Renal shear wave elastography for the assessment of nephron hypertrophy: a cross-sectional study in chronic kidney disease.

PURPOSE: To investigate the association of renal elasticity to microscopic findings of nephron hypertrophy and nephrosclerosis. METHODS: Patients who underwent renal biopsy were enrolled. Renal elasticity was measured by acoustic radiation force impulse, and nephron size (glomerular volume, non-sclerotic glomerular density, and mean profile tubular area) and nephrosclerosis (globally sclerotic glomeruli and interstitial fibrosis) were estimated. Nephron hypertrophy was indicated by larger glomerular volume, larger tubular area, and lower non-sclerotic glomerular density. Nephrosclerosis was indicated by a higher percentage of globally sclerotic glomeruli and higher severity of fibrosis. RESULTS: Renal elasticity was negatively correlated with glomerular volume (r = - 0.480, P = 0.024) and mean tubular area (r = - 0.469, P = 0.028), but it was not correlated with non-sclerotic glomerular density (r = 0.205, P = 0.359), percentage of globally sclerotic glomeruli (r = 0.057, P = 0.800), and severity of fibrosis (r = 0.014, P = 0.950). In a multiple linear regression analysis, glomerular volume and mean tubular area were independently associated with renal elasticity (std ß = - 0.454, P = 0.015 and std ß = - 0.577, P = 0.007, respectively). CONCLUSION: Renal elasticity was correlated with microstructural findings of nephron hypertrophy. Measuring renal elasticity could help in detecting kidney disease.

Age-Related Renal Microvascular Changes: Evaluation by Three-Dimensional Digital Imaging of the Human Renal Microcirculation Using Virtual Microscopy.

The renal microvasculature is targeted during aging, sometimes producing chronic kidney disease (CKD). Overdiagnosis of CKD in older persons is concerning. To prevent it, a new concept of "healthy aging" is arising from a healthy renal donor study. We investigated the renal microcirculatory changes of three older persons and compared them with that of one patient with nephrosclerosis using a three-dimensional (3D) reconstruction technique that we previously developed. This method uses a virtual slide system and paraffin-embedded serial sections of surgical material that was double-immunostained by anti-CD34 and anti-α smooth muscle actin (SMA) antibodies for detecting endothelial cells and medial smooth muscle cells, respectively. In all cases, the 3D images proved that arteriosclerotic changes in large proximal interlobular arteries did not directly induce distal arterial change or glomerulosclerosis. The nephrosclerotic patient showed severe hyalinosis with luminal narrowing of small arteries directly inducing glomerulosclerosis. We also visualized an atubular glomerulus and intraglomerular dilatation of an afferent arteriole during healthy aging on the 3D image and showed that microcirculatory changes were responsible for them. Thus, we successfully visualized healthy aged kidneys on 3D images and confirmed the underlying pathology. This method has the ability to investigate renal microcirculatory damage during healthy aging.

Postoperative Compensatory Changes and Blood Flow Parameter of the Preserved Kidney in Elderly Living Related Donors Evaluated by Doppler Ultrasonography.

INTRODUCTION: Elderly kidney donors have recently become more common in living related kidney transplantation in Japan. Therefore, it is important to evaluate whether kidney function in elderly donors after nephrectomy is preserved over long periods of time. Doppler ultrasonography measurement is practical for donors after nephrectomy because it involves simple and noninvasive examinations. Doppler ultrasonography can detect compensatory hypertrophy and blood flow parameters, namely resistive index (RI) and pulsatility index (PI), of the preserved kidney in living donors. PATIENTS AND METHODS: Our study included 58 donors, divided into 2 groups according to age; the elderly donor group was comprised of those 65 years old or older. We measured length, width, and short diameter of the preserved kidney using Doppler ultrasonography, and calculated kidney volume. RESULTS: The elderly group was comprised of 13 patients. In this group, the median preserved kidney volume was 145.0 cm(3) (101.8-193.5) before nephrectomy, and 127.6 cm(3) (99.0-183.4) and 145.5 cm(3) (141.3-148.6) at 1 and 12 months after nephrectomy, respectively. We did not observe significant compensatory hypertrophy in the preserved kidneys of elderly donors postoperatively. Both the mean PI and RI values of elderly donors increased progressively after nephrectomy. No compensatory hypertrophy occurred in the preserved kidneys of elderly donors, although the PI and RI did increase in these donors. CONCLUSION: Our results indicate that nephrectomy caused nephrosclerosis in the preserved kidneys of elderly donors and that prevention of hypertension may be important after nephrectomy in elderly donors.

