Ultrasound in Crohn’s disease of the small bowel

Abstract

Objective: The purpose of this work is to prospectively evaluate high resolution ultrasonography with graded compression in the ability to detect Crohn's disease of the small bowel (CDSB) together with its complications and activity signs, compared with enteroclysis, CT and immunoscintigraphy in the mirror of the final diagnosis. Methods and material: In a series of 73 consecutive patients, who were referred for enteroclysis with suspected Crohn's disease of the small bowel computed tomography (CT), ultrasound (US), immunoscintigraphy with ^99mTc labeled monoclonal antigranulocyte antibody (AGAb) examinations were performed within 10 days from each other. For the final evaluation the diagnosis of CDSB was based on combination of clinical and enteroclysis findings (73 cases) and in 17 cases additional surgical and pathological data were available. The results of other modalities were blinded to the radiologists performing and reading out the exams. The diagnostic values of each modality was assessed also in those 18 patients, who had early Crohn’s disease. In the group of 43 patients with proven CDSB who had all the four imaging modalities, the modalities were compared in their ability to demonstrate various pathological conditions related to CD. Increased (>500 ml/min) flow measured by Doppler US in the superior mesenteric artery and increased color signs in the gut wall seen by power Doppler sonography were compared to CDAI. Results: Of the 73 patients the combination of enteroclysis and clinical tests demonstrated CDSB in 47. The sensitivity, specificity and accuracy of ultrasound were 88.4, 93.3 and 90.4%, respectively. Enteroclysis was the most accurate method. CT was more sensitive than US, but less specific. The accuracy of US, CT and scintigraphy were similar. In the group of 18 patients, who had early CDSB, the sensitivity of US decreased to only 67%, CT and scintigraphy had higher values. Intra- and perimural abscesses, and sinus tracts were also more frequently visualized by US, especially if they were small. US was superior than CT in detecting stenoses and skip lesions, but inferior to enteroclysis. US and CT detected more fistulas, than enteroclysis. Compared to CT, US detected more cases with mesenteric lymphadenopathy, equal cases with abscesses and free peritoneal fluids. In detecting mesenteric inflammatory proliferation CT, and in detecting colonic involvement CT and immunoscintigraphy were slightly superior than graded compression US. Patterns of mural stratification detected by ultrasound correlated well with the enteroclysis severity stages. There was only 59% agreement between increased superior mesenteric artery flow detected by Doppler sonography and CDAI, and 60.5% agreement between increased number of Color pixels in the gut wall measured by power Doppler and increased CDAI. Conclusion: High resolution graded compression sonography is a valuable tool for detecting small intestinal Crohn's disease. It has similar diagnostic values as CT. However in early disease the sensitivity substantially decreases. In known Crohn's disease for following disease course, evaluating relapses and extramural manifestations US is an excellent tool. Doppler and Power Doppler activity measurements do not correlate well with the more widespread clinical activity index.

Introduction

The principle tools for the diagnosis of Crohn's disease are colonoscopy with multiple biopsies and barium examinations, both giving superb visualization of the mucosa [1], [2]. However, colonoscopy is invasive and is limited in assessing superficial mucosal involvement. Involvement of the small bowel alone occurs in 30–40% of the cases and the iliocoecal region is involved in about 50% [3]. Experienced colonoscopists can cannulate the terminal ileum only in 70–80% of the cases [4], [5]. For evaluating the extent of small bowel involvement enteroclysis is the accepted method. Colonoscopy, barium enema and enteroclysis can not directly depict the transmural extent of the inflammation or extraintestinal complications of the disease. CT is considered to be the tool for detecting the extramural extent of the disease [6], [7].

Ultrasonography is also reported to be accurate in detecting wall thickening associated with small intestinal Crohn's disease [8].

Beside diagnosing Crohn's disease in patients, who have symptoms suspicious of it, ultrasound may be useful in following up patients with known diagnosis to detect complications [9] or assessing the actual activity [10].

The purpose of this study is to prospectively evaluate the ability of high resolution ultrasonography with graded compression in detecting Crohn's disease of the small bowel (CDSB) compared with CT, enteroclisis and immunoscintigraphy in the mirror of the final diagnosis. We wanted to assess also the value of ultrasound in detecting complications needing surgical intervention and assessing disease activity, which may be an indicator of under- or overtreatment.