Patient guide · Endoscopy
Flexible sigmoidoscopy, the left-sided colon camera — quick prep, no full colonoscopy, powerful in the right patient.
Flexible sigmoidoscopy uses a shorter endoscope to inspect the rectum and left colon. Requires only a phosphate enema, no sedation, and takes 10–15 minutes. First-line for fresh rectal bleeding, distal colitis and left-sided polyp surveillance.
Reviewed by Pulse Atlas Editorial Board () · Last reviewed 2026-07-30 · Next review 2027-07-30 · 5 min read
Why it matters
- 01
Quick, targeted, well-tolerated
Ten to fifteen minutes with only a phosphate enema — no full bowel prep, no sedation, no lost day.
- 02
The right first test
For fresh rectal bleeding, distal colitis and left-sided polyp surveillance, flexi sig answers the clinical question directly.
- 03
Diagnostic and therapeutic
Polyps can be biopsied or removed at the same visit, with a same-day written report.
Key facts
Flexible sigmoidoscopy in six lines.
A quick, plain-English summary of the procedure, the preparation and where it fits alongside a full colonoscopy.
| Fact | Detail |
|---|---|
| Definition | An endoscopic examination of the rectum and sigmoid colon. |
| Preparation | A phosphate enema at home two hours before — no full bowel prep. |
| Sedation | Usually none required; local comfort measures are enough. |
| Procedure duration | 10–15 minutes from insertion to withdrawal. |
| Diagnostic + therapeutic | Biopsies and polypectomy can be performed at the same visit. |
| Relationship to colonoscopy | Complements full colonoscopy — selected cases only, not a replacement for whole-colon assessment. |
Preparation
What to expect, step by step.
From referral to walking out with a report — the scope itself takes just ten to fifteen minutes.
Phase 1 · Before your scope
Referral and enema prep at home
Phase 2 · On the day
~10–15 minutes at the clinic
Phase 3 · After
Same-day walk-out and report
- 01
Before
Referral and consultation
A short consultation confirms the indication, medications to hold, and any anticoagulation planning before the procedure.
- 02
Before
Phosphate enema at home
A phosphate enema is self-administered at home about two hours before your appointment to clear the left colon.
- 03
On the day
Attend the endoscopy clinic
Arrive 20 minutes before your slot for check-in, consent and a change into a hospital gown.
- 04
On the day
Left-lateral position on the couch
You lie on your left side with knees drawn up — the standard, most comfortable position for a flexi sig.
- 05
On the day
Scope inserted to the splenic flexure
The flexible sigmoidoscope is passed gently through the rectum and sigmoid, typically as far as the splenic flexure.
- 06
On the day
Polyps biopsied or removed
Any polyp identified is biopsied or removed at the same sitting, and images are captured for the report.
- 07
After
Same-day walk-out with report
Because sedation isn’t usually used, you walk out the same day with a written report and a clear next step.
What it shows
What a flexible sigmoidoscopy can pick up.
Direct visualisation of the rectum and sigmoid — the commonest sources of fresh rectal bleeding, distal inflammation and left-sided polyps.
-
Haemorrhoids
Internal and external haemorrhoids are visualised and graded, with treatment options discussed.
-
Distal ulcerative colitis
Left-sided inflammation, ulceration and friability characteristic of distal UC.
-
Rectal polyp or adenoma
Adenomatous polyps are removed or biopsied at the same visit for histological assessment.
-
Rectal cancer
A rectal mass or high-grade lesion — direct referral onto the 2-week-wait colorectal pathway.
-
Diverticular disease (sigmoid)
Diverticula in the sigmoid colon are documented and correlated with symptoms.
-
Radiation proctitis
Telangiectasia and mucosal changes following pelvic radiotherapy — often amenable to targeted therapy.
-
Solitary rectal ulcer
A characteristic distal ulcer, often linked to disordered defaecation and rectal prolapse.
-
Red flag: rectal mass or high-grade lesion
Any suspicious mass or high-grade dysplasia triggers the 2-week-wait colorectal pathway.
Next steps
What happens after your flexi sig.
The onward pathway depends on findings and histology — from reassurance through medical therapy to surgical referral.
-
Reassurance if normal
A normal flexible sigmoidoscopy is reassuring for left-sided pathology and, in the right clinical context, closes the loop.
-
Polypectomy at time of scope
Small polyps are typically removed during the same procedure using snare or forceps polypectomy.
-
Full colonoscopy for high-risk polyps
Advanced adenomas or multiple polyps prompt a full colonoscopy to inspect and clear the right colon.
-
IBD medical therapy
Confirmed distal ulcerative colitis is treated with topical mesalazine or systemic therapy under gastroenterology.
-
Surgical referral for cancer
A rectal cancer diagnosis is referred urgently to the colorectal MDT for staging and treatment planning.
-
Iron replacement for anaemia
Iron deficiency anaemia is corrected with oral or intravenous iron alongside investigation of the underlying cause.
-
Repeat surveillance interval
Polyp histology and IBD activity guide the interval to the next scope — typically one, three or five years.
-
Structured follow-up
A written plan is issued so you and your GP know exactly what happens next, and when.
Red flags
When lower-GI symptoms become urgent.
The presentations that warrant urgent — sometimes 2-week-wait — action rather than a routine appointment.
