Estimation of Liver Fibrosis in Patients With MASLD Screening Criteria Through Endoscopic Ultrasound-guided Shear Wave vs Transabdominal Ultrasound and Transient Elastography: The RUMIPAMBA Diagnostic Trial

Metabolic dysfunction-associated steatotic liver disease (MASLD), formerly non-alcoholic fatty liver disease (NAFLD), is an umbrella term which involves simple liver steatosis, metabolic-associated steatohepatitis (MASH) and MASH-related liver cirrhosis. Liver steatosis relies on imaging or biomarkers, but liver biopsy remains the gold standard for its diagnosis and grading. It comprehends intracellular accumulation of triacylglycerol (TAG) as microvascular or macrovascular lipid droplets in at least 5% of hepatocytes. Liver biopsy is invasive, requires a high-quality biopsy sample, can mislead a diagnosis due to sampling bias, depends on pathologist interpretation variability and implies adverse events related to the punction.

There are non-invasive resources useful for the screening and surveillance of liver steatosis and fibrosis. Apart from serum biomarkers, non-invasive technologies designed for this purpose use transabdominal ultrasound (US)-based elastography, namely: US strain, acoustic radiation force impulse (ARFI), point shear wave elastography (pSWE), two-dimension shear wave elastography (2D-SWE) and vibration-controlled transient elastography (VCTE). Although VCTE presents anatomical limitations when used in overweight patients or assessing the right hepatic lobe, it is largely accepted by international guidelines for assessing liver steatosis and fibrosis. Endoscopic ultrasound (EUS)-guided shear wave elastography (SWE) is independent of the anatomical proportions of the patients, and it permits a more reliable right hepatic lobe evaluation. However, it is an invasive and high-cost procedure.

VCTE, US-ARFI and EUS-SWE determine liver fibrosis quantitatively in terms of liver stiffness through kiloPascals. There are four important gaps in the literature: First, the diagnostic accuracy of VCTE for liver steatosis has been profoundly analysed in NAFLD, but in a wide spectrum of liver fibrosis patients, from absent to cirrhosis. These limits finding extrapolations for screening and surveillance. Second, comparisons between VCTE, US-ARFI and EUS-SWE have concentrated on liver fibrosis or cirrhosis, but they have not been compared head-to-head in the context of absent-to-mild liver fibrosis vs controls. Third, there is no determined diagnostic accuracy for EUS-SWE for an early liver fibrosis estimation in MASLD patients. It is useful considering EUS is becoming a more popular procedure. Finally, and to be consequent with the third point, the identification and grading of liver steatosis and fibrosis still need to be described in the nowadays called MASLD patients.

The present study aims to determine the difference in the estimation of liver fibrosis among VCTE, US-ARFI and EUS-SWE in patients with clinical criteria of MASLD screening but absent-to-mild liver fibrosis, according to non-invasive methods.

This study has been called by the authors through the acronym RUMIPAMBA, which means "Role of endoscopic Ultrasound-guided shear wave for MASLD-related liver steatosis and fibrosis Identification in Patients with Absent to Mild Basal fibrosis, based on non-invasive Analytical laboratory tests". In the general culture, Rumipamba is the name of an archaeological prehispanic and preincaic park from Quito, the capital city of Ecuador.