P0280 Evaluation of the diagnostic accuracy of trans-perineal ultrasound for predicting rectal histoendoscopic remission in Ulcerative Colitis (The TRINITY Study): A prospective, paired, comparative study with endoscopic ultrasound and trans-abdominal ultrasound
Authors: Pal P , Mateen M A , Sekaran A , Pooja K , Basha J , Tandan M , Gupta R , Lakhtakia S , Reddy D N 
Published: January 2025

Abstract

Background
Rectum, frequently involved in Ulcerative colitis (UC) is challenging to evaluate using trans-abdominal sonography (TAS). Earlier single centre study have shown that rectal total wall thickness (TWT) (&lt;4 mm) on trans-perineal ultrasound (TPUS) accurately predicts rectal inflammation(1). Inspite of being point-of-care, TPUS can only evaluate the lower rectum (~5 cm) and studies with trans-vaginal ultrasound have shown higher cut offs for rectal TWT(2). This study (comparison of TRIple Rectal UltrasouNd Imaging Technology : TRINITY) aimed to comprehensively evaluate the diagnostic accuracy of TPUS in predicting rectal histoendoscopic activity, using endoscopic ultrasound (EUS) as the reference standard.

Methods
114 UC patients [age 18-70 yr (median- 37), 64 % male, E1: 16, E2: 61, E3: 37] underwent point-of-care TAS and TPUS followed by sigmoidoscopy with biopsy and rectal EUS. On TAS and TPUS, rectal TWT (average of anterior and posterior) and vascularity (Modified Limberg Score, MLS) were evaluated. On EUS, rectal TWT (average of upper, middle and lower and separately lower), vascularity (MLS), mucosal thickness (MT), and submucosal thickness (SMT) were measured. Diagnostic accuracy for predicting endoscopic activity (Ulcerative colitis endoscopic index of severity: UCEIS&gt;1 in rectum) and histologic activity (Nancy Index≥1) was evaluated using receiver operating characteristic (ROC) curves.

Results
For prediction of both endoscopic and histologic activity, EUS outperformed TPUS. TAS was not useful (p&gt;0.05)
For endoscopic activity (n=114):
EUS: Mucosal thickness&gt;0.95 mm: AUC:0.95 (p&lt;0.001); average TWT&gt; 4 mm: AUC:0.89 (p&lt;0.001); Vascularity (MLS) &gt;1: AUC:0.93 (p&lt;0.001); SMT&gt;2.2 mm: AUC:0.84,(p&lt;0.001).
TPUS: rectal TWT &gt;5.6 mm: AUC:0.68 (p=0.001); MLS ≥1:AUC:0.74 (p&lt;0.001).
TAS: TWT &gt;6.3 mm:AUC: 0.57(p=0.25); MLS ≥1:AUC: 0.61 (p=0.04).
For predicting histologic activity(n=81):
EUS: lower rectal vascularity (MLS ≥1): AUC: 0.84, p&lt;0.001; SMT&gt;2.1 mm: AUC: 0.71, p&lt;0.001; MT≥1 mm: AUC:0.81, p&lt;0.001; TWT&gt;5.6 mm: AUC:0.65, p=0.02.
TPUS:rectal TWT≥ 5.6 mm: AUC:0.65 (p=0.02); vascularity (MLS≥1) AUC: 0.65 (p=0.036).
TAS:TWT ≥ 6.3 mm: AUC:0.56, p=0.44; vascularity (MLS ≥1), AUC:0.59, p=0.18.

Conclusion
Although EUS remains the gold standard for assessing rectal inflammation, its invasive nature limits routine clinical use. TPUS offers a point-of-care, non-invasive alternative with moderate accuracy for predicting histoendoscopic remission with higher cut off levels contrary to previous reports. Further refinements in TPUS techniques and protocols are warranted to enhance its widespread applicability in clinical practice.

References
1.Sagami S, Kobayashi T, Aihara K, Umeda M, Morikubo H, Matsubayashi M, Kiyohara H, Nakano M, Ohbu M, Hibi T. Transperineal ultrasound predicts endoscopic and histological healing in ulcerative colitis. Aliment Pharmacol Ther. 2020 Jun;51(12):1373-1383. doi: 10.1111/apt.15767. Epub 2020 May 7. PMID: 32383166.
2.Pal P, Mateen MA, Pooja K, Gupta R, Tandan M, Reddy DN. Trans-vaginal ultrasound for rectal visualization in inflammatory bowel disease: A pilot case-control study. Indian J Gastroenterol. 2024 Feb;43(1):267-270. doi: 10.1007/s12664-023-01492-z. PMID: 38064130.

Figure 1. Diagnostic accuracies of ultrasound parameters

Figure 2. ROC analysis for endoscopic and histologic activity