A clinical MRI investigation of the relationship between kidney volume measurements and renal function in patients with renovascular disease

Kidney segmentation in neck-to-knee body MRI of 40,000 UK Biobank participants

The UK Biobank is collecting extensive data on health-related characteristics of over half a million volunteers. The biological samples of blood and urine can provide valuable insight on kidney function, with important links to cardiovascular and metabolic health. Further information on kidney anatomy could be obtained by medical imaging. In contrast to the brain, heart, liver, and pancreas, no dedicated Magnetic Resonance Imaging (MRI) is planned for the kidneys. An image-based assessment is nonetheless feasible in the neck-to-knee body MRI intended for abdominal body composition analysis, which also covers the kidneys. In this work, a pipeline for automated segmentation of parenchymal kidney volume in UK Biobank neck-to-knee body MRI is proposed. The underlying neural network reaches a relative error of 3.8%, with Dice score 0.956 in validation on 64 subjects, close to the 2.6% and Dice score 0.962 for repeated segmentation by one human operator. The released MRI of about 40,000 subjects can be processed within one day, yielding volume measurements of left and right kidney. Algorithmic quality ratings enabled the exclusion of outliers and potential failure cases. The resulting measurements can be studied and shared for large-scale investigation of associations and longitudinal changes in parenchymal kidney volume.

Renal and renal sinus fat volumes as quantified by magnetic resonance imaging in subjects with prediabetes, diabetes, and normal glucose tolerance

Purpose

We hypothesize that MRI-based renal compartment volumes, particularly renal sinus fat as locally and potentially independently acting perivascular fat tissue, increase with glucose intolerance. We therefore analyze the distribution of renal volumes in individuals with normal glucose levels and prediabetic and diabetic individuals and investigate potential associations with other typical cardiometabolic biomarkers.

Material and methods

The sample comprised N = 366 participants who were either normoglycemic (N = 230), had prediabetes (N = 87) or diabetes (N = 49), as determined by Oral Glucose Tolerance Test. Other covariates were obtained by standardized measurements and interviews. Whole-body MR measurements were performed on a 3 Tesla scanner. For assessment of the kidneys, a coronal T1w dual-echo Dixon and a coronal T2w single shot fast spin echo sequence were employed. Stepwise semi-automated segmentation of the kidneys on the Dixon-sequences was based on thresholding and geometric assumptions generating volumes for the kidneys and sinus fat. Inter- and intra-reader variability were determined on a subset of 40 subjects. Associations between glycemic status and renal volumes were evaluated by linear regression models, adjusted for other potential confounding variables. Furthermore, the association of renal volumes with visceral adipose tissue was assessed by linear regression models and Pearson’s correlation coefficient.

Results

Renal volume, renal sinus volume and renal sinus fat increased gradually from normoglycemic controls to individuals with prediabetes to individuals with diabetes (renal volume: 280.3±64.7 ml vs 303.7±67.4 ml vs 320.6±77.7ml, respectively, p < 0.001). After adjustment for age and sex, prediabetes and diabetes were significantly associated to increased renal volume, sinus volume (e.g. β_Prediabetes = 10.1, 95% CI: [6.5, 13.7]; p<0.01, β_Diabetes = 11.86, 95% CI: [7.2, 16.5]; p<0.01) and sinus fat (e.g. β_Prediabetes = 7.13, 95% CI: [4.5, 9.8]; p<0.001, β_Diabetes = 7.34, 95% CI: [4.0, 10.7]; p<0.001). Associations attenuated after adjustment for additional confounders were only significant for prediabetes and sinus volume (ß = 4.0 95% CI [0.4, 7.6]; p<0.05). Hypertension was significantly associated with increased sinus volume (β = 3.7, 95% CI: [0.4, 7.0; p<0.05]) and absolute sinus fat volume (β = 3.0, 95% CI: [0.7, 5.3]; p<0.05). GFR and all renal volumes were significantly associated as well as urine creatinine levels and renal sinus volume (β = 1.6, 95% CI: [0.1, 2.9]; p<0.05).

Conclusion

Renal volume and particularly renal sinus fat volume already increases significantly in prediabetic subjects and is significantly associated with VAT. This shows, that renal sinus fat is a perivascular adipose tissue, which early undergoes changes in the development of metabolic disease. Our findings underpin that renal sinus fat is a link between metabolic disease and associated chronic kidney disease, making it a potential imaging biomarker when assessing perivascular adipose tissue.

