Alterations in the Liver Fat Fraction Features Examined by Magnetic Resonance Imaging Following Bariatric Surgery: a Self-Controlled Observational Study

Comparison of reader agreement, correlation with liver biopsy, and time-burden sampling strategies for liver proton density fat fraction measured using magnetic resonance imaging in patients with obesity: a secondary cross-sectional study

Background

The magnetic resonance imaging (MRI)-based proton density fat fraction (PDFF) has become popular for quantifying liver fat content. However, the variability of the region-of-interest (ROI) sampling strategy may result in a lack of standardisation of this technology. In an effort to establish an accurate and effective PDFF measurement scheme, this study assessed the pathological correlation, the reader agreement, and time-burden of different sampling strategies with variable ROI size, location, and number.

Methods

Six-echo spoiled gradient-recalled-echo magnitude-based fat quantification was performed for 50 patients with obesity, using a 3.0-T MRI scanner. Two readers used different ROI sampling strategies to measure liver PDFF, three times. Intra-reader and inter-reader agreement was evaluated using intra-class correlation coefficients and Bland‒Altman analysis. Pearson correlations were used to assess the correlation between PDFFs and liver biopsy. Time-burden was recorded.

Results

For pathological correlations, the correlations for the strategy of using three large ROIs in Couinaud segment 3 (S3 3L-ROI) were significantly greater than those for all sampling strategies at the whole-liver level (P < 0.05). For inter-reader agreement, the sampling strategies at the segmental level for S3 3L-ROI and using three large ROIs in Couinaud segment 6 (S6 3L-ROI) and the sampling strategies at the whole-liver level for three small ROIs per Couinaud segment (27S-ROI), one large ROI per Couinaud segment (9L-ROI), and three large ROIs per Couinaud segment (27S-ROI) had limits of agreement (LOA) < 1.5%. For intra-reader agreement, the sampling strategies at the whole-liver level for 27S-ROI, 9L-ROI, and 27L-ROI had both intraclass coefficients > 0.995 and LOAs < 1.5%. The change in the time-burden was the largest (100.80 s) when 9L-ROI was changed to 27L-ROI.

Conclusions

For hepatic PDFF measurement without liver puncture biopsy as the gold standard, and for general hepatic PDFF assessment, 9L-ROI sampling strategy at the whole-liver level should be used preferentially. For hepatic PDFF with liver puncture biopsy as the gold standard, 3L-ROI sampling strategy at the puncture site segment is recommended.

How much abdominal fat do obese patients lose short term after laparoscopic sleeve gastrectomy? A quantitative study evaluated with MRI

Background

This study aimed to elucidate the changes in the amount of abdominal adipose tissue after laparoscopic sleeve gastrectomy in obese Chinese patients over a relatively short follow-up period and to analyze the differences in the effects of surgery between genders.

Methods

Ninety-one patients were enrolled in the study, including 18 males and 73 females. These patients underwent laparoscopic sleeve gastrectomy between November 2017 and November 2019. Before and short term after surgery, the areas of subcutaneous/visceral adipose tissue and the liver proton density fat fraction were calculated with upper abdominal magnetic resonance (MR) examinations.

Results

Approximately 100 days after surgery, the median values of weight loss and body mass index reduction were 23.1 kg and 8.1 kg/m², respectively. The patients achieved a greater absolute loss of subcutaneous adipose tissue index than of visceral adipose tissue index (3.2×10^-3 vs. 1.6×10^-3, P<0.001). The amount of weight loss, body mass index loss and absolute/relative reduction in visceral adipose tissue index were much greater in males than in females (31.7 vs. 21.7 kg, P<0.001; 9.8 vs. 7.9 kg/m², P=0.016; 2.5×10^-3 vs. 1.3×10^-3, P=0.007; 28.2% vs. 20.9%, P=0.029). There was a correlation between decreased amounts in subcutaneous and visceral adipose tissue in sum and weight loss (r=0.282, P=0.032). The absolute/relative reduction in visceral adipose tissue index was also correlated with absolute/relative reduction in liver proton density fat fraction (r=0.283, P=0.013; r=0.372, P=0.001).

Conclusions

The reductions in body weight and visceral fat were more significant in male patients. The sum of absolute reduction in subcutaneous and visceral fat deposits was correlated with weight loss, in all patients enrolled. For severely obese patients, an upper abdominal MR examination could assess the body tissue composition and how it changes after bariatric surgery.

Metabolic surgery in China: present and future

Obesity and its related complications comprise a serious public health problem worldwide, and obesity is increasing in China. Metabolic surgery is a new type of treatment with unique advantages in weight loss and obesity-related metabolic complications. The pathogenesis of obesity is complex and not yet fully understood. Here, we review the current efficacy and safety of metabolic surgery, as well as recent progress in mechanistic studies and surgical procedures in China. The exciting and rapid advances in this field provide new opportunities for patients with obesity and strike a balance between long-term effectiveness and safety.

