Clinical significance of renal cortical thickness in patients with chronic kidney disease

Renal and Genitourinary Ultrasound Evaluation in Emergency and Critical Care: An Overview

Renal and genitourinary ultrasound are fundamental resources employed by emergency and critical care healthcare providers to make prompt diagnoses and perform ultrasound-guided procedures. At the bedside, ultrasound can aid in the diagnosis of relevant pathologies, such as post-renal obstruction or kidney stones, and life-threatening conditions such as aortic dissection or hemoperitoneum. A narrative overview was performed, providing an updated review of renal and genitourinary ultrasound for emergency and critical care healthcare providers, emphasizing its advantages and the latest advances in the field. A thorough summary that can be utilized as a guide for emergency and critical care healthcare providers is presented. The daily hemodynamic management of critically ill patients involves the implementation of new protocols, such as VexUS or the evaluation of the renal resistance index. The role of ultrasound in managing acute nephropathy and genitourinary issues is increasingly crucial given its bedside availability, thus this imaging modality not only facilitates the initiation of therapeutic interventions but also provides swift prognostic insights that are vital to provide tailored patient care. As further advances in ultrasound will arise, it is important for healthcare providers to foster the use of these technologies capable of improving patient outcomes.

Objectified kidney ultrasound echogenicity and size metrics as potential predictors for kidney function in children

BACKGROUND

Kidney echogenicity is typically determined subjectively but may have a quantifiable relationship to kidney function. Similarly, kidney length has been shown to correlate with kidney function. This study sought to quantify echogenicity using readily available software. Secondarily, we aimed to evaluate the correlation between quantified echogenicity and kidney length to the estimated glomerular filtration rate (eGFR) in children with acute kidney injury (AKI) and chronic kidney disease (CKD).

METHODS

In a single-center retrospective observational study, echogenicity index (EI) was determined using a ratio of right kidney to liver mean pixel density. The kidney length ratio (KLR) was determined by the actual to predicted lengths of both kidneys. Both variables were correlated to eGFR using correlation analyses and predictive capacity was determined with receiver operating characteristic curve (ROC) analysis.

RESULTS

Of 94 subjects, 46% (43/94) had AKI, 28% (26/95) had CKD and 26% (25/95) were controls. The higher the EI the lower the eGFR (r = - 0.46, p < 0.0001). EI between 1.0 and 1.1 predicted an eGFR < 90 ml/min/1.73m2 with an AUC of 0.71-0.78 while an EI between 1.1 and 1.2 predicted an eGFR < 60 ml/min/1.73m2 with AUC of 0.75-0.80. Overall, the larger the KLR the lower the eGFR (r = - 0.25, p 0.018).

CONCLUSION

We have developed an accessible methodology to quantify kidney echogenicity. Overall, there was an inverse correlation between EI and eGFR in pediatric CKD and AKI. However, these correlations did not persist within subgroups which could be due to small sample size and heterogeneity of etiologies. Overall, KLR had a weaker correlation to eGFR, compared to EI. Despite these correlations, both EI and KLR had "fair" to "good" performance as a biomarker for an eGFR < 60 ml/min/1.73m2.

Kidney shape statistical analysis: associations with disease and anthropometric factors

BACKGROUND

Organ measurements derived from magnetic resonance imaging (MRI) have the potential to enhance our understanding of the precise phenotypic variations underlying many clinical conditions.

METHODS

We applied morphometric methods to study the kidneys by constructing surface meshes from kidney segmentations from abdominal MRI data in 38,868 participants in the UK Biobank. Using mesh-based analysis techniques based on statistical parametric maps (SPMs), we were able to detect variations in specific regions of the kidney and associate those with anthropometric traits as well as disease states including chronic kidney disease (CKD), type-2 diabetes (T2D), and hypertension. Statistical shape analysis (SSA) based on principal component analysis was also used within the disease population and the principal component scores were used to assess the risk of disease events.