Predictive Value of Duplex Ultrasound for Significant In-Stent Restenosis after Percutaneous Transluminal Renal Artery Stent Placement: A Propensity Score Matching Analysis

To evaluate the value of pre-stenting and early post-stenting (<1 mo) duplex ultrasound parameters in predicting significant in-stent restenosis (ISR), we matched significant ISR patients 1:1 with controls without ISR in pre-stenting and early post-stenting (<1 mo) periods, respectively, using propensity score matching. Duplex ultrasound parameters, such as renal length difference between non-lesion side and lesion side within patient, trans-lesion peak systolic velocity and renal aortic ratio, were compared between cases and controls, and the area under the receiver operating characteristic curve (AUROC) was charted to predict ISR. After propensity score matching, 28 cases were matched in the pre-stenting period and 16 cases in the early post-stenting time period. Pre-stenting renal length difference, early post-stenting peak systolic velocity and renal aortic ratio showed significant differences in case-control comparisons. Early post-stenting peak systolic velocity (AUROC: 0.826, cutoff: 141 cm/s) and renal aortic ratio (AUROC: 0.770, cutoff: 1.75) performed well in predicting significant ISR and may serve as non-invasive markers in ISR surveillance.

Determination of single-kidney glomerular filtration rate (GFR) with CT urography versus renal dynamic imaging Gates method

OBJECTIVES

To present a single-kidney CT-GFR measurement and compare it with the renal dynamic imaging Gates-GFR.

MATERIALS AND METHODS

Thirty-six patients with hydronephrosis referred for CT urography and 99mTc-DTPA renal dynamic imaging were prospectively included. Informed consent was obtained from all patients. The CT urography protocol included non-contrast, nephrographic, and excretory phase imaging. The total CT-GFR was calculated by dividing the CT number increments of the total urinary system between the nephrographic and excretory phase by the products of iodine concentration in the aorta and the elapsed time, then multiplied by (1- Haematocrit). The total CT-GFR was then split into single-kidney CT-GFR by a left and right kidney proportionality factor. The results were compared with single-kidney Gates-GFR by using paired t-test, correlation analysis, and Bland-Altman plots.

RESULTS

Paired difference between single-kidney CT-GFR (45.02 ± 13.91) and single-kidney Gates-GFR (51.21 ± 14.76) was 6.19 ± 5.63 ml/min, p<0.001, demonstrating 12.1% systematic underestimation with ±11.03 ml/min (±21.5%) measurement deviation. A good correlation was revealed between both measurements (r=0.87, p<0.001).

CONCLUSION

The proposed single-kidney CT-GFR correlates and agrees well with the reference standard despite a systematic underestimation, therefore it could be a one-stop-shop for evaluating urinary tract morphology and split renal function.

KEY POINTS

• A new CT method can assess split renal function • Only using images from CT urography and the value of haematocrit • A one-stop-shop CT technique without additional radiation dose.

Effect of various environments and computed tomography scanning parameters on renal volume measurements in vitro: A phantom study

Kidney volume is an important parameter in clinical practice, and accurate assessment of kidney volume is vital. The aim of the present study was to evaluate the effect of various environments, tube voltages, tube currents and slice thicknesses on the accuracy of a novel segmentation software in determining renal volume on computed tomography (CT) images. The volumes of potatoes and porcine kidneys were measured on CT images and compared with the actual volumes, which were determined by a water displacement method. CT scans were performed under various situations, including different environments (air or oil); tube voltages/tube currents (80 kVp/200 mAs, 120 kVp/200 mAs, 120 kVp/100 mAs); and reconstructed slice thicknesses (0.75 or 1.5 mm). Percentage errors (PEs) relative to the reference standards were calculated. In addition, attenuation and image noise under different CT scanning parameters were compared. Student's t-test was also used to analyze the effect of various conditions on image quality and volume measurements. The results indicated that the volumes measured in oil were closer to the actual volumes (P<0.05). Furthermore, attenuation and image noise significantly increased when using a tube voltage of 80 kVp, while the mean PEs between 120 and 80 kVp voltages were not significantly different. The mean PEs were greater when using a tube current of 100 mAs compared with a current of 200 mAs (P<0.05). In addition, the volumes measured on 1.5 mm slice thickness were closer to the actual volumes (P<0.05). In conclusion, different environments, tube currents and slice thicknesses may affect the volume measurements. In the present study, the most accurate volume measurements were obtained at 120 kVp/200 mAs and a slice thickness of 1.5 mm.

