Contralateral renal change in a unilateral ureteral obstruction rat model using intravoxel incoherent motion diffusion-weighted imaging.

OBJECTIVES: Most functional magnetic resonance research has primarily examined alterations in the affected kidney, often neglecting the contralateral kidney. Our study aims to investigate whether imaging parameters accurately depict changes in both the renal cortex and medulla in a unilateral ureteral obstruction rat model, thereby showcasing the utility of intravoxel incoherent motion (IVIM) in evaluating contralateral renal changes. METHODS: Six rats underwent MR scans and were subsequently sacrificed for baseline histological examination. Following the induction of left ureteral obstruction, 48 rats were scanned, and the histopathological examinations were conducted on days 3, 7, 10, 14, 21, 28, 35, and 42. The apparent diffusion coefficient (ADC), pure molecular diffusion (D), pseudodiffusion (D*), and perfusion fraction (f) values were measured using IVIM. RESULTS: On the 10th day of obstruction, both cortical and medullary ADC values differed significantly between the UUO10 group and the sham group (p < 0.01). The cortical D values showed statistically significant differences between UUO3 group and sham group (p < 0.01) but not among UUO groups at other time point. Additionally, the cortical and medullary f values were statistically significant between the UUO21 group and the sham group (p < 0.01). Especially, the cortical f values exhibited significant differences between the UUO21 group and the UUO groups with shorter obstruction time (at time point of 3, 7, 10, 14 day) (p < 0.01). CONCLUSIONS: Significant hemodynamic alterations were observed in the contralateral kidney following renal obstruction. IVIM accurately captures changes in the unobstructed kidney. Particularly, the cortical f value exhibits the highest potential for assessing contralateral renal modifications.

Automated Segmentation of Kidney Cortex and Medulla in CT Images: A Multisite Evaluation Study.

BACKGROUND: In kidney transplantation, a contrast CT scan is obtained in the donor candidate to detect subclinical pathology in the kidney. Recent work from the Aging Kidney Anatomy study has characterized kidney, cortex, and medulla volumes using a manual image-processing tool. However, this technique is time consuming and impractical for clinical care, and thus, these measurements are not obtained during donor evaluations. This study proposes a fully automated segmentation approach for measuring kidney, cortex, and medulla volumes. METHODS: A total of 1930 contrast-enhanced CT exams with reference standard manual segmentations from one institution were used to develop the algorithm. A convolutional neural network model was trained (n=1238) and validated (n=306), and then evaluated in a hold-out test set of reference standard segmentations (n=386). After the initial evaluation, the algorithm was further tested on datasets originating from two external sites (n=1226). RESULTS: The automated model was found to perform on par with manual segmentation, with errors similar to interobserver variability with manual segmentation. Compared with the reference standard, the automated approach achieved a Dice similarity metric of 0.94 (right cortex), 0.90 (right medulla), 0.94 (left cortex), and 0.90 (left medulla) in the test set. Similar performance was observed when the algorithm was applied on the two external datasets. CONCLUSIONS: A fully automated approach for measuring cortex and medullary volumes in CT images of the kidneys has been established. This method may prove useful for a wide range of clinical applications.

Symptomatic renal papillary varicosities and medullary nephrocalcinosis.

BACKGROUND: Nephrocalcinosis is often asymptomatic but can manifest with renal colic or hematuria. There is no reported association between nephrocalcinosis and renal vascular malformations, which may also be a source of hematuria. We herein present a case of a patient with hematuria related to nephrocalcinosis and renal papillary varicosities. These varicosities were diagnosed and successfully treated with flexible ureteroscopy and laser fulguration. CASE PRESENTATION: A 24-year-old female with a history of epilepsy (on zonisamide), recent uncomplicated pregnancy, and new diagnosis of nephrocalcinosis presented with right flank pain and intermittent gross hematuria. Imaging revealed intermittent right sided hydronephrosis. A cystoscopy identified hematuria from the right ureteral orifice. Diagnostic flexible ureteroscopy revealed numerous intrapapillary renal stones and varicose veins of several renal papillae. A 200 µm holmium laser fiber was used to unroof these stones and fulgurate the varicosities with resolution of her symptoms for several months. She later presented with left-sided symptoms and underwent left ureteroscopy with similar findings and identical successful treatment. CONCLUSION: Unilateral hematuria from discrete vascular lesions of the renal collecting system may be obscured by other benign co-existing conditions, such as nephrocalcinosis and nephrolithiasis. Although a simultaneous presentation is rare, flexible ureteroscopy with laser fulguration offers an ideal diagnostic and therapeutic modality for these concurrent conditions if symptoms arise.

