Background/Aims: Some suggest MRI to be superior to ultrasound in Crohn's disease. We analyzed how often MR enterography (MRE) following a routine ultrasound leads to a change in therapeutic decision. Material and Methods: We retrospectively evaluated 47 patients with Crohn's disease undergoing routine ultrasound examination. Actual medical history, complete blood count, C-reactive protein (CRP), and sonographic findings were assessed independently by two specialists who retrospectively provided a therapeutic proposal. Additionally, all patients received MRE. Thereafter, the specialists had to provide a new therapeutic concept regarding all the available information. Results: Evaluation of the rectum was not successful by ultrasound, but MRE gave good results. Only 1 of 7 abscesses was identified sonographically. Three of the abscesses missed at sonography were localized in the perirectal/perianal region. MRE detected more inflamed bowel segments, but ultrasound assessment of anatomically fixed bowel parts showed good recognition by MRE. With increasing CRP values, we found more positive results of ultrasound and MRE. Therapeutic change was suggested in only 18 patients. Conclusions: Ultrasound should be performed by an experienced examiner, and a proctological examination should be added. MRE is justified in cases of discrepancy between clinical findings and the results of diagnostic ultrasound and, moreover, if Crohn's lesions are suspected at sites proximal to the terminal or neoterminal ileum. Copyright (C) 2010 S. Karger AG, Basel