Utility of Ultrasound-Guided Attenuation Parameter (UGAP) in Renal Angiomyolipoma (AML): First Results.

Angiomyolipoma (AML) are the most common benign solid renal mass. Differentiation from malignant tumours is essential. Imaging features in ultrasound may overlap between malignant lesions, especially between renal cell carcinoma (RCC) and AML. So far, sectional imaging has been necessary for reliable differentiation. The aim of this study is to evaluate the use of the ultrasound-guided attenuation parameter (UGAP), a recently established tool for assessing hepatic steatosis, in the differentiation of AMLs from other renal masses. Therefore, 27 patients with unknown solid renal masses were examined by ultrasound including UGAP. The attenuation was assessed qualitatively by attenuation map and quantitatively in comparison to the surrounding renal tissue. UGAP was applicable in 26/27 patients. Findings were compared with CT/MRI as the current imaging standard. A total of 18 AML and 9 other renal tumours were found. The diagnostic performance of B-Mode (hyperechogenic lesion) ultrasound was 77.8% in identifying AML. The diagnostic performance of the attenuation map showed a diagnostic performance of 92.6%, whereby UGAP measurements were successful in 76.9% of cases. Quantitatively, we found a significant difference (p < 0.034) in mean measured attenuation between AML (0.764 ± 0.162 dB/cm/MHz) vs. other renal tumours (0.658 ± 0.155 dB/cm/MHz). The best performance was found by a combined parameter of a hyperechogenic lesion with a positive attenuation map with an accuracy of 95.0%. In conclusion, UGAP may represent a possibility for differentiating solid renal lesions more accurately by ultrasound, especially classic hyperechoic AMLs from other renal lesions. Further studies are needed to increase the diagnostic reliability further.

Spatial profiling of in vivo diffusion-weighted MRI parameters in the healthy human kidney.

OBJECTIVE: Diffusion-weighted MRI is a technique that can infer microstructural and microcirculatory features from biological tissue, with particular application to renal tissue. There is extensive literature on diffusion tensor imaging (DTI) of anisotropy in the renal medulla, intravoxel incoherent motion (IVIM) measurements separating microstructural from microcirculation effects, and combinations of the two. However, interpretation of these features and adaptation of more specific models remains an ongoing challenge. One input to this process is a whole organ distillation of corticomedullary contrast of diffusion metrics, as has been explored for other renal biomarkers. MATERIALS AND METHODS: In this work, we probe the spatial dependence of diffusion MRI metrics with concentrically layered segmentation in 11 healthy kidneys at 3 T. The metrics include those from DTI, IVIM, a combined approach titled "REnal Flow and Microstructure AnisotroPy (REFMAP)", and a multiply encoded model titled "FC-IVIM" providing estimates of fluid velocity and branching length. RESULTS: Fractional anisotropy decreased from the inner kidney to the outer kidney with the strongest layer correlation in both parenchyma (including cortex and medulla) and medulla with Spearman correlation coefficients and p-values (r, p) of (0.42, <0.001) and (0.37, <0.001), respectively. Also, dynamic parameters derived from the three models significantly decreased with a high correlation from the inner to the outer parenchyma or medulla with (r, p) ranges of (0.46-0.55, <0.001). CONCLUSIONS: These spatial trends might find implications for indirect assessments of kidney physiology and microstructure using diffusion MRI.

URI-CADS: A Fully Automated Computer-Aided Diagnosis System for Ultrasound Renal Imaging.