Accurate kidney surface reconstruction from 3D ultrasonography for volume assessment: First clinical evaluation

An accurate, repeatable and noninvasive measurement of kidney volume is an important but difficult task for nephrologists. This paper proposes a new kidney volumetry method by reconstructing the kidney surface from three-dimensional ultrasonography (3DUS) using statistical shape model (SSM). The measurement starts with picking sparse points on the kidney contour from 3DUS images. Then an accurate 3D kidney surface mesh can be reconstructed from the input points using the SSM in a fine-tune way. The kidney volume is finally calculated from the surface using divergence theorem of Gauss. The accuracy and repeatability of the proposed method have been validated on 36 patients. The results demonstrate that the proposed method is a promising solution for clinical evaluation of the kidney volume.

Renal artery stenosis-when to screen, what to stent?

Renal artery stensosis (RAS) continues to be a problem for clinicians, with no clear consensus on how to investigate and assess the clinical significance of stenotic lesions and manage the findings. RAS caused by fibromuscular dysplasia is probably commoner than previously appreciated, should be actively looked for in younger hypertensive patients and can be managed successfully with angioplasty. Atheromatous RAS is associated with increased incidence of cardiovascular events and increased cardiovascular mortality, and is likely to be seen with increasing frequency. Evidence from large clinical trials has led clinicians away from recommending interventional revascularisation towards aggressive medical management. There is now interest in looking more closely at patient selection for intervention, with focus on intervening only in patients with the highest-risk presentations such as flash pulmonary oedema, rapidly declining renal function and severe resistant hypertension. The potential benefits in terms of improving hard cardiovascular outcomes may outweigh the risks of intervention in this group, and further research is needed.

Different genetic impact in the development of renal length and width: a twin study

BACKGROUND

Ultrasound measurements of renal dimensions are conventionally limited to renal length, shape and cortical thickness. These are regarded as adequate for normal therapeutic decision-making and volume measurements are reserved for a few clinical trials. However, there is no evidence concerning the degree to which renal length or volume is independently susceptible to heritable and environmental influences.

AIM

We aimed to determine whether renal length or width (as a surrogate of volume) was more influenced by heritability.

METHODS

A single operator measured renal length and width in 114 adult monozygotic and same-sex dizygotic Hungarian twin pairs (mean age 43.6 ± 16.3 years), using an Esaote MyLab 70X ultrasound machine with curved array transducer (1-8 MHz, CA431).

RESULTS

Analysis of within-pair co-twin correlations adjusted for age and gender showed that the age- and sex-adjusted heritability of average renal length was 51% (95% confidence interval, 29-72%). Renal width showed negligible genetic influence. Common environmental effects had no influence, and unshared environments were responsible for 49-80% of the variance, mainly renal width.

CONCLUSIONS

This study is the first to demonstrate the moderate heritability and limited environmental influence on renal length, and the contrasting lack of heritability of renal width, which is mainly influenced by unshared environmental components, that is lifestyle habits. Renal width therefore better represents the influence of modifiable environmental factors than renal length. The results suggest that renal width not length should be reported to facilitate early detection and monitoring of renal disease.

A simple method to estimate renal volume from computed tomography

INTRODUCTION

Renal parenchymal volume can be used clinically to estimate differential renal function. Unfortunately, conventional methods to determine renal volume from computed tomography (CT) are time-consuming or difficult due to software limitations. We evaluated the accuracy of simple renal measurements to estimate renal volume as compared with estimates made using specialized CT volumetric software.

METHODS

We reviewed 28 patients with contrast-enhanced abdominal CT. Using a standardized technique, one urologist and one urology resident independently measured renal length, lateral diameter and anterior-posterior diameter. Using the ellipsoid method, the products of the linear measurements were compared to 3D volume measurements made by a radiologist using specialized volumetric software.