RESULTS

We show that CKD, T2D and hypertension were associated with kidney shape. Age was associated with kidney shape consistently across disease groups. Body mass index (BMI) and waist-to-hip ratio (WHR) were also associated with kidney shape for the participants with T2D. Using SSA, we were able to capture kidney shape variations, relative to size, angle, straightness, width, length, and thickness of the kidneys, within disease populations. We identified significant associations between both left and right kidney length and width and incidence of CKD (hazard ratio (HR): 0.74, 95% CI: 0.61-0.90, p < 0.05, in the left kidney; HR: 0.76, 95% CI: 0.63-0.92, p < 0.05, in the right kidney) and hypertension (HR: 1.16, 95% CI: 1.03-1.29, p < 0.05, in the left kidney; HR: 0.87, 95% CI: 0.79-0.96, p < 0.05, in the right kidney).

CONCLUSIONS

The results suggest that shape-based analysis of the kidneys can augment studies aiming at the better categorisation of pathologies associated with chronic kidney conditions.

Left Renal Vein Division during Open Surgical Repair for Abdominal Aortic Aneurysm May Cause Long-Term Kidney Remodeling

BACKGROUND

Left renal vein division (LRVD) is a maneuver performed during open surgical repair for abdominal aortic aneurysms. Even so, the long-term effects of LRVD on renal remodeling are unknown. Therefore, we hypothesized that interrupting the venous return of the left renal vein might cause renal congestion and fibrotic remodeling of the left kidney.

METHODS

We used a murine left renal vein ligation model with 8-week-old to 12-week-old wild-type male mice. Bilateral kidneys and blood samples were harvested postoperatively on days 1, 3, 7, and 14. We assessed the renal function and the pathohistological changes in the left kidneys. In addition, we retrospectively analyzed 174 patients with open surgical repairs between 2006 and 2015 to assess the influence of LRVD on clinical data.

RESULTS

Temporary renal decline with left kidney swelling occurred in a murine left renal vein ligation model. In the pathohistological assessment of the left kidney, macrophage accumulation, necrotic atrophy, and renal fibrosis were observed. In addition, Myofibroblast-like macrophage, which is involved in renal fibrosis, was observed in the left kidney. We also noted that LRVD was associated with temporary renal decline and left kidney swelling. LRVD did not, however, impair renal function in long-term observation. Additionally, the relative cortical thickness of the left kidney in the LRVD group was significantly lower than that of the right kidney. These findings indicated that LRVD was associated with left kidney remodeling.

CONCLUSIONS

Venous return interruption of the left renal vein is associated with left kidney remodeling. Furthermore, interruption in the venous return of the left renal vein does not correlate with chronic renal failure. Therefore, we suggest careful follow-up of renal function after LRVD.

Diagnosis of Chronic Kidney Disease and Assessing Glomerular Filtration Rate

Chronic kidney disease (CKD) is a silent progressive disease. It is diagnosed by assessing filtration and markers of kidney damage such as albuminuria. The diagnosis of CKD should include not only assessing the glomerular filtration rate (GFR) and albuminuria but also the cause. The CKD care plan should include documentation of the trajectory and prognosis. The use of a combination of serum cystatin C and creatinine concentration offers a more accurate estimation of GFR. Social determinants of health are important to address as part of the diagnosis because they contribute to CKD disparities.

Ultrasound Renal Score to Predict the Renal Disease Prognosis in Patients with Diabetic Kidney Disease: An Investigative Study