[CME Sonography 99/Answers: Kidney Echo Changes]. / CME-Sonografie 99/Antworten: Veränderungen der Nierenechogenität.

CME Sonography 99/Answers: Kidney Echo Changes Abstract. Normal kidneys have a smooth contour, kidney length 9-12 cm, volume 90-180 ml/1.73 m2 body surface, parenchyma width 13-18 mm and an echogenicity of the cortex which is hypoechoic compared to the liver and spleen, as well as medullary pyramids, which are again hypoechoic compared to the cortex. Digital ultrasound images enable the echogenicity to be measured between 0 (black) and 255 (white). A normal quotient between the echogenicity of the liver and the renal cortex is 1.0-1.4. A normal quotient between the spleen and the renal cortex is> 1.0. The normal quotient between the renal cortex and the renal medulla is> 1.0. In diffuse renal parenchyma diseases, changes in echogenicity are observed. There are kidneys with increased echogenicity of the cortex and a ratio to liver and spleen of <1.0 and kidneys with hyperechoic renal medulla and the ratio between renal cortex and renal medulla <1.0.

[CME Sonography 99: Kidney Echo Changes]. / CME-Sonografie 99: Veränderungen der Nierenechogenität.

CME Sonography 99: Kidney Echo Changes Abstract. Normal kidneys have a smooth contour, kidney length 9-12 cm, volume 90-180 ml/1.73 m2 body surface, parenchyma width 13-18 mm and an echogenicity of the cortex which is hypoechoic compared to the liver and spleen, as well as medullary pyramids, which are again hypoechoic compared to the cortex. Digital ultrasound images enable the echogenicity to be measured between 0 (black) and 255 (white). A normal quotient between the echogenicity of the liver and the renal cortex is 1.0-1.4. A normal quotient between the spleen and the renal cortex is >1.0. The normal quotient between the renal cortex and the renal medulla is >1.0. In diffuse renal parenchyma diseases, changes in echogenicity are observed. There are kidneys with increased echogenicity of the cortex and a ratio to liver and spleen of <1.0 and kidneys with hyperechoic renal medulla and the ratio between renal cortex and renal medulla <1.0.

Assessment of chronic allograft injury in renal transplantation using diffusional kurtosis imaging.

BACKGROUND: Chronic allograft injury (CAI) is a significant reason for which many grafts were lost. The study was conducted to assess the usefulness of diffusional kurtosis imaging (DKI) technology in the non-invasive assessment of CAI. METHODS: Between February 2019 and October 2019, 110 renal allograft recipients were included to analyze relevant DKI parameters. According to estimated glomerular filtration rate (eGFR) (mL/min/ 1.73 m2) level, they were divided to 3 groups: group 1, eGFR ≥ 60 (n = 10); group 2, eGFR 30-60 (n = 69); group 3, eGFR < 30 (n = 31). We performed DKI on a clinical 3T magnetic resonance imaging system. We measured the area of interest to determine the mean kurtosis (MK), mean diffusivity (MD), and apparent diffusion coefficient (ADC) of the renal cortex and medulla. We performed a Pearson correlation analysis to determine the relationship between eGFR and the DKI parameters. We used the receiver operating characteristic curve to estimate the predicted values of DKI parameters in the CAI evaluation. We randomly selected five patients from group 2 for biopsy to confirm CAI. RESULTS: With the increase of creatinine, ADC, and MD of the cortex and medulla decrease, MK of the cortex and medulla gradually increase. Among the three different eGFR groups, significant differences were found in cortical and medullary MK (P = 0.039, P < 0.001, P < 0.001, respectively). Cortical and medullary ADC and MD are negatively correlated with eGFR (r = - 0.49, - 0.44, - 0.57, - 0.57, respectively; P < 0.001), while cortical and medullary MK are positively correlated with eGFR (r = 0.42, 0.38; P < 0.001). When 0.491 was set as the cutoff value, MK's CAI assessment showed 87% sensitivity and 100% specificity. All five patients randomly selected for biopsy from the second group confirmed glomerulosclerosis and tubular atrophy/interstitial fibrosis. CONCLUSION: The DKI technique is related to eGFR as allograft injury progresses and is expected to become a potential non-invasive method for evaluating CAI.