RESULTS

LINEAR KIDNEY MEASUREMENTS WERE HIGHLY CONSISTENT BETWEEN THE UROLOGIST AND THE UROLOGY RESIDENT (INTRACLASS CORRELATION COEFFICIENTS: 0.97 for length, 0.96 for lateral diameter, and 0.90 for anterior-posterior diameter). Average renal volume was 170 (SD: 36) cm(3) using the ellipsoid method compared with 186 (SD 37) cm(3) using volumetric software, for a mean absolute bias of -15.2 (SD 15.0) cm(3) and a relative volume bias of -8.2% (p < 0.001). Thirty-one of 56 (55.3%) estimated volumes were within 10% of the 3D measured volume and 54 of 56 (96.4%) were within 30%.

CONCLUSION

Renal volume can be easily approximated from contrast-enhanced CT scans using the ellipsoid method. These findings may obviate the need for 3D volumetric software analysis in certain cases. Prospective validation is warranted.

Assessment of kidney volumes from MRI: acquisition and segmentation techniques

OBJECTIVE

The prevalence of chronic kidney disease (CKD) is increasing worldwide. In Europe alone, at least 8% of the population currently has some degree of CKD. CKD is associated with serious comorbidity, reduced life expectancy, and high economic costs; hence, early detection and adequate treatment of kidney disease are important.

CONCLUSION

We review state-of-the-art MRI acquisition techniques for CKD, with a special focus on image segmentation methods used for the estimation of kidney volume.

Renal volumetric analysis: a new paradigm in renal mass treatment assessment

Abstract Background and Purpose: Multiple renal volumetric assessment studies have correlated parenchymal volume with the glomerular filtration rate. The objective of this study was to compare renal volumes before and after treatment of renal masses with either partial nephrectomy or radiofrequency ablation (RFA).

PATIENTS AND METHODS

We reviewed our prospectively collected database of patients with renal masses who were treated between November 2001 and January 2011 with robot-assisted laparoscopic partial nephrectomy (RALPN), laparoscopic RFA (LRFA), or CT-guided percutaneous RFA (CTRFA). Digital Imaging and Communications in Medicine CT imaging data were analyzed in an open-source viewer. Volumetric calculations were used to measure the normal, enhancing bilateral renal parenchyma and tumor volumes. Normal parenchymal volume loss was compared among treatments.

RESULTS

There were 96 patients (68 men) with an average age of 68.0 (36-84) years who met our inclusion criteria. The average tumor diameter, tumor volume, and nephrometry score (NS) was 3.5 cm, 32.0 cm(3), and 7.1 in RALPN (n=26), 2.6 cm, 9.8 cm(3), and 7.1 in CTRFA (n=47), and 2.9 cm, 14.3 cm(3), and 7.2 in LRFA (n=23) groups. The percent change in the operated kidney volume was similar in RALPN (-12%±15), CTRFA (-13%±16), and LRFA (-17%±18) groups. NS was the only variable in a multivariate linear regression model that correlated with the amount of volume lost in the ipsilateral kidney.

CONCLUSIONS

Our retrospective volumetric analysis of renal parenchyma before and after partial nephrectomy or RFA of renal masses revealed that all treatments produce similar volume of collateral damage.

Automatic measurement of renal volume in children using 99mTc dimercaptosuccinic acid SPECT: normal ranges with body weight

OBJECTIVE

The purpose of this study was to automate volume measurement of pediatric kidneys using Technetium-99m-dimercaptosuccinic acid (99mTc DMSA) SPECT. Assessment of renal size is essential in making an accurate clinical diagnosis and in evaluating normal and abnormal renal growth. Existing techniques for measuring renal length and volume are often observer-dependent and are limited by interobserver variability.

MATERIALS AND METHODS

An automated method using 99mTc DMSA SPECT was developed to measure renal length, volume, and 2D/3D split renal functions. An adaptive threshold was used for segmentation of renal images. To improve measurement accuracy of renal volumes, a boundary-weighted integration and a linear correction from phantom experiments were applied. Using the new automated software, we evaluated 620 normal kidneys in 310 patients aged 1 to 21 years.

