Noncontrast MRE exams recommended for children with IBD
When a magnetic resonance enterography (MRE) scan is performed for routine evaluation of pediatric patients with known or suspected inflammatory bowel disease (IBD), a gadolinium-based contrast agent (GBCA) may not be necessary. A study conducted by researchers from Saint Louis University School of Medicine and published in the March 21, 2019, online edition of Pediatric Radiology showed that contrast agents did not improve detection of active inflammation in the terminal ileum and colon compared to noncontrast MRE.
MRE is the primary exam ordered for children with suspected or known Crohn’s disease, ulcerative colitis, or indeterminate colitis. Besides not exposing pediatric patients to ionizing radiation, MRE provides excellent soft-tissue resolution and proven utility for functional imaging through cine acquisitions. Children with IBD undergo multiple CE MREs to monitor and assess treatment response.
When children require contrast administration, the examination time lengthens, the risk of motion artifact increases, extended sedation time may be required, and the patient may have an allergic reaction or retain gadolinium. For these reasons, researchers led by Shannon G. Farmakis, MD, medical director of pediatric radiology at SSM Health Cardinal Glennon Children’s Hospital in St. Louis, MO, conducted a retrospective study to evaluate if GBCAs are necessary to diagnose active bowel inflammation.
The study consisted of 77 patients ranging in age from 7 to 18 years, 58 of whom had known and 19 had suspected IBD. A pediatric radiologist and a body radiologist reviewed in consensus the MRE images in three separate sessions. They analyzed noncontrast MRE sequences in the first session, CE MRE sequences only in the second session, and all image sequences in the third. The radiologists assessed five sections of the bowel, noting abnormal bowel wall thickening, bowel wall edema, bowel wall diffusion restriction, abnormal bowel wall enhancement, and skip lesions. They measured length of bowel disease, if inflamed, and also recorded a variety of non-bowel findings associated with IBD.
The authors provided detailed statistics of each element identified in their assessments.They stated that “the administration of a contrast agent did not significantly affect sensitivity or specificity; pre-contrast MRE and post-contrast MRE demonstrated similar sensitivities and specificities for detecting active bowel inflammation.” They stated that images with contrast are superior for detecting penetrating complications, such as fistulas, sinus tracts, phlegmon, and abscesses.
They also noted that the sensitivity of both pre- and postcontrast MRE are poor compared to combined findings of endoscopic and histopathological results. “Our results indicate that endoscopy with biopsy is better at diagnosing active inflammation than MRE,” they wrote, while adding that MRE and endoscopy are complementary methods of evaluating IBD. They pointed out that MRE can evaluate large areas of the small bowel and detect extraluminal abnormalities. MRE is also not limited to just evaluating the bowel mucosa, but also can evaluate the other layers of the bowel wall.
Based on the study findings, the authors recommend that CE imaging be reserved for evaluating pediatric patients with acutely worsening symptoms or symptoms that are not improving with treatment.
REFERENCE
- Kim SJ, Ratchford TL, Buchanan PM, et al. Diagnostic accuracy of non-contrast magnetic resonance enterography in detecting active bowel inflammation in pediatric patients with diagnosed or suspected inflammatory bowel disease and to determine the necessity of gadolinium-based contrast agents. Pediatr Radiol. Published online March 21 2019. doi: 10.1007/s00247-019-04369-6