Ultrasound is a widespread imaging modality, with special application in medical fields such as nephrology. However, automated approaches for ultrasound renal interpretation still pose some challenges: (1) the need for manual supervision by experts at various stages of the system, which prevents its adoption in primary healthcare, and (2) their limited considered taxonomy (e.g., reduced number of pathologies), which makes them unsuitable for training practitioners and providing support to experts. This paper proposes a fully automated computer-aided diagnosis system for ultrasound renal imaging addressing both of these challenges. Our system is based in a multi-task architecture, which is implemented by a three-branched convolutional neural network and is capable of segmenting the kidney and detecting global and local pathologies with no need of human interaction during diagnosis. The integration of different image perspectives at distinct granularities enhanced the proposed diagnosis. We employ a large (1985 images) and demanding ultrasound renal imaging database, publicly released with the system and annotated on the basis of an exhaustive taxonomy of two global and nine local pathologies (including cysts, lithiasis, hydronephrosis, angiomyolipoma), establishing a benchmark for ultrasound renal interpretation. Experiments show that our proposed method outperforms several state-of-the-art methods in both segmentation and diagnosis tasks and leverages the combination of global and local image information to improve the diagnosis. Our results, with a 87.41% of AUC in healthy-pathological diagnosis and 81.90% in multi-pathological diagnosis, support the use of our system as a helpful tool in the healthcare system.

Renal Imaging in Stone Disease: Which Modality to Choose?

Numerous imaging modalities are available to the provider when diagnosing or surveilling kidney stones. The decision to order one over the other can be nuanced and especially confusing to non-urologic practitioners. This manuscript reviews the main modalities used to image stones in the modern era - renal bladder ultrasound, Kidney Ureter Bladder plain film radiography (KUB), magnetic resonance imaging (MRI), and non-contrast computerized tomography (NCCT). While NCCT has become the most popular and familiar modality for most practitioners, particularly in the acute setting, ultrasound is a cost-effective technology that is adept at monitoring interval stone development in patients and evaluating for the presence of hydronephrosis. KUB and MRI also occupy unique niches in the management of urolithiasis. In the correct clinical setting, each of these modalities has a role in the acute workup and management of suspected nephrolithiasis.

Motion compensated renal diffusion weighted imaging.

PURPOSE: To assess the effect of respiratory motion and cardiac driven pulsation in renal DWI and to examine asymmetrical velocity-compensated diffusion encoding waveforms for robust ADC mapping in the kidneys. METHODS: The standard monopolar Stejskal-Tanner pulsed gradient spin echo (pgse) and the asymmetric bipolar velocity-compensated (asym-vc) diffusion encoding waveforms were used for coronal renal DWI at 3T. The robustness of the ADC quantification in the kidneys was tested with the aforementioned waveforms in respiratory-triggered and breath-held cardiac-triggered scans at different trigger delays in 10 healthy subjects. RESULTS: The pgse waveform showed higher ADC values in the right kidney at short trigger delays in comparison to longer trigger delays in the respiratory triggered scans when the diffusion gradient was applied in the feet-head (FH) direction. The coefficient of variation over all respiratory trigger delays, averaged over all subjects was 0.15 for the pgse waveform in the right kidney when diffusion was measured in the FH direction; the corresponding coefficient of variation for the asym-vc waveform was 0.06. The effect of cardiac driven pulsation was found to be small in comparison to the effect of respiratory motion. CONCLUSION: Short trigger delays in respiratory-triggered scans can cause higher ADC values in comparison to longer trigger delays in renal DWI, especially in the right kidney when diffusion is measured in the FH direction. The asym-vc waveform can reduce ADC variation due to respiratory motion in respiratory-triggered scans at the cost of reduced SNR compared to the pgse waveform.

Outcomes of Robot-Assisted Laparoscopic Pyeloplasty Based on Degree of Obstruction on Preoperative Tc-99 MAG-3 Renal Scintigraphy.