Renal disease associated with type 2 diabetes mellitus (T2DM) has become the leading cause of chronic kidney disease (CKD). Renal ultrasonography is an imaging examination required in the work-up of renal disease. This study aimed to identify the differences in renal ultrasonographic findings between patients with and without DM, and to evaluate the relationship between renal ultrasound findings and renal prognosis in patients with DM. A total of 252 patients who underwent renal ultrasonography at Chungnam National University Hospital were included. Kidney disease progression was defined as a ≥10% decline in the annual estimated glomerular filtration rate (eGFR), which, in this paper, is referred to as ΔeGFR/year, or the initiation of renal replacement therapy after follow-up. The renal scoring system was evaluated by summing up the following items: the value of renal parenchymal echogenicity (0: normal; 1: mildly increased; and 2: increased) and the shape of the cortical margin (0: normal and 1: irregular; right kidney length/height (RH-0 or 1), mean cortical thickness/renal length/height (CKH-0 or 1), and cortical thickness/parenchymal thickness (CK/PK-0 or 1) based on the median: 0-above median, and 1-below median). Patients with DM had thicker renal PKH than those without, despite having lower eGFRs (0.91 ± 0.15, 0.86 ± 0.14, p = 0.006). In the progression group, the renal scores were significantly higher than those from the non-progression group. In the multivariate logistic regression analysis, the higher renal scores, presence of DM, and younger age were independently predicted for renal disease progression after adjusting for confounding variables, such as the presence of hypertension, serum hemoglobin and albumin levels, and UPCR. In conclusion, patients with high renal scores were significantly associated with renal disease progression. Our results suggest that renal ultrasonography at the time of diagnosis provides useful prognostic information in patients with kidney disease.

Ultrasonographic quantitative evaluation of acute and chronic renal disease using the renal cortical thickness to aorta ratio in dogs

The renal cortical thickness (RCT) has been correlated with renal function. Previous studies have also reported that the RCT:Abdominal aorta(Ao) ratio is constant in normal dogs with various physical factors. This multi-center, retrospective, analytical study aimed to determine if there are differences between actual RCT and predicted value of RCT considering physical factors in dogs with acute or chronic renal disease. We also aimed to demonstrate whether the RCT and Ao ratio index would be useful for evaluating renal pathology. A total of 54 dogs with acute or chronic renal disease and 30 normal healthy dogs were included in this study. The RCT was measured at the center of the renal pyramid as the shortest distance perpendicular to the renal capsule from the base of the renal medullary pyramid at three points. The diameter of the Ao was measured just caudal to the branch of the left renal artery in the sagittal plane in systole. The RCT:Ao ratio of chronic kidney disease (CKD) patients was 0.50 ± 0.11 (mean ± standard deviation). The RCT:Ao ratio in normal dogs was 0.67 ± 0.07. The RCT:Ao ratio in patients with acute kidney injury (AKI) was 0.83 ± 0.05. There was a statistically significant difference between normal dogs and dogs with CKD (P < 0.001) and between normal dogs and dogs with AKI (P < 0.001). In conclusion, findings from the current study supported using the RCT:Ao ratio as a non-invasive quantitative method for characterizing kidney pathology in dogs with acute or chronic renal disease.

Nrf2 deficiency deteriorates diabetic kidney disease in Akita model mice

Oxidative stress is an essential component in the progression of diabetic kidney disease (DKD), and the transcription factor NF-E2-related factor-2 (Nrf2) plays critical roles in protecting the body against oxidative stress. To clarify the roles of Nrf2 in protecting against DKD, in this study we prepared compound mutant mice with diabetes and loss of antioxidative defense. Specifically, we prepared compound Ins2^Akita/+ (Akita) and Nrf2 knockout (Akita::Nrf2^-/-) or Akita and Nrf2 induction (Akita::Keap1^FA/FA) mutant mice. Eighteen-week-old Akita::Nrf2^-/- mice showed more severe diabetic symptoms than Akita mice. In the Akita::Nrf2^-/- mouse kidneys, the glomeruli showed distended capillary loops, suggesting enhanced mesangiolysis. Distal tubules showed dilation and an increase in 8-hydroxydeoxyguanosine-positive staining. In the Akita::Nrf2^-/- mouse kidneys, the expression of glutathione (GSH) synthesis-related genes was decreased, and the actual GSH level was decreased in matrix-assisted laser desorption/ionization mass spectrometry imaging analysis. Akita::Nrf2^-/- mice exhibited severe inflammation and enhancement of infiltrated macrophages in the kidney. To further examine the progression of DKD, we compared forty-week-old Akita mouse kidney compounds with Nrf2-knockout or Nrf2 mildly induced (Akita::Keap1^FA/FA) mice. Nrf2-knockout Akita (Akita::Nrf2^-/-) mice displayed severe medullary cast formation, but the formation was ameliorated in Akita::Keap1^FA/FA mice. Moreover, in Akita::Keap1^FA/FA mice, tubule injury and inflammation-related gene expression were significantly suppressed, which was evident in Akita::Nrf2^-/- mouse kidneys. These results demonstrate that Nrf2 contributes to the protection of the kidneys against DKD by suppressing oxidative stress and inflammation.

