International expert guidance for defining and monitoring small bowel strictures in Crohn's disease on intestinal ultrasound: a consensus statement

Background

Diagnostic imaging using CT enterography, magnetic resonance enterography, and intestinal ultrasound are important tools in evaluating stricturing Crohn's disease. Definitions of strictures have been developed for CT enterography and magnetic resonance enterography. However, expert recommendations for definitions and treatment response of strictures on intestinal ultrasound are not available. The aim of this study was to standardise definitions, diagnosis, and treatment response criteria in small bowel stricturing Crohn's disease on intestinal ultrasound.

Methods

Using modified RAND–University of California Los Angeles Appropriateness Method, a diverse expert panel of 13 gastroenterologists, seven radiologists, and two patient representatives was assembled. A total of 466 statements on definitions and response to therapy of stricturing Crohn's disease on intestinal ultrasound were generated from a systematic review and from expert opinion, with subsequent rating for appropriateness. Two rounds of voting with an interposed survey result discussion were performed. Statements were classified as inappropriate, uncertain, or appropriate based on the median panel rating and degree of disagreement. Appropriateness was rated using a nine-point Likert scale (1 being inappropriate, 9 being highly appropriate).

Findings

A naive or anastomotic small bowel Crohn's disease stricture on intestinal ultrasound is defined by the combination of bowel wall thickening, luminal narrowing, and pre-stenotic dilation. Bowel wall thickness is defined as being more than 3 mm. Luminal narrowing is defined as either a luminal diameter reduction of more than 50% in the narrowest area and relative to a normal adjacent bowel loop, or a luminal diameter of less than 1 cm. Pre-stenotic dilation is defined as more than 2·5 cm or an increase in bowel diameter relative to a normal adjacent bowel loop. Definitions for grading hyperaemia, inflammatory fat, wall stratification, intestinal ultrasound machine technical parameters, and image acquisition were also devised. Treatment response of strictures was defined as reduction in stricture length, bowel wall thickening, luminal narrowing, pre-stenotic dilation, and motility abnormalities.

Interpretation

To our knowledge, this is the first intestinal ultrasound appropriateness rating exercise conducted for defining, diagnosing, and measuring response to therapy in small bowel stricturing Crohn's disease and informs future clinical use and intestinal ultrasound index development for clinical trials.

Funding

Leona M and Harry B Helmsley Charitable Trust.