CT Colonography (CTC)

CT Colonography uses a CT scanner to produce two-dimensional and three-dimensional images of the large bowel (also known as the colon and rectum) and abdomen to help detect polyps and cancers.

CTC is an alternative test for people who are too frail to have a colonoscopy or if there are other clinical reasons why a colonoscopy may not be suitable.

The CTC service is based in the CT Scan Department (Ground Floor, BeCAD), St Mark’s Hospital at Central Middlesex Hospital (CMH) where there is a dedicated CT scanner. Additionally, there are very limited CTC appointments at our other hospital sites within the LNWUH Trust (at Northwick Park Hospital and Ealing Hospital). 

Please read your patient letter carefully to make sure you attend the correct hospital site for your CTC scan. 

CTC is available via the NHS at St Mark’s Hospital if your hospital Doctor or GP feels that your symptoms or problems may potentially be due to cancer of the large bowel, or they would like to exclude this condition. This is accomplished via the Two Week Wait (2WW) upper and lower gastrointestinal cancer referral pathways. Please speak to your doctor who will advise you if this is appropriate, and if so they can submit a referral to our service.

You will be required to take bowel preparation for the CTC scan.  Please follow the instructions closely to make sure your bowel is as empty and clean as possible.  Keeping to the diet will improve the accuracy of your scan.

Patient Information Leaflets

Please click on the links below for our standard morning or standard afternoon bowel preparation instructions. Alternative bowel preparations may be given in patient-specific circumstances.

Morning appointments are 8.30 a.m. to 2.00 p.m.
Gastrografin Preparation Sheet for CT Colonography (Morning Appointments)

Afternoon appointments are after 2.00 p.m.
Gastrografin Preparation Sheet for CT Colonography (Afternoon Appointments)

You can read further patient information regarding CTC here:
CT Colonography Information For Patients

Appointment Queries

If you have an appointment query please call:

For appointments booked at St Mark’s Hospital, Central Middlesex and St Mark’s Hospital at Northwick Park: 07826 513567

For appointments booked at St Mark’s Hospital at Ealing Hospital: 020 8967 5181


Although there are three CTC scan locations at the LNWUH Trust, most take place at St Mark’s Hospital, Central Middlesex. There are a very limited number of appointments for St Mark’s patients at Northwick Park and Ealing Hospital.

St Mark’s Hospital, Central Middlesex: CT Scan Department, Ground Floor BeCAD, Central Middlesex Hospital, Acton Lane, London NW10 7NS

St Mark’s Hospital at Northwick Park: CT Scan Department, Level 4, Northwick Park Hospital, Watford Road, Harrow, Middlesex HA1 3UJ

St Mark’s Hospital at Ealing Hospital: CT Scan Department, Ground Floor Level 2, Ealing Hospital, Uxbridge Road, Southall, Middlesex UB1 3HW