Correlation of Sonographic Parameters with Renal Function in Patients with Newly Diagnosed Chronic Kidney Disease

AIMS

To correlate sonographic renal parameters (mean renal cortical thickness, length and volume) with renal functions in patients with newly diagnosed chronic kidney disease. To predict the best renal parameter correlating with renal functions in patients with newly diagnosed chronic kidney disease.

MATERIAL AND METHODS

A hospital-based prospective cross-sectional study was conducted in the Department of Radiodiagnosis, Indira Gandhi Medical College and Hospital, Shimla, in 78 adults with newly diagnosed chronic kidney disease visiting the hospital from December 2019 to November 2020.

RESULTS

A statistically significant positive correlation was found between eGFR and mean renal length, mean renal cortical thickness, and mean renal volume (p <0.001).The strongest correlation was shown between mean renal volume and eGFR (r = 0.90, r² = 0.82; p-value <0.001).

CONCLUSIONS

Renal volume and cortical thickness should be considered along with traditional renal parameters.

Sonographic Measurement of Renal Sinus Fat to Renal Cortical Thickness Ratio Is a Better Predictor of Chronic Kidney Disease Than Cortical Thickness Alone

Objective:

The aim was to determine if the renal sinus fat-to-cortical thickness ratio was a better predictor of chronic kidney disease (CKD) than cortical thickness alone.

Materials and Methods:

A total of 199 patients were included in the study. Renal fat, parenchyma, and cortical thicknesses were evaluated by sonography retrospectively. Same day serum glomerular filtration rate (GFR) values were obtained and correlated.

Results:

The study patients had an average fat-to-cortical thickness ratio <0.4 and had a 63% probability of developing renal failure. The probability increased almost linearly from 65% to 85% for patients with a ratio between 0.4 and 0.5, and then plateaued at 85% probability for a ratio >0.5. Additionally, the average fat-to-cortical thickness ratio was statistically significant ( P-value = .02) in predicting progression to renal failure, compared to a cortical thickness alone ( P-value = .12 and P-value = .39 for the left and right kidney, respectively). However, when evaluating individual kidneys for the average fat-to-cortical thickness ratio, only the left kidney showed a statistical significance ( P-value = .02 and P-value = .08 on the left and right, respectively).

Conclusion:

The renal sinus fat-to-cortical thickness ratio has a significant negative correlation to GFR, specifically for the left kidney. The probability of developing renal failure increases with higher ratios. The renal sinus fat-to-cortical thickness ratio may also be better than cortical thickness alone in predicting progression toward CKD and it acts as an internal control for differences in body size.

A Hybrid Random Forest Classifier for Chronic Kidney Disease Prediction from 2D Ultrasound Kidney Images

Chronic kidney disease (CKD) is one of the causes of mortality in almost all countries across the globe and the notable thing is its asymptomatic nature in the early stages. This disease is characterized by the gradual loss of kidney function in an individual. Frequently chronic kidney disease is diagnosed based on the Estimated Glomerular Filtration Rate (eGFR) determined from blood and urine tests. In order to reduce the risk factors arising due to chronic kidney disease, it is essential to be diagnosed in the earlier stages itself. This work proposes an automated chronic kidney disease detection based on the textural features of the kidney using a hybrid random forest classifier from 2D ultrasound kidney images. The proposed classifier is compared with the other competing machine learning classifiers through experimenting on a dataset of 150 images and gives a better accuracy of [Formula: see text] with [Formula: see text] of recall and precision, thus proving it to be promising in detecting CKD noninvasively in the early stages.

