Sigmoidoscopy: preparation and procedure

At a glance

A flexible sigmoidoscopy is a common procedure that allows a doctor to directly examine the rectum and lower colon using a thin, flexible camera tube. It is used to investigate symptoms, screen for conditions, and sometimes treat issues found during the examination.

It is less extensive than a colonoscopy, requires simpler preparation, and is usually done without sedation. Most people find it manageable, and it provides important diagnostic information.

Why it is done

A sigmoidoscopy may be recommended to:

• Investigate rectal bleeding — to identify the source
• Assess bowel changes — persistent change in bowel habits
• Screen for polyps or cancer — particularly in bowel cancer screening programmes
• Evaluate inflammation — suspected IBD, proctitis, or colitis
• Follow up on previous findings
• Assess conditions that affect the lower bowel and rectum

Preparation

The enema

The main preparation is usually a self-administered enema, done one to two hours before the procedure. The enema clears the lower bowel to give the doctor a clear view.

• You will be given an enema kit with instructions
• It is used at home or at the clinic, depending on the arrangement
• It works within 15 to 30 minutes
• You will need access to a toilet during this period

Diet

• Some clinics ask you to eat lightly the day before
• You may be asked to avoid high-fibre foods or red/purple foods that could obscure the view
• Clear fluids are usually fine
• Specific instructions vary — follow the guidance from your clinic

On the day

• Wear comfortable, loose clothing
• Eat a light breakfast if instructed (or nothing if told to fast)
• Arrange transport if you think you may feel unwell afterwards, though most people are fine to travel independently
• Allow about an hour for the appointment

What happens during the procedure

Before

• You change into a gown
• A nurse or doctor explains the procedure and obtains consent
• You may be offered Entonox (gas and air) for comfort — this is optional
• Sedation is usually not needed but may be available if you prefer

The examination

1. Positioning — you lie on your left side with knees drawn up
2. Lubrication and insertion — the scope is lubricated and gently inserted through the anus
3. Advancement — the scope is slowly advanced through the rectum and into the sigmoid colon
4. Air inflation — a small amount of air is pumped in to gently inflate the bowel, providing a better view. This may cause a bloating or cramping sensation
5. Examination — the doctor examines the bowel lining on a screen as the scope is withdrawn
6. Biopsies — if needed, small tissue samples can be taken painlessly through the scope
7. Withdrawal — the scope is slowly removed

How it feels

• Pressure — as the scope is inserted and advanced
• Bloating or cramping — from the air used to inflate the bowel
• An urge to open the bowels — this is normal and expected
• Brief discomfort at certain points as the scope navigates bends in the colon
• Generally tolerable — most people describe it as uncomfortable but manageable

After the procedure

• You can get dressed and leave fairly quickly
• Some bloating and wind is normal for a few hours — the air introduced during the procedure passes naturally
• You can eat and drink normally
• Light cramping may persist briefly
• If biopsies were taken, you may notice slight bleeding — this is normal
• Results of biopsies typically take one to two weeks

Returning to normal

• Most people resume normal activities the same day
• If you had sedation (unusual for sigmoidoscopy), you will need someone to take you home and should rest for the day
• There are no lasting restrictions

What the doctor may find

Common findings include:

• Hemorrhoids — internal hemorrhoids are often visible
• Polyps — small growths that may be benign but can be removed for testing
• Inflammation — signs of proctitis, colitis, or other inflammatory conditions
• Normal findings — often the most common result, which is reassuring
• Fissures or other conditions — visible in the lower canal

Tips from people who have had one

• The anticipation is worse than the reality — the most consistent feedback
• Breathe through the uncomfortable moments — deep breathing helps
• The air is the most uncomfortable part — it passes within hours
• It is over quickly — most people are surprised by how brief it is
• Ask questions — understanding what is happening reduces anxiety
• It is worth doing — the information it provides is valuable for managing your health