New Research Shows Bariatric Surgery Patients Should Be Evaluated for Liver Disease

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Nonalcoholic fatty liver disease affects an estimated 70% of people with obesity and 85% to 95% of those with morbid obesity. Individuals undergoing bariatric surgery who have diabetes are known to be at high-risk of nonalcoholic steatohepatitis (NASH), the progressive form of fatty liver disease. Otherwise, it's unclear which subgroups of bariatric surgery patients need a referral to hepatology.

In a retrospective study, Elan R. Witkowski, MD, MS, minimally invasive surgeon at Massachusetts General Hospital, and colleagues determined that dyslipidemia and elevated liver enzymes, as well as diabetes, are risk factors for NASH or fibrosis in patients undergoing bariatric surgery. Their findings are published in Surgery for Obesity and Related Diseases.

Patient Characteristics

The research team studied 2,557 adults who underwent routine liver biopsy at the time of bariatric surgery between January 1, 2001 and December 31, 2017. The average age of the cohort was 46 and 72% were female. About one-fifth of patients (23%) had a preoperative diagnosis of fatty liver disease; other common comorbidities were hypertension (57%), dyslipidemia (33%) and diabetes (29%).

Liver Histology

• Normal: 38%
• Steatosis: 61%
• NASH: 31%
• Fibrosis: 29% (Stage 1: 22% of all patients; Stage 2: 4.2%; Stage 3: 2.9%; Stage 4: 0.7%)

Risk Factors for NASH

On multivariable analysis, laboratory abnormalities associated with NASH were:

• Elevated hemoglobin A1C (≥5.7%)
• Low concentrations of high-density lipoprotein cholesterol (≤50 mg/dL for women, ≤40 mg/dL for men)
• Elevated triglycerides (>200 mg/dL)
• Elevated aspartate aminotransferase (AST) and alanine aminotransferase (ALT) (>30 IU/L)
• AST to ALT ratio <0.8

Counterintuitively, a preoperative diagnosis of fatty liver disease was inversely correlated with NASH. Black race was associated with a significantly reduced risk of NASH. Older age and increased body mass index (BMI) did not influence the risk.

Risk Factors for Fibrosis

Laboratory abnormalities associated with fibrosis included elevated hemoglobin A1C, low concentrations of high-density lipoprotein cholesterol, elevated liver enzymes and an AST to ALT ratio <0.8. As with NASH, a preoperative diagnosis of fatty liver disease was inversely correlated with fibrosis. Sex, age, race and BMI were not significantly associated with fibrosis.

Applying the Results to Practice

Given the high prevalence of advanced liver disease in this population, patients scheduled for bariatric surgery should be clinically evaluated, and many may benefit from liver biopsy at the time of surgery. A lack of history of fatty liver disease should not preclude liver biopsy.

The authors refer patients to a hepatologist if the biopsy shows Stage 2 to Stage 4 fibrosis. These individuals may benefit from monitoring for improvement of fatty liver disease—and for hepatocellular carcinoma. In patients with Stage 3 or Stage 4 fibrosis, cancer risk remains elevated despite histologic improvements in the liver.

The lack of association between age/BMI and NASH/fibrosis confirms previous research. It may be that the additional risk of progressive fatty liver disease plateaus at high BMI. Thus, younger patients who are obese or morbidly obese may have a higher risk of advanced fatty liver disease than previously thought.

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