Renal fat fraction is significantly associated with the risk of chronic kidney disease in patients with type 2 diabetes

Renal Fat Accumulation Assessed by MRI or CT and Its Association with Clinical and Metabolic Disorders: A Systematic Imaging Review

Background: The term "fatty kidney" refers to the accumulation of fat within the kidney. There is no clear definition of a fatty kidney. In our previous study, we defined a fatty kidney as one with fat accumulation of more than 4% in the kidney as detected by magnetic resonance imaging (MRI). This condition is associated with renal inflammation and contributes to the development of kidney dysfunction. Fat accumulation in the kidney can be detected using imaging modalities such as computed tomography (CT) or MRI. Given the clinical importance of renal fat deposition, the aim of this review was to investigate how imaging findings in this condition correlate to disease prevalence and metabolic disorders. Methods: A systematic review was conducted in accordance with the PRISMA guidelines. The databases searched included PubMed, Scopus, Web of Science, and Cochrane Library up to August 2024. Studies employing MRI or CT for renal fat quantification were included. Data were extracted, and their quality was assessed using the QUADAS-2 tool. Results: Twenty-eight studies comprising 6994 participants met the inclusion criteria. Most studies used MRI (75%) for fat quantification, with CT limited to renal sinus evaluation. Renal fat fractions (FFs) ranged from 0.4% to 55.3%, with higher values consistently observed in individuals with obesity, diabetes, chronic kidney disease, and hypertension. A consistent positive association was observed between fatty kidney and fatty liver, suggesting shared pathogenic mechanisms. Conclusions: Fatty kidney appears to be a distinct and clinically relevant entity with strong links to metabolic dysfunction. Imaging-based quantification-particularly MRI-offers a promising tool for early detection, yet standardization is needed. The findings underscore the need for further research into fatty kidney as a modifiable risk factor for renal and cardiovascular disease.

Multiorgan Imaging for Interorgan Crosstalk in Cardiometabolic Diseases

Cardiometabolic diseases encompass a group of conditions characterized by metabolic and inflammatory abnormalities that increase the risk of diabetes and cardiovascular disease. These syndromes involve multiple organs, including the heart, arterial system, brain, skeletal muscle, adipose tissue, hematopoietic system, liver, kidneys, and pancreas. The crosstalk between these organs contributes to the development of disease. Advances in imaging techniques, such as magnetic resonance imaging, magnetic resonance spectroscopy, computed tomography, and positron emission tomography, have revolutionized the evaluation of these conditions. Hybrid imaging modalities, such as positron emission tomography/computed tomography and positron emission tomography/magnetic resonance imaging, provide unique insights into the anatomy and metabolic alterations occurring in response to cardiometabolic risk factors. These methods are particularly valuable for assessing multisystemic involvement and interorgan crosstalk, revealing critical interactions such as the brain-heart axis, the heart-liver axis, and the fat-muscle-heart dynamics. This review discusses the role of state-of-the-art imaging techniques in evaluating the pathophysiological mechanisms underlying these complex syndromes and the clinical applications of the different imaging techniques in the assessment of cardiometabolic diseases.

Renal ectopic fat deposition and hemodynamics in type 2 diabetes mellitus assessment with magnetic resonance imaging

OBJECTIVES

To assess renal perfusion and ectopic fat deposition in patients with type 2 diabetes mellitus (T2DM), and to evaluate the effects of ectopic fat deposition on renal hemodynamics.

METHODS

All participants underwent quantitative magnetic resonance imaging (MRI) to measure the cortical and medullary renal blood flow (RBF) and proton density fat fraction (PDFF). Patients with T2DM were classified into three groups according to the estimated glomerular filtration rate (mL/min/1.73 m2). One-way analysis of variance was used to assess differences among groups. Pearson's correlation coefficient was used to analyze correlations. Additionally, a receiver operating characteristic (ROC) curve was constructed to assess diagnostic performance.

RESULTS

Renal PDFF values of the renal cortex and medulla, as well as perirenal fat thickness, were significantly different among the four groups: healthy control < T2DM < diabetic kidney disease (DKD) I-II < DKD III-IV. Additionally, significant differences in cortical and medullary RBF values were observed among the four groups: healthy control > T2DM > DKD I-II > DKD III-IV. A significant negative correlation was observed between renal PDFF and RBF values. Medullary RBF values demonstrated the best performance in discriminating T2DM from DKD with the largest area under the ROC curve (AUC) of 0.971. The cortical PDFF achieved the largest AUC (0.961) for distinguishing DKD I-II from DKD III-IV.

