CT Colonoscopy

Limited-preparation, low-dose CT colonography is a useful minimally invasive option to evaluate the colon of elderly patients who are medically unfit or unsuitable for colonoscopy, according to a study published in the May issue of the American Journal of Roentgenology.

Aoife Keeling, department of academic radiology, Beaumont Hospital, Dublin, and colleagues, conducted a prospective study over a 15-month period (December 2005 through February 2007) of 67 frail elderly patients. Patients were included in the study if they were referred for CTC because of a clinical suspicion of colorectal cancer and were considered to have reduced functional status and were unsuitable for conventional colonoscopy.

The clinical indications for referral for CTC included eitherone or a combination of the following: iron-deficiency anemia (n= 36, 54%), recent change in bowel habit (n = 16, 24%), lowergastrointestinal hemorrhage (n = 16, 24%), and weight loss (n= 20, 30%). Twelve patients (18%) had a history of a failed colonoscopy. The 49 women in the study (mean age of 80 years) accounted for 73 percent of the study population. The mean age of the 18 male participants was 78 years.

After CTC , the 67 patients in the study were routinely followed up in the medical or surgical outpatient department. One patient had a follow-up CTC examination to monitoran 8-mm colonic polyp, but, according to the authors, no patients with negative findingson the initial CTC were scheduled for follow-up because theobjective of the CTC examination was simply to rule out a largecolonic cancer and not to screen the patient for small polyps.

The authors reported that overall image quality was scored good to excellent in 84 percent of all colonic segments for all scan positions. Colonic abnormalities were identified in 18 percent of the patients (12), including four colonic tumors, two polyps and seven colonic strictures. Incidentalextraintestinal findings were detected in 43 patients (64%), includingnine patients with lesions radiologically consistent with malignancy.

The study showed that limited-preparation, low-dose CTC is feasible and a minimally invasive technique with which to evaluate the colon and exclude gross pathology in elderly frail patients. The results also suggest, the authors wrote, that the technique could be useful in evaluating other groups with poor functional status, such as patients with mental impairments.

The authors also pointed out that conventional colonoscopy, as well as standard CTC, requires that patients received full cathartic colonic preparation. “Purgative agentscan contribute to dehydration, particularly if consumed in anunsupervised outpatient setting,” the authors wrote. “These agents in particularare poorly tolerated by elderly patients and those with diminishedfunction status.” The introduction of a limited-preparation CTC technique in their department has, the authors reported, reduced the number of patients—particularly elderly patients--referred for barium enema.

Furthermore, the authors wrote, while limited-preparation CTC is probably not sensitive for colonic polyps less than 1 cm , these “polyps are of doubtful clinical significancein frail elderly patients. A negative result at CTC often eliminatesthe need for further investigation in patients clinically unfitfor more invasive investigative procedures.”