-
Rectal cancer
A mass or high-grade lesion on flexi sig is a colorectal 2-week-wait referral without delay.
-
Iron deficiency anaemia
Unexplained iron deficiency anaemia warrants full-colon and upper-GI investigation, not flexi sig alone.
-
Change in bowel habit
A persistent change in bowel habit in adults over 50 should be investigated urgently.
-
Weight loss
Unintentional weight loss with lower-GI symptoms is a red flag for malignancy and requires urgent work-up.
-
Fresh rectal bleeding with mass
Bright red bleeding accompanied by a palpable rectal mass mandates same-day assessment.
-
Ulcerative colitis flare
An acute UC flare with bloody diarrhoea and systemic upset needs urgent gastroenterology review.
-
Post-radiotherapy proctitis
Persistent bleeding or pain after pelvic radiotherapy warrants endoscopic assessment and targeted treatment.
-
IBD dysplasia
Dysplasia identified in long-standing colitis is discussed at the IBD MDT — surveillance intensifies.
-
Recurrent post-polypectomy bleed
Delayed or recurrent bleeding after polyp removal is uncommon but requires same-day endoscopic review.
Reading your report
A flexi sig report can look intimidating. It isn’t.
Whatever the finding, the report keeps to the same four parts.
A quiet reminder
The report is written for your doctor, not for you — and that’s normal.
If you would like us to talk you through it before your follow-up, just ask.
- 01 Header
Indication and preparation
Your details, the reason for the procedure, and confirmation of the enema preparation and any medications held.
- 02 Technique
Extent of examination
The depth reached (typically the splenic flexure), views obtained, and instrument used.
- 03 Findings
Mucosa, polyps and pathology
Vessel pattern, inflammation, diverticula, polyps and any lesions — with size, morphology and site for each.
- 04 Impression
The conclusion: read this first
A concise summary and the concrete next step — reassurance, surveillance interval, further imaging or 2-week-wait referral.
Frequently asked
Everything patients ask about flexible sigmoidoscopy.
Quick answers on preparation, how it differs from a colonoscopy, polyp removal and when to seek urgent care.
-
What is a flexible sigmoidoscopy?
A flexible sigmoidoscopy — often shortened to “flexi sig” — is an endoscopic examination of the rectum and sigmoid colon using a shorter, thinner scope than a colonoscopy. It typically reaches as far as the splenic flexure and is used for fresh rectal bleeding, distal colitis and left-sided polyp surveillance.
-
How is it different from a colonoscopy?
A colonoscopy examines the entire colon and requires a full bowel prep and usually sedation. A flexi sig examines only the rectum and left colon, requires just a phosphate enema and usually no sedation, and takes ten to fifteen minutes.
-
How do I prepare, and does it hurt?
Preparation is a single phosphate enema at home about two hours before your appointment — no fasting or laxative regime. The procedure is well-tolerated; most patients describe pressure or cramping rather than pain, and sedation is not usually required.
-
When is a flexi sig the right test?
It is first-line for fresh rectal bleeding in patients under 50 without red-flag features, for distal ulcerative colitis assessment, and for left-sided polyp surveillance. If whole-colon assessment is needed — iron-deficiency anaemia, right-sided symptoms, IBD extent — a full colonoscopy is preferred.
-
What happens if a polyp is found?
Small polyps are typically removed during the same procedure using snare or forceps polypectomy, and sent for histology. Larger or higher-risk polyps may prompt a full colonoscopy to inspect and clear the right colon.
-
When should I seek urgent care instead?
Heavy rectal bleeding with collapse, severe abdominal pain, or signs of sepsis after a scope are 999 or A&E events, not a private appointment. A rectal mass, unexplained iron deficiency anaemia, or weight loss with change in bowel habit warrants the 2-week-wait colorectal pathway.
Sources
Where this guide comes from.
- British Society of Gastroenterology. Guidelines on colonoscopy and flexible sigmoidoscopy.
- NHS Bowel Cancer Screening Programme.
- NICE. Colorectal cancer (NG151).
- European Society of Gastrointestinal Endoscopy (ESGE). Clinical guidelines.
Reviewed by Pulse Atlas Editorial Board (). Last reviewed 2026-07-30. Next review 2027-07-30.
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In practice, in London
The honest picture around flexible sigmoidoscopy in London
With flexible sigmoidoscopy, the London question is usually about report turnaround and the radiologist reading it — not whether the scan is available. The wait for flexible sigmoidoscopy on the NHS depends heavily on where you live and how urgently the referral is graded. Central and West London private clinics can normally book within a week, with imaging or a procedure slot to follow shortly after. It’s worth being honest about the reason for going private: usually it’s time, not a fundamentally different test.
In practice, a private flexible sigmoidoscopy appointment in London means a named consultant, a proper hour in the room (or the equivalent on a video call), and a report you can actually read. Most of the imaging suites and endoscopy units we use sit within a mile of Harley Street or in Chelsea and Fulham, and turnaround on findings is measured in days, not weeks. For flexible sigmoidoscopy specifically, the difference between a routine report and a sub-speciality read is where private care earns its keep.
We’re careful about what a private pathway for flexible sigmoidoscopy can and can’t promise. It can compress a wait, put you in front of a subspecialist quickly, and get a proper report in your hands within a week. It can’t rewrite what the imaging or the bloods say. Setting that expectation up front tends to make the whole experience less stressful.