
  • not passing stool for several days, or new belly pain

Make an appointment with your doctor if:

  • you have never had these symptoms checked by a doctor or nurse — whatever your age
  • you have had rectal bleeding for more than 3 weeks
  • your bowel movements have been looser, thinner or more frequent than usual for 3 weeks or more, or you have lost weight without trying
  • symptoms have not settled after a week or so, or keep coming back
  • you notice a new lump near your anus, between your buttocks or in your belly, or an itch or discharge that does not clear
  • you have new leakage or trouble controlling your bowels
  • you are 45 or over, or have a family history of bowel cancer or inflammatory bowel disease, and any of these symptoms are new for you

If you are unsure, it is always reasonable to ask. If things feel overwhelming, call or text 988 (Suicide & Crisis Lifeline) or chat at 988lifeline.org, any time. If you don’t feel safe, call 911.

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Discreet symptom tracking

Symptoms that come and go? Keep track, day by day.

For hemorrhoids, fissures, fistulas and other anal and rectal problems. A short, discreet email asks how things have been, and saves each answer, so you can look back at every flare and every good week in your own words. If you haven’t had your symptoms checked, see your doctor first.

  • About ten seconds a check-in. No app, no password.
  • Nothing in the subject or preview says what it’s about.
  • Each Sunday, a link to your week, ready for your next appointment.
Start tracking →

Your notes

Your check-in

Takes about ten seconds.

20:00
Example. Nothing on the lock screen hints at symptoms or conditions.

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Narrow stools: causes and when to worry

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