Concierge gastrointestinal imaging · London
CT colonoscopy, virtual colonoscopy — the low-sedation alternative for bowel cancer screening.
CT colonoscopy (also called CT colonography or virtual colonoscopy) uses low-dose CT and rectal gas insufflation to inspect the large bowel without sedation. A modern alternative to colonoscopy for older, frail or high-risk patients — and for screening.
Why patients choose us
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The right hands
We route you to a consultant gastrointestinal radiologist — the person who reads your CT colonography decides the answer.
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Often answers within 48 hours
A written report from the reporting consultant within 48 hours, with onward colonoscopy or MDT pathway if we find something.
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Independent, and free
We are paid by no clinic, so the recommendation is impartial and costs you nothing.
Key facts
CT colonoscopy at a glance.
The essentials for anyone considering CT colonography — what it is, what it needs, and where the limits are.
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Definition
Low-dose CT of the abdomen and pelvis with rectal gas insufflation of the colon.
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No sedation required
Unlike colonoscopy, CT colonography needs no sedation and no recovery period.
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Full bowel prep
Bowel prep and faecal-tagging preparation over the two days before the scan.
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Excellent sensitivity
Excellent sensitivity for polyps ≥ 6 mm — comparable to colonoscopy for clinically significant lesions.
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Cannot biopsy
CT-C is diagnostic only — any abnormal finding needs colonoscopy for biopsy or polypectomy.
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Modern alternative
A modern alternative to colonoscopy in older, frail or high-risk patients, and for screening.
The problem
Not everyone can — or wants to — have optical colonoscopy.
Sedation, older age, frailty, high cardiovascular risk or previous failed colonoscopy all shift the balance. CT colonography is the modern alternative — with a consultant gastrointestinal radiologist reporting the study.
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Screening without sedation?
CT-C is a well-validated screening test for average and high-risk patients who prefer not to be sedated.
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Older or frail patient?
A gentler alternative to colonoscopy for patients where sedation carries meaningful risk.
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Failed or incomplete colonoscopy?
CT-C completes the assessment when optical colonoscopy cannot reach the caecum.
Preparation and journey
From consultation to report — what happens, in order.
Full bowel prep and faecal-tagging over the two days before the scan is essential — the accuracy of the study depends on it.
Phase 1 · Before your scan
Consent, bowel prep, faecal-tagging
Phase 2 · On the day
~10 minutes on the table
Phase 3 · After
Report within 48 hours
- 01
Before
Consultation and consent
A short consultation to confirm indication, allergies, previous surgery and consent for the scan.
- 02
Before
Bowel prep + faecal-tagging (2 days)
Low-residue diet, oral bowel-prep laxative and a faecal-tagging agent over the two days before the scan.
- 03
On the day
Attend for scan
Arrive in comfortable clothing. Change into a gown. No sedation, no cannula in most cases.
- 04
On the day
Rectal tube for gas insufflation
A thin, soft rectal tube gently insufflates carbon dioxide to distend the colon.
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On the day
Scan takes ~10 minutes prone and supine
You are scanned lying on your back and then on your front — around ten minutes on the table in total.
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After
Extra-colonic organs also reviewed
The radiologist reviews the whole abdomen and pelvis, not just the colon.
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After
Radiologist report within 48 hours
A written report from the reporting consultant within 48 hours, with a clear next step.
Typical end-to-end: 3–5 days including bowel prep. Report: within 48 hours.
What it shows
When CT colonoscopy is the right test.
CT colonography answers a specific question — is there anything in the colon that needs an endoscopic look — and, because the whole abdomen and pelvis is imaged, it flags meaningful extra-colonic findings too.
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Colonic polyps ≥ 6 mm
Detected with sensitivity comparable to optical colonoscopy for clinically significant polyps.
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Colorectal cancer
Characterises mass lesions and stages the local extent, with onward colonoscopy for biopsy.
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Diverticular disease
Maps the distribution and severity of diverticulosis and any complicating features.
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Colonic strictures
Identifies benign and malignant narrowings that would be difficult to traverse endoscopically.
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Extra-colonic incidental findings
The whole abdomen and pelvis is imaged — meaningful findings outside the colon are reported.
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AAA (aortic aneurysm)
An abdominal aortic aneurysm is a common — and important — incidental finding.
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Renal / hepatic lesions
Kidney and liver lesions can be detected and characterised on the same scan.
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Red flag: colonic mass or high-grade lesion — urgent colonoscopy + biopsy
Any suspected malignancy is escalated to a two-week wait pathway for colonoscopy and biopsy.
Next steps
What happens after the scan.
CT colonography is diagnostic only — the treatment steps happen elsewhere. Here is where each finding goes next.
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Colonoscopy for any abnormal finding
Optical colonoscopy remains the definitive step for biopsy or polypectomy after an abnormal CT-C.
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Two-week wait pathway
Suspected malignancy is escalated to a two-week wait colorectal pathway.
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Polypectomy at colonoscopy
Polyps identified on CT-C are removed endoscopically at a follow-up colonoscopy.
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Repeat CT-C surveillance
Interval CT colonography for surveillance where colonoscopy is unsuitable or declined.
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Colorectal surgery referral
Surgical opinion for confirmed cancer, complex polyps or symptomatic strictures.
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Multi-disciplinary team review
MDT discussion for any confirmed malignancy, guiding staging and treatment.
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Address extra-colonic findings
Meaningful findings outside the colon — AAA, renal or hepatic lesions — routed to the right specialist.
