Flexible sigmoidoscopy

Overview

A flexible sigmoidoscopy is a test that lets a doctor look inside the lower part of your large bowel (the colon and rectum). It uses a thin, flexible tube with a tiny camera on the end.

Yes, flexible sigmoidoscopy is a common test used to investigate bowel symptoms and to screen for bowel cancer, especially in people over 50.

It is most often done in adults, particularly those over 50 years old or those with symptoms such as blood in the stool, persistent diarrhoea, or a family history of bowel cancer.

Symptoms

Common symptoms

• Rectal bleeding (blood in your stool or on the toilet paper)
• Persistent change in bowel habits (diarrhoea or constipation lasting more than a few weeks)
• Abdominal pain or discomfort
• Feeling that your bowel doesn't empty completely

Symptoms in children

• Flexible sigmoidoscopy in children is rare, but may be used to investigate chronic diarrhoea, blood in stool, or suspected inflammatory bowel disease (such as Crohn's disease).

Symptoms in older adults

• Same symptoms as adults, plus screening for bowel cancer is often recommended starting at age 50–60.

Causes

Main causes

• To investigate symptoms such as rectal bleeding, chronic diarrhoea, or abdominal pain
• To screen for colorectal cancer in people over 50 or with a family history
• To monitor known conditions like ulcerative colitis or Crohn's disease

Risk factors

• Age over 50
• Family history of colorectal cancer or polyps
• Personal history of inflammatory bowel disease (Crohn's, ulcerative colitis)
• Personal history of polyps or colorectal cancer

When to see a doctor

See a doctor urgently if:

• See a doctor or go to urgent care if you have new, heavy rectal bleeding that persists for more than a few hours.
• Also seek urgent care if you have severe abdominal pain with fever or vomiting.

Book a routine appointment if:

• Make a routine appointment if you have ongoing changes in bowel habits (diarrhoea or constipation lasting more than 3 weeks).
• See your doctor if you notice blood in your stool, even once, especially if you are over 50.
• Talk to your doctor about screening if you are over 50 or have a family history of bowel cancer.

Diagnosis

Flexible sigmoidoscopy is itself a diagnostic test. Your doctor will recommend it based on your symptoms, age, and risk factors. Before the test, you may need a stool test or blood test to check for other causes.

Tests that may be done

• Flexible sigmoidoscopy (the key test)
• Stool tests (to check for blood or infection)
• Blood tests (to check for anaemia or inflammation)
• Colonoscopy (if the sigmoidoscopy finds something that needs a fuller view of the whole colon)

What to expect at your appointment

Before the test, you will usually need to use an enema to empty your lower bowel. You lie on your left side. The doctor gently passes the scope into your rectum. Air is pumped in to open the bowel so the camera can see clearly. You may feel a strong urge to pass wind or a mild ‘crampy’ feeling. The test takes about 10 to 15 minutes. The doctor can remove polyps or take small tissue samples (biopsies) during the test.

Treatment

Treatment depends on what the flexible sigmoidoscopy finds. The test itself is not a treatment, but it helps guide the next steps.

Self-care at home

• After the test, you can eat and drink normally.
• You may feel bloated or have mild cramping; passing gas helps.
• If you had polyps removed, follow your doctor's advice about eating and activity.

Medical treatments

If the test finds inflammation (like in ulcerative colitis or Crohn's disease), doctors may prescribe anti-inflammatory medicines or other drugs to control the condition. If polyps are found, they can often be removed during the sigmoidoscopy. If cancer is found, treatment may involve surgery, chemotherapy, or radiotherapy – your specialist will discuss the best options.

When is surgery considered?

Surgery is considered if a large or advanced cancer is found, or if polyps cannot be safely removed during the sigmoidoscopy. Your doctor will refer you to a surgeon if needed.

Living with this condition

For most people, a flexible sigmoidoscopy is a one-off test. After it, you can return to normal activities right away. If the test finds a condition that needs monitoring, such as ulcerative colitis, you will have regular follow-up appointments.

Lifestyle tips

• Follow your doctor’s recommendations for follow-up tests or medications.
• If you had polyps removed, you may need a repeat sigmoidoscopy or colonoscopy in 1 to 5 years.

Diet and exercise

No special diet or exercise changes are needed after the test. If you have a condition like inflammatory bowel disease, your doctor may advise a diet that reduces symptoms.

Mental health and emotional wellbeing

Worrying about test results is normal. If you feel anxious, talk to your doctor or a mental health professional. Remember that most findings are treatable, and early detection improves outcomes. If you are feeling overwhelmed or need to talk, contact a crisis helpline in your area.

Prevention

Flexible sigmoidoscopy itself cannot be prevented – it is a diagnostic test. However, it can help prevent bowel cancer by finding and removing polyps before they become cancer. A healthy diet, regular exercise, and avoiding smoking and heavy alcohol use may reduce your risk of bowel problems.

Screening programmes

Flexible sigmoidoscopy is one of several screening tests for colorectal cancer. In the UK, the NHS offers bowel cancer screening using faecal immunochemical tests (FIT) and colonoscopy for people aged 60 to 74. Your doctor can advise you on which screening is right for you.

Complications

If left untreated

• If a condition like colorectal cancer is found but not treated, it may grow and spread to other parts of the body.
• Untreated inflammatory bowel disease may cause long-term damage to the bowel lining.
• Bleeding from polyps can lead to anaemia (low red blood cells).

Long-term outlook

Most findings from a flexible sigmoidoscopy are treatable, especially when caught early. Polyps are very common and usually harmless when removed. Even if cancer is found, early-stage bowel cancer has a high chance of being cured. Your doctor will give you a clear plan based on your results.

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