PET/CT fleshes out extent of inflammatory bowel disease

Inflammatory bowel disease (IBD) such as Crohn’s disease and ulcerative colitis are conventionally evaluated with endoscopy and histology, but imaging with 18F-FDG PET/CT could provide a more thorough picture of intestinal inflammation, according to a study published in the March edition of The Journal of Nuclear Medicine.

Dominik Bettenworth, MD, from University of Münster’s Department of Medicine in Münster, Germany, and colleagues described how 18-F FDG PET/CT imaging provides a non-invasive means of evaluating patients with inflammatory bowel conditions by quantifying increased metabolic activity in diseased areas of the colon.

Colonoscopy is still the gold standard for the evaluation of inflammatory bowel disease, but there are limitations to evaluating the dynamics of inflammatory response and changes in mucosal lesions that denote disease progression or remission. Repeated colonoscopies for periodic staging of the disease are not only uncomfortable for patients but also could be limited by complications such as intestinal stricture.

“Because treatment of IBD has been focused toward a tight control of disease activity to avoid disease progression and functional impairment of the bowel, the appropriate method for disease monitoring still needs to be determined,” wrote the authors. “In this context, mucosal healing as assessed by colonoscopy has been established as a marker widely used in clinical trials. However, because Crohn disease transmurally involves the complete intestinal tract, more enhanced imaging methods are deemed necessary.”

Investigators evaluated IBD in animal models, specifically dextran sodium sulfate (DSS) colitis, which involves extensive tissue damage and inflammatory response, and compared preclinical 18F-FDG PET/CT imaging and histological results with 18F-FDG PET/CT imaging in 25 human patients with suspected Crohn’s disease after endoscopy.

Results of 18F-FDG PET were in line with indications of IBD, including histological inflammation score and weight loss. The CT component provided information about anatomic structures and was found to help map different areas of the colon for a better determination of localization and disease activity. FDG metabolism indicated a range of cellular processes involved in IBD, including changes in neutrophil activity and mucosal T cell infiltration in ongoing inflammation.

“The data suggest that in some patients the transmural inflammatory process might not be noticeable by endoscopy,” wrote the authors. “It is therefore necessary to evaluate in future studies whether patients with ongoing 18F-FDG PET/CT activity are at risk for an unfavorable disease outcome such as early relapse or stricture formation. Because evolving treatment strategies are focusing on changing the disease behavior by inducing a deep remission, it might therefore also be reasonable to include 18F-FDG PET/CT in the diagnostic repertoire of Crohn disease.”

However, questions remain about when the use of 18F-FDG PET/CT would best benefit patients with Crohn’s and other inflammatory bowel conditions. Further investigation will be needed to determine how the imaging technique might be expanded in general clinical use as an alternative or supplement to endoscopy, the researchers concluded.