CONCLUSIONS

Quantitative MRI effectively evaluates renal perfusion and ectopic fat deposition in T2DM patients, aiding in assessing kidney function and disease progression. Additionally, renal ectopic fat deposition may be an important risk factor for renal hemodynamic injury.

CRITICAL RELEVANCE STATEMENT

Quantitative MRI could serve as a radiation-free imaging modality for assessing renal perfusion and ectopic fat deposition, which may be an important risk factor for DKD progression.

KEY POINTS

Quantitative MRI can be used to assess kidney function and monitor disease progression in patients with T2DM. In patients with T2DM, decreased renal perfusion, increased renal ectopic fat deposition, and kidney damage were significantly correlated. Renal ectopic fat deposition may be an important risk factor for renal hemodynamic injury.

Perspectives on the profiling of renal risk in obesity

With the formal designation of obesity as a primary disease process, early detection of its end-organ consequences and the prognostication of long-term risk will become an important aspect of its clinical management. Obesity is increasingly recognized as a treatable risk factor for chronic kidney disease. However, profiling of kidney health and estimation of renal risk remain relatively underemphasized in obesity and nephrology care guidelines. The establishment of clinical protocols that facilitate the detection of early-stage renal impairment in obesity and incorporate profiling of an individual's risk of progression, could help guide strategies to break the causal association between obesity and chronic kidney disease. Currently, checks on kidney health in patients with obesity are prompted due to the presence of obesity complications such as cardiovascular and/or metabolic disease and routine screening relies upon the use of estimated glomerular filtration rate equations. Ample evidence exists to demonstrate that these equations are of limited utility in the setting of excess body weight and intentional weight loss. The present article presents the case that an expanded model of renal risk profiling should be developed for obesity medicine, suggesting feasible means of incorporating important risk factors and biomarker profiling alongside a more targeted assessment of directly measured GFR and renal functional reserve in at risk patients. The development of such a model or variation thereof should be prioritized to guide the targeted deployment of obesity treatments with proven reno-protective effects.

A Predictive Nomogram for the Occurrence of Gastroesophageal Reflux Disease After Sleeve Gastrectomy: A Study Based on Preoperative HERM

Purpose

Gastroesophageal reflux disease (GERD) is a common complication after laparoscopic sleeve gastrectomy (LSG); This study aimed to construct a model that can predict the incidence of GERD after LSG by exploring the correlation between the results of high-resolution esophageal manometry (HREM) and the incidence of GERD after LSG.

Patients and Methods

We collected the clinical data of patients who had undergone HREM before bariatric surgery from September 2013 to September 2019 at the bariatric center of our hospital. The Gerd-Q scores during the postoperative follow-up were collected to determine the incidence of GERD. A logistic regression analysis was performed to explore the correlation of the HREM results and general clinical data with the incidence of GERD after LSG.

Results

The percentage of synchronous contractions, lower esophageal sphincter (LES) resting pressure, and history of smoking were correlated with the development of GERD after LSG, with the history of smoking and percentage of synchronous contractions as risk factors and LES resting pressure as a protective factor. The training set showed an area under the ROC curve (AUC) of the nomogram model of 0.847. The validation set showed an AUC of 0.761. The decision and clinical impact curves showed a high clinical value for the prediction model.

Conclusion

The HREM results correlated with the development of GERD after LSG, with the percentage of synchronous contractions and LES resting pressure showing predictive value. Combined with the history of smoking, the predictive model showed a high confidence and clinical value.

Perirenal fat and chronic kidney disease in type 2 diabetes: The mediation role of afferent arteriolar resistance

AIM

Perirenal fat (PRF) is an independent predictor for chronic kidney disease (CKD) in type 2 diabetes mellitus (T2DM) patients. Previous studies speculated that PRF may promote renal dysfunction through affecting renal hemodynamics. To verify this hypothesis, we studied the relationship between PRF and renal hemodynamics in T2DM.

METHODS

91 T2DM patients were included. PRF thickness (PRFT) was measured by magnetic resonance imaging. Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were determined by renal dynamic imaging. Renal vascular resistance (RVR), glomerular hydrostatic pressure (PGLO), afferent (RA) and efferent (RE) arteriolar resistance were calculated by Gomez equations. Multiple linear regression was used to determine the relationship between PRFT and renal hemodynamics. Mediation analysis was conducted to estimate the mediation effects of renal hemodynamics on the relationship between PRF and CKD.

