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P160. Diagnostic medical radiation exposure in a cohort of IBD patients

S. Chatu1, A. Poullis1, R. Holmes1, R. Greenhalgh2, R.C. Pollok1

1St George's Hospital NHS Trust, Gastroenterology, London, United Kingdom; 2St George's Hospital NHS Trust, Radiology, London, United Kingdom

Background: Diagnostic imaging plays a vital role in the diagnosis and management of inflammatory bowel disease (IBD). Increasing use of imaging, particularly computed tomography (CT) has led to concerns about the malignant potential of diagnostic medical radiation from a cumulative dose as low as 50 mSv-equivalent to 5 CT abdomen scans. The aim of this study was to quantify radiation exposure in IBD patients referred directly from primary care, and determine predictors of exposure to potentially harmful levels of ionising radiation.

Methods: Patients with a diagnosis of Crohn's disease (CD) or ulcerative colitis (UC) were prospectively recruited from clinic between January 2011 and June 2011. Demographic and clinical data were obtained by scrutinizing medical records. The number and type of imaging procedures was obtained from the radiology database which was first set up in 1990, we only included those diagnosed after the database was initiated. The effective dose of radiation from each test was estimated from published standardised tables. Cumulative effective dose (CED) was calculated for each subject by summing the effective doses of radiation from diagnosis until end of study period which was June 2011. Cox regression analysis was performed to assess for factors associated with potentially harmful levels of ionising radiation defined as total CED >50 mSv.

Results: The cohort included 415 patients (218 CD, 197 UC). Median disease duration for CD and UC was 8.3 and 7.7 years respectively. Mean age at diagnosis was 30.8 and 36.9 years for CD and UC respectively. Median CED was 7.2 mSv (IQR: 3.0 to 22.7) in CD and 2.8 mSv (IQR: 0.8 to 8.9) in UC patients. A total of 32 patients (8%) received a CED >50 mSV, which included 29 CD and 3 UC patients. Multivariate analysis revealed IBD related surgery was an independent predictor of CED >50 mSv with a HR of 7.7. CT imaging, followed by barium studies contributed most to the total CED exposure.

Conclusions: This large study has demonstrated that about 1 in 10 patients with IBD; in particular those with CD are exposed to potentially harmful levels of ionising radiation. A history of IBD related surgery was significantly associated with this level of exposure. Clinicians should log cumulative radiation exposure and where possible alternative modalities such as magnetic resonance imaging and small intestine contrast ultrasonography should be utilised since IBD patients are already predisposed to malignancy as a result of chronic inflammation and therapy.