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

Type 2 diabetes albuminuric and non-albuminuric phenotypes have different morphological and functional ultrasound features of diabetic kidney disease

AIMS

Whether different diabetic kidney disease (DKD) phenotypes recognise differences in morphological and vascular properties of the kidney is still unexplored. We evaluated the potential role of kidney ultrasonography in differentiating DKD phenotypes in subjects with type 2 diabetes.

MATERIALS AND METHODS

This is a cross-sectional, single-centre study. Total (TRV) and parenchymal renal volumes (PRV) were calculated by applying the ellipsoid formula for conventional (2D) ultrasonography and with manual segmentation for 3D ultrasonography, and then adjusted for body surface area (aTRV, aPRV). Renal resistive index (RI) was contextually determined. DKD phenotypes have been defined based on increased urinary albumin-to-creatinine ratio (ACR >30 mg/g) and/or reduced eGFR (<60 ml/min/1.73 m² ). Recruitment was planned to have groups of the same size.

RESULTS

Among 256 subjects, 26.2% had No-DKD, 24.6% increased albuminuria only (Alb⁺ ), 24.2% non-albuminuric DKD (Alb^- DKD), and 25.0% albuminuric DKD (Alb⁺ DKD). Compared to No-DKD, RI was significantly higher in all DKD phenotypes, being the highest in Alb⁺ DKD, and with a significant trend of RI > 0.70 to increase across phenotypes. In comparison with No-DKD, both 2D and 3D volumes were increased in Alb⁺ and significantly reduced in Alb^- DKD as well as in Alb⁺ DKD, with significantly lower volumes in Alb^- DKD as compared to Alb⁺ DKD at the same reduced levels of eGFR. In adjusted regressions, compared to No-DKD, RI was associated with Alb⁺ ; both RI and aPRV3D were associated with Alb⁺ DKD; only aPRV3D with Alb^- DKD. Compared to No-DKD, Receiver Operating Characteristic curve analyses, designed taking into account conventional risk factors, showed that US parameters did not ameliorate the characterisation of Alb⁺ and Alb⁺ DKD, while aPRV3D significantly improved the phenotyping of Alb^- DKD.

CONCLUSIONS

As a novel information, we reported that, in type 2 diabetes, the emerging normoalbuminuric DKD phenotype showed reduced TRVs and PRVs even when compared, at similarly reduced eGFR levels, with Alb⁺ DKD opening. In perspective, these findings suggest a possible role of imaging for better discrimination of DKD phenotypes in clinical practice.

Kidney Ultrasound for the Nephrologist: A Review

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

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.

Timing urinary tract reconstruction in rats to avoid hydronephrosis and fibrosis in the transplanted fetal metanephros as assessed using imaging

Chronic kidney disease leads to high morbidity rates among humans. Kidney transplantation is often necessary for severe symptoms; however, options for new curative treatments are desired because of donor shortage. For example, it has been established that the kidneys can efficiently generate urine after transplantation of the metanephros, ureter, and bladder as a group. After transplantation, the urine can indirectly flow into the recipient's bladder using a stepwise peristaltic ureter system method where the anastomosis is created via the recipient's ureter for urinary tract reconstruction. However, the growth of the regenerated metanephros varies significantly, whereas the time window for successful completion of the stepwise peristaltic ureter system that does not cause hydronephrosis of the metanephros with bladder (ureter) is quite narrow. Therefore, this study was conducted to periodically and noninvasively evaluate the growth of the transplanted metanephros, ureter, and bladder in rats through computed tomography and ultrasonography. The ultrasonographic findings highly correlated to the computed tomography findings and clearly showed the metanephros and bladder. We found that the degree of growth of the metanephros and the bladder after transplantation differed in each case. Most of the rats were ready for urinary tract reconstruction within 21 days after transplantation. Optimizing the urinary tract reconstruction using ultrasonography allowed for interventions to reduce long-term tubular dilation of the metanephros due to inhibited overdilation of the fetal bladder, thereby decreasing the fibrosis caused possibly by transforming growth factor-β1. These results may be significantly related to the long-term maturation of the fetal metanephros and can provide new insights into the physiology of transplant regeneration of the metanephros in higher animals. Thus, this study contributes to the evidence base for the possibility of kidney regeneration in human clinical trials.

