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Noninvasive Tool Rules Out Need for Liver Biopsy in Patients Undergoing Bariatric Surgery

Key findings

  • This retrospective study of 2,465 patients evaluated the clinical utility of noninvasive risk calculators for detecting liver fibrosis in patients undergoing bariatric surgery
  • The prevalence of advanced fibrosis in this population was relatively low at 3.4%
  • A NAFLD fibrosis score <1.455 was associated with the highest sensitivity (true positive rate, 85%) and negative predictive value (99%) for advanced fibrosis
  • The fibrosis-4 index and the aspartate aminotransferase-to-platelet ratio index did not perform adequately in this cohort
  • Avoiding biopsy in this population could result in time and cost savings while sparing low-risk patients an unnecessary procedure

Patients with obesity are at particularly high risk of nonalcoholic fatty liver disease (NAFLD), including steatohepatitis/fibrosis. When they undergo bariatric surgery, it's important to determine whether fibrosis is present because if it is, patients need careful postoperative monitoring for esophageal varices and hepatocellular carcinoma.

Most surgeons don't perform routine liver biopsies during bariatric surgery because of the added time, cost and risk of bleeding. Several noninvasive risk calculators for fibrosis have been developed, but the characteristics of patients undergoing bariatric surgery differ from those of the patients in whom the calculators were originally validated.

At Massachusetts General Hospital, patients have undergone routine liver biopsies during bariatric surgery for many years. Using that cohort for validation, Brooks V. Udelsman, MD, MHS, clinical fellow in the Department of Surgery at Massachusetts General Hospital, Elan Witkowski, MD, MS, minimally invasive surgeon in the Mass General Department of General and Gastrointestinal Surgery, and colleagues determined that the NAFLD fibrosis score is suitable for ruling out fibrosis in patients undergoing first-time routine bariatric procedures. Their research appears in Surgery for Obesity and Related Diseases.

Study Methods

The study subjects were 2,465 adults who underwent routine hepatic wedge biopsy during primary Roux-en-Y gastric bypass, sleeve gastrectomy or laparoscopic adjustable gastric banding between 2001 and 2017. Biopsy was "routine" for a surgeon if performed in ≥95% of cases.

A total of 85 patients (3.4%) had advanced fibrosis, defined as Brunt stages 3–4. For each patient, the researchers calculated the fibrosis-4 (FIB-4) index, the NAFLD fibrosis score and the aspartate aminotransferase-to-platelet ratio index (APRI).

Calculator Performance—Advanced Fibrosis

A NAFLD fibrosis score <1.455 was associated with the highest sensitivity (true positive rate, 85%) and negative predictive value (99%); 13 patients who had advanced fibrosis were falsely negative.

The specificity (true negative rate) was 99% for both FIB-4 >2.67 and the APRI, but the positive predictive values were only 55% and 65%, respectively.

Calculator Performance—Moderate to Advanced Fibrosis

Since moderate fibrosis often prompts referral to hepatology, the researchers re-evaluated the calculators for patients with stage ≥2 fibrosis. The results were largely the same as those seen for severe fibrosis.

Guidance for Surgeons

These calculators have little utility in ruling in advanced fibrosis, but they can identify a sizeable number of patients who are unlikely to have advanced fibrosis and can be spared an unnecessary procedure.

The custom at Mass General is to perform the biopsy at the beginning of each bariatric operation with an ultrasonic dissector or scissors and cautery. This allows observation and confirmation of hemostasis through the remainder of the procedure. During the years covered by this study, the rate of postoperative hemorrhage requiring reoperation or transfusion was ~1%, comparable to published rates.

Theoretical complications include bile leak or pathologic adhesions, but they did not occur during the 17-year experience.

of patients scheduled for bariatric surgery had advanced fibrosis

sensitivity of an NAFLD fibrosis score

negative predictive value of an NAFLD fibrosis score

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