Characterization Of Renal Masses Research Articles

Cross-sectional imaging evaluation of renal masses

Cross-sectional imaging modalities including multidetector computed tomography (MDCT) and magnetic resonance imaging (MRI) are the diagnostic standard in detection, characterization, and staging of renal masses due to their high sensitivity and specificity. Currently, most renal masses are incidentally diagnosed by imaging for other medical reasons. Recent developments have improved image acquisition with high resolution, while simultaneously reducing radiation dose. CT imaging is the most accessible cross-sectional imaging method and is, therefore, the standard technique. MRI is indicated in patients who are allergic to intravenous CT contrast medium, in patients with renal insufficiency, or in younger patients. Further characterization of renal masses is possible with functional imaging including dual energy CT, perfusion CT, or diffusion-weighted MRI. Contrast-enhanced ultrasound allows detection of even subtle enhancement in hypovascular lesions with high sensitivity and can add valuable information to CT and MRI studies.

Effect of Model-Based Iterative Reconstruction on CT Number Measurements Within Small (10-29 mm) Low-Attenuation Renal Masses.

The purpose of this study was to assess the effect of model-based iterative reconstruction (MBIR) on CT number measurements within small (10-29 mm) low-attenuation renal masses. One hundred 10- to 29-mm exophytic or endophytic low-attenuation renal lesions imaged with CT (unenhanced and nephrographic [100 seconds] phases, 120 kVp, variable mA, 2.5-mm slice thickness) were identified in 100 patients. The raw CT source data were prospectively reconstructed twice: once using Veo MBIR and once using a blend of 30% adaptive statistical iterative reconstruction (ASiR) and filtered back projection (FBP). Lesions were chosen to form four equal-sized (n = 25) groups stratified by lesion size (10-19 or 20-29 mm) and growth pattern (endophytic or exophytic). Attenuation (in HU) was measured using identical ROIs and compared with two-tailed t tests. The effects of patient diameter and lesion anatomy on attenuation discrepancies of 5 HU or more were assessed using binary logistic regression. Mean MBIR attenuation was not significantly different than mean 30% ASiR/FBP attenuation in the overall study population (unenhanced phase, 17 ± 13 vs 17 ± 13 HU, p = 0.74; nephrographic phase, 31 ± 27 vs 30 ± 26 HU, p = 0.89) or in any subgroup (p = 0.63-0.95). Only lesion size predicted discrepancies of 5 HU or more (p = 0.008; odds ratio, 1.20 [95% CI, 1.05-1.34] per 1 mm decrease) (p = 0.19-0.98 for the other variables). Seven lesions had enhancement of 20 HU or more with only one reconstruction method (MBIR = 4; 30% ASiR = 3). Veo MBIR has no significant or consistent effect on attenuation measurements within small (10-29 mm) low-attenuation renal masses and is therefore unlikely to change clinically accepted attenuation thresholds for renal mass characterization.

Renal Masses With Equivocal Enhancement at CT: Characterization With Contrast-Enhanced Ultrasound.

The purpose of this article is to retrospectively investigate in two radiology centers the role of contrast-enhanced ultrasound in the characterization of renal masses with equivocal enhancement at CT (i.e., with a density increase of 10-20 HU between unenhanced and contrast-enhanced scans) not characterized with conventional ultrasound modes. Forty-seven renal lesions (range, 0.8-7.7 cm; average, 2.6 cm) with equivocal enhancement at CT underwent contrast-enhanced ultrasound using sulfur hexafluoride-filled microbubbles. Examinations were digitally recorded for retrospective blinded evaluation by two radiologists with 20 and 10 years' experience in urologic imaging. Histologic results were available for 30 of 47 (64%) lesions (25 primary malignant tumors, two metastases, and three primary benign lesions). Two lesions increased in size and complexity during the follow-up and were considered malignant. One Bosniak category III and 14 category IIF cysts were stable after a follow-up of at least 3 years and were considered benign. ROC curve analysis was used to assess the capability of contrast-enhanced ultrasound to differentiate benign from malignant lesions. Twelve likely complex cystic lesions at gray-scale ultrasound were cystic also on contrast-enhanced ultrasound and reference procedures. Eleven of 34 lesions that appeared solid at gray-scale ultrasound were cystic on contrast-enhanced ultrasound and reference procedures. One lesion considered likely solid by one radiologist and possibly cystic by the other was a solid tumor at contrast-enhanced ultrasound and histologic analysis. The diagnostic performance of contrast-enhanced ultrasound to characterize the lesions as benign or malignant was high for both readers (AUC, 0.958 and 0.966, respectively). Contrast-enhanced ultrasound is effective for characterizing renal lesions presenting with equivocal enhancement at CT.

Renal Tumor Biopsy for Small Renal Masses: A Single-center 13-year Experience

BackgroundRenal tumor biopsy (RTB) for the characterization of small renal masses (SRMs) has not been widely adopted despite reported safety and accuracy. Without pretreatment biopsy, patients with benign tumors are frequently overtreated. ObjectiveTo assess the diagnostic rate of RTBs, to determine their concordance with surgical pathology, and to assess their impact on management. Design, setting, and participantsThis is a single-institution retrospective study of 529 patients with biopsied solid SRMs ≤4cm in diameter. RTBs were performed to aid in clinical management. Outcome measurements and statistical analysisDiagnostic and concordance rates were presented using proportions. Factors that contributed to a diagnostic biopsy were identified using a multivariable logistic regression. Results and limitationsThe first biopsy was diagnostic in 90% (n=476) of cases. Of the nondiagnostic biopsies, 24 patients underwent a second biopsy of which 83% were diagnostic. When both were combined, RTBs yielded an overall diagnostic rate of 94%. Following RTB, treatment could have been avoided in at least 26% of cases because the lesion was benign. Tumor size and exophytic location were significantly associated with biopsy outcome. RTB histology and nuclear grade were highly concordant with final pathology (93% and 94%, respectively). Adverse events were low (8.5%) and were all self-limited with the exception of one. Although excellent concordance between RTB and final pathology was observed, only a subset of patients underwent surgery following biopsy. Thus it is possible that some patients were misdiagnosed. ConclusionsRTB of SRMs provided a high rate of diagnostic accuracy, and more than a quarter were benign. Routine RTB for SRMs informs treatment decisions and diminishes unnecessary intervention. Our results support its systematic use and suggest that a change in clinical paradigm should be considered. Patient summaryRenal tumor biopsy (RTB) for pretreatment identification of the pathology of small renal masses (SRMs) is safe and reliable and decreases unnecessary treatment. Routine RTB should be considered in all patients with an indeterminate SRM for which treatment is being considered.

MP22-04 EVOLUTION OF 3-D PHYSICAL MODELS OF RENAL MALIGNANCIES USING MULTI-MATERIAL 3-D PRINTERS

INTRODUCTION AND OBJECTIVES: Construction of high fidelity individualized physical three-dimensional (3-D) models of renal units with enhancing renal lesions may aid patients, trainees and clinicians in their appreciation, characterization, localization and extirpation of suspicious renal masses. We present the evolution of these 3-D models during our single institution experience. METHODS: Pre-operative computerized tomographies were used along with proprietary software to import images into the 3-D printer. Sterolithography additive manufacturing, a technique in which an ultraviolet laser is used to cure a photosensitive resin in sequential, horizontally oriented layers was employed to build the models (Medical Modeling Inc., Golden, CO). We printed 20 models with four different variations on materials and properties for 12 patients with renal masses. Subsequently the patients underwent surgical extirpation of their renal masses. RESULTS: The four model types are demonstrated in figure 1. Initially, the models were made a firm plastic with only renal parenchyma and the mass being contrasted by a clear and pink resin. Subsequently, the collecting system and vasculature were added to the models. A second type of firm model allowed for multiple different colors to represent independently normal parenchyma, renal mass, vasculature, and collecting system. More recently, we have developed two malleable type models that enable the pre-operative simulation of tumor resection and renorrhaphy. Patients, their families and trainees consistently stated that the models enhanced their understanding of the renal tumor in relation to surrounding normal renal parenchyma and hilar structures. CONCLUSIONS: Pre-operative physical 3-D models using readily available printing techniques can be constructed and may potentially influence both patients’ and trainees’ understanding of renal malignancies. With experience, 3-D printing has evolved such that models more closely approximate actual renal units.

Renal cell carcinoma: histological classification and correlation with imaging findings.

Renal cell carcinoma (RCC) is the seventh most common histological type of cancer in the Western world and has shown a sustained increase in its prevalence. The histological classification of RCCs is of utmost importance, considering the significant prognostic and therapeutic implications of its histological subtypes. Imaging methods play an outstanding role in the diagnosis, staging and follow-up of RCC. Clear cell, papillary and chromophobe are the most common histological subtypes of RCC, and their preoperative radiological characterization, either followed or not by confirmatory percutaneous biopsy, may be particularly useful in cases of poor surgical condition, metastatic disease, central mass in a solitary kidney, and in patients eligible for molecular targeted therapy. New strategies recently developed for treating renal cancer, such as cryo and radiofrequency ablation, molecularly targeted therapy and active surveillance also require appropriate preoperative characterization of renal masses. Less common histological types, although sharing nonspecific imaging features, may be suspected on the basis of clinical and epidemiological data. The present study is aimed at reviewing the main clinical and imaging findings of histological RCC subtypes.

Imaging the renal mass: a historical review.

A matter of months after Roentgen's landmark discovery in 1895, Roentgen's rays were focused on diseases and disorders of the urinary tract, specifically the kidney. At the dawn of the 20th century, urologists in the United States and around the world quickly recognized that by using a variety of metal stylets and radiopaque contrast agents, such as silver salts, the upper urinary tract, namely the ureter, pelvis, and calyces, could be depicted with radiography. Renal cysts and tumors were diagnosed on the basis of deformities in the kidney. Retrograde pyelography dominated the imaging evaluation of the kidney until the discovery of a safe intravenous method for urinary tract imaging (ie, intravenous pyelography). Pioneers and pathfinders in the field of contrast media development and radiologic procedures helped give radiologists the lead role in the work-up of renal masses, an area where urologists once held forth. The subspecialty of uroradiology was born in the middle of the 20th century. Intravenous urography, nephrotomography, and diagnostic angiography with pharmacologic manipulation followed by cyst or mass puncture and biopsy yielded unrivaled specificity for the diagnosis and staging of benign and malignant renal masses. The advent of cross-sectional and multiplanar imaging and the profound effects they had and continue to have on the discovery and characterization of renal masses has been detailed in the pages of Radiology since the 1920s. Ultrasonography, nuclear imaging, computed tomographic scanning, magnetic resonance imaging, and positron emission tomography each have made a claim to a part of the imaging algorithm of modern uroradiologic practice.

Percutaneous renal tumour biopsy

The use of percutaneous renal tumour biopsy (RTB) as a diagnostic tool for the histological characterization of renal masses has increased dramatically within the last 30 years. This increased utilization has paralleled advances in imaging techniques and an evolving knowledge of the clinical value of nephron sparing surgery. Improved biopsy techniques using image guidance, coupled with the use of smaller gauge needles has led to a decrease in complication rates. Reports from series containing a large number of cases have shown the non-diagnostic rate of RTB to range from 4% to 21%. Re-biopsy has been shown to reduce this rate, while the use of molecular markers further improves diagnostic sensitivity. In parallel with refinements of the biopsy procedure, there has been a rapid expansion in our understanding of the complexity of renal cell neoplasia. The 2013 Vancouver Classification is the current classification for renal tumours, and contains five additional entities recognized as novel forms of renal malignancy. The diagnosis of tumour morphotype on RTB is usually achievable on routine histology; however, immunohistochemical studies may be of assistance in difficult cases. The morphology of the main tumour subtypes, based upon the Vancouver Classification, is described and differentiating features are discussed.

Solid Renal Masses: What the Numbers Tell Us

Solid renal masses are most often incidentally detected at imaging as small (≤ 4 cm) localized lesions. These lesions comprise a wide spectrum of benign and malignant histologic subtypes, but are largely treated with surgical resection given the limited ability of imaging to differentiate among them with consistency and high accuracy. Numerous studies have thus examined the ability of CT and MