Introduction

^​Intestinal ultrasound (IUS) is gaining increasing acceptance as a reliable tool for tight monitoring of ulcerative colitis (UC). Although several IUS scores have been proposed, none has been formally implemented into official recommendations of international scientific societies.

Aims & Methods

We aimed to compare an IUS score validated for Crohn’s disease (CD), the International Bowel Ultrasound Segmental Activity Score (IBUS-SAS)¹, with other IUS scores specifically developed for UC, in terms of correlation with endoscopic activity.
Patients with UC ≥ 18 years old undergoing partial or full colonoscopy between April 2023 and January 2024 were prospectively included. Endoscopic evaluation of at least the sigmoid colon was mandatory for inclusion, and patients with proctitis (Montreal E1) were excluded. Endoscopic activity was scored with both the Mayo Endoscopic Subscore (MES) and the Ulcerative Colitis Endoscopic Index of Severity (UCEIS), and defined by MES ≥ 1 and UCEIS ≥ 2. Moderate endoscopic activity was determined by a MES = 2 or an UCEIS = 5-6, while severe activity was defined by a MES = 3 or an UCEIS ≥ 7. IUS was performed within 4 weeks of endoscopy. The IBUS-SAS, the Milan Ultrasound Criteria (MUC)², the UC-IUS score³, the US Score from Parente et al.⁴, and the Hata index⁵ were included in the analysis. Applicability of the Civitelli index⁶, an IUS score developed for pediatric patients, was also evaluated. The Spearman’s rank coefficient [rho = ρ] was used to perform correlations, while receiver operating characteristic (ROC) curves were compared with the Hanley & McNeil method.

Results

Collectively, 104 patients were included in the study. The majority of patients (61.5%) had extensive colitis (Montreal E3), with half of them having an active disease at endoscopy (54.8% using MES and 48.1% using UCEIS). IUS examination was performed at a median time of 8 days (IQR 2-15) after endoscopy. All the investigated scores were significantly able to distinguish between the 3 grades of severity of colonic inflammation, using both MES and UCEIS as a reference, with the exception of the Parente’s US Score for the severe endoscopic activity assessed with UCEIS [0 (IQR 0-1) for UCEIS < 7 vs 1 (IQR 0-1) for UCEIS ≥ 7, p=0.09]. The IBUS-SAS showed a strong correlation with endoscopic activity, both with MES (ρ = 0.71, p < 0.01) and UCEIS (ρ = 0.73, p < 0.01) assessments. The Area Under the Curve (AUC) of IBUS-SAS to detect an endoscopic activity of at least moderate severity (MES ≥ 2 and UCEIS ≥ 5) was 0.85 and 0.90, respectively. The optimal cutoff to detect a MES ≥ 2 and UCEIS ≥ 5 was > 11 (sensitivity 75% and specificity 82%) and > 22 (sensitivity 92% and specificity 80%), respectively. Both cut-offs showed progressive increase from mild to severe activity, with IBUS-SAS maintaining a consistently high AUC at different thresholds. Consistent with IBUS-SAS results, all the investigated UC-developed IUS scores correlated with both the MES and the UCEIS (p < 0.01). AUC values and relative comparisons between the AUC are detailed in Table 1.

Table 1. Relative comparisons between the AUC of each score to detect a MES ≥ 2 (A, top-right) and an UCEIS ≥ 5 (B, bottom-left) are reported.
Grey rows and columns: AUC values (with 95%CI).
White cells: p-values obtained via the Hanley and McNeil method (significant p-values are shown in bold).

Conclusion

In this study we provide a successful validation of 6 IUS scores for UC. The IBUS-SAS has an optimal performance in predicting endoscopic activity also in patients with UC, despite having been developed initially for CD.

References

1. Novak KL, Nylund K, Maaser C, et al. Expert Consensus on Optimal Acquisition and Development of the International Bowel Ultrasound Segmental Activity Score [IBUS-SAS]: A Reliability and Inter-rater Variability Study on Intestinal Ultrasonography in Crohn's Disease. J Crohns Colitis 2021;15:609-616
2. Allocca M, Fiorino G, Bonovas S, et al. Accuracy of Humanitas Ultrasound Criteria in Assessing Disease Activity and Severity in Ulcerative Colitis: A Prospective Study. J Crohns Colitis 2018;12:1385-1391
3. Bots S, Nylund K, Löwenberg M, et al. Intestinal Ultrasound to Assess Disease Activity in Ulcerative Colitis: Development of a novel UC-Ultrasound Index. J Crohns Colitis 2021;15:1264-1271
4. Parente F, Molteni M, Marino B, et al. Are colonoscopy and bowel ultrasound useful for assessing response to short-term therapy and predicting disease outcome of moderate-to-severe forms of ulcerative colitis?: a prospective study. Am J Gastroenterol 2010;105:1150-7
5. Kinoshita K, Katsurada T, Nishida M, et al. Usefulness of transabdominal ultrasonography for assessing ulcerative colitis: a prospective, multicenter study. J Gastroenterol 2019;54:521-529
6. Civitelli F, Di Nardo G, Oliva S, et al. Ultrasonography of the colon in pediatric ulcerative colitis: a prospective, blind, comparative study with colonoscopy. J Pediatr 2014;165:78-84.e2

Disclosure

GD reports speaker fees from Alfasigma, Johnson & Johnson, Novartis, Pfizer, Takeda, and has served in advisory board for Celltrion Healthcare and Pfizer. The other authors have no conflict of interests to declare.