IBD Patients Have High Exposure to Ionizing Radiation

By Marilynn Larkin

October 08, 2019

NEW YORK (Reuters Health) - Patients in Ontario with inflammatory bowel disease (IBD), and particularly those with Crohn's disease (CD), are at risk for high exposure to ionizing radiation from abdominal computed tomography (CT) scanning, an observational study reveals.

Increasing magnetic resonance imaging (MRI) scanning may reduce the risk, the study authors say.

"IBD providers need to take into consideration cumulative exposure to ionizing radiation in our IBD population, especially since onset of disease is relatively young," Dr. Geoffrey Nguyen of the University of Toronto told Reuters Health by email. "We need to consider whether the abdominal imaging will change management, how urgent it is, and what imaging modality can answer the specific clinical question?"

That said, he noted, "It is important to emphasize that CT scanning has important uses and is sometimes the preferred imaging in IBD. For example, if we are worried about an intra-abdominal perforation or obstruction in CD, abdominal CT would be the imaging modality of choice."

Dr. Nguyen and colleagues reviewed information on abdominal diagnostic imaging in IBD patients in health administrative databases in Ontario between 1994 and 2016.

As reported online September 27 in Inflammatory Bowel Diseases, 72,933 incident IBD cases (34,448 CD and 38,485 UC) occurred during the study period. Cases were age- and sex-matched to controls. Overall, the mean age at diagnosis was about 39 and about half were women.

During the first five years after diagnosis, IBD patients were exposed to nearly six-fold higher doses of cumulative ionizing radiation attributable to abdominal imaging compared with non-IBD controls (18.6 mSv vs 2.9 mSv).

Cumulative ionizing radiation exposure was higher in CD than UC (26.0 mSv vs. 12.0 mSv), with CD patients more than twice as likely to exceed 50 mSv (15.6% vs. 6.2%) and 100 mSV (5.0% vs. 2.1%). Ionizing radiation exposure varied by geographic region, and those with lower incomes were more likely to have high exposure.

Abdominal MRI use peaked between 2007 and 2012, having increased annually at 34%, and coincided with an annual 2% decline in abdominal CT use.

The authors state, "Utilization of abdominal MRI in IBD has risen dramatically over the last decade and has likely contributed to a decline in use of CT scans. However, these increasing trends may not be sustainable given the decelerating growth rate toward the end of the study period."

"Infrastructural capacity (in Ontario) to perform MRI and development of alternatives that also involve low or no ionizing radiation exposure" are likely behind the deceleration, Dr. Nguyen said.

"The wait times for small bowel MRI in Ontario can vary across the province, ranging from a few weeks to several months," he noted. "In high-volume specialized IBD centers in downtown Toronto, the wait times sometimes exceeded a year for small bowel MRI."

"So, I think part of that plateauing is due to the province as a whole approaching its capacity to perform MRI," he said.

"At the same time," he added, "we are increasingly using low-dose CT enterography, which uses considerably less radiation than a conventional CT and provides very similar actionable clinical information."

"As clinicians," he continued, "we have to weigh the often long wait times for MRI against the relatively small amount of ionizing radiation exposure from low-dose CT. We also have growing experience with the use of ultrasound to visualize parts of the small bowel that are frequently affected by Crohn's disease and also use that as an alternative."

"I would guess that most of the excess use of abdominal CT is probably in urgent settings like the emergency department," he said. "Consequently, educational initiatives from physician organizations would not only have to include IBD providers, but also emergency physician providers."

"I think perhaps the most powerful impact might come from patient advocacy groups like Crohn's and Colitis Canada," he noted. "Educating patients about the potential risk of cumulative ionizing radiation could empower them to be more involved in deciding when to undergo imaging studies that involve ionizing radiation."

Gastroenterologist and internist Dr. Niket Sonpal, adjunct professor at Touro College in New York City, told Reuters Health by email, "Additional research is needed not only to confirm the findings but also to stratify radiation dosing and long-term consequences".

"I agree that preferential allocation to the subset of patients who are at risk for high ionizing radiation exposure (is needed), including younger patients," he said. "The sensitivity and specificity are relatively equal and MRI has the inherent benefit."

"However," he added, "this would mean increasing clinician knowledge of the paradigm shift, insurer awareness to pay for said MRIs, and patient access to the MRI machines - all three of which are the true challenges in bringing about a solution (to the problem) that this study raises."

SOURCE: http://bit.ly/2LWByih

Inflamm Bowel Dis 2019.

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