Hepatic steatosis and reduction in steatosis following bariatric weight loss surgery differs between segments and lobes
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The purpose of this study was to (1) evaluate proton density fat fraction (PDFF) distribution across liver segments at baseline and (2) compare longitudinal segmental PDFF changes across time points in adult patients undergoing a very low-calorie diet (VLCD) and subsequent bariatric weight loss surgery (WLS).
We performed a secondary analysis of data from 118 morbidly obese adult patients enrolled in a VLCD-WLS program. PDFF was estimated using magnitude-based confounder-corrected chemical-shift-encoded (CSE) MRI in each hepatic segment and lobe at baseline (visit 1), after completion of VLCD (visit 2), and at 1, 3, and 6 months (visits 3–5) following WLS. Linear regressions were used to estimate the rate of PDFF change across visits. Lobar and segmental rates of change were compared pairwise.
Baseline PDFF was significantly higher in the right lobe compared to the left lobe (p < 0.0001). Lobar and segmental PDFF declined by 3.9–4.5% per month between visits 1 and 2 (preoperative period) and by 4.3–4.8% per month between visits 1 and 3 (perioperative period), but no significant pairwise differences were found in slope between segments and lobes. For visits 3–5 (postoperative period), lobar and segmental PDFF reduction was much less overall (0.4–0.8% PDFF per month) and several pairwise differences were significant; in each case, a right-lobe segment had greater decline than a left-lobe segment.
Baseline and longitudinal changes in fractional fat content in the 5-month postoperative period following WLS vary across segments, with right-lobe segments having higher PDFF at baseline and more rapid reduction in liver fat content.
• Baseline and longitudinal changes in liver fat following bariatric weight loss surgery vary across liver segments.
• Methods that do not provide whole liver fat assessment, such as liver biopsy, may be unreliable in monitoring longitudinal changes in liver fat following weight loss interventions.
KeywordsFatty liver Bariatric surgery Magnetic resonance imaging
Chronic liver disease
Nonalcoholic fatty liver disease
Proton density fat fraction
Spoiled gradient-recalled echo
Very low-calorie diet (VLCD)
Weight loss surgery
We acknowledge NIH T32 EB005970-09, R01 DK083380, R01 DK088925, R01 DK100651, and K24 DK102595 grants, and GE Healthcare for providing research support.
This study has received funding from NIH T32 EB005970-09, R01 DK083380, R01 DK088925, R01 DK100651, and K24 DK102595 grants, and GE Healthcare.
Compliance with ethical standards
The scientific guarantor of this publication is Claude B Sirlin.
Conflict of interest
Claude Sirlin has received grants from Gilead, GE Healthcare, Siemens, GE MRI, Bayer, GE Digital, GE Ultrasound, ACR Innovation, and Philips. He also is a consultant for GE Healthcare, Bayer, Boehringer Ingelheim, AMRA, and Fulcrum, and is on advisory board for AMRA, Guerbet, and VirtualScopics. The remaining authors of this manuscript have no conflict of interest to declare.
Statistics and biometry
All statistical analyses were performed by a staff statistician (Tanya Wolfson) under the supervision of a faculty statistician (Anthony Gamst) from the University of California San Diego who are both co-authors of this paper and have over 20 years of experience.
Written informed consent was obtained from all subjects (patients) in this study.
Institutional Review Board approval was obtained.
Study subjects or cohorts overlap
The cohort of a recent study by Luo et al published in Surgical Endoscopy, although not entirely identical, quite overlaps with our cohort. This paper was published in a surgical journal by the surgical team involved in this research. In contrast to our study, Luo et al have examined changes in liver volume and total liver fat rather than assessing and comparing segmental liver fat. They have also included data from complex-based MR exams, whereas in our study, only magnitude-based MR examinations were included.
• diagnostic or prognostic study
• multi-center study
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