How to Use MRI for Measuring Liver Fat Levels in Patients Who Have Undergone Bariatric Surgery

Magnetic resonance imaging (MRI) is an effective method for measuring liver fat levels in obese patients who undergone weight loss surgery, according to researchers from the University of Wisconsin School of Medicine and Public Health.

In their study recently published in Radiology, the researchers set to out to determine how bariatric surgery influences changes in liver fat. Gastric bypass and sleeve gastrectomy have successfully helped obese patients lose weight. However, physicians are mostly in the dark about how these surgeries lower liver fat, since it’s challenging to quantify liver fat non-invasively, and biopsies can’t viably evaluate liver fat over time.

The researchers considered MRI to be one possible solution for monitoring changes in liver fat post-bariatric surgery. They used a technique called quantitative chemical shift-encoded MRI (CSE-MRI) to generate an analysis of liver fat called a proton density fat fraction (PDFF). For their study, they measured the liver fat of 50 obese patients who had undergone bariatric surgery. CSE-MRI was performed twice before surgery and then multiple times over the course of the year post surgery.

Around six to 10 months after surgery, the average PDFF among participants dropped from 18 percent to 5 percent, which is considered the maximum of the normal range. The mean time to reach a normal PDFF level was approximately five months.

"The results showed a rapid early phase of improvements in liver fat, followed by a phase of continued improvements at a slower pace," said study co-author B. Dustin Pooler, MD, adjunct assistant professor at UW School of Medicine. "The changes began with the initiation of the low-calorie diet and occurred in advance of the overall improvements in BMI among the patients."