A Physiologic Analysis of Endoscopic Sleeve Gastroplasty (ESG): Effects of ESG on Non-Alcoholic Steatohepatitis (NASH) and Portal Pressure Gradient in Patients With Obesity and NASH With Advanced Fibrosis

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease worldwide. Affecting approximately one-third of the United States (U.S.) population, the prevalence of NAFLD increases to 90% in patients with obesity. In 25% of patients, NAFLD progresses to a more severe form-non-alcoholic steatohepatitis (NASH)-which further increases the risks of cirrhosis and hepatocellular carcinoma. In 2017, the lifetime costs of caring for NASH patients in the U.S. were estimated at $222.6 billion, with the cost of caring for the advanced NASH (fibrosis stage ≥ 3) being $95.4 billion. It is projected that the number of NASH cases will increase by 63% from 2015 to 2030.

Liver biopsy (LB) remains the gold standard for diagnosing NASH. Although the presence of fibrosis is not required for diagnosis, fibrosis stage is the strongest predictor of liver-related outcomes, with stages 3 and 4 being associated with a mortality relative risk of 6.7 and 11.1, respectively, compared to no fibrosis. Traditionally, LB has been performed via a percutaneous or transjugular approach. With advancements in endoscopic ultrasound (EUS) technologies, EUS-guided LB (EUS-LB) has emerged as an alternative means, with a 90%-100% diagnostic yield and 0-0.9% adverse event (AE) rate.

In patients with advanced fibrosis, the main determinant of decompensation and mortality is the presence of portal hypertension (PH), defined as hepatic venous portal gradient (HVPG) > 5 mmHg. In 2017, Dr. Guadalupe Garcia-Tsao (Co-I) further subcategorized compensated cirrhosis into those with no PH (HVPG ≤ 5 mmHg), mild PH (HVPG > 5 but < 10 mmHg) and clinically significant PH (HVPG ≥ 10 mmHg) given the differences in their pathophysiological mechanisms, prognosis and potentially therapeutic approach.

Traditionally, HVPG is obtained by subtracting the free hepatic venous pressure (FHVP) from the wedged hepatic venous pressure (WHVP), which is used as a surrogate of portal venous pressure (PVP). In 2016, Dr. Marvin Ryou (Co-I) reported the safety and technical feasibility of measuring true PVP and HVP and thus directly assess portal pressure gradient (PPG) in pigs using a digital pressure wire delivered through an EUS-based needle. Since then, the technology has progressed with the current device consisting of an EUS-based needle connected to a digital compact manometer. Studies in humans now report 92%-100% technical success without AEs (compared to 7-9% AE rate for traditional LB).

The mainstay of treatment for NASH remains weight loss achieved via lifestyle modification (LM). Previous studies show a correlation between weight loss and improvement in histologic features of NASH with approximately 10% total weight loss (TWL) required for fibrosis regression. Nevertheless, the average weight loss associated with LM is 3.8%, with less than 10% of patients able to achieve the 10% TWL threshold, leaving the majority of NASH patients undertreated.