Presence of mesenteric lymph nodes on magnetic resonance enterography (MRE) can diagnose proximal bowel (jejunum) involvement in patients with Crohn’s disease, according to a study published in the journal Therapeutic Advances in Gastroenterology.¹

Maconi et al carried out a study of 64 patients with Crohn’s disease in whom magnetic resonance enterography (MRE) and video capsule endoscopy examinations had been performed within one year, from August 2013 to February 2021. The mean age of the participants was 33.9 years and more than half of the study population was male (54.7%). The mean duration of the disease was 5.16 years. The MR enterography examinations were retrospectively scrutinized for mesenteric lymph nodes adjacent to the proximal small bowel (jejunum) at the left upper quadrant (LUQ) and whether the presence of these lymph nodes correlated with the proximal small bowel disease revealed by video capsule endoscopy as per the Lewis score. A normal Lewis score or clinically insignificant inflammation was <135, mild inflammation as score between 135 and 790 and moderate to severe inflammation as score greater than 790. Only lymph nodes larger than 0.5 cm were considered.

Twenty-four (37.5%) out of the 64 study subjects were identified to have proximal bowel disease on video capsule endoscopy. The researchers noted a significant association between regional lymph nodes in the jejunal mesentery and jejunal disease as evident on VCE (p < 0.001).

MRE showed presence of proximal mesenteric lymph nodes at the LUQ in 20 patients. Of these, 15 (75%) had jejunal disease as seen on video capsule endoscopy. No mesenteric lymph nodes at LUQ were evident in 44 patients; of these, 35 (79.5%) did not have jejunal disease on video capsule endoscopy. These observations, therefore, indicate a sensitivity of 62.5%, specificity of 87.5% for LUQ mesenteric lymph node involvement with negative predictive value of 79.5% and positive predictive value of 75% for jejunal Crohn’s disease. The number of regional lymph nodes was higher in patients with jejunal disease versus patients who did not have jejunal disease; 2.63 vs 0.78 (mean), respectively. “No significant association was found between mean regional Lewis scores at VCE indicative of disease activity and regional lymph nodes at MRE (mean Lewis score: 886.07 vs 367.22, p = 0.11). The authors also observed that “Other MRE features of lymph nodes were not significantly predictive of jejunal CD”.

This study, which examined the predictive potential of mesenteric lymph nodes for proximal bowel Crohn’s disease, has demonstrated that the two were positively associated. Fifteen out of the 24 patients with proximal bowel involvement had positive regional lymph nodes at the LUQ. With a NPV of nearly 80% and PPV of 75%, presence of mesenteric lymph nodes on MRE therefore can be adopted as a useful clinical indicator for proximal bowel involvement in patients with Crohn’s disease, even if the bowel wall is apparently normal on imaging. Such patients usually have an adverse prognosis and therefore may require further endoscopic evaluation of the proximal small bowel to confirm these findings and appropriate management.

Reference

1. Giovanni Maconi, et al. Diagnostic significance of mesenteric lymph node involvement in proximal small bowel Crohns disease. Therap Adv Gastroenterol. 2022 Aug 22;15:17562848221118664. doi: 10.1177/17562848221118664.