Full Professor of Radiology, Director Radiology Unit, Sant’Andrea University Hospital, Rome, ITALY
CT colonography (CTC) is a robust and reliable imaging test of the colon. The technique is easy, less labor-intensive than barium enema and conventional colonoscopy (CC) and is inherently safer with a rate of reported procedure-related complications lower than barium enema itself. The success rate of CTC is approximately 100%, if bowel preparation and distension are optimal and no sedation is required. From the patient’s perspective, the major advantages of CTC include the very brief time required to perform the examination, the absence of contrast enemas and the potential for same-day CC when polyps are detected.
The issue of diagnostic accuracy of CT Colonography (CTC) for colo-rectal cancer (CRC) and polyps has been a source of debate for a long time, because of the conflicting results of some of the papers published in the literature. However, data from recent meta-analyses and large trials (SIGGAR, ACRIN, IMPACT, COCOS) all agree that, for CRC detection, CTC is largely superior to barium enema and has similar sensitivity to conventional colonoscopy (CC). And also for the detection of advanced adenomas, diagnostic accuracy is close to CC. Despite the good results there are still some open issues: the significance of diminutive ( Current CTC indications include the evaluation of Patients who had undergone a previous incomplete CC or those who are unfit for CC (elderly and frail individuals, patients with underlying severe clinical conditions, or with contraindication to sedation). CTC can also be efficiently used in the assessment of diverticular disease (excluding patients with acute diverticulitis, where the exam should be postponed), before laparoscopic surgery for CRC (to have an accurate localization of the lesion), in the evaluation of colonic involvement in the case of deep pelvic endometriosis (replacing barium enema). CTC is also a safe procedure in patients with colostomy. For CRC screening, CTC should be considered an opportunistic screening test (not available for population, or mass screening) to be offered to asymptomatic average-risk individuals, of both genders, starting at age 50. The use in individuals with positive family history should be discussed with the Patient first. Absolute contraindication is to propose CTC for surveillance of genetic syndromes and chronic inflammatory bowel diseases (in particular, ulcerative colitis).
The use of CTC in the follow-up after surgery for CRC is achieving interesting evidences despite the fact that literature data are still relatively weak in terms of numerosity of the studied populations. In Patients who underwent previous polypectomy CTC cannot be recommended as first test because debate is still open.
It is desirable that in the future CTC would be the first-line and only diagnostic test for colonic diseases, leaving to CC only a therapeutic role.
Take -Home Messages:
CT colonography is a robust, accurate and noninvasive diagnostic test for the detection of colonic polyps and cancer
CT colonography can completely replace double-contrast barium enema and it is complementary to Colonoscopy
Current CTC indications include the evaluation of Patients who had undergone a previous incomplete Colonoscopy, those who are unfit for Colonoscopy (elderly and frail individuals, patients with underlying severe clinical conditions, or with contraindication to sedation) and those with a suspected or known diverticular disease
CTC can be offered as an opportunistic CRC screening test, if the patient is correctly informed about pros and cons of this technique in comparison with other currently available tests