Kidney Ultrasound for the Nephrologist: A Review

Ultrasound imaging is a key investigatory step in the evaluation of chronic kidney disease and kidney transplantation. It uses nonionizing radiation, is noninvasive, and generates real-time images, making it the ideal initial radiographic test for patients with abnormal kidney function. Ultrasound enables the assessment of both structural (form and size) and functional (perfusion and patency) aspects of kidneys, both of which are especially important as the disease progresses. Ultrasound and its derivatives have been studied for their diagnostic and prognostic significance in chronic kidney disease and kidney transplantation. Ultrasound is rapidly growing more widely accessible and is now available even in handheld formats that allow for bedside ultrasound examinations. Given the trend toward ubiquity, the current use of kidney ultrasound demands a full understanding of its breadth as it and its variants become available. We described the current applications and future directions of ultrasound imaging and its variants in the context of chronic kidney disease and transplantation in this review.

Measurement of renal cortical thickness using ultrasound in normal dogs: a reference range study considering bodyweight and body condition score

The renal cortical thickness (RCT) reflects the pathological condition of the kidney, and measuring this parameter can help diagnose renal fibrosis in dogs. The normal reference range of RCT in dogs is broad (3-8 mm) because of the extreme diversity in body size. Therefore, this retrospective, reference interval, and observational design study aimed to establish a normal reference range for RCT in dogs measured using ultrasound by considering bodyweight (BW), body surface area (BSA), body condition score (BCS), and abdominal aorta (Ao) diameter. A total of 60 dogs met the inclusion criteria, and abdominal ultrasound images and medical records of these dogs were analyzed. RCT was measured at 1-3 points where the renal capsule and broad base of the medullary pyramid were clearly observed. Ao diameter was measured caudal to the branch of the left renal artery in the mid-sagittal view. The RCT showed positive correlations with BW and BSA and a negative correlation with BCS, which can be described as follows: RCT (mm) = 0.131 × BW - 0.166 × BCS + 3.580. The RCT:Ao ratio was 0.70 ± 0.09 (mean ± standard deviation). No significant differences were found in the RCT:Ao ratio depending on BW or BCS. In conclusion, the RCT:Ao ratio and relative RCT considering both BW and BCS are potentially useful for evaluating the normality of the renal cortex on ultrasound examination in dogs with various physiques.

Ultrasonographic predictors in chronic kidney disease: A hospital based case control study

BACKGROUND

Prevalence of Chronic Kidney Disease (CKD) is increasing globally with the concomitant upsurge in diabetes mellitus and hypertension. We explored the research question whether Ultrasonographic (US) renal parameters are potential predictors of CKD?

MATERIALS AND METHODS

A case control study was conducted at a tertiary care hospital that included 50 confirmed cases of CKD and 100 nondiseased controls. Renal length, renal parenchymal thickness, and renal cortical thickness were measured in both cases and controls by ultrasound examination. Corticomedullary differentiation and renal cortical echogenicity were also assessed.

RESULTS

US parameters of renal length, renal parenchymal thickness, and renal cortical thickness were found to be significantly and strongly associated with the presence of CKD. The strongest association was observed with renal cortical echogenicity (OR 27.33, 95% CI 8.82-84.63). The association of reduced renal cortical thickness (OR 6.14, 95% CI 1.59-23.62), and renal length (OR 2.72, 95% CI 1.13-8.26) were independent and significant predictors of presence of CKD.

