IBUS-SAS Score Calculator

Introduction

Welcome to the IBUS-SAS Calculator! This tool helps assess endoscopic activity for inflammatory bowel disease.

The IBUS-SAS Calculator is a specialized tool designed to assist healthcare professionals in assessing activity in inflammatory bowel disease (IBD). By inputting key ultrasound findings such as bowel wall thickness, intestinal fat, Doppler signals, and bowel wall stratification, the calculator provides a standardized score to help predict endoscopic activity with high sensitivity and specificity.

This tool is particularly useful for non-invasive monitoring and evaluating disease activity, offering a reliable alternative to endoscopic procedures. Use the form below to calculate the IBUS-SAS score and gain valuable insights into the severity of the disease for improved patient care and management.

 

Formula of the IBUS-SAS Score

IBUS−SAS = 4×BWT + 15×I−FAT + 7×CDS + 4×BWS

 

Explanation of the 4 variables in the IBUS-SAS calculator

The IBUS-SAS Calculator uses four key ultrasound-based variables to assess the activity of inflammatory bowel disease (IBD). Each variable reflects a specific aspect of disease pathology, contributing to the overall score.

– Bowel Wall Thickness (BWT)

What It Measures: The thickness of the bowel wall, measured in millimeters (mm).

Why It Matters:

• An increased bowel wall thickness is a hallmark of inflammation in IBD.
• A value greater than 3 mm typically suggests disease activity.
• Higher thickness correlates with greater severity of inflammation.

 

– Intestinal Fat (I-FAT)

What It Measures: The presence of fat surrounding the intestines, assessed as absent, uncertain, or present.

Why It Matters:

• Fat wrapping or “creeping fat” is a common feature of Crohn’s disease.
• This variable reflects chronic inflammation and is associated with complications such as strictures or fistulas.

Scale:

• 0: Absent (normal)
• 1: Uncertain (borderline)
• 2: Present (indicative of disease activity)

 

– Color Doppler Signal (CDS)

What It Measures: Blood flow within the bowel wall, as detected by Doppler ultrasound.

Why It Matters:

• Increased blood flow indicates hypervascularity, a marker of acute inflammation.
• Doppler signals help differentiate between active and inactive disease.

Scale:

• 0: Absent (no blood flow detected)
• 1: Short signals (minimal blood flow)
• 2: Long signals inside the bowel wall (active inflammation)
• 3: Long signals both inside and outside the bowel wall (severe activity)

 

– Bowel Wall Stratification (BWS)

What It Measures: The integrity of the bowel wall’s layers, assessed for structural abnormalities.

Why It Matters:

• Normal stratification indicates healthy bowel tissue.
• Loss of stratification or focal/extensive disruption is a marker of inflammation and potential complications.

Scale:

• 0: Normal (intact layers)
• 1: Uncertain (minor changes)
• 2: Focal changes (<3 cm)
• 3: Extensive changes (>3 cm)

 

How to calculate and interpret IBUS-SAS

Each variable contributes to the overall IBUS-SAS score, which is calculated as follows:

IBUS-SAS = (4 × BWT) + (15 × I-FAT) + (7 × CDS) + (4 × BWS)

 

A higher score suggests more severe disease activity:

• • Score > 37.5:
    • Predicts endoscopic activity with high sensitivity (94%) and specificity (91%) (reference 1).
    • Another study shows that a IBUS-SAS score > 25.2 has a sensitivity of 82.2% and specificity of 100% (reference), which is very good a ruling out acitve inflammation.
  • Score 22.8-37.5:
    • Borderline result / mild inflammation.
  • Score < 22.8 and 23.8:
    • Predicts endoscopic remission with sensitivity 95% and specificity 83% (reference 2) and sensitivity of 91.4%, and specificity of 84.8% (reference 3).

 

By analysing these variables together, the IBUS-SAS Calculator provides a comprehensive assessment of inflammation, helping guide clinical decisions and treatment strategies.

 

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I’m a consultant gastroenterologist and endoscopist at Vejle Hospital, part of the University Hospital of Southern Denmark. My main focus is on inflammatory bowel disease, endoscopy, and intestinal ultrasound. Outside of work, I enjoy playing piano and guitar, blogging about various topics, and staying active through padel. (LinkedIn).

 

 

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Have a great one. Kind regards.

Lars 🍀