Abdominal Aortic Calcification in Living Kidney Donors.

OBJECTIVE: This study assesses the association between abdominal aortic calcification (AAC) and renal function of living kidney donors and evaluate AAC as a surrogate marker for nephrosclerosis. METHODS: Between January 2010 and March 2013, 287 donors who underwent living donor nephrectomy were enrolled. We analyzed computed tomography angiographies and quantified AAC scores by calculating the Agatston score for the abdominal aorta. The donors were stratified into the non-AAC group (AAC score = 0; n = 238) and the AAC group (AAC score >0; n = 49). The relationship between AAC and perioperative estimated glomerular filtration rate was analyzed. For the 180 donors consenting to implantation biopsy, the nephrosclerosis score was defined as the sum of abnormalities, including glomerulosclerosis, tubular atrophy, interstitial fibrosis, and arteriosclerosis. RESULTS: The mean AAC score was 185.5 ± 263.3 in the AAC group. The AAC group was older than the non-AAC group (51.1 ± 6.1 vs 37.9 ± 11 years; P < .001). Perioperative renal function was not different between the 2 groups. However, among the AAC group, donors with an AAC score of >100 were associated with delayed renal function recovery (P = .035). Donors with AAC were more likely to have glomerulosclerosis (50.0% vs 29.1%; P = .022), tubular atrophy (62.5% vs 33.1%; P = .002), and a higher nephrosclerosis score (P = .002). CONCLUSIONS: Living donors with an AAC score of >100 require close observation because they have a higher probability of delayed renal function recovery after donation. AAC is associated with nephrosclerosis in healthy adults.

Automated assessment of renal cortical surface roughness from computerized tomography images and its association with age.

RATIONALE AND OBJECTIVES: Nephrosclerosis occurs with aging and is characterized by increased kidney subcapsular surface irregularities at autopsy. Assessments of cortical roughness in vivo could provide an important measure of nephrosclerosis. The purpose of this study was to develop and validate an image-processing algorithm for quantifying renal cortical surface roughness in vivo and determine its association with age. MATERIALS AND METHODS: Renal cortical surface roughness was measured on contrast-enhanced abdominal computed tomography (CT) images of potential living kidney donors. A roughness index was calculated based on geometric curvature of each kidney from three-dimensional images and compared to visual observation scores. Cortical roughness was compared between the oldest and youngest donors, and its interaction with cortical volume and age assessed. RESULTS: The developed quantitative roughness index identified significant differences in kidneys with visual surface roughness scores of 0 (minimal), 1 (mild), and 2 (moderate; P < .001) in a random sample of 200 potential kidney donors. Cortical roughness was significantly higher in the 94 oldest (64-75 years) versus 91 youngest (18-25 years) potential kidney donors (P < .001). Lower cortical volume was associated with older age but not with roughness (r = -0.03, P = .75). The association of oldest age group with roughness (odds ratio [OR] = 1.8 per standard deviation [SD] of roughness index) remained significant after adjustment for total cortex volume (OR = 2.0 per SD of roughness index). CONCLUSIONS: A new algorithm to measure renal cortical surface roughness from CT scans detected rougher surface in older compared to younger kidneys, independent of cortical volume loss. This novel index may allow quantitative evaluation of nephrosclerosis in vivo using contrast-enhanced CT.

Renal transplant elasticity ultrasound imaging: correlation between normalized strain and renal cortical fibrosis.

After transplantation, over a widely variable time course, the cortex of the transplanted kidney becomes stiffer as interstitial fibrosis develops and renal function declines. Elasticity ultrasound imaging (EUI) has been used to assess biomechanical properties of tissue that change in hardness as a result of pathologic damage. We prospectively assessed the hardness of the renal cortex in renal transplant allograft patients using a normalized ultrasound strain procedure measuring quasi-static deformation, which was correlated with the grade of renal cortical fibrosis. To determine cortical strain, we used 2-D speckle-tracking software (EchoInsight, Epsilon Imaging, Ann Arbor, MI, USA) to perform offline analysis of stored ultrasound loops capturing deformation of renal cortex and its adjacent soft tissue produced by pressure applied using the scanning transducer. Normalized strain is defined as the mean developed strain in the renal cortex divided by the overall mean strain measured in the soft tissues from the abdominal wall to pelvic muscles. Using the Banff scoring criteria for renal cortical fibrosis as the gold standard, we classified 20 renal transplant allograft biopsy tissue samples into two groups: group 1 (n = 10) with mild (<25%) renal cortical fibrosis and group 2 (n = 10) with moderate (26%-50%) renal cortical fibrosis. An unpaired two-tailed t-test was used to determine the statistical difference in strains between patients with mild and those with moderate renal cortical fibrosis. Receiver operating characteristic curve analysis was performed to assess the accuracy of developed strain and normalized strain in predicting moderate renal cortical fibrosis. The reference strain did not significantly differ between the two groups (p = 0.10). However, the developed renal cortical strain in group 1 with mild fibrosis was higher than that in group 2 with moderate fibrosis (p = 0.025). The normalized strain in group 1 was also higher than that in group 2 (p = 0.0014). The areas under receiver operating characteristic curves for developed strain and normalized strain were 0.78 and 0.95, respectively. The optimal cutoff for distinguishing moderate renal cortical fibrosis was -0.08 for developed strain (sensitivity = 0.50, specificity = 1.0) and 2.5 for normalized strain (sensitivity = 0.80, specificity = 1.0). In summary, renal cortex strain is strongly correlated with grade of renal cortical fibrosis. Normalized strain is superior to developed strain in distinguishing moderate from mild renal cortical fibrosis. We conclude that free-hand real-time strain EUI may be useful in assessing the progression of cortical fibrosis in renal transplant allografts. Further prospective study using this method is warranted.

Nephrosclerosis and carotid atherosclerosis: lessons from kidney donor histology.

AIM: Carotid artery intima media thickness (CA-IMT) measurement has been shown to be a safe and reproducible method to assess severity of atherosclerosis. The association between nephrosclerosis and systemic atherosclerosis is not clear. In this study, we investigated the association between CA-IMT and nephrosclerosis in a group of kidney transplant donors. METHODS: Forty seven potential kidney transplant donors were included. CA-IMT was measured by B-Mode ultrasonography. Kidney allograft biopsy samples were obtained during the transplantation operation and chronic glomerular, vascular and tubulointertitial changes were semiquantitatively scored according to the Banff classification. RESULTS: Mean age was 52 ± 12 years and 55% of the cases were younger than 55 years. Mean CA-IMT was 0.74 ± 0.19 mm and 48% had IMT values > 0.75 mm. Chronicty index was ≥5 in 55% of the cases. Chronicity index was higher in cases older than 55 years. Age and CA-IMT were significantly correlated with chronic vascular changes and chronicity index. CA-IMT > 0.75 mm had a 46% sensitivity and 90% specificity to predict nephrosclerosis. Positive and negative predictive values were 85% and 57%, respectively. CONCLUSION: Aging leads to detrimental changes in every part of the vasculature of the human body. CA-IMT is correlated with the level of nephrosclerosis. Measurement of CA-IMT reflects nephrosclerosis especially in older patients.

[X-ray control of the kidneys and their development in the long-term period after surgical correction of hydronephrosis in children]. / Rentgenologicheskii kontrol' za sostoianiem i razvitiem pochek v otdalennye sroki posle operativnoi korrektsii gidronefroza u detei.

After surgical correction of hydronephrosis, the development of the kidneys was studied in 40 patients (44 hydronephroses) operated on at the age of 8 months to 12 years. Postoperative follow-ups lasted at least 10 and 25 years. X-ray planimetric studies made it possible to quantitatively characterize the growth of the kidney, the increase or decrease in its parenchymal area, the appearance or progression of prior nephrosclerosis. X-ray studies could yield an objective assessment of the trend in renal development. By supplementing the data of excretory urography, radiological techniques and ultrasonography provided additional data on the kidney and its parenchyma. Analysis of the results of the X-ray planimetric studies have indicated that 28 patients (32 kidneys) had a uniform increase in the areas of the kidney and its parenchyma by 50-100%; in 9 patients, the parenchyma increased by 2.5-4 times, the area of the kidney became only 50-100% larger. There was progression of nephrosclerosis with a 3-10% decrease in the area of parenchyma along with a 24-80% growth of the organ only in 3 cases after a quite satisfactory growth in the organ. These data show it necessary to perform long-term follow-ups of patients under the control of X-ray study as the most objective radiation diagnostic technique.

Ultrasonography in chronic renal failure.

