title: Lymphoid nodular hyperplasia of the terminal ileum can mimic active crohn disease on MR enterography.
abstract: OBJECTIVE
  The purpose of this article is to describe the MRI findings associated with lymphoid nodular hyperplasia at MR enterography and test the ability of radiologists to differentiate healthy control subjects from patients with Crohn disease (CD).
  
  
  METHODS
  Ethical approval was granted for this retrospective study. Thirty-five subjects (nine with lymphoid nodular hyperplasia, 13 with CD, and 13 control subjects) who had undergone MR enterography and ileocolonoscopy were identified from the hospital database. Two abdominal radiologists, working in consensus and blinded to diagnosis, scored enteric MR images for T2 signal, contrast enhancement, mural thickness, and diffusion-weighted imaging (DWI) signal and measured the apparent diffusion coefficient (ADC) in all three groups. Scores were compared using the Kruskal-Wallis test.
  
  
  RESULTS
  T2 signal and contrast enhancement were judged subjectively to be greater in patients with lymphoid nodular hyperplasia and CD than control subjects (p < 0.001). Mural thickness was greater for patients with lymphoid nodular hyperplasia (median, 6.0 mm) and CD (median, 7.3 mm) than control subjects (median, 2.3 mm) (p < 0.001). Lymphoid nodular hyperplasia and CD increased subjective DWI signal and reduced ADC in comparison with normal control subjects; median ADC was 1.34 × 10(-3) mm(2)/s for lymphoid nodular hyperplasia, 1.36 × 10(-3) mm(2)/s for CD, and 1.86 × 10(-3) mm(2)/s for control subjects (p < 0.001). None of T2 signal, contrast enhancement, wall thickness, DWI signal, or ADC value significantly differed between lymphoid nodular hyperplasia and CD. Lymphoid nodular hyperplasia was erroneously diagnosed as CD in blinded assessment in four of nine cases (44%), whereas all cases of CD and healthy control subjects were correctly classified.
  
  
  CONCLUSIONS
  Lymphoid nodular hyperplasia alters both subjective and quantitative MRI parameters, including T2 signal, contrast enhancement, mural thickness, and ADC. In a subset of patients, lymphoid nodular hyperplasia may be indistinguishable from CD on MR enterography.
authors.affiliation: 1 Centre for Medical Imaging, University College London, Podium Level 2, University College Hospital, 235 Euston Rd, London, NW1 2BU, United Kingdom.
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Plumb
authors.forename: Douglas A
authors.initials: DA
authors.lastname: Pendsé
authors.forename: Sara
authors.initials: S
authors.lastname: McCartney
authors.forename: Shonit
authors.initials: S
authors.lastname: Punwani
authors.forename: Steve
authors.initials: S
authors.lastname: Halligan
authors.forename: Stuart A
authors.initials: SA
authors.lastname: Taylor
mesh_terms: D000293:Adolescent; D003424:Crohn Disease / Q000473:pathology*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007078:Ileal Neoplasms / Q000473:pathology*; D007082:Ileum / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D019310:Pseudolymphoma / Q000473:pathology*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D016037:Single-Blind Method; D055815:Young Adult
keywords: Crohn disease; MR enterography; diffusion-weighted imaging; lymphoid nodular hyperplasia