Objective: Management of symptomatic ureteropelvic junction (UPJ) obstruction with hydronephrosis and discordant Tc-99 mercaptoacetyltriglycine (MAG-3) renal scintigraphy is challenging. In this study we describe long-term outcomes of patients who underwent robot-assisted laparoscopic pyeloplasty for the correction of symptomatic UPJ obstruction with discordant preoperative Tc-99m MAG-3 renal scintigraphy. Methods: Patients undergoing robot-assisted laparoscopic pyeloplasty for symptomatic UPJ obstruction at a single academic center from 2009 to 2021 were retrospectively reviewed. Patients were categorized into three groups with varying degrees of obstruction based on preoperative MAG-3 imaging: Group 1: no obstruction (Lasix T1/2 clearance <10 minutes), Group 2: equivocal obstruction (Lasix T1/2 clearance 10-20 minutes), and Group 3: obstruction (Lasix T1/2 clearance >20 minutes. Pyeloplasty success was defined as resolution of symptoms and improvement/stable computed tomography (CT) imaging or MAG-3 scintigraphy. Failure was defined as persistence of symptoms with either obstruction on functional imaging, worsening hydronephrosis, or subsequent intervention. Results: A total of 125 cases were identified, with a median patient age of 35 years. Dismembered pyeloplasty technique was performed in 98.4% of cases. Median preoperative split renal function on MAG-3 scintigraphy was the only statistically significant (p = 0.003) difference in preoperative characteristics between the three groups. There were 15 postoperative complications, with a rate of Clavien-Dindo grade 3 or higher complications of 4.8%. Overall pyeloplasty success was 92.8%, with success rates of 100% (15/15) and 97% (32/33) in the no obstruction and equivocal obstruction groups, respectively. Median time to pyeloplasty failure was 20.4 months. Conclusion: Robot-assisted laparoscopic pyeloplasty is a safe and effective surgical intervention for correcting UPJ obstruction. Patients with symptoms of UPJ obstruction and discordant functional imaging studies demonstrate similar or improved success rates after pyeloplasty compared with patients with documented high-grade obstruction. Based on these findings preoperative renal scan may not be reliable in appropriate selection of candidacy for pyeloplasty.

Evaluation of N-(6-[18F]Fluoropyridin-3-yl)glycine PET renography to detect renal function progression in a rat model of diabetic nephropathy.

OBJECTIVE: Given the limitation of biomarkers to predict the renal function progression in diabetic nephropathy, N-(6-[18F]Fluoropyridin-3-yl)glycine (6-[18F]FPyGly) was used to evaluate renal function progression in a rat model of diabetic nephropathy. METHODS: Twenty male Sprague-Dawley rats were randomly divided into four groups, including the healthy control group (HC group), diabetic nephropathy group (DNM group), routine diet treated diabetic nephropathy group (RDNM group), and high fat/high sucrose -diet-fed diabetic nephropathy group (HDNM group). All renal function parameters were determined from animal PET renograms. P and Tmax represent the curve peak counts and the time to the curve peak counts of 6-[18F]FPyGly in kidneys after injection, C1/2 and the 15 min/Peak ratio represent the time from peak to 1/2 peak in the clearance phase, and the ratio of the curve counts at 15 min to the curve peak counts. RESULTS: P, Tmax, C1/2, and 15 min/peak ratio of each rat were significantly correlated with S-Cr, BUN. There were significant differences in Tmax, P, serum creatinine (SCr), and blood urea nitrogen (BUN) levels between HC and DNM groups. P and the 15 min/Peak ratio were significantly different among DNM, RDNM, and HDNM groups, while Tmax and C1/2 were only significantly different between DNM and RDNM or HDNM groups. There only was a significant difference in BUN between the DNM and HDNM groups. CONCLUSION: The renal function parameters P, Tmax, C1/2 and 15 min/peak value obtained by dynamic renal imaging based on 6-[18F]FPyGly could reflect changes of renal function in rats, which had a good correlation with SCr and BUN, and showed more efficient in the diagnosis of diabetic nephropathy and renal function classification than SCr and BUN.

Evolving Medical Imaging Techniques for the Assessment of Delayed Graft Function: A Narrative Review.