CONCLUSIONS

Specific US parameters of renal cortical echogenicity, cortical thickness, and length of kidney have a strong potential for independently establishing the diagnosis and evaluation of progression of CKD.

Diagnostic performance of renal ultrasonography in detecting chronic kidney disease of various severity

Background

Association between early diagnosis of chronic kidney disease (CKD) and low morbidity and mortality rate has been proven. Thus, tools for early CKD diagnosis are vital. Ultrasonography has been widely used to diagnose and monitor the progression of CKD.

Objectives

To determine the performance of selected renal ultrasonographic parameters for the diagnosis of early CKD.

Methods

In a cohort of patients diagnosed with CKD (n = 100), diagnostic performance of ultrasonographically measured renal length (RL), renal cortical thickness (RCT), and parenchymal thickness (PT) was determined using receiver operating curve analysis; correlation of each parameter with the associated comorbidities and serum creatinine (Scr) levels was also determined. Severity of CKD was graded with estimated glomerular filtration rates (eGFR).

Results

Of all patient participants, 85 had severity grades 2 or 3. Mean (standard deviation) Scr was 1.88 (0.60) mg/dL; eGFR was 43.3 (11.85) mL/min/1.73 m2. RL was 9.01 (0.83) cm, PT was 1.32 (0.22) cm, and RCT was 6.0 (0.10) mm. PT and RCT were positively correlated with eGFR (P = 0.01 and 0.002, respectively). Early CKD was better predicted by PT (area under the curve (AUC) 0.735; 82% sensitivity; 30% specificity; 68% positive predictive value (PPV)) and RCT (AUC 0.741; 82% sensitivity; 48% specificity; 51% PPV); severe CKD was better predicted by RL (AUC 0.809; 67% sensitivity; 26% specificity, 45% PPV; 13% negative predictive value).

Conclusion

Index ultrasonic parameters show a diagnostic role in different stages of CKD. The index ultrasound and biochemical parameters showed a complementary role in predicting renal dysfunction.

Ultrasonographic Renal Dimensions Amongst Adult Nigerian Diabetics: Correlation with Clinical, Anthropometric and Metabolic Risk Factors

Diabetes is now becoming a major public health problem globally. It is increasingly associated with renal diseases, particularly chronic kidney disease worldwide. A simple, accurate, reproducible and non-invasive method of evaluation is necessary for early morphological assessment for timely intervention, diagnosis, treatment, and evaluation of renal diseases in diabetes mellitus. In this cross-sectional comparative study, among one hundred and four adult diabetic cases and fifty-three healthy controls, the ultrasonographic renal dimensions were determined and compared in both cases and controls. Correlations were sought between the renal dimensions and the clinical, anthropometric, and metabolic characteristics of the study population. The dimensions of the kidneys in diabetic cases versus controls were; lengths (9.94± 0.76cm vs 9.27 ± 0.90 and 10.28 ± 0.87cm vs 9.41± 1.02cm(p=<0.001), cortical thickness (1.77± 0.28cm vs 1.26± 0.49cm, p<0.001 and 1.89± 0.52cm vs 1.37± 0.78cm, p<0.001 and volumes (121.9± 39.50cm3 vs 107.8± 29.82cm, p=0.026 and 136.3± 45.09cm3 vs 118.8± 33.79cm3, (p=0.015) were significantly higher in Diabetes mellitus cases on the right and left respectively. The waist circumference, fasting blood sugar, postprandial blood sugar, cholesterol, and urinary albumin, all had correlations with the mean kidney length. Taking together, the ultrasonographic renal lengths, cortical thickness, and volumes are increased in diabetic disease without renal function compromise compared to age-, gender- and body mass index-matched non-diabetic controls. The clinical, anthropometric, and metabolic parameters of the diabetes cases also showed significant correlations with mean kidney length.

Consensus-based technical recommendations for clinical translation of renal ASL MRI

OBJECTIVES

This study aimed at developing technical recommendations for the acquisition, processing and analysis of renal ASL data in the human kidney at 1.5 T and 3 T field strengths that can promote standardization of renal perfusion measurements and facilitate the comparability of results across scanners and in multi-centre clinical studies.

METHODS

An international panel of 23 renal ASL experts followed a modified Delphi process, including on-line surveys and two in-person meetings, to formulate a series of consensus statements regarding patient preparation, hardware, acquisition protocol, analysis steps and data reporting.

RESULTS

Fifty-nine statements achieved consensus, while agreement could not be reached on two statements related to patient preparation. As a default protocol, the panel recommends pseudo-continuous (PCASL) or flow-sensitive alternating inversion recovery (FAIR) labelling with a single-slice spin-echo EPI readout with background suppression and a simple but robust quantification model.

DISCUSSION

This approach is considered robust and reproducible and can provide renal perfusion images of adequate quality and SNR for most applications. If extended kidney coverage is desirable, a 2D multislice readout is recommended. These recommendations are based on current available evidence and expert opinion. Nonetheless they are expected to be updated as more data become available, since the renal ASL literature is rapidly expanding.

Consensus-based technical recommendations for clinical translation of renal ASL MRI

Objectives

This study aimed at developing technical recommendations for the acquisition, processing and analysis of renal ASL data in the human kidney at 1.5 T and 3 T field strengths that can promote standardization of renal perfusion measurements and facilitate the comparability of results across scanners and in multi-centre clinical studies.

Methods

An international panel of 23 renal ASL experts followed a modified Delphi process, including on-line surveys and two in-person meetings, to formulate a series of consensus statements regarding patient preparation, hardware, acquisition protocol, analysis steps and data reporting.

Results

Fifty-nine statements achieved consensus, while agreement could not be reached on two statements related to patient preparation. As a default protocol, the panel recommends pseudo-continuous (PCASL) or flow-sensitive alternating inversion recovery (FAIR) labelling with a single-slice spin-echo EPI readout with background suppression and a simple but robust quantification model.

Discussion

This approach is considered robust and reproducible and can provide renal perfusion images of adequate quality and SNR for most applications. If extended kidney coverage is desirable, a 2D multislice readout is recommended. These recommendations are based on current available evidence and expert opinion. Nonetheless they are expected to be updated as more data become available, since the renal ASL literature is rapidly expanding.

Electronic supplementary material

The online version of this article (10.1007/s10334-019-00800-z) contains supplementary material, which is available to authorized users.

Automation of the kidney function prediction and classification through ultrasound-based kidney imaging using deep learning

Prediction of kidney function and chronic kidney disease (CKD) through kidney ultrasound imaging has long been considered desirable in clinical practice because of its safety, convenience, and affordability. However, this highly desirable approach is beyond the capability of human vision. We developed a deep learning approach for automatically determining the estimated glomerular filtration rate (eGFR) and CKD status. We exploited the transfer learning technique, integrating the powerful ResNet model pretrained on an ImageNet dataset in our neural network architecture, to predict kidney function based on 4,505 kidney ultrasound images labeled using eGFRs derived from serum creatinine concentrations. To further extract the information from ultrasound images, we leveraged kidney length annotations to remove the peripheral region of the kidneys and applied various data augmentation schemes to produce additional data with variations. Bootstrap aggregation was also applied to avoid overfitting and improve the model's generalization. Moreover, the kidney function features obtained by our deep neural network were used to identify the CKD status defined by an eGFR of <60 ml/min/1.73 m2. A Pearson correlation coefficient of 0.741 indicated the strong relationship between artificial intelligence (AI)- and creatinine-based GFR estimations. Overall CKD status classification accuracy of our model was 85.6% -higher than that of experienced nephrologists (60.3%-80.1%). Our model is the first fundamental step toward realizing the potential of transforming kidney ultrasound imaging into an effective, real-time, distant screening tool. AI-GFR estimation offers the possibility of noninvasive assessment of kidney function, a key goal of AI-powered functional automation in clinical practice.