Bariatric surgery for non-alcoholic fatty liver disease in individuals with obesity (Base-NAFLD): protocol of a prospective multicenter observational follow-up study

BACKGROUND

Bariatric surgery may be indicated in patients with nonalcoholic fatty liver disease (NAFLD) to achieve and maintain the degree of weight loss required to ensure therapeutic effects. However, bariatric surgery is still underrecognized in the treatment of NAFLD, including its inflammatory subtype, nonalcoholic steatohepatitis (NASH). Moreover, there is a lack of follow-up outcome data on different types of bariatric surgery in patients with NAFLD. This study aims to adequately assess the effect of bariatric surgery on NAFLD remission in obese patients.

METHODS

This prospective multicentre observational follow-up study will include 142 obese patients with NAFLD scheduled to undergo one of the following surgical procedures: sleeve gastrostomy, Roux-en-Y gastric bypass, and one anastomosis gastric bypass. The primary outcome is the complete remission rate of NAFLD one year postoperatively, which is defined by liver fat fraction < 5% on magnetic resonance imaging; the secondary outcomes includes (i) changes in NASH and liver fibrosis biopsy findings, (ii) changes in body weight and abdominal adipose weight, (iii) resolution of obesity-related comorbidities, and (iv) incidence of adverse events. A long-term follow-up related to this study will also be conducted.

DISCUSSION

This study will provide a necessary and preliminary foundation for the early identification and targeted treatment of patients with NAFLD who can be referred for bariatric surgery, as indicated for management of obesity and metabolic disease.

TRIAL REGISTRATION

Clinicaltrials.gov: NCT04366999. Registered 21 April 2020. ( https://clinicaltrials.gov/ct2/show/NCT04366999 ).

Alterations in the Serum Urate Concentrations after Bariatric Surgery: a Short-Term Prospective Observational Study

BACKGROUND

Bariatric surgery is associated with a reduced incidence of hyperuricaemia during the long follow-up time. However, few studies have elucidated the alterations in serum urate (SU) levels in the short-term post-surgery period.

PURPOSE

To identify the alterations in SU concentrations in individuals with obesity at 1 week, 1 month, and 3 months after bariatric surgery and determine the risk factors for alterations during the first 3 post-surgery months.

METHODS

Thirty-four patients were enrolled. Pre- and post-operative variables were collected at baseline and at each follow-up point. A paired t-test was applied to investigate the relationship between the major parameters. A linear mixed model was performed to analyse the variations of SU concentrations with time.

RESULTS

Compared with baseline levels, SU levels significantly increased at 1 week, then declined significantly at 1 month after surgery (P < 0.05). At the 3-month follow-up, a significant decrease in SU levels was detected compared with that in baseline levels (P < 0.001). In univariate regression analysis, age, sex, weight, body mass index, triglyceride (TG), total cholesterol (TC), creatinine (Cr), and medications were all risk factors for alterations in SU concentrations post-surgery. In the final model, sex, weight, Cr, age, TC, Cr * age, and Cr * TC were established.

CONCLUSIONS

Surgeons should be cognizant of the significant increase in SU levels in the first postoperative week. Alterations in SU concentrations during the first 3 post-operative months were associated with sex, age, weight, Cr, and TC levels at baseline.

The Clinical Value and Appropriateness Criteria of Upper Abdominal Magnetic Resonance Examinations in Patients Before and After Bariatric Surgery: a Study of 837 Images

PURPOSE

The abdominal magnetic resonance (MR) examinations have been increasingly applied in patients with obesity. However, few studies analyzed the appropriateness of this examination. This study is aimed to evaluate the feasibility and clinical value of upper abdominal MR in quantification of visceral/subcutaneous adipose tissue (VAT/SAT) and liver fat fraction (LFF) in patients before and after bariatric surgery.

METHODS

All patients who underwent bariatric surgery from November 2017 to November 2019 in the prospectively maintained, IRB-approved database of our institution were queried. The images of all MR studies were retrospectively reviewed and analyzed.

RESULTS

In total, 570 patients with 837 upper abdominal MR examinations were analyzed. The VAT/SAT can be clearly visualized and quantified on fat liver acquisition with volume acceleration-flexible (LAVA-Flex) sequence. The present rate of a single axial slice at the level of the L1-L2 intervertebral disc was 93.1% (779/837). The LFF could be quantitatively evaluated on all of the proton density fat fraction (PDFF) maps (100%, 837/837). Occasional findings may include cholelithiasis, cysts, hepatic hemangioma, and renal angiomyolipoma, which can be clearly diagnosed by MR.

CONCLUSION

The upper abdominal MR is featured by well feasibility and clear clinical value when applying in patients with obesity. We can use the results to do clinical research and evaluate obesity-related disease risks before and after surgery, thus providing suggestions to choose the type of surgery for patients with different risk levels in the future. MR scanning including fat LAVA-Flex images with the inclusion of L1-L2 level and PDFF measurements is suggested for the VAT/SAT/LFF quantification.

TRIAL REGISTRATION

NCT03520699.