Mesenteric lymph nodes in MR enterography. Are they reliable followers of bowel in active Crohn's disease?

To demonstrate magnetic resonance enterography (MRE) features of mesenteric lymph nodes (LN) in patients with Crohn's disease (CD) and investigate whether they follow enhancement or apparent diffusion coefficient (ADC) parameters of bowel. This study was approved by the institutional review board. A total of 788 MREs from patients with CD were retrospectively reviewed. Eighty-eight patients, aged 16-66 years, including 59 active cases, were enrolled based on inclusion criteria. In each MRE, two segments (normal and abnormal) and two LNs (regional and non-regional) were independently suggested, consensually chosen, and analyzed by two radiologists. Signal-to-noise (SNR) and contrast-to-noise (CNR) ratios were calculated to assess signal intensities (SI) at 30, 60 and 180 s after contrast administration, as well as slope of enhancement (SOE). Enhancement parameters and ADC values were compared. Regional LNs showed significantly higher SI₃₀, SI₆₀ and SI₁₈₀ (CNR and SNR) and lower ADC values in active vs. inactive groups (all p<0.05) without significant difference in number or size. Strong correlations were demonstrated between abnormal segments and regional LNs in active group in terms of SI₃₀, SI₆₀, SI₁₈₀, SOE_0-30 and ADC values (r = 0.679 to 0.774, all p<0.001). SI₁₈₀, SOE_60-180 and ADC values were moderately correlated between abnormal segments and regional LNs in inactive group (r = 0.448 to 0.595, all p<0.05). In logistic regression analyses, SOE_0-30 and ADC value of regional LNs independently predicted active CD. Mesenteric LNs follow quantitative enhancement and diffusion parameters of bowel in active CD. SOE_0-30 and ADC value of LN could predict disease activity. (orig.)