Background: The purpose of this study was to investigate the characteristic sonographic features, such as focal disappearance of the wall stratification sign (FD sign), of longitudinal ulcers in patients with Crohn disease (CD).
Methods: A total of 545 sonographic examinations of patients with Crohn disease (n = 166), ulcerative colitis (n = 196), bacterial colitis (n = 78), ischemic colitis (n = 63), pseudomembranous colitis (n = 32), Behçet's disease (n = 7), and collagenous colitis (n = 3) were extracted. The sonographic findings were compared with those of a barium contrast study, colonoscopy, and resected specimens. In transverse views of the bowel segment, wall stratification was investigated. The FD sign was defined as the disappearance of the layered structure observed in a single portion of the bowel circumference. Prevalence of the FD sign was investigated for each disease.
Results: Eighty lesions (76 CD, 1 ulcerative colitis, 2 ischemic colitis, 1 Behçet's disease) with active single longitudinal ulcers were detected by barium contrast study and endoscopy. Among them, the FD sign was detected by ultrasonography (US) in 73 lesions (91.3%). No lesions with the FD sign were found by US without radiological or endoscopic findings of longitudinal ulcers. An in vitro study (water-immersion method) of resected specimens revealed that the FD sign reflected the focal destruction of wall stratification caused by the deep longitudinal ulceration.
Conclusions: Ultrasonographic findings of FD sign are correlated with the existence of deep longitudinal ulcers, which are most frequently found in CD. US is a useful diagnostic modality for detecting longitudinal ulcers in patients with CD.