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While endoscopy is the gold standard for assessing treatment response and remission in ulcerative colitis (UC), intestinal ultrasound (IUS) has been proposed as a faster, noninvasive, and less costly alternative. Recently, a group led by Floris de Voogd, MD, of Amsterdam University Medical Center in the Netherlands, evaluated IUS against endoscopy for monitoring patients with moderate to severe UC.

The promising results of this small prospective study were published in and de Voogd discussed them in the following interview with the Reading Room.

What prompted you and your colleagues to undertake this small study?

de Voogd: The overall interest in IUS is rising, as it has several advantages over endoscopy, being noninvasive, fast, low-cost, and requiring no patient preparation. Previous research had investigated IUS versus endoscopy for diagnosing UC flares, but studies assessing response with IUS have been few -- especially ones with robust comparative control standards, such as endoscopy and histology.

Did you begin with the expectation that IUS would be effective for monitoring response to treatment?

de Voogd: Yes, previous studies such as the one of UC patients published in 2020 by showed response assessment was feasible and accurate with IUS. However, most studies did not perform a second endoscopy and correlate those findings to IUS findings. We hypothesized that response at endoscopy would highly correlate with response on IUS, with bowel wall thickness (BWT) being of main interest.

What was the design of the study and how was response assessed?

de Voogd: We recruited 30 patients, 27 of whom completed follow-up in a prospective-design study. IUS, endoscopy, and biopsies were taken at baseline and after 8 weeks of treatment with the JAK inhibitor tofacitinib.

IUS, endoscopy (endoscopic Mayo score and the Ulcerative Colitis Endoscopic Index Severity score), and histology (Robarts Histopathology Index) were blindly scored. Endoscopic endpoints were endoscopic remission, response, and improvement. For IUS, BWT, hyperemia, and other parameters were scored by two blinded readers.

What were the main findings?

de Voogd: BWT correlated with endoscopic scores and histology. BWT was lower when the endoscopic endpoints were reached and showed a more pronounced decrease when endoscopic response was reached.

Furthermore, we determined accurate cutoff values for BWT to determine endoscopic endpoints. The submucosa emerged as the thickest wall layer, and that is an interesting finding, as UC is often described as a mucosal disease. Transmural assessment might therefore provide interesting and novel insights about UC patients.

Were there any other significant parameters for IUS-UC correlation?

de Voogd: Colour Doppler for hyperemia assessment was another parameter of interest, but BWT remained of greatest interest, especially for determining endoscopic remission.

Is this assessment modality ready to be widely used?

de Voogd: We currently perform IUS on a daily basis in our center, and it provides fast and accurate information on disease activity and treatment response for patients with UC and also with Crohn's disease.

We've also noticed increasing interest in IUS in Europe, Australia, and Asia, as well as very recently in the U.S. The International Bowel Ultrasound Group offers a training curriculum, with the next two starting this month in New York and in March 2023 in Chicago.

What's the next research step that needs to be taken and is your group recruiting patients for further study?

de Voogd: The next step is to validate our results in a larger cohort. The validation of an IUS score is currently a work in progress. Although not significant in our study, it is also of interest to determine the additional value of fecal calprotectin combined with IUS parameters during response assessment.

What's the overall take-home message for gastroenterologists treating UC?

de Voogd: The bottom line is that IUS is an accurate way to determine endoscopic response and remission in UC. It also correlates with histological inflammation, with the most affected wall layer being the submucosa. It should be noted, however, that IUS is of limited use for assessment of the rectum, so response assessment in proctitis is generally difficult.

You can read the abstract of the study here.