May 16, 2012

Laxative-Free Way to Detect Intestinal Polyps

(Ivanhoe Newswire) — The mere thought of getting a standard colonoscopy makes some people shudder in their seats, and unfortunately, prevents many people from receiving the critically important check-up. But there is a new procedure that may make the whole process a bit easier to endure.

Typically, the standard optical colonoscopy involves the examination of the internal surface of the colon using a lit fiber-optic tube with a camera at the end. The preparation is what drives people away from this life-saving procedure, involving up to a gallon of liquid for laxative preparation and sedatives.

A new study conducted at the MGH, Brigham and Women´s Hospital, North Shore Medical Center and the Veteran´s Administration Medical Center at the University of California at San Francisco researched the effectiveness a CT-scan-based form of colonoscopy that does not require laxative preparation or sedation. 604 patients who were scheduled for a colonoscopy screening between June 2005 and October 2010 prepared for the procedure with two days of a low-fiber diet and the oral ingestion of small doses of a contract agent to label fecal material in the colon. Using software programs created by the MGH team, they subtracted labeled feces from the CT images and analyzed them for the presence of lesions. They mainly searched for adenomas, the type of polyps that are most likely to develop into cancer.

The laxative-free CT procedure was completed within the 5 weeks scheduled before the patients´ scheduled optical colonoscopies. The gastroenterologists that performed the standard colonoscopies were not informed of the identified polyps in the first procedure until the initial examination was completed; a second-pass colonoscopy was then allowed to confirm and remove any missed polyps if necessary. Three MGH radiologists who are trained in virtual cleansing and lesion detection systems interpreted the CT Colonography results, but were blinded to the results of the colonoscopies and diagnoses of any removed tissues. Additionally, patients completed written surveys about their experiences and shed light on which method of colonoscopy they preferred.

The results of the laxative-free CT method were comparable to the standard colonoscopy method, identifying more than 90 percent of adenomas that were 10 mm or larger. Although it did not do as well at identifying smaller polyps, those lesions aren´t as likely to show cancer-related cellular changes as adenomas. 85% of the colonoscopy-confirmed lesions were 10% or larger; three cases of colon cancer were diagnosed among the study group, all 10 mm or larger and detected by both screening methods. When examining the patient surveys, 62% of respondents agreed that the laxative-free CT colonoscopy was the more preferable method. Additionally, the radiation dose is lower for CT Colonography than diagnostic CT scanning, so it would be safe for widespread screening.

The results of this study could greatly influence how many instances of colon cancer are identified and prevented if these results hold up in larger trials. The biggest issue is motivating people to get screened in the first place because of the known discomfort, but if the discomfort is removed, more lives can be saved. Dr. Michael Zalis, MD, director of CT Colonography at MGH imaging and leader of the study was quoted as saying that "our results suggest that this more patient-friendly form of screening is feasible and can perform well enough to really help screen patients."

Source: Annals of Internal Medicine, May 2012