Many chronic renal diseases lead to the final common state of decrease in renal size, parenchymal atrophy, sclerosis and fibrosis. The ultrasound image show a smaller kidney, thinning of the parenchyma and its hyperechogenicity (reflecting sclerosis and fibrosis). The frequency of renal cysts increases with the progression of the disease. Ultrasound generally does not allow for the exact diagnosis of an underlying chronic disease (renal biopsy is usually required), but it can help to determine an irreversible disease, assess prognosis and avoid unnecessary diagnostic or therapeutic procedures. The main exception in which the ultrasound image does not show a smaller kidney with parenchymal atrophy is diabetic nephropathy, the leading cause of chronic and end-stage renal failure in developed countries in recent years. In this case, both renal size and parenchymal thickness are preserved until end-stage renal failure. Doppler study of intrarenal vessels can provide additional information about microvascular and parenchymal lesions, which is helpful in deciding for or against therapeutic intervention and timely planning for optimal renal replacement therapy option.

Heterogeneity of renal cortical circulation in hypertension assessed by dynamic computed tomography.

The aim of this study was to assess the grade of heterogeneous disturbance in the renal cortical circulation using dynamic computed tomography and to investigate the relationship between the heterogeneity of renal cortical circulation and hypertension. We studied 125 patients who underwent dynamic computed tomography (CT) for various abdominal diseases and had no serious hemodynamic abnormalities. In dynamic computed tomography under appropriate conditions, each pixel (image element), less than 1 mm2, has a CT number that is in proportion to the concentration of contrast media, which reflects the blood volume in the pixel. The image was constructed at the hilus level about 50 s after the start of a continuous infusion of contrast medium. The mean and standard deviation were calculated from the CT numbers in the renal cortex. The coefficient of variation, ie, the standard deviation divided by the mean value, was used as the index of the heterogeneity of renal cortical circulation. The coefficient of variation was significantly (P < .001) greater in the hypertensive patients (n = 48, 0.174 +/- 0.006 [mean +/- SE]) than in normotensive subjects (n = 77, 0.140 +/- 0.004). The coefficient increased in parallel with the patient's age and with the grade of renal surface irregularity. In the patients whose serum creatinine levels were normal, this parameter also had a significant relationship (r = 0.367, P < .0001) with serum creatinine. These results suggest that the heterogeneity of renal cortical circulation is increased in hypertension and is also associated with aging. This parameter may become a sensitive indicator to detect slight deterioration in the renal cortical circulation.

Renal vasculature in essential hypertension: racial differences.

In an attempt to explain the greater morbidity from essential hypertension in the black as compared with the white race, we evaluated the intrarenal vasculature of 27 patients with hypertension (19 white and 8 black). All patients had mild-to-moderate hypertension (mean arterial pressure, 110 to 125 mm Hg), normal renal function, and minimal target-organ damage. All patients had selective renal angiograms, which were evaluated for arterial nephrosclerosis. Additionally, renal blood flow was estimated by the clearance of para-aminohippurate. Patient age, blood pressure, and plasma renin activity did not differ between the two races. Black hypertensives had significantly (P less 0.01) more severe nephrosclerosis than the white patients. Renal blood flow was lower (P less than 0.05) in black patients (390 +/- 35 ml/min - m2 body surface area) than white patients (473 +/- 19 ml/min - m2 body surface area). These findings may help to explain racial differences in morbidity and mortality from essential hypertension.

Epinephrine renal venography.

Experience with the use of epinephrine renal venography in 60 patients with various renal disease is reviewed. The technique offers an important supplement to selective arteriography. It is of particular value in the diagnosis of avascular infiltrative tumors of the renal parenchyma and pelvis. Further, it is of value in the detailed demonstration of renal vein thrombosis and in seeking the cause of unexplained gross hematuria. It can also aid in evaluating expansile avascular renal masses and renal parenchymal disease. The authors found only a relatively low value for epinephrine renal venography in the diagnosis of hypervascular renal tumors and the early detection of venous extension of hypernephromas.

[The value of roentgen examination in reno-vascular hypertension (author's transl)]. / Die Bedeutung der Röntgenuntersuchung bei renovaskulärer Hypertonie

Renal arteriography plays a definitive role in diagnosis and evaluation of renal artery stenosis. Because of its high reliability and low risk, arteriography is more frequently being performed on the basis of clinical indications without reliance on screening tests. Arteriography will indicate the presence of stenosis, its cause, and the presence or absence of hemodynamic significance, and it is useful in evaluating the post-operative patient. Renal vein renin determinations are sometimes needed in evaluating the hemodynamic significance of the lesion. Arteriography may also reveal juxtaglomerular cell tumors, chronic renal inflammatory disease, or other diseases of renal parenchyma which could cause hypertension.