Sonographic renal length and volume of normal Thai children versus their Chinese and Western counterparts

BACKGROUND

Renal size is an important indicator in the diagnosis of renal diseases and urinary tract infections in children.

PURPOSE

The purpose of this study is twofold. First, it aimed to measure the renal length and calculate the renal volume of normal Thai children using 2-dimensional ultrasonography (2D-US) and study their correlations with somatic parameters. Second, it aimed to compare the age-specific renal size of normal Thai children with the published data of their Western and Chinese counterparts.

METHODS

A total of 321 children (150 boys, 171 girls; age, 6-15 years) with a normal renal profile were prospectively recruited. All subjects underwent 2D-US by an experienced pediatric radiologist and the renal length, width, and depth were measured. Renal volume was calculated using the ellipsoid formula as recommended. The data were compared between the left and right kidneys, the sexes, and various somatic parameters. The age-specific renal lengths were compared using a nomogram derived from a Western cohort that is currently referred by many Thailand hospitals, while the renal volumes were compared with the published data of a Chinese cohort.

RESULTS

No statistically significant difference (P<0.05) was found between sexes or the right and left kidneys. The renal sizes had strong correlations with height, weight, body surface area, and age but not with body mass index. The renal length of the Thai children was moderately correlated (r=0.59) with that of the Western cohort, while the age-specific renal volume was significantly smaller (P<0.05) than that of the Chinese children.

CONCLUSION

Therefore, we concluded that the age-specific renal length and volume obtained by 2D-US would vary between children in different regions and may not be suitably used as an international standard for diagnosis, although further studies may be needed to confirm our findings.

How reliable is renal ultrasound to measure renal length and volume in patients with chronic kidney disease compared with magnetic resonance imaging?

Background

Renal length, volume, and parenchymal thickness are important clinical parameters, yet data concerning the accuracy and reproducibility of ultrasound (US)-based renal length and volume assessment in patients with chronic kidney disease (CKD) are scarce.

Purpose

To establish whether renal length, volume, and parenchymal thickness can be reliably measured with renal US in patients with CKD.

Material and Methods

All participants underwent renal US, immediately followed by 3-T magnetic resonance imaging (MRI). Renal length, width, transverse diameter, and parenchyma thickness were measured with both methods; renal volume was calculated using the ellipsoid formula. A total of 45 patients with CKD (eGFR [mean ± SD] 57.4 ± 4.4 mL/min/1.73 m2) and 46 participants without CKD (eGFR 97.0 ± 2.4 mL/min/1.73 m2) were included.

Results

US-measured renal length correlated strongly with MRI-measured renal length in no-CKD patients (Spearman’s r = 0.83 and 0.85 for the right and left kidney, respectively; P < 0.005) and CKD patients (r = 0.89 and 0.92 for the right and left kidney, respectively; P < 0.005). There was a significant but weaker correlation between MRI- and US-measured right and left renal volume (r = 0.72, P < 0.005) in no-CKD (r = 0.74 and r = 0.72, respectively; for both: P < 0.005) and CKD patients (r = 0.83 and 0.85, P < 0.005). Weak to moderate correlations were found for parenchyma thickness for the right (CKD group: r = 0.29, no-CKD: r = 0.23; for both: P < 0.05) and left kidney (CKD: r = 0.52, no-CKD group: r = 0.37, P < 0.05). Both intra-observer (Pearson’s correlations of 0.82 for the right and 0.89 for the left kidney) and inter-observer (Lin’s correlation coefficient of 0.90 for the right and 0.82 for the left kidney) reproducibility of US-assessed renal length was high.

Conclusions

US-based assessment of renal length in CKD patients is comparable to MRI measures. Both intra- and inter-observer reproducibility of US-assessed renal length in CKD patients are high. Measurements of US renal volume and parenchymal thickness should, however, be interpreted with caution.

Reproducibility of renal volume measurement in adults using 3-dimensional sonography

OBJECTIVES

The purpose of this study was to determine the interobserver reproducibility of renal volume measurement performed by 3-dimensional (3D) sonography.

