Crohn's disease lymphadenopathy: MR imaging findings

To assess mesenteric lymph nodes in patients with different Crohn's disease subtypes identified on MR Enteroclysis.

Thirty-four patients, categorized into three different Crohn's disease subgroups, underwent MR Enteroclysis. A high resolution coronal true FISP sequence with fat saturation was applied to assess mesenteric lymph node anatomic distribution, size and shape. Their enhancement ratio (ER) was calculated by dividing signal intensity of each node to signal intensity of nearby vessel on T1 weighted FLASH images, acquired 75 s after intravenous administration of gadolinium. A one-way analysis of variance statistical test was applied to investigate any significant differences regarding mean ER among different disease subgroups.

Two hundred and eighty-three mesenteric lymph nodes were assessed, 231 in patients with active inflammatory (AI) disease, 36 in patients with fibrostenotic (FS) and 16 in patients with fistulizing/perforating (FP) disease. Maximum and minimum diameters were 3.2 and 0.3 cm, respectively. 75% of the lymph nodes presented with an oval shape. The majority were identified as being ileocolic (34%) and paracolic (31%). AI subgroup lymph nodes presented with the highest mean ER (0.783+/-0.17) followed by FP (0.706+/-0.1) and FS subgroup (0.652+/-0.17) lymph nodes. The differences in mean values of ER of mesenteric lymph nodes between AI and FS subtypes were statistically significant (p<0.0001), while mean ER between nodes of FP and the other two subtypes did not present statistically significant differences.

ER of mesenteric lymph nodes identified on MR Enteroclysis may vary across different subtypes of Crohn's disease. Such differences may be valuable in clinical practice.