Frequency of Increased Liver Stiffness in US Bariatric Surgery Candidates

Overview

This study analyzed data from NHANES 2017–2018 to assess the prevalence of metabolic-associated fatty liver disease (MAFLD) and elevated liver stiffness among US adults eligible for bariatric surgery. Elevated liver stiffness, a surrogate for liver fibrosis, was measured using vibration-controlled transient elastography (VCTE), revealing significant rates of liver fibrosis in this population.

Background

Obesity prevalence in US adults has risen dramatically, with severe obesity tripling since the late 1980s. This trend has contributed to an increased burden of MAFLD, affecting up to 75% of patients with type 2 diabetes. Liver fibrosis stage is the strongest predictor of liver-related outcomes, but pharmacologic treatments are lacking, making weight loss through lifestyle or bariatric surgery the main therapeutic approach. Despite guidelines not recommending routine liver imaging in bariatric candidates, elastography may help identify advanced fibrosis, yet population-level data remain scarce.

Data Highlights

The study utilized NHANES 2017–2018 data, a nationally representative survey of approximately 5000 US participants annually. Liver stiffness was measured by VCTE using FibroScan® devices, with trained technicians performing assessments. Clinical and laboratory data including BMI, diabetes status, liver enzymes, and fibrosis indices (FIB-4) were collected. The analysis focused on adults meeting bariatric surgery criteria, assessing prevalence of MAFLD and elevated liver stiffness as a marker of fibrosis.

Key Findings

• Obesity affects 42.4% of US adults, with severe obesity (BMI ≥ 40 kg/m2) increasing from 2.8% to 9.2% between 1988–1994 and 2017–2018.
• MAFLD prevalence is approximately 37–39% in the general adult US population and about 75% among patients with type 2 diabetes.
• Elevated liver stiffness measured by VCTE serves as a noninvasive surrogate for liver fibrosis in bariatric surgery candidates.
• Weight loss of ≥10% is associated with near-universal resolution of steatohepatitis and fibrosis improvement, but only 10% of patients achieve this through lifestyle changes alone.
• Bariatric surgery is effective in inducing sustained weight loss and improving liver inflammation and fibrosis.
• Current guidelines suggest elastography may be considered to identify advanced fibrosis in bariatric candidates, but routine imaging is not standard practice.

Clinical Implications

Clinicians evaluating bariatric surgery candidates should consider the high prevalence of MAFLD and potential advanced fibrosis in this population. Incorporating noninvasive liver stiffness measurement via elastography may aid in risk stratification and guide perioperative management. Given the limited pharmacologic options, bariatric surgery remains a key intervention to achieve meaningful liver disease improvement.

Conclusion

This population-based analysis highlights the substantial burden of elevated liver stiffness indicative of fibrosis among US adults eligible for bariatric surgery. These findings support the integration of liver disease assessment in the preoperative evaluation to optimize patient outcomes.

References

1. National Center for Health Statistics 2017–2018 -- NHANES Data Overview
2. American Diabetes Association 2017 -- Diabetes Diagnostic Criteria
3. Echosens FibroScan® Model 502 V2 Touch -- VCTE Methodology