PURPOSE OF REVIEW: Delayed graft function (DGF) is a significant complication that contributes to poorer graft function and shortened graft survival. In this review, we sought to evaluate the current and emerging role of medical imaging modalities in the assessment of DGF and how it may guide clinical management. SOURCES OF INFORMATION: PubMed, Google Scholar, and ClinicalTrial.gov up until February 2021. METHODS: This narrative review first examined the pathophysiology of DGF and current clinical management. We then summarized relevant studies that utilized medical imaging to assess posttransplant renal complications, namely, DGF. We focused our attention on noninvasive, evolving imaging modalities with the greatest potential for clinical translation, including contrast-enhanced ultrasound (CEUS) and multiparametric magnetic resonance imaging (MRI). KEY FINDINGS: A kidney biopsy in the setting of DGF can be used to assess the degree of ischemic renal injury and to rule out acute rejection. Biopsies are accompanied by complications and may be limited by sampling bias. Early studies on CEUS and MRI have shown their potential to distinguish between the 2 most common causes of DGF (acute tubular necrosis and acute rejection), but they have generally included only small numbers of patients and have not kept pace with more recent technical advances of these imaging modalities. There remains unharnessed potential with CEUS and MRI, and more robust clinical studies are needed to better evaluate their role in the current era. LIMITATIONS: The adaptation of emerging approaches for imaging DGF will depend on additional clinical trials to study the feasibility and diagnostic test characteristics of a given modality. This is limited by access to devices, technical competence, and the need for interdisciplinary collaborations to ensure that such studies are well designed to appropriately inform clinical decision-making.

MOTIF DE LA REVUE: La reprise retardée de la fonction du greffon (RRFG) est une complication importante susceptible d'affecter négativement la fonction du greffon et de réduire sa survie. Dans cette revue, nous cherchions à évaluer le rôle actuel et grandissant des modalités d'imagerie médicale dans l'évaluation de la RRFG et la façon dont cela pourrait orienter la prise en charge clinique. SOURCES: PubMed, Google Scholar et ClinicalTrial.gov jusqu'à février 2021. MÉTHODOLOGIE: Notre revue narrative portait d'abord sur la physiopathologie de la RRFG et la prise en charge clinique actuelle. Nous avons par la suite résumé les études pertinentes ayant utilisé l'imagerie médicale pour évaluer les complications rénales post- transplantation, notamment la RRFG. Nous avons concentré notre attention sur les modalités d'imagerie non effractives et évolutives présentant le plus grand potentiel d'application clinique, notamment l'échographie de contraste (CEUS) et l'imagerie par résonance magnétique (IRM) multiparamétrique. PRINCIPAUX RÉSULTATS: Dans les cas de RRFG, une biopsie du rein peut être utilisée pour évaluer l'ampleur des lésions rénales ischémiques et pour exclure le rejet aigu. Les biopsies s'accompagnent de complications et pourraient être limitées par des biais d'échantillonnage. Des études préliminaires examinant les CEUS et l'IRM ont montré que ces modalités permettaient une distinction entre les deux causes les plus fréquentes de la RRFG (nécrose tubulaire aiguë et rejet aigu), mais ces études portaient généralement sur de petits nombres de patients et n'avaient pas suivi les plus récents progrès techniques de ces modalités d'imagerie. Il subsiste un potentiel non exploité avec les CEUS et l'IRM. Des études cliniques plus robustes sont nécessaires pour mieux évaluer leur rôle à l'heure actuelle. LIMITES: L'adaptation des approches émergentes pour l'imagerie en contexte de RRFG dépendra d'essais cliniques supplémentaires qui examineront la faisabilité et les caractéristiques des tests diagnostiques d'une modalité donnée. Cela est limité par l'accès aux appareils, la compétence technique et la nécessité de collaborations interdisciplinaires afin de s'assurer que ces études sont bien conçues et qu'elles puissent éclairer adéquatement la prise de décisions cliniques.

Evaluation of Radiographic Contrast-Induced Nephropathy by Functional Diffusion Weighted Imaging.

