Ionizing Radiation Exposure in Adults with Inflammatory Bowel Disease

From The Onion:

In the largest reported cohort to date, GC Nguyen et al (Inflamm Bowel Dis 2020; 26: 898-906) describe the ionization radiation exposure (IRE) in individuals (≥18 years) with inflammatory bowel disease (IBD).

Methods: N=72,933 with IBD,1994-2016. During 1st 5 yrs after diagnosis, IRE was estimated in a retrospective matched cohort in Ontario.

Key findings:

  • IBD patients were exposed to nearly 6-fold IRE due to abdominal imaging compared to controls: 18.6 mSv vs 2.9 mSv
  • Patients with CD had higher IRE than UC: 26 mSv vs 12 mSv (P<0.001).  CD patients were more likely to have >50 mSv exposure (15.6% vs 6.2%) and >100 mSv 5.0% vs 2.1%
  • Women were less likely to have high IRE compared to males
  • Residents in the poorest neighborhoods were 27% more likely to have IRE >100 mSv.  Socioeconomic status was an independent factor after accounting for comorbidities. The authors speculate that this could be related to increased use of emergency rooms where they may be more likely to receive a CT.
  • The use of CT scan began to decline after 2007…likely explained by the rise of MRE studies.

While strict guidelines on IRE are lacking, the International Commission on Radiological Protection has suggested that occupational exposure (eg. nuclear workers) should be limited to <100 mSv over 5 years and not more than 50 mSv in a single year.

My take: We need to continue efforts to reduce IRE due to concerns about subsequent secondary malignancies. This likely means avoiding CT for non-emergencies and working with our ED colleagues to think carefully about lifetime IRE in IBD patients.

Related blog posts:

Additional references:

  • -AJR 2001; 176: 289-96. Estimated risks of radiation-induced fatal cancer from pediatric CT
  • -Br J Radiol 2012; 85: 523-28.  Justification of CTs -some not needed
  • -AJR 2010; 194: 868-73.  Lower CT radiation doses in pediatric patients.  ‘Image gently’
  • -Arch Intern Med 2009; 169: 2078-86.

From LA Times:


How much radiation from your CT scanner?

Our children’s hospital, along with many others, has made a concerted effort to reduce radiation exposure by adjusting CT scan settings.  Even a single abdominal CT scan may confer a small but real risk of developing cancer.  The trade-off with low-dose CT techniques has been a concern about poor image quality.  New research indicates that low-dose CT scan is not inferior to standard-dose CT with respect to detecting appendicitis (NEJM 2012; 366: 1596-605).

This single-center study examined 441 patients assigned in a single-blind fashion to low-dose CT (median dose: 116 mGy-cm) in comparison to 447 patients receiving a standard-dose CT (median dose: 521 mGy-cm).  All patients had CT for suspected appendicitis.  The negative appendectomy rate was 3.5% in the low-dose group and 3.2% in the standard-dose group.  There was no significant difference in appendiceal perforation rate or proportion of patients needing more imaging.

How much radiation do your patients receive with a CT scan?

Related newspaper article:

FDA issues guidelines to lower radiation exposure in children:

Related posts:

Magnetic resonance enterography for Crohn’s disease

More imaging needed?

Additional references:

  • -NEJM 2010; 363: 1, 4. Safety of CT.  Can have overdose of radiation and even standard doses could cause complications.  Also, a big issue is downstream unnecessary testing due to incidental findings.
  • -JPGN 2011; 52: 280. Documents high exposure to radiation in large IBD pediatric cohort.
  • -J Clin Gastroenterol 2011; 45: 34-39. High levels of ionizing radiation thru CT scan in pts with IBD.
  • -Pediatr Radiology 2002; 32: 217-313. Minimizing radiation exposure, risk/benefit of CT. Proceedings from conference.
  • -Pediatr Radiology 2002; 32: 700-706. Risk of CT for young child: ~ 1 in 1000 risk of fatal cancer later in life.