METHODS

We conducted an exploratory, quantitative, observational, and descriptive cross-sectional study. We calculated ranges, means, and standard deviations of the renal volumes obtained with 3D sonography by 2 different examiners from a sample of 30 patients. The interobserver reproducibility was assessed by calculating intraclass correlation coefficients (ICCs) and by construction of Bland-Altman plots.

RESULTS

The ICC between the right 3D renal volumes obtained by examiners 1 and 2 was 0.8552 (95% confidence interval, 0.7153-0.9292), showing excellent reproducibility (P < .0001). For the left 3D renal volumes obtained by examiners 1 and 2, the ICC was 0.6411 (95% confidence interval, 0.3652-0.8135), showing average to good reproducibility (P = .0001). The Bland-Altman plots showed mean differences ± SD of -4.8% ± 23.9% between the right renal volumes obtained by examiners 1 and 2 and -2.2% ± 38% between the left renal volumes. The 95% limits of agreement between the right renal volumes obtained by examiners 1 and 2 were -28.7% to 19%, whereas those between the left renal volumes were -40.2% to 35.7%.

CONCLUSIONS

Three-dimensional sonography showed good interobserver reproducibility, which was better for the right kidney. It appears necessary to establish standardized techniques for acquisition of sonographic renal volumes.

Comparison between different imaging techniques in the evaluation of malignant breast lesions: can 3D ultrasound be useful?

PURPOSE

This study was done to assess the feasibility of three-dimensional ultrasonography (3D-US) for volume calculation of solid breast lesions.

MATERIALS AND METHODS

The volumes of 36 malignant lesions were measured using conventional 2D-US, 3D-US and magnetic resonance imaging (MRI) and compared with that obtained with histology (standard of reference). With 2D Ultrasouns, volume was estimated by measuring three diameters and calculating volume with the mathematical formula for spheres. With 3D-US, stored images were retrieved and boundaries of masses were manually outlined; volume calculation was performed with VOCAL software. For MRI, volume measurements were obtained with special software for 3D reconstructions, after each lesion had been manually outlined. Histology measured the three main diameters and the volume was estimated using the mathematical formula for spheres. Interclass correlation coefficient (ICC) and Bland-Altman plots were used to assess agreement between the volumes measured.

RESULTS

ICC indicated that a good level of concordance was identified between 3D-US and histology (0.79). According to the Bland-Altman analysis, limits of agreement of mean differences of the volumes measured with the three imaging modalities were comparable with histology: -2 ÷ 1.5 cm(3) for 3D-US; -2.3 ÷ 1.3 cm(3) for 2D-US and -2.2 ÷ 1.6 cm(3) for MRI.

CONCLUSIONS

3D-US is a reliable method for the volumetric assessment of breast lesions. 3D-US is able to provide valuable information for the preoperative evaluation of lesions.

Estimation of feline renal volume using computed tomography and ultrasound

Renal volume estimation is an important parameter for clinical evaluation of kidneys and research applications. A time efficient, repeatable, and accurate method for volume estimation is required. The purpose of this study was to describe the accuracy of ultrasound and computed tomography (CT) for estimating feline renal volume. Standardized ultrasound and CT scans were acquired for kidneys of 12 cadaver cats, in situ. Ultrasound and CT multiplanar reconstructions were used to record renal length measurements that were then used to calculate volume using the prolate ellipsoid formula for volume estimation. In addition, CT studies were reconstructed at 1 mm, 5 mm, and 1 cm, and transferred to a workstation where the renal volume was calculated using the voxel count method (hand drawn regions of interest). The reference standard kidney volume was then determined ex vivo using water displacement with the Archimedes' principle. Ultrasound measurement of renal length accounted for approximately 87% of the variability in renal volume for the study population. The prolate ellipsoid formula exhibited proportional bias and underestimated renal volume by a median of 18.9%. Computed tomography volume estimates using the voxel count method with hand-traced regions of interest provided the most accurate results, with increasing accuracy for smaller voxel sizes in grossly normal kidneys (-10.1 to 0.6%). Findings from this study supported the use of CT and the voxel count method for estimating feline renal volume in future clinical and research studies.