RESULTS

In all, 99.4% of renal volume measurement was inter-/intraobserver reproducible without manual intervention. Correlations between renal size (volume and length) and growth parameters (age and body weight) were evaluated by nonlinear regression modeling. Body weight was found to be the best predictor of kidney volume and length (P < 0.0001). Normal ranges were established according to body weight.

CONCLUSIONS

Automatic renal volume measurement with 99mTc DMSA SPECT demonstrates high observer reproducibility, and it is useful for achieving accurate assessment of renal growth using sequential measurements. The renal growth models generated by this study will aid physicians in evaluating and monitoring renal growth.

Relation between total renal volume and renal function: Usefulness of 3D sonographic measurements with a matrix array transducer

OBJECTIVE

The aims of this study were to evaluate the reproducibility of 3D sonography with a matrix array transducer as a means of measuring renal volume and to investigate correlations between renal volume and renal function.

SUBJECTS AND METHODS

One hundred twenty subjects (20 consecutively registered patients with one of the five stages of chronic renal disease and 20 healthy volunteers [stage 0 renal function]) were enrolled. Individual renal volume was determined by two independent observers using 2D sonographic and 3D matrix array transducer sonographic data. The reproducibility of volume measurement was evaluated for both of these methods. After total renal volume was normalized to body surface area, correlations between normalized total renal volume and estimated glomerular filtration rate (GFR) were evaluated. Differences in normalized total renal volume related to stage of renal function also were evaluated.

RESULTS

The reproducibility of 3D sonographic measurements obtained with a matrix array transducer was greater than that of 2D sonographic measurements. The correlation between normalized total renal volume obtained with matrix array transducer 3D sonography and estimated GFR for two observers (r = 0.809 and 0.813; p < 0.001) was better than that between normalized total renal volume obtained with 2D sonography and estimated GFR (r = 0.696 and 0.715; p < 0.001). The mean normalized total renal volumes obtained with matrix array transducer 3D sonography in stages 0 and 1 were significantly larger than those in other stages (p < 0.001). The mean normalized total renal volume in stage 5 disease was significantly smaller than the volumes in the other stages (p < 0.001).

CONCLUSION

Three-dimensional sonography with a matrix array transducer is a reliable means of measuring renal volume during evaluations of patients with reduced renal function.

Renal parenchymal preservation after percutaneous renal angioplasty and stenting

BACKGROUND

The intent of endovascular therapy for symptomatic atherosclerotic renal artery stenosis (ARAS) is to preserve parenchyma and avoid renal-related morbidity. The aim of this study is to examine the impact of renal artery intervention on parenchymal preservation.

METHODS

We performed a retrospective analysis of records from patients who underwent endovascular intervention for ARAS and were followed by duplex ultrasound between 1990 and 2008. Renal volume (in cm(3)) was estimated in all patients as renal length (cm) x renal width (cm) x renal depth (cm) x 0.5. The normal renal volume was calculated as 2 x body weight (kg) in cm(3). Failure of preservation was considered to be a persistent 10% decrease in volume. Clinical benefit defined as freedom from renal-related morbidity (increase in persistent creatinine >20% of baseline, progression to hemodialysis, death from renal-related causes) was calculated.

RESULTS

Five hundred ninety-two renal artery interventions were performed. One hundred eighty-six kidneys suffered parenchymal loss (>5%) with an actuarial parenchymal loss rate of 29% +/- 1% at five years respectively. There were no significant differences in age, gender, starting renal volume, or kidney size. However, patients with parenchymal loss had lower eGFR (45 +/- 24 vs 53 +/- 24 mL/min/1.73 m(2); Loss vs noLoss, P = .0002, Mean +/- SD) higher resistive index (0.75 +/- 0.9 vs 0.73 +/- 0.10; P = .0001) and worse nephrosclerosis grade (1.43 +/- 0.55 vs 1.30 +/- 0.49; P = .006) then those not suffering parenchymal loss. Parenchymal loss was associated with significantly worse five-year survival (26% +/- 4% vs 48% +/- 2%; Loss vs noLoss; P < .001) and freedom from renal-related morbidity (70% +/- 5% vs 82% +/- 2%; P < .05) with increased numbers progressing to dialysis (17% vs 7%; P < .006).

