Prediction of the need for surgical intervention in obstructive Crohn's disease by¹⁸F-FDG PET/CT

We preoperatively determined the accuracy of ¹⁸F-FDG PET/CT for differentiating fixed muscle hypertrophy and fibrotic stenoses from acute transmural inflammatory stenoses in patients with Crohn's disease (CD) scheduled to undergo surgical resection for obstructive symptoms. Methods: Seventeen patients with known CD prospectively underwent ¹⁸F-FDG PET/CT before already-planned surgery for obstructive symptoms. Image interpretation was by consensus of 2 readers with knowledge of patient participation in the study but not of other clinical history. Lesions were qualitatively graded on a 5-point scale for the presence of increased ¹⁸F-FDG uptake consistent with active inflammation. Maximum lean standardized uptake value (SUL_max) was determined for lesions scored 1 or more. Imaging results were compared with the pathologic grading of inflammation and pre-dominant histopathologic subtype for each patient's surgical specimen, whether mainly inflammation, fibrosis, or muscle hypertrophy. Results: Thirteen of the 17 patients underwent surgery (median, 28 d after PET/CT; range, 2-148 d), and 12 of these 13 had histopathologic correlation. Despite the predominant histopathologic subtype (inflammation, 5; fibrosis, 4; and muscle hypertrophy, 3), acute and chronic inflammation, fibrosis (median, 50%; range, 40%290%), and muscle hypertrophy (median, 20-fold thickening; range, 9- to 40-fold thickening) were found in all patients. SUL_max was significantly higher in severe than in mild-to-moderate chronic inflammation (8.2 ± 2.8 vs. 4.7 ± 2.5, P = 0.04). No patient with predominantly fibrosis or muscle hypertrophy (n = 7) had an SUL_max greater than 8. Visually, 10 of 12 patients on PET/CT were considered to have active inflammation of the bowel. Conclusion: Patients with CD who undergo surgery for obstructive symptoms have histopathologically mixed findings of inflammation, fibrosis, and muscle hypertrophy. Qualitative PET interpretations were quite sensitive, but additional semiquantitative analyses using SUL_max helped identify patients with active inflammation. This information may be beneficial for referring gastroenterologists considering medical therapy versus surgery for patients with CD who present with obstructive symptoms.