Trial Information

Multidetector-Row CT Colonography: Optimisation of Reduced Bowel Preparation Regimes and Diagnostic Performance in Comparison to Colonoscopy

CT colonography has been shown to be accurate in detection of colorectal neoplasia in
enriched patient populations and is generally preferred by patients to conventional
endoscopy and barium enema. It is advocated as an acceptable alternative for colorectal
cancer screening and is increasingly used in the investigation of symptomatic patients.
Ideally, like conventional colonoscopy, CT colonography requires a clean colon, free of
residual stool and fluid. There is however good evidence that the arduous bowel purgation
regimes required may produce adverse effects such as electrolyte imbalance, and are more
detrimental to overall patient experience and compliance than any subsequent investigation.
An ability to perform CT colonography with reduced bowel purgation, whilst maintaining
acceptable diagnostic accuracy, would undoubtedly make the technique a more attractive
proposition both for population screening and investigation of symptomatic patients.

Interest has been generated in the use of orally ingested dilute barium or ionated contrast
medium prior ro CT colonography to "label" or "tag" residual fluid or faecal matter reduced
laxative. Such oral contrast agents are highly attenuating to X-rays such that labeled
residual bowel contents appear white on CT scanning and are readily distinguished from true
colonic pathology.

Despite the early promise of a few limited studies, there is no consensus as to the optimum
oral contrast type, dose and concentration. Anecdotally barium tends to best label solid
residue whereas iodinated contrast best labels fluid, but this assumption has not been
proven. Furthermore it is known that iodinated contrast tends to draw fluid into the bowel,
producing a wet colon, which may not be suited to CT colonography. However, this indrawing
of fluid by iodinated contrast such as gastrograffin produces a mild laxative effect, which
may obviate the need for further formal purgation.

The study aims to establish the optimum reduced preparation-tagging regimen, establish
patient experience and document diagnostic performance compared to conventional colonoscopy.