CONCLUSION

While parenchymal preservation occurs in most patients, parenchymal loss occurs in 31% of patients and is associated with markers of impaired parenchymal perfusion (resistive index and nephrosclerosis grade) at the time of intervention. Pre-existing renal size or volumes were not predictive of parenchymal loss. Parenchymal loss is associated with a significant decrease in survival and a marked increased renal related morbidity and progression to hemodialysis.

Renal atrophy secondary to chemoradiotherapy of abdominal malignancies

PURPOSE

To identify factors predictive of renal atrophy after chemoradiotherapy of gastrointestinal malignancies.

METHODS AND MATERIALS

Patients who received chemotherapy and abdominal radiotherapy (RT) between 2002 and 2008 were identified for this study evaluating change in kidney size and function after RT. Imaging and biochemical data were obtained before and after RT in 6-month intervals. Kidney size was defined by craniocaudal measurement on CT images. The primarily irradiated kidney (PK) was defined as the kidney that received the greater mean kidney dose. Receiver operating characteristic (ROC) curves were generated to predict risk for renal atrophy.

RESULTS

Of 130 patients, median age was 64 years, and 51.5% were male. Most primary disease sites were pancreas and periampullary tumors (77.7%). Median follow-up was 9.4 months. Creatinine clearance declined 20.89%, and size of the PK decreased 4.67% 1 year after completion of chemoradiation. Compensatory hypertrophy of the non-PK was not seen. Percentage volumes of the PK receiving ≥10 Gy (V(10)), 15 Gy (V(15)), and 20 Gy (V(20)) were significantly associated with renal atrophy 1 year after RT (p = 0.0030, 0.0029, and 0.0028, respectively). Areas under the ROC curves for V(10), V(15), and V(20) to predict >5% decrease in PK size were 0.760, 0.760, and 0.762, respectively.

CONCLUSIONS

Significant detriments in PK size and renal function were seen after abdominal RT. The V(10), V(15), and V(20) were predictive of risk for PK atrophy 1 year after RT. Analyses suggest the association of lower-dose renal irradiation with subsequent development of renal atrophy.

Effects of renal volume and single-kidney glomerular filtration rate on renal functional outcome in atherosclerotic renal artery stenosis

BACKGROUND

Renal functional outcome is unpredictable after revascularization of high-grade atherosclerotic renal artery stenosis (RAS). 'Hibernating' parenchyma describes acute parenchymal injury where renal dysfunction is potentially reversible with treatment of the stenosis. We analysed renal parenchymal volume (PV) and single-kidney glomerular filtration rate (SK-GFR) characteristics to identify kidneys with hibernating parenchyma and hence determine renal functional outcome after revascularization.

METHODS

Fifty patients with > or =50% RAS underwent baseline analyses: (i) PV using magnetic resonance imaging; (ii) radioisotopic SK-GFR. Twenty-one patients (27 kidneys) underwent renal revascularization and 29 medical therapy alone.

RESULTS

Patients with revascularized kidneys manifesting high PV:SK-GFR showed improvement in global estimated GFR compared to conservatively managed counterparts at 6 months and 1 year (6 months: 6.2 +/- 2.9 versus -3.7 +/- 6.8, P = 0.038; 1 year: 3.5 +/- 3.0 versus -5.1 +/- 5.1 ml/min/1.73 m(2), P = 0.021). Twelve revascularized patients (16 kidneys) underwent repeat SK-GFR 4 months post-revascularization. Six of 16 revascularized kidneys had high baseline PV:SK-GFR and showed improved SK-GFR compared to kidneys with low or normal PV:SK-GFR (6.3 +/- 2.0 versus -0.9 +/- 4.2 ml/min, P = 0.002).

CONCLUSIONS

Our data suggest that, after revascularization, GFR improvement is likely if there is a disproportionately higher baseline PV:SK-GFR in the RAS kidney. Analysing these parameters can potentially identify these 'hibernating' kidneys and aid determination of renal functional outcome in RAS.

Gadolinium-enhanced magnetic resonance imaging for renovascular disease and nephrogenic systemic fibrosis: critical review of the literature and UK experience

PURPOSE

To examine the positive reporting bias regarding the link with gadolinium (Gd) exposure and nephrogenic systemic fibrosis (NSF) in patients with renal impairment. This link has impacted strongly the international radiology safety guidelines. We believe that positive reporting bias has prevailed in the literature and that very few patients with a glomerular filtration rate (GFR) 15-29 mL/min (stage 4 chronic kidney disease [CKD]) should be regarded as high risk.