Contrast-induced nephropathy (CIN) resembles an important complication of radiographic contrast medium (XCM) displayed by a rise in creatinine levels 48-72 h after XCM administration. The purpose of the current study was to evaluate microstructural renal changes due to CIN in high-risk patients by diffusion weighted (DWI) and diffusion tensor imaging (DTI). Fifteen patients (five CIN and ten non-CIN) scheduled for cardiological intervention were included in the study. All patients were investigated pre- and post-intervention on a clinical 3T scanner. After anatomical imaging, renal DWI was performed by a paracoronal echo-planar-imaging sequence. Renal clinical routine serum parameters and advanced urinary injury markers were determined to monitor renal function. We observed a drop in cortical and medullar apparent diffusion coefficient (ADC) and fractional anisotropy (FA) before and after XCM administration in the CIN group. In contrast, the non-CIN group differed only in medullary ADC. The decrease of ADC and FA was apparent even before serum parameters of the kidney changed. In conclusion, DWI/DTI may be a useful tool for monitoring high-risk CIN patients as part of multi-modality based clinical protocol. Further studies, including advanced analysis of the diffusion signal, may improve the identification of patients at risk for CIN.

The old becomes new: advances in imaging techniques to assess nephron mass in children.

Renal imaging is widely used in the assessment of surrogate markers of nephron mass correlated to renal function. Autopsy studies have tested the validity of various imaging modalities in accurately estimating "true" nephron mass. However, in vivo assessment of nephron mass has been largely limited to kidney volume determination by ultrasonography (US) in pediatric populations. Practical limitations and risks create challenges in incorporating more precise 3D volumetric imaging, like magnetic resonance imaging (MRI), and computed tomography (CT) technologies, compared to US for routine kidney volume assessment in children. Additionally, accounting for structural anomalies such as hydronephrosis when estimating renal parenchymal area in congenital anomalies of the kidney and urinary tract (CAKUT) is important, as it correlates with chronic kidney disease (CKD) progression. 3D imaging using CT and MRI has been shown to be superior to US, which has traditionally relied on 2D measurements to estimate kidney volume using the ellipsoid calculation. Recent innovations using 3D and contrast-enhanced US (CEUS) provide improved accuracy with low risk. Indexing kidney volume to body surface area in children is an important standard that may allow early detection of CKD progression in high-risk populations. This review highlights current understanding of various imaging modalities in assessing nephron mass, discusses applications and limitations, and describes recent advances in the field of imaging and kidney disease. Although renal imaging has been a long-standing, essential tool in assessing kidney disease, innovation and new applications of established technologies provide important tools in the study and management of kidney disease in children.

Feasibility of quantitative susceptibility mapping (QSM) of the human kidney.

OBJECTIVE: To evaluate the feasibility of in-vivo quantitative susceptibility mapping (QSM) of the human kidney. METHODS: An axial single-breath-hold 3D multi-echo sequence (acquisition time 33 s) was completed on a 3 T-MRI-scanner (Magnetom Prisma, Siemens Healthineers, Erlangen, Germany) in 19 healthy volunteers. Graph-cut-based unwrapping combined with the T2*-IDEAL approach was performed to remove the chemical shift of fat and to quantify QSM of the upper abdomen. Mean susceptibility values of the entire, renal cortex and medulla in both kidneys and the liver were determined and compared. Five subjects were measured twice to examine the reproducibility. One patient with severe renal fibrosis was included in the study to evaluate the potential clinical relevance of QSM. RESULTS: QSM was successful in 17 volunteers and the patient with renal fibrosis. Anatomical structures in the abdomen were clearly distinguishable by QSM and the susceptibility values obtained in the liver were comparable to those found in the literature. The results showed a good reproducibility. Besides, the mean renal QSM values obtained in healthy volunteers (0.04 ± 0.07 ppm for the right and - 0.06 ± 0.19 ppm for the left kidney) were substantially higher than that measured in the investigated fibrotic kidney (- 0.43 ± - 0.02 ppm). CONCLUSION: QSM of the human kidney could be a promising approach for the assessment of information about microscopic renal tissue structure. Therefore, it might further improve functional renal MR imaging.