Does the renal parenchymal thickness affect the efficacy of the retrograde intrarenal surgery? A prospective cohort study.

Retrograde intrarenal surgery (RIRS) is one of the minimally invasive main treatment modalities in renal stone disease. There are many factors which affect stone-free rate (SFR). Our study was based on the hypothesis that higher renal parenchymal thickness (RPT) which may include higher average number of nephrons provides better diuresis. We investigated the efficacy of RPT on success of RIRS. This study is a single-centered prospective surgical cohort study. A total of 383 patients were analyzed. Regularly followed 304 patients with unilateral kidney stone at single pole or renal pelvis and who underwent single-session RIRS were included in the final analysis, and the patients' preoperative and postoperative 1st and 3rd months' data were evaluated. RPT was measured on the non-contrast computed tomography (CT) images. ROC analysis was performed to estimate the cutoff value of RPT for SFR. Univariate and multivariate logistic regression analyses were used to model the relationship between RPT and SFR after RIRS. ROC analysis revealed the best cutoff value of the RPT for predicting residual stone as 19 mm for both the 1st and 3rd month visits with Youden indexes of 0.397 and 0.406, respectively. To the best of our knowledge, this is the first study which evaluated the effect of RPT on the efficacy of RIRS. RPT measurement is a cost-effective method that can be easily performed on routinely applied non-contrast CT and may have predictive value for the surgical success in patients with nephrolithiasis.

Classification of the renal papillary abnormalities by flexible ureteroscopy: evaluation of the 2016 version and update.

INTRODUCTION: To assess the use of the 2016 proposed classification of the renal papillary abnormalities during flexible ureteroscopy that aims to standardize their description. PATIENTS AND METHODS: We performed a prospective monocentric single operator collection of the data using this classification during 88 consecutive flexible ureteroscopies required for renal stones treatment. Outcome measurements and statistical analysis: data of stones analysis (microscopy and infrared spectrophotometry) and of serum and urines biochemical samples have been compared with the results of the classified endoscopic descriptions. RESULTS: Mean duration of description was 81.4 s. We reported that 83% of the patients had Randall plaques (RP), as only 4.5% of the patients had no abnormality. Concerning the papillary stones and anchored stones were observed in 30.7% and aspect of intraductal crystallization (Sc) in 15.9%. Erosions were present in 55.7% and extrophic papillae in 8%. Sa1 and Pa2 were significantly correlated to RP, anchored stones (Sa) to papillary erosions and calcium phosphate stones to intraductal crystallization. Hypercalciuria was significantly higher in Sa2 than Sa1 stones. CONCLUSIONS: The different descriptions in the 2016 classification were confirmed by the results of this study. Papillary abnormalities are consequences of stones development. Their descriptions could also improve the follow-up and the diagnosis of a metabolic lithogenesis. We recommend their systematic description during ureteroscopy. Some improvements are proposed to update this classification.

Multimodal imaging reveals a unique autofluorescence signature of Randall's plaque.

Kidney stones frequently develop as an overgrowth on Randall's plaque (RP) which is formed in the papillary interstitium. The organic composition of RP is distinct from stone matrix in that RP contains fibrillar collagen; RP in tissue has also been shown to have two proteins that are also found in stones, but otherwise the molecular constituents of RP are unstudied. We hypothesized that RP contains unique organic molecules that can be differentiated from the stone overgrowth by fluorescence. To test this, we used micro-CT-guided polishing to expose the interior of kidney stones for multimodal imaging with multiphoton, confocal and infrared microscopy. We detected a blue autofluorescence signature unique to RP, the specificity of which was also confirmed in papillary tissue from patients with stone disease. High-resolution mineral mapping of the stone also showed a transition from the apatite within RP to the calcium oxalate in the overgrowth, demonstrating the molecular and spatial transition from the tissue to the urine. This work provides a systematic and practical approach to uncover specific fluorescence signatures which correlate with mineral type, verifies previous observations regarding mineral overgrowth onto RP and identifies a novel autofluorescence signature of RP demonstrating RP's unique molecular composition.