RESULTS

All patients were divided into three groups according to the tertiles of PRFT. Compared with patients in tertile 1, GFR and ERPF were significantly decreased in patients in tertile 3, while RVR and RA were significantly increased. PRFT was negatively correlated with GFR, ERPF and PGLO, and positively correlated with RVR and RA after adjustment for sex, age, visceral adipose tissue and treatments with ACE inhibitors/angiotensin receptor blockers and sodium-glucose cotransporter protein-2 inhibitors. Moreover, RVR and RA mediated the effect of PRF on GFR, with a mediated proportion of 29.1 % and 41.4 % respectively.

CONCLUSION

In T2DM patients, PRF was negatively correlated with GFR, and positively correlated with RA. RA mediated the relationship between PRF and CKD.

Quantitative assessment of renal steatosis in patients with type 2 diabetes mellitus using the iterative decomposition of water and fat with echo asymmetry and least squares estimation quantification sequence imaging: repeatability and clinical implications

Background

Fatty kidney disease is linked to renal function damage, but there is no noninvasive tool for monitoring renal fat accumulation. This study aimed to explore the repeatability of the iterative decomposition of water and fat with echo asymmetry and least squares estimation quantification (IDEAL-IQ) sequence imaging in quantifying renal fat deposition and to assess the differences observed in patients with type 2 diabetes mellitus (T2DM).

Methods

A total of 26 healthy participants underwent two IDEAL-IQ scans without repositioning, and the repeatability of the imaging technique was assessed with Bland-Altman analysis. Additionally, 96 patients with T2DM underwent a single IDEAL-IQ scan for the examination of renal fat deposition. The patients with T2DM were classified into three groups based on their estimated glomerular filtration rate (eGFR). One-way analysis of variance was used to analyze the differences of renal fat depositions between the groups. Receiver operating characteristic curve analysis was used to assess the diagnostic performance of IDEAL-IQ.

Results

Bland-Altman analyses showed narrower limits of agreement and a significant correlation (r=0.81; P<0.05) between the two IDEAL-IQ scans. Statistically significant differences between the healthy volunteers and patients with T2DM, diabetic kidney disease (DKD) I-II, and or DKD III-IV were found in renal parenchymal proton-density fat fraction (PDFF) values (P<0.001). Renal parenchymal PDFF was negatively correlated with eGFR (r=-0.437; P<0.001) and positive correlated with serum creatinine level (µmol/L) (r=0.421; P<0.001). The area under the curve of IDEAL-IQ in discriminating between the healthy volunteers and patients with T2DM was 0.857. For discriminating T2DM from DKD I-II and DKD III-IV, the IDEAL-IQ had an area under the curve of 0.689 and 0.823, respectively.

Conclusions

IDEAL-IQ is a promising and reproducible technique for the assessment of renal fat deposition and identification of risk of DKD in patients with T2DM. Moreover, IDEAL-IQ imaging is expected to improve the sensitivity and specificity of early renal function damage and staging assessment of patients with T2DM.

Renal fat deposition measured on dixon-based MRI is significantly associated with early kidney damage in obesity

PURPOSE

To investigate the renal fat deposition on Dixon-based magnetic resonance imaging (MRI) and to explore the predictive value of renal fat biomarkers of magnetic resonance (MR-RFBs) for early kidney damage in obesity.

METHODS

This prospective study included 56 obese volunteers and 47 non-obese healthy volunteers. All volunteers underwent renal magnetic resonance examinations. The differences in MR-RFBs [including renal proton density fat fraction (PDFF), renal sinus fat volume (RSFV), and perirenal fat thickness (PRFT)] measured on Dixon-based MRI between the obese and non-obese volunteers were analyzed using a general linear model, taking sex, age, diabetes, and hypertension as covariates. The relationship between estimated glomerular filtration rate (eGFR) and demographic, laboratory, and imaging parameters in obese volunteers was examined by correlation analysis.