MATERIALS AND METHODS

To examine this, we conducted the following steps: 1. A critical literature search on NSF. 2. An analysis of our centers magnetic resonance angiography (MRA) experience since 1999. 3. A survey of participating centers of the multicenter ASTRAL trial to assess whether any patients screened or enrolled into ASTRAL had developed NSF.

RESULTS

The vast majority (90%) of NSF cases reported in the literature have occurred in patients with endstage renal disease treated with dialysis; very have had stable stage 4 or 5 (nondialysis) CKD. In all, 562 patients were followed up at our center: 30.4% were CKD4, 14.4% CKD5, 5.3% on dialysis, and 0.2% had renal transplants when imaged. No patients developed any symptoms or signs of NSF. In all, 347 patients were enrolled into ASTRAL on the basis of MRA (32% CKD4/5). One patient out of 45 centers (CKD5, received two Gd scans) developed NSF. Approximately 5 times as many patients were screened as were entered into ASTRAL.

CONCLUSION

No cases of NSF were observed at our center. By extrapolation, 1/1735 patients screened for the ASTRAL trial developed NSF, giving a crude incidence rate of 0.06%. We would argue that patients with CKD4 can safely undergo Gd-MRA, albeit using a minimal dose of a macrocyclic agent and avoiding repeat doses.

Usefulness of renal volume measurements obtained by a 3-dimensional sonographic transducer with matrix electronic arrays

OBJECTIVE

The purpose of this study was to examine the feasibility of 3-dimensional (3D) sonography using a matrix array transducer to measure renal volume.

METHODS

One hundred consecutive patients with a normal serum creatinine level and kidney appearance on computed tomography (CT) performed within 2 months before sonography were enrolled in this study. Two hundred individual renal volumes were blindly obtained by the ellipsoid formula, the stacked ellipse method, the voxel count method using routine 2-dimensional (2D) sonographic data, 3D sonographic data using a matrix array transducer, and CT data, respectively. The voxel count method was validated as the reference standard by the water displacement method in 10 cadaveric pig kidneys (r = 0.99; P < .001). Renal volumes determined by 2D and 3D sonography were compared with volumes determined by CT.

RESULTS

Volumes determined by 2D sonography were significantly lower than those determined by CT (P < .001) but similar to those determined by 3D sonography (P = .78). The percent volume error of 3D sonography (mean +/- SD, -2.2% +/- 3.7%) was significantly lower than that of 2D sonography (-15.7% +/- 11.8%) with CT as the standard (P < .001). The correlation coefficient between 3D sonography and CT (r = 0.98; P < .0001) was better than that between 2D sonography and CT (r = 0.83; P < .0001). In addition, Bland-Altman analysis revealed that the limits of agreement between 3D sonography and CT (-9.7% to 5.1%) were narrower than those between 2D sonography and CT (-45.6% to 9.8%).

CONCLUSIONS

Three-dimensional sonography with a matrix array transducer can significantly reduce renal volume measurement errors and offers a reliable means of determining renal volumes.

MRI estimation of total renal volume demonstrates significant association with healthy donor weight

PURPOSE

The purpose of this study was to correlate total renal volume (TRV) calculations, obtained through the voxel-count method and ellipsoid formula with various physical characteristics.

MATERIALS AND METHODS

MRI reports and physical examination from 210 healthy kidney donors (420 kidneys), on whom renal volumes were obtained using the voxel-count method, were retrospectively reviewed. These values along with ones obtained through a more traditional method (ellipsoid formula) were correlated with subject height, body weight, body mass index (BMI), and age.

RESULTS

TRV correlated strongly with body weight (r=0.7) and to a lesser degree with height, age, or BMI (r=0.5, -0.2, 0.3, respectively). The left kidney volume was greater than the right, on average (p<0.001). The ellipsoid formula method over-estimated renal volume by 17% on average which was significant (p<0.001).

CONCLUSIONS

Body weight was the physical characteristic which demonstrated the strongest correlation with renal volume in healthy subjects. Given this finding, a formula was derived for estimating the TRV for a given patient based on the his or her weight: TRV = 2.96 x weight (kg) + 113+/-64.