Reproducibility of bowel ultrasonography in the evaluation of Crohn's disease

Abstract

Background

Bowel ultrasonography is increasingly used in the detection and follow-up of patients with Crohn's disease, but a limitation to its further diffusion is the lack of standardisation of ultrasonography parameters.

Aims

This study aimed to standardise the most common bowel ultrasonography parameters in order to develop an unequivocal imaging interpretation and to assess bowel ultrasonography reproducibility.

Patients

Twenty patients with Crohn's disease were examined.

Methods

Six ultrasonographers (mean bowel ultrasonography experience = 16 years) performed the study. They chose and discussed a common assessment methodology concerning eight ultrasonography parameters: bowel wall thickness, bowel wall pattern, bowel wall blood flow, enlarged mesenteric lymph nodes, mesenteric hypertrophy, abdominal free fluid, and stenosis or fistulae at four preliminary meetings. The day of the study operators were randomised to two rooms where they independently and in turn performed ultrasonography scans. Interobserver agreement was scored by kappa statistics.

Results

Excellent k values were observed for bowel wall thickness (0.72–1). k Values were poor for bowel wall pattern (−0.22–0.85) and good for bowel wall blood flow (0.53–0.89). The presence of lymph nodes was reproducible (0.56–0.90) except in one case (0.25). Concordance on free fluid was excellent (0.85–1), whereas that on mesenteric hypertrophy was generally poor (0.14–0.69). Agreement was excellent for stenosis (0.81–1) whereas that for fistula was fair in room abscesses (0.31–0.48) and very good in room B (0.87–1).

Conclusion

Bowel ultrasonography signs used in Crohn's disease can be standardised as most of them showed a fair to good reproducibility. In particular, bowel wall thickness, the most relevant parameter for Crohn's disease detection, showed an excellent reproducibility.

Introduction

Recent technological advances in ultrasonography (US) and the consequent availability of high frequency transducers have allowed an increasing use of US evaluation of small and large bowel (B-US). This imaging technique offers many benefits in the study of the intestinal tract being a safe, cheap and non-invasive examination, easily repeatable in the patient clinical follow-up. In this regard, several studies showed that US bowel examination could be useful in inflammatory bowel diseases (IBD) where it has been reported of value both in the detection of Crohn's disease (CD) [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19] and of its complications [20], [21], [22], [23].

The detection and assessment of gastrointestinal diseases, CD included, relies on some characteristics of the bowel itself, such as the presence of bowel wall thickening and/or luminal narrowing, the echo pattern and vascularisation of the bowel wall and other indirect US signs (e.g. the presence of mesenteric lymphadenopathy and/or of fluid within the abdominal cavity). In addition, US can be used in assessing the presence of the possible complications of CD, some of which (fistula (F) and/or abscesses (A)) can be observed mainly in patients with active disease, whereas stenosis (S) could be present both in inactive and active disease.

Thanks to its many advantages, B-US has been proposed as a useful tool, preliminary to other more expensive and invasive investigations in assessing patients with clinically suspected CD [19]. Currently, however, a lack of standardisation of the US parameters commonly used in CD and the still reduced number of skilled ultrasonographers in this technique are limiting the use of this imaging modality. In addition, to our knowledge there are no studies in the literature regarding the reproducibility of B-US for the interpretation of US signs of CD.

The aim of this study was to choose and standardise some B-US parameters, commonly used in the detection and follow-up of patients with CD, in order to develop an unequivocal imaging interpretation and, secondly, to assess the interobserver agreement among different ultrasonographists, expert in B-US, from different centres, in the evaluation of these predefined US parameters. In our opinion this would be the first step to developing a univocal US imaging interpretation and possibly to organising B-US training in the future.