RESULTS

Obese volunteers had higher MR-RFBs than non-obese volunteers after controlling for confounders (all p < 0.001). Renal PDFF (r = - 0.383; p = 0.004), RSFV (r = - 0.368; p = 0.005), and PRFT (r = - 0.451; p < 0.001) were significantly negatively correlated with eGFR in obesity. After adjusting for age, sex, body mass index, diabetes, hypertension, visceral adipose tissue, subcutaneous adipose tissue, renal PDFF, and RSFV, PRFT remained independently negatively associated with eGFR (β = - 0.587; p = 0.003).

CONCLUSIONS

All MR-RFBs are negatively correlated with eGFR in obesity. The MR-RFBs, especially PRFT, may have predictive value for early kidney damage in obesity.

Associations between metabolic dysfunction-associated fatty liver disease, chronic kidney disease, and abdominal obesity: a national retrospective cohort study

Metabolic dysfunction-associated fatty liver disease (MAFLD) and chronic kidney disease (CKD) present notable health challenges, however, abdominal obesity has received scant attention despite its potential role in exacerbating these conditions. Thus, we conducted a retrospective cohort study using the National Health and Nutrition Examination Surveys III (NHANES III) of the United States from 1988 to 1994 including 9161 participants, and mortality follow-up survey in 2019. Statistical analyze including univariable and multivariable Logistic and Cox regression models, and Mediation effect analyze were applied in study after adjustment for covariates. Our findings revealed that individuals with both abdominal obesity and MAFLD were more likely to be female, older and exhibit higher prevalence of advanced liver fibrosis (7.421% vs. 2.363%, p < 0.001), type 2 diabetes mellitus (T2DM) (21.484% vs. 8.318%, p < 0.001) and CKD(30.306% vs. 16.068%, p < 0.001) compared to those with MAFLD alone. MAFLD (adjusted OR: 1.392, 95% CI 1.013-1.913, p = 0.041), abdominal obesity (adjusted OR 1.456, 95% CI 1.127-1.880, p = 0.004), abdominal obesity with MAFLD (adjusted OR 1.839, 95% CI 1.377-2.456, p < 0.001), advanced fibrosis(adjusted OR 1.756, 95% CI 1.178-2.619, p = 0.006) and T2DM (adjusted OR 2.365, 95% CI 1.758-3.183, p < 0.001) were independent risk factors of CKD. The abdominal obese MAFLD group had the highest all-cause mortality as well as mortality categorized by disease during the 30-year follow-up period. Indices for measuring abdominal obesity, such as waist circumference (WC), waist-hip ratio (WHR), and lipid accumulation product (LAP), elucidated a greater mediation effect of MAFLD on CKD compared to BMI on CKD (proportion mediation 65.23%,70.68%, 71.98%, respectively vs. 32.63%). In conclusion, the coexistence of abdominal obesity and MAFLD increases the prevalence and mortality of CKD, and abdominal obesity serves as a mediator in the association between MAFLD and CKD.

Are we ready for an adipocentric approach in people living with type 2 diabetes and chronic kidney disease?

We are entering a new era in the management of adiposity-based chronic disease (ABCD) with type 2 diabetes (T2D) and related chronic kidney disease (CKD). ABCD, T2D and CKD can affect almost every major organ system and have a particularly strong impact on the incidence of cardiovascular disease (CVD) and heart failure. ABCD and the associated insulin resistance are at the root of many cardiovascular, renal and metabolic (CKM) disorders, thus an integrated therapeutic framework using weight loss (WL) as a disease-modifying intervention could simplify the therapeutic approach at different stages across the lifespan. The breakthrough of highly effective WL drugs makes achieving a WL of >10% possible, which is required for a potential T2D disease remission as well as for prevention of microvascular disease, CKD, CVD events and overall mortality. The aim of this review is to discuss the link between adiposity and CKM conditions as well as placing weight management at the centre of the holistic CKM syndrome approach with a focus on CKD. We propose the clinical translation of the available evidence into a transformative Dysfunctional Adipose Tissue Approach (DATA) for people living with ABCD, T2D and CKD. This model is based on the interplay of four essential elements (i.e. adipocentric approach and target organ protection, dysfunctional adiposity, glucose homeostasis, and lifestyle intervention and de-prescription) together with a multidisciplinary person-centred care. DATA could facilitate decision-making for all clinicians involved in the management of these individuals, and if we do this in a multidisciplinary way, we are prepared to meet the adipocentric challenge.