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Lifestyle and diet advice
Fibre, hydration and lifestyle guidance to reduce future colorectal risk.
Our vetted London network
A small panel of clinics, we picked them.
Partners across central, north, west and south London. Not listed publicly — introductions are made privately, once we understand your case.
Selection criteria
How we choose every clinic in our network.
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Consultant gastrointestinal radiologists reporting every case
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Modern low-dose CT scanners with dedicated CT colonography protocols
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Faecal-tagging bowel prep supplied and explained in advance
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Onward colorectal surgery, gastroenterology and MDT pathway if significant disease is found
Red flags and safety
What we escalate — and why.
CT colonography is very safe. The important part is what we do with the answers — the findings below all have a defined onward pathway.
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Colorectal cancer
Suspected cancer is escalated to a two-week wait colorectal pathway for colonoscopy and biopsy.
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Complex polyp needing surgery
Large or complex polyps may require surgical rather than endoscopic removal.
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Colonic perforation (rare)
Perforation from gas insufflation is very rare with CO2 and modern protocols, but recognised.
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Extra-colonic malignancy
The whole abdomen and pelvis is imaged — occasionally a cancer outside the colon is found.
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Ovarian mass on scan
Adnexal or ovarian masses may be identified and routed to gynaecology.
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AAA needing surveillance
An abdominal aortic aneurysm may be found incidentally and routed to vascular surgery.
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Renal mass
A renal lesion may need dedicated MRI or urology review.
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Post-radiotherapy stricture
Patients with prior pelvic radiotherapy can have strictures that shape the reporting and next step.
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Concurrent iron deficiency anaemia
Iron-deficiency anaemia warrants full GI investigation — CT-C is one part of that work-up.
Reading your report
A CT colonography 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 scan, and the quality of bowel prep and colonic distension.
- 02 Technique
CT protocol and views
Low-dose CT protocol, prone and supine acquisitions, and any intravenous contrast used.
- 03 Findings
Colon segment-by-segment + extra-colonic
Segment-by-segment description of the colon, polyps by size and morphology, plus extra-colonic organs.
- 04 Impression
The conclusion: read this first
Overall assessment and the concrete next step — colonoscopy, surveillance, or reassurance.
Recognised by major UK insurers
Cover depends on your policy and clinic; we confirm with your insurer before booking.
Frequently asked
Everything we get asked about CT colonoscopy.
Quick answers on bowel prep, sedation, safety, and when a follow-up colonoscopy is needed.
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What is CT colonoscopy?
CT colonoscopy — also called CT colonography or virtual colonoscopy — is a low-dose CT scan of the abdomen and pelvis with rectal gas insufflation of the colon. It inspects the large bowel for polyps, cancer and other disease without sedation.
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How is it different from a normal colonoscopy?
Optical colonoscopy uses a flexible camera and typically requires sedation. CT colonography uses low-dose CT with gas distension and requires no sedation. CT-C cannot take biopsies — an abnormal finding still needs colonoscopy — but it is often preferred for older, frail or high-risk patients and for screening.
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Do I need bowel prep for CT colonoscopy?
Yes. Full bowel prep with a low-residue diet, oral laxative and a faecal-tagging agent over the two days before the scan is essential — the accuracy of the study depends on it.
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How long does the scan take?
The scan itself takes around ten minutes — you are imaged prone and supine. Allow around 30–45 minutes at the clinic in total.
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Is CT colonoscopy safe?
Yes. The radiation dose is low and CO2 insufflation is used, which is rapidly absorbed and much better tolerated than air. Colonic perforation is very rare. The main limitation is that biopsy is not possible.
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When would I need a follow-up colonoscopy?
Any abnormal finding — polyp ≥ 6 mm, suspected mass, or unexplained wall thickening — is followed up with optical colonoscopy for direct visualisation and biopsy or polypectomy.
Sources and guidance
- Royal College of Radiologists. Guidance on CT colonography.
- NICE. Colorectal cancer (NG151).
- European Society of Gastrointestinal and Abdominal Radiology. CT colonography guidelines.
- British Society of Gastroenterology. Guidelines on the diagnosis and management of colorectal disease.
Last reviewed 2026-07-30. Next review 2027-07-30. Reading time approximately 6 minutes.
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In practice, in London
Why private CT colonoscopy moves differently in London
With CT colonoscopy, the London question is usually about report turnaround and the radiologist reading it — not whether the scan is available. The NHS route for CT colonoscopy is thorough, but the queue is real. Most patients we speak with have been told to expect anywhere from a handful of weeks to several months, depending on their local trust and how the referral is graded. Going private in London usually collapses that window to a matter of days — often the same week if the diary allows. It isn’t about jumping a queue so much as buying time back while you still have the flexibility to plan around it.
Once you’re in the private system for CT colonoscopy, the pace picks up noticeably. Consultant slots run to time, imaging is usually available in the same building or a short walk away, and the report comes back typed and detailed. It’s the coordination that tends to feel different — one person on the other end of the phone, not a switchboard. For CT colonoscopy specifically, the difference between a routine report and a sub-speciality read is where private care earns its keep.
Honesty about expectations is part of the job. A private CT colonoscopy appointment in London won’t change the underlying medicine — the guidelines, the consultants, and the equipment are largely the same as on the NHS. What it changes is speed, continuity, and the amount of time you get to actually talk through the findings. Everyone we route to is GMC-registered and works within CQC-regulated facilities.