Bowel Ultrasound in Crohn Disease: Current Role and Future Applications

Barium X-ray series and endoscopy are currently considered the most effective means for evaluating patients with known or suspected Crohn disease (CD) involving the small bowel or the colon. They provide excellent visualization of the bowel mucosa, thus showing any abnormal surface patterns, and may also reveal intestinal complications such as strictures and  stulae (1–4); in addition, barium studies can be used to evaluate the exact anatomical location of CD and its extent within the bowel, as well as the number of stenoses. This is useful in planning the most appropriate procedure for patients destined for surgery (i.e. stricturoplasty or resection). However, these imaging techniques provide limited information concerning the extent of transmural and peri-intestinal abnormalities, they are not feasible in all patients (i.e. patients with severe disease or bowel obstruction), they are not easily repeatable, and, for barium studies only, they imply radiation exposure, which contraindicates their use in children and in women of childbearing age. In recent years, the wider availability of high-resolution ultrasound (US) has greatly improved the diagnostic accuracy of this procedure in the assessment of bowel diseases (5–9); however, uncertainty persists as to its strengths and limitations, as well as to its place in relation to other imaging techniques in patients with complicated or uncomplicated CD (10). A review has been made of the current role of bowel US in the diagnostic work-up of patients with CD, focusing, in particular, on its use in de ning the anatomical extent of disease at primary diagnosis and during follow-up, and detecting intra-abdominal complications such as strictures, abscesses and  stulae. The potential use of US in assessing disease activity as well as the improvement in its diagnostic capability with the use of contrast agents is also discussed. De nition of anatomical location and disease extent Even if the role of US in CD diagnosis has been extensively investigated and well established (5–7), its usefulness in de ning the anatomical location of the disease and the extent of CD within the affected bowel segment is still uncertain. This is because of the limited number of studies so far available comparing the accuracy of bowel US with barium X-ray, endoscopy and surgery in detecting CD lesions; moreover, since most of these studies are retrospective or, when prospective, have been performed in small series of CD patients with diseases mainly con ned to the small bowel, their results should be interpreted with caution. As far as the accuracy of bowel US in de ning the anatomical location of CD is concerned, only  ve studies, to date, have speci cally focused on this issue. Brignola et al. (11), comparing US with scintigraphy in 31 patients with X-ray-ascertained CD, showed a relatively low sensitivity of US (73%) in revealing colonic and/or intestinal CD lesions, with a speci city of 93%. Better results were obtained in two other small prospective studies, one by Solvig et al. (12), the other by Maconi et al. (8), where Indium leukocyte scintigraphy and barium X-ray, respectively, were used as gold standards for the detection of small bowel CD. Both studies reported good sensitivity (95% and 93%, respectively) of US for assessing terminal ileal diseases, but both found the technique to be less accurate in the detection of other CD localizations (i.e. 81% for the right colon (8)). Likewise, Schwerk et al. (13) found a good sensitivity of US in detecting isolated CD of the small bowel (92%), whereas US enabled correct anatomical assessment of the disease in 91% of patients with ileocolitis and 89% of those with Crohn colitis alone. The largest prospective study has recently been performed by our group in 296 consecutive patients with proven CD having undergone complete radiographic evaluation of the