Re: ¹⁸F-FDG PET-MR enterography in predicting histological active disease using the Nancy index in ulcerative colitis: a randomized controlled trial

Dear Sir,

We read with interest the article by Li et al. “¹⁸F-FDG PET-MR enterography in predicting histological active disease using the Nancy index in ulcerative colitis: a randomized controlled trial. Eur J Nucl Med Mol Imaging” [1]. The authors describe that among the parameters of ¹⁸F-FDG PET-MR enterography, the maximum standardized uptake value (SUV_max) ratio of bowel segment to the liver has the highest specificity and diagnostic accuracy to predict histologically active inflammation in ulcerative colitis (UC). They compared the sensitivity and specificity of SUV_max ratios between patients with and without bowel purgation and reported that bowel cleaning reduced the specificity of the SUV_max ratio.

Our group has previously reported that PET-CT detected intestinal inflammatory activity in UC patients [2]. We included 10 UC patients in deep remission defined as the absence of symptoms, endoscopic or histological activity. There was no bowel purgative in our study. We identified that 4 patients (40%) had increased uptake of ¹⁸F-FDG despite deep remission.

Both our study and this new one by Li and colleagues demonstrate that PET imaging is an excellent non-invasive diagnostic modality to assess histologic and endoscopic inflammation in UC patients, and suggest that deeper levels of metabolically active inflammation occur and may be a novel endpoint for management and understanding the pathophysiology of UC.