Human cadaver study evaluating a new measurement technique for graft volumes after sinus floor elevation

PURPOSE

Volumetric data can be used as complementary information to characterize grafting materials. The aim of this cadaveric study was to analyze a noncommercial measurement technique based on the novel concept of an "interactive rigid registration algorithm" (IRRA). Parameters analyzed included the reproducibility of IRRA measurements and their reliability in comparison with the established measurement technique of "region growing segmentation thresholding" (RGST).

MATERIALS AND METHODS

Three human skulls were used to simulate a total of 18 sinus grafts, using three incremental grafting procedures in each sinus (three skulls ×t wo sinuses × three grafting increments). Radiopaque impression material was used for the simulated grafts, whose volumes were recorded by computed tomography from three different tilt angles. The reproducibility of IRRA measurements and the reliability of volumetric results obtained with both the IRRA and RGST techniques were evaluated by appropriate intraclass correlation coefficient (ICC) and Bland-Altman analysis.

RESULTS

ICC greater than 0.9 indicated close to perfect agreement of the results obtained with both methods and good reproducibility of the IRRA measurements. Bland-Altman analysis demonstrated good inter-method and intramethod agreement.

CONCLUSIONS

The IRRA measurement technique can be recommended as a noninvasive tool to evaluate graft volumes in human maxillary sinuses.

Measurement of renal dimensions in vivo: A critical appraisal

Kidney volume is regarded as the most precise indicator of kidney size. However, volume assessment is not widely used clinically because its measurement is difficult due to the complex kidney shape. Apart from the conventional methods of measurement of renal dimensions from X-rays, ultrasound scan, computed tomography scan and magnetic resonance imaging have evolved as the three best modalities for this purpose currently. Assessment of kidney size should also be made individually since many factors like body mass index, height, gender, age, position of kidneys, sex, stenoses and number of renal arteries influence the measurements. In this paper, we have critically analysed the advantages and disadvantages of the various methods of renal morphometry, by reviewing the literature spanning over the period of 1976 - 2009.

Ultrasound-guided biopsy of focal lesions using three-dimensional ultrasound with a matrix array transducer: comparison with 2-dimensional ultrasound in a phantom study

OBJECTIVES

To investigate the feasibility of biopsy-guided 3-dimensional (3D) ultrasound (US) with a matrix array transducer (3D US-MAT), using the lateral and/or elevation tilt modes.

MATERIALS AND METHODS

Both inexperienced and experienced examiners performed biopsy experiments using a freehand technique on agar-based phantoms with 2-dimensional (2D) US guidance and 3D US-MAT guidance allowing real-time biplane imaging, using the lateral tilt mode and/or elevation tilt mode. Each phantom contained 4 targets of different sizes, and there were 3 different types of phantom, each having a different distance between the target and the surface. In every session, each target was aimed at 3 times, with 3 different distances between the transducer and puncture site, which resulted in 36 biopsies (3 biopsies per target × 4 targets × 3 phantoms, each of which was uniquely identified by size, depth, and angle). This procedure was carried out by each of 2 examiner twice by 2D US and twice by 3D US-MAT, resulting in paired data for each biopsy and each examiner. Target variables were target specimen length (TSL), procedure time, and agreement between the TSL of the first and second procedure by each examiner with identical biopsy parameters as a reliability measure.

RESULTS

The intraexaminer agreements between the TSLs with the 3D US-MAT in both inexperienced (r = 0.84) and experienced (r = 0.93) examiners were higher than with the 2D US (r = 0.59 with P = 0.0066, and r = 0.87 with P = 0.06, respectively). However, the procedure time with the 3D US-MAT was significantly longer than with the 2D US. The TSL were significantly longer with 3D US-MAT than with 2D US for both the examiners; the inexperienced examiner (P < 0.001) benefited more than his experienced colleague (P = 0.024). In addition, the 3D US-MAT had significant benefits for the acquisition of TSL with small target diameters and for targets with shallow locations; with more acute puncture angles for both the examiners (all P < 0.05).

CONCLUSIONS

Using a 3D US-MAT guidance improves the reliability and precision of biopsies, particularly under difficult conditions and for inexperienced examiners.

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.