Physiological system analysis of the kidney by high-temporal-resolution T2∗ monitoring of an oxygenation step response.

PURPOSE: Examine the feasibility of characterizing the regulation of renal oxygenation using high-temporal-resolution monitoring of the T2∗ response to a step-like oxygenation stimulus. METHODS: For T2∗ mapping, multi-echo gradient-echo imaging was used (temporal resolution = 9 seconds). A step-like renal oxygenation challenge was applied involving sequential exposure to hyperoxia (100% O2 ), hypoxia (10% O2 + 90% N2 ), and hyperoxia (100% O2 ). In vivo experiments were performed in healthy rats (N = 10) and in rats with bilateral ischemia-reperfusion injury (N = 4). To assess the step response of renal oxygenation, a second-order exponential model was used (model parameters: amplitude [A], time delay [Δt], damping constant [D], and period of the oscillation [T]) for renal cortex, outer stripe of the outer medulla, inner stripe of the outer medulla, and inner medulla. RESULTS: The second-order exponential model permitted us to model the exponential T2∗ recovery and the superimposed T2∗ oscillation following renal oxygenation stimulus. The in vivo experiments revealed a difference in Douter medulla between healthy controls (D < 1, indicating oscillatory recovery) and ischemia-reperfusion injury (D > 1, reflecting aperiodic recovery). The increase in Douter medulla by a factor of 3.7 (outer stripe of the outer medulla) and 10.0 (inner stripe of the outer medulla) suggests that this parameter might be rather sensitive to (patho)physiological oxygenation changes. CONCLUSION: This study demonstrates the feasibility of monitoring the dynamic oxygenation response of renal tissues to a step-like oxygenation challenge using high-temporal-resolution T2∗ mapping. Our results suggest that the implemented system analysis approach may help to unlock questions regarding regulation of renal oxygenation, with the ultimate goal of providing imaging means for diagnostics and therapy of renal diseases.

Ultrasound to address medullary sponge kidney: a retrospective study.

BACKGROUND: Medullary sponge kidney (MSK) is a rare disease characterized by cystic dilatation of papillary collecting ducts. Intravenous urography is still considered the gold standard for diagnosis. We identified a cohort of patients from our outpatient clinic with established diagnosis of MSK to outline some ultrasonographic characteristics that may help establish a diagnosis. METHODS: We conducted a retrospective study of patients seen between January 1st 2009 and January 1st 2019 in our clinic. Out of 4321 patients, 18 had a diagnosis of MSK. We reviewed their clinical and family history, laboratory data and imaging studies. Specifically, we focused on ultrasound imaging. RESULTS: Patients were referred to our outpatient clinic because of renal impairment (44%), family history of nephropathy (17%), nephrolithiasis or an established diagnosis of MSK (39%). Seventy-two percent of patients presented with chronic kidney disease, 22% required hemodialysis. Urinary tract infections (44%), nephrolithiasis (33%), microscopic hematuria (50%) and proteinuria (44%) were reported. Seven patients underwent computed tomography; all of them received ultrasound. Ultrasound examination showed bilateral renal cysts, usually small and located in the renal medulla, and microcalcifications located in the medulla or within the cysts. CONCLUSION: We identified a peculiar tetrad associated with MSK: 1) hypoechoic medullary areas, 2) hyperechoic spots, 3) microcystic dilatation of papillary zone, 4) multiple calcifications (linear, small stones or calcified intracystic sediment) in each papilla. The presence of this diagnostic tetrad, added to laboratory data and clinical history, could be helpful in the differential diagnosis to identify patients with MSK.

Diffusion tensor imaging in renal artery stenosis: a preliminary report.

OBJECTIVE: To investigate the diffusion properties in the kidneys affected by renal artery stenosis (RAS) using diffusion tensor imaging (DTI). METHODS: In this prospective study, 35 patients with RAS and 15 patients without renal abnormalities were enrolled and examined using DTI. Cortical and medullary regions of interest (ROIs) were located to obtain the corresponding values of the apparent diffusion coefficient (ADC) and fractional anisotropy (FA). The cortical and medullary ADC and FA were compared in the kidney affected by variable degrees of stenosis (RAS 50-75% and >75%) vs controls, using the one-way ANOVA and Student's t-test. The Spearman correlation test was used to correlate the mean ADC and FA values in the cortex and medulla with the estimate glomerular filtration rate (eGFR). RESULTS: For the controls, the ADC value was significantly (p = 0.03) higher in the cortex than in the medulla; the FA value was significantly (p = 0.001) higher in the medulla than in the cortex. Compared with the controls, a significant reduction in the cortical ADC was present with a RAS of 50-75% and >75% (p = 0.001 and 0.041, respectively); a significant reduction in the medullary FA was verified only for RAS >75% (p = 0.023). The Spearman correlation test did not show a statistically significant correlation between the cortical and medullary ADC and FA, and the eGFR. CONCLUSION: The alterations of the diffusional parameters caused by RAS can be detected by DTI and could be useful in the diagnostic evaluation of these patients. ADVANCES IN KNOWLEDGE: 1. Magnetic resonance DTI could provide useful information about renal involvement in RAS.2. Magnetic resonance DTI allows non-invasive repeatable evaluation of the renal parenchyma, without contrast media.

Can distinction between the renal cortex and outer medulla on ultrasonography predict estimated glomerular filtration rate in canine chronic kidney diseases?

BACKGROUND: Quantitative evaluation of renal cortical echogenicity (RCE) has been tried and developed in human and veterinary medicine. OBJECTIVES: The objective of this study was to propose a method for evaluating RCE quantitatively and intuitively, and to determine associations between ultrasonographic renal structural distinction and estimated glomerular filtration rate (eGFR) in canine chronic kidney disease (CKD). METHODS: Data were collected on 63 dogs, including 27 with normal kidney function and 36 CKD patients. Symmetric dimethylarginine and creatinine concentrations were measured for calculating eGFR. RCE was evaluated as 3 grades on ultrasonography images according to the distinction between the renal cortex and outer medulla. The RCE grade of each kidney was measured. RESULTS: There was a significant difference in eGFR between the group normal and CKD (p < 0.001). As mean of RCE grades (the mean values of each right and left kidney's RCE grade) increases, the proportion of group CKD among the patients in each grade increases (p < 0.001). Also, severity of RCE (classified as "high" if any right or left kidney evaluated as RCE grade 3, "low" otherwise) and eGFR is good indicator for predicting group CKD (p < 0.001). CONCLUSIONS: The degree of distinction between the renal cortex and the outer medulla is closely related to renal function including eGFR and the RCE grade defined in this study can be used as a method of objectively evaluating RCE.

Application of diffusion tensor imaging and blood oxygenation level-dependent magnetic resonance imaging to assess bilateral renal function induced by Iohexol in rabbits.

BACKGROUND: Blood oxygenation level-dependent magnetic resonance imaging (BOLD-MRI) and diffusion tensor imaging (DTI) are useful methods for investigating the morphology and function of the kidneys, including revealing unilateral renal damage. Nevertheless, these techniques have not yet been applied for bilateral renal function. The aim of this study was to investigate whether the combination of DTI and BOLD could be used to examine different degrees of contrast-induced acute kidney injury (CI-AKI) in bilateral kidneys compared to standard methods such as serum creatinine (SCr) detection. METHODS: Forty-Two New Zealand white rabbits were divided into two groups: the experimental group and the control group. Physiological saline and iodine contrast agent (iohexol, 1.0 g iodine/kg, 1.0 ml/sec) were injected via the right renal artery. DTI and BOLD-MR data were acquired longitudinally at the baseline and 1, 24, 48, and 72 h after high-pressure syringe injection to measure the apparent diffusion coefficient (ADC), fractional anisotropy (FA) and relative transverse relaxation rate (R2*). After the MR scan at each time point, three rabbits in each group were sacrificed, and changes in SCr and hypoxia-inducible factor-1α (HIF-1α) were analyzed using histopathology and immunochemistry. RESULTS: Twenty-four hours after iohexol administration, the values of ADC and FA decreased significantly (P < 0.05), while R2* values increased (P < 0.05) in the renal cortex (CO), outer medulla (OM) and inner medulla (IM). Besides, significant negative correlations were observed among ADC, FA, and R2* in CO, OM, and IM (all P < 0.001, r = - 0.654-0.828). CONCLUSIONS: DTI and BOLD can simultaneously and non-invasively assess different degrees of CI-AKI in bilateral kidneys.

Role of Chemical Exchange Saturation Transfer and Magnetization Transfer MRI in Detecting Metabolic and Structural Changes of Renal Fibrosis in an Animal Model at 3T.

OBJECTIVE: To investigate the value of combined chemical exchange saturation transfer (CEST) and conventional magnetization transfer imaging (MT) in detecting metabolic and structural changes of renal fibrosis in rats with unilateral ureteral obstruction (UUO) at 3T MRI. MATERIALS AND METHODS: Thirty-five Sprague-Dawley rats underwent UUO surgery (n = 25) or sham surgery (n = 10). The obstructed and contralateral kidneys were evaluated on days 1, 3, 5, and 7 after surgery. After CEST and MT examinations, 18F-labeled fluoro-2-deoxyglucose positron emission tomography was performed to quantify glucose metabolism. Fibrosis was measured by histology and western blots. Correlations were compared between asymmetrical magnetization transfer ratio at 1.2 ppm (MTRasym(1.2ppm)) derived from CEST and maximum standard uptake value (SUVmax) and between magnetization transfer ratio (MTR) derived from MT and alpha-smooth muscle actin (α-SMA). RESULTS: On days 3 and 7, MTRasym(1.2ppm) and MTR of UUO renal cortex and medulla were significantly different from those of contralateral kidneys (p < 0.05). On day 7, MTRasym(1.2ppm) and MTR of UUO renal cortex and medulla were significantly different from those of sham-operated kidneys (p < 0.05). The MTRasym(1.2ppm) of UUO renal medulla was fairly negatively correlated with SUVmax (r = -0.350, p = 0.021), whereas MTR of UUO renal medulla was strongly negatively correlated with α-SMA (r = -0.744, p < 0.001). CONCLUSION: CEST and MT could provide metabolic and structural information for comprehensive assessment of renal fibrosis in UUO rats in 3T MRI and may aid in clinical monitoring of renal fibrosis in patients with chronic kidney disease.

Nanoscale Analysis of Randall's Plaques by Electron Energy Loss Spectromicroscopy: Insight in Early Biomineral Formation in Human Kidney.

Idiopathic kidney stones originate mainly from calcium phosphate deposits at the tip of renal papillae, known as Randall's plaques (RPs), also detected in most human kidneys without stones. However, little is known about the mechanisms involved in RP formation. The localization and characterization of such nanosized objects in the kidney remain a real challenge, making their study arduous. This study provides a nanoscale analysis of the chemical composition and morphology of incipient RPs, characterizing in particular the interface between the mineral and the surrounding organic compounds. Relying on data gathered from a calculi collection, the morphology and chemical composition of incipient calcifications in renal tissue were determined using spatially resolved electron energy-loss spectroscopy. We detected microcalcifications and individual nanocalcifications found at some distance from the larger ones. Strikingly, concerning the smaller ones, we show that two types of nanocalcifications coexist: calcified organic vesicles and nanometric mineral granules mainly composed of calcium phosphate with carbonate in their core. Interestingly, some of these nanocalcifications present similarities with those reported in physiological bone or pathological cardiovascular biominerals, suggesting possible common formation mechanisms. However, the high diversity of these nanocalcifications suggests that several mechanisms may be involved (nucleation on a carbonate core or on organic compounds). In addition, incipient RPs also appear to present specific features at larger scales, revealing secondary calcified structures embedded in a fibrillar organic material. Our study proves that analogies exist between physiological and pathological biominerals and provides information to understand the physicochemical processes involved in pathological calcification formation.

Comparison of multi-delay FAIR and pCASL labeling approaches for renal perfusion quantification at 3T MRI.

OBJECTIVE: To compare the most commonly used labeling approaches, flow-sensitive alternating inversion recovery (FAIR) and pseudocontinuous arterial spin labeling (pCASL), for renal perfusion measurement using arterial spin labeling (ASL) MRI. METHODS: Multi-delay FAIR and pCASL were performed in 16 middle-aged healthy volunteers on two different occasions at 3T. Relative perfusion-weighted signal (PWS), temporal SNR (tSNR), renal blood flow (RBF), and arterial transit time (ATT) were calculated for the cortex and medulla in both kidneys. Bland-Altman plots, intra-class correlation coefficient, and within-subject coefficient of variation were used to assess reliability and agreement between measurements. RESULTS: For the first visit, RBF was 362 ± 57 and 140 ± 47 mL/min/100 g, and ATT was 0.47 ± 0.13 and 0.70 ± 0.10 s in cortex and medulla, respectively, using FAIR; RBF was 201 ± 72 and 84 ± 27 mL/min/100 g, and ATT was 0.71 ± 0.25 and 0.86 ± 0.12 s in cortex and medulla, respectively, using pCASL. For both labeling approaches, RBF and ATT values were not significantly different between visits. Overall, FAIR showed higher PWS and tSNR. Moreover, repeatability of perfusion parameters was better using FAIR. DISCUSSION: This study showed that compared to (balanced) pCASL, FAIR perfusion values were significantly higher and more comparable between visits.

Prevalence and clinical significance of the medullary rim sign identified on ultrasound of feline kidneys.

OBJECTIVES: The medullary rim sign (MRS) is an ultrasonographic (US) feature identified in normal and diseased feline kidneys. The prevalence and potential clinical significance of the MRS in a referral hospital cat population was investigated. METHODS: Retrospective case-control study. US images from 661 cats were reviewed. Cats with an MRS were identified and compared with equal number of time-matched control cats. Medical data and MRS features, including thickness, intensity and symmetry, were collected. Associations between independent variables and the MRS were examined with conditional and unconditional logistic regression, with initial univariable, and subsequent multivariable analysis. RESULTS: Of the 661 reviewed cats, 243 (36.8 per cent) showed a variation of the MRS. A thin MRS (133 cats) was not associated with azotaemic renal disease (P=0.87). A thick MRS (110 cats) was associated with azotaemic renal disease (P=0.001). There was an association between the presence of MRS and a final diagnosis of feline infectious peritonitis (FIP) (P=0.028). CONCLUSIONS: The MRS is a common finding in cats. In this cat population, a thick MRS was associated with azotaemic renal disease, while a thin MRS was not. In cases with a clinical suspicion of FIP, the MRS may be related to the underlying disease process and not be an incidental finding.

Renal hemodynamics and fatty acid uptake: effects of obesity and weight loss.

Human studies of renal hemodynamics and metabolism in obesity are insufficient. We hypothesized that renal perfusion and renal free fatty acid (FFA) uptake are higher in subjects with morbid obesity compared with lean subjects and that they both decrease after bariatric surgery. Cortical and medullary hemodynamics and metabolism were measured in 23 morbidly obese women and 15 age- and sex-matched nonobese controls by PET scanning of [15O]-H2O (perfusion) and 14(R,S)-[18F]fluoro-6-thia-heptadecanoate (FFA uptake). Kidney volume and radiodensity were measured by computed tomography, cardiac output by MRI. Obese subjects were re-studied 6 mo after bariatric surgery. Obese subjects had higher renal volume but lower radiodensity, suggesting accumulation of water and/or lipid. Both cardiac output and estimated glomerular filtration rate (eGFR) were increased by ~25% in the obese. Total renal blood flow was higher in the obese [885 (317) (expressed as median and interquartile range) vs. 749 (300) (expressed as means and SD) ml/min of controls, P = 0.049]. In both groups, regional blood perfusion was higher in the cortex than medulla; in either region, FFA uptake was ~50% higher in the obese as a consequence of higher circulating FFA levels. Following weight loss (26 ± 8 kg), total renal blood flow was reduced (P = 0.006). Renal volume, eGFR, cortical and medullary FFA uptake were decreased but not fully normalized. Obesity is associated with renal structural, hemodynamic, and metabolic changes. Six months after bariatric surgery, the hemodynamic changes are reversed and the structural changes are improved. On the contrary, renal FFA uptake remains increased, driven by high substrate availability.