The Fatty Kidney and Beyond: A Silent Epidemic

As the prevalence of obesity rises in the United States, so does the incidence of obesity-related kidney disease. Obesity itself is an independent risk factor for chronic kidney disease where the pathophysiology is complex, involving altered hemodynamics, renin-angiotensin-aldosterone system overactivation, and adipokines leading to inflammation and fibrosis. Obesity-related kidney disease comprises both obesity-related glomerulopathy and fatty kidney disease. Obesity-related glomerulopathy is a consequence of glomerular hyperfiltration and often presents clinically with subnephrotic proteinuria and pathologically with glomerulomegaly with or without focal glomerulosclerosis. Fatty kidney disease is the effect of renal ectopic fat contributing to chronic kidney disease. Whether the renal ectopic fat is a distinct clinical entity or a pathologic mechanism contributing to obesity-related glomerulopathy, the treatment paradigm of weight and proteinuria reduction remains the same. We present the pathophysiology behind obesity-related kidney disease, clinical outcomes, and treatment strategies, which include lifestyle interventions, use of renin-angiotensin-aldosterone system inhibitors, glucagon-like peptide 1 receptor agonists, sodium-glucose co-transporter-2 inhibitors, and bariatric surgery. With old and novel therapeutics, we are attempting to stave off the silent epidemic that obesity-related kidney disease is becoming.

Kidney lipid dysmetabolism and lipid droplet accumulation in chronic kidney disease

Chronic kidney disease (CKD) is a global health problem with rising incidence and prevalence. Among several pathogenetic mechanisms responsible for disease progression, lipid accumulation in the kidney parenchyma might drive inflammation and fibrosis, as has been described in fatty liver diseases. Lipids and their metabolites have several important structural and functional roles, as they are constituents of cell and organelle membranes, serve as signalling molecules and are used for energy production. However, although lipids can be stored in lipid droplets to maintain lipid homeostasis, lipid accumulation can become pathogenic. Understanding the mechanisms linking kidney parenchymal lipid accumulation to CKD of metabolic or non-metabolic origin is challenging, owing to the tremendous variety of lipid species and their functional diversity across different parenchymal cells. Nonetheless, multiple research reports have begun to emphasize the effect of dysregulated kidney lipid metabolism in CKD progression. For example, altered cholesterol and fatty acid metabolism contribute to glomerular and tubular cell injury. Newly developed lipid-targeting agents are being tested in clinical trials in CKD, raising expectations for further therapeutic development in this field.

mDIXON-Quant for differentiation of renal damage degree in patients with chronic kidney disease

Background

Chronic kidney disease (CKD) is a complex syndrome with high morbidity and slow progression. Early stages of CKD are asymptomatic and lack of awareness at this stage allows CKD to progress through to advanced stages. Early detection of CKD is critical for the early intervention and prognosis improvement.

Purpose

To assess the capability of mDIXON-Quant imaging to detect early CKD and evaluate the degree of renal damage in patients with CKD.

Study type

Retrospective.

Population

35 patients with CKD: 18 cases were classifified as the mild renal damage group (group A) and 17 cases were classifified as the moderate to severe renal damage group (group B). 22 healthy volunteers (group C).

Field strength/sequence

A 3.0 T/T1WI, T2WI and mDIXON-Quant sequences.

Assessment

Transverse relaxation rate (R2*) values and fat fraction (FF) values derived from the mDIXON-Quant were calculated and compared among the three groups.

Statistical tests

The intra-class correlation (ICC) test; Chi-square test or Fisher's exact test; Shapiro-Wilk test; Kruskal Wallis test with adjustments for multiplicity (Bonferroni test); Area under the receiver operating characteristic (ROC) curve (AUC). The significance threshold was set at P < 0.05.

Results

Cortex FF values and cortex R2* values were significantly different among the three groups (P=0.028, <0.001), while medulla R2* values and medulla FF values were not (P=0.110, 0.139). Cortex FF values of group B was significantly higher than that of group A (Bonferroni adjusted P = 0.027). Cortex R2* values of group A and group B were both significantly higher than that of group C (Bonferroni adjusted P = 0.012, 0.001). The AUC of cortex FF values in distinguishing group A and group B was 0.766. The diagnostic efficiency of cortex R2* values in distinguishing group A vs. group C and group B vs. group C were 0.788 and 0.829.

Conclusion

The mDIXON-Quant imaging had a potential clinical value in early diagnosis of CKD and assessing the degree of renal damage in CKD patients.