11C-PABA as a PET Radiotracer for Functional Renal Imaging: Preclinical and First-in-Human Study.

para-Aminobenzoic acid (PABA) has been previously used as an exogenous marker to verify completion of 24-h urine sampling. Therefore, we hypothesized that PABA radiolabeled with 11C might allow high-quality dynamic PET of the kidneys with less radiation exposure than other agents because of its shorter biologic and physical half-life. We evaluated if 11C-PABA can visualize renal anatomy and quantify function in healthy rats and rabbits and in a first-in-humans study on healthy volunteers. Methods: Healthy rats and rabbits were injected with 11C-PABA intravenously. Subsequently, dynamic PET was performed, followed by postmortem tissue-biodistribution studies. 11C-PABA PET was directly compared with the current standard, 99mTc-mercaptoacetyltriglycin, in rats. Three healthy human subjects also underwent dynamic PET after intravenous injection of 11C-PABA. Results: In healthy rats and rabbits, dynamic PET demonstrated a rapid accumulation of 11C-PABA in the renal cortex, followed by rapid excretion through the pelvicalyceal system. In humans, 11C-PABA PET was safe and well tolerated. There were no adverse or clinically detectable pharmacologic effects in any subject. The cortex was delineated on PET, and the activity gradually transited to the medulla and then pelvis with high spatiotemporal resolution. Conclusion:11C-PABA demonstrated fast renal excretion with a very low background signal in animals and humans. These results suggest that 11C-PABA might be used as a novel radiotracer for functional renal imaging, providing high-quality spatiotemporal images with low radiation exposure.

Evaluation of kidney function throughout the heart failure trajectory - a position statement from the Heart Failure Association of the European Society of Cardiology.

Appropriate interpretation of changes in markers of kidney function is essential during the treatment of acute and chronic heart failure. Historically, kidney function was primarily assessed by serum creatinine and the calculation of estimated glomerular filtration rate. An increase in serum creatinine, also termed worsening renal function, commonly occurs in patients with heart failure, especially during acute heart failure episodes. Even though worsening renal function is associated with worse outcome on a population level, the interpretation of such changes within the appropriate clinical context helps to correctly assess risk and determine further treatment strategies. Additionally, it is becoming increasingly recognized that assessment of kidney function is more than just glomerular filtration rate alone. As such, a better evaluation of sodium and water handling by the renal tubules allows to determine the efficiency of loop diuretics (loop diuretic response and efficiency). Also, though neurohumoral blockers may induce modest deteriorations in glomerular filtration rate, their use is associated with improved long-term outcome. Therefore, a better understanding of the role of cardio-renal interactions in heart failure in symptom development, disease progression and prognosis is essential. Indeed, perhaps even misinterpretation of kidney function is a leading cause of not attaining decongestion in acute heart failure and insufficient dosing of guideline-directed medical therapy in general. This position paper of the Heart Failure Association Working Group on Cardio-Renal Dysfunction aims at improving insights into the interpretation of renal function assessment in the different heart failure states, with the goal of improving heart failure care.

Contrast-Enhanced Ultrasound in Renal Imaging and Intervention.

PURPOSE OF REVIEW: In recent years, there has been renewed interest in the use of contrast-enhanced ultrasound (CEUS) in abdominal imaging and intervention. The goal of this article is to review the practical applications of CEUS in the kidney, including renal mass characterization, treatment monitoring during and after percutaneous ablation, and biopsy guidance. RECENT FINDINGS: Current evidence suggests that CEUS allows accurate differentiation of solid and cystic renal masses and is an acceptable alternative to either computed tomography (CT) or magnetic resonance imaging (MRI) for characterization of indeterminate renal masses. CEUS is sensitive and specific for diagnosing residual or recurrent renal cell carcinoma (RCC) following percutaneous ablation. Furthermore, given its excellent spatial and temporal resolution, CEUS is well suited to demonstrate tumoral microvascularity associated with malignant renal masses and is an effective complement to conventional grayscale ultrasound (US) for percutaneous biopsy guidance. Currently underutilized, CEUS is an important problem-solving tool in renal imaging and intervention whose role will continue to expand in coming years.

In vivo magnetic resonance imaging techniques for structural and functional characterization of murine model kidneys.

Murine models are used in a wide range of renal studies, from those assessing the role of molecular and genetic factors in mammalian development and congenital diseases, to developing and screening new therapeutics. In studies of these models, magnetic resonance imaging (MRI) techniques are playing an ever increasing role in characterizing both structural and functional changes of the kidneys. This chapter details the use of MRI for this purpose-from acquisition to image analysis. An overview of the wide range of characterization that can be performed by this technology is first given. Next, basic image analysis and more advanced image processing techniques are detailed. The utility of MR for characterizing anatomical and physiological properties of murine models of disease is supplemented with data from our work studying polycystic kidney disease.

18 F-Labeled Derivatives of Irbesartan for Angiotensin†II Receptor PET Imaging.

The renin angiotensin aldosterone system (RAAS) is a hormonal cascade involved in the regulation of blood pressure and electrolyte balance, and represents a common target for the treatment of various diseases including hypertension, heart failure, and diabetes. Herein we present a novel 18 F-labeled derivative of the drug irbesartan, one of the most prescribed angiotensin II type 1 receptor (AT1 R) antagonists, for in vivo positron emission tomography (PET). This allows the in vivo measurement of AT1 R expression, and thus the evaluation of functional changes in its expression under pathophysiological conditions. We followed various synthetic approaches optimized for the introduction of fluorine into different positions of the aliphatic side chain of irbesartan. Radioligand binding studies revealed that fluorine atoms at specified positions (α-position (IC50 =6.6 nm) and δ-position (IC50 =8.5 nm) of the aliphatic side chain) do not alter the binding properties of irbesartan (IC50 =1.6 nm). After successful radiolabeling with fluorine-18 in a radiochemical yield of 11 %, we observed high renal uptake in healthy rats and pigs, which could be decreased by pretreatment with the parent compound irbesartan.

Establishing the presence or absence of chronic kidney disease: Uses and limitations of formulas estimating the glomerular filtration rate.

The development of formulas estimating glomerular filtration rate (eGFR) from serum creatinine and cystatin C and accounting for certain variables affecting the production rate of these biomarkers, including ethnicity, gender and age, has led to the current scheme of diagnosing and staging chronic kidney disease (CKD), which is based on eGFR values and albuminuria. This scheme has been applied extensively in various populations and has led to the current estimates of prevalence of CKD. In addition, this scheme is applied in clinical studies evaluating the risks of CKD and the efficacy of various interventions directed towards improving its course. Disagreements between creatinine-based and cystatin-based eGFR values and between eGFR values and measured GFR have been reported in various cohorts. These disagreements are the consequence of variations in the rate of production and in factors, other than GFR, affecting the rate of removal of creatinine and cystatin C. The disagreements create limitations for all eGFR formulas developed so far. The main limitations are low sensitivity in detecting early CKD in several subjects, e.g., those with hyperfiltration, and poor prediction of the course of CKD. Research efforts in CKD are currently directed towards identification of biomarkers that are better indices of GFR than the current biomarkers and, particularly, biomarkers of early renal tissue injury.

Quantitative Three-Dimensional Tissue Cytometry to Study Kidney Tissue and Resident Immune Cells.

Analysis of the immune system in the kidney relies predominantly on flow cytometry. Although powerful, the process of tissue homogenization necessary for flow cytometry analysis introduces bias and results in the loss of morphologic landmarks needed to determine the spatial distribution of immune cells. An ideal approach would support three-dimensional (3D) tissue cytometry: an automated quantitation of immune cells and associated spatial parameters in 3D image volumes collected from intact kidney tissue. However, widespread application of this approach is limited by the lack of accessible software tools for digital analysis of large 3D microscopy data. Here, we describe Volumetric Tissue Exploration and Analysis (VTEA) image analysis software designed for efficient exploration and quantitative analysis of large, complex 3D microscopy datasets. In analyses of images collected from fixed kidney tissue, VTEA replicated the results of flow cytometry while providing detailed analysis of the spatial distribution of immune cells in different regions of the kidney and in relation to specific renal structures. Unbiased exploration with VTEA enabled us to discover a population of tubular epithelial cells that expresses CD11C, a marker typically expressed on dendritic cells. Finally, we show the use of VTEA for large-scale quantitation of immune cells in entire human kidney biopsies. In summary, we show that VTEA is a simple and effective tool that supports unique digital interrogation and analysis of kidney tissue from animal models or biobanked human kidney biopsies. We have made VTEA freely available to interested investigators via electronic download.

Evaluation of abnormal radiological findings in children aged 2 to 36 months followed by recurrent urinary tract infection: a retrospective study.

Our aim is to determine the rational usage of imaging techniques in order to prevent or minimize permanent renal damage in recurrent urinary tract infections (UTIs). This study was enrolled children aged between 2 and 36 months, following-up with the diagnosis of recurrent UTI. All children had ultrasonography (USG) and dimercaptosuccinic acid scanning, 39 of them had underwent on voiding cystourethrography. There were 133 children (87 girls, 46 boys) with the mean age of 32.82 ± 38.10 months included into the study. Forty-three kidney units were normal in ultrasonogram of which seven units had reflux whereas among 35 units with hydronephrosis 22 units had reflux. Sensitivity and specificity presence of hydronephrosis in ultrasonogram for prediction of reflux was 75.9% and 73.5%, respectively. There were 19 dilated ureters in ultrasonogram, and among them 14 had reflux. Sensitivity and specificity of presence with ureteral dilatation in ultrasonogram for prediction of reflux was found as 48.3% and 89.8%, respectively. The sensitivity of parenchymal thinning seen in ultrasonogram for the evaluation of renal parenchyma was 15.9%, whereas specificity was 98.2% .Sensitivity and specificity of dimercaptosuccinic acid for prediction of reflux was 51.6% and 72.3%, respectively. The normal ultrasonogram findings cannot rule out neither possibility of reflux presence nor development of renal scarring. Therefore, DMSA scanning has major role both in determination of parenchymal damage and prevention of scarring. Also we get an important result as ureteral dilatation seen in USG, related to presence of reflux.

Renal Ultrasound, Dialysis Catheter Placement, and Kidney Biopsy Experience of US Nephrology Fellows.

Procedures are a key component to the practice of nephrology. The Accreditation Council for Graduate Medical Education (ACGME) requires nephrology fellows to acquire skills and demonstrate competency in the performance of several procedures during fellowship training, including temporary hemodialysis catheter placement, biopsy of native and transplanted kidneys, and various dialytic therapies. It is also required that fellows acquire competency in the interpretation of renal imaging, including renal ultrasound, during their training. To gain a more recent perspective of nephrology fellows' experiences regarding renal ultrasonography, dialysis catheter placement, and kidney biopsies, we carried out a national survey of nephrology fellows in May 2014. A majority of the programs did not offer formal clinical training in renal ultrasonography. In addition, a significant percentage of fellows in adult nephrology may not be acquiring the required procedural skills and competency during fellowship training. In this perspective, we explore some of the reasons for this occurrence and propose some measures that the nephrology training community can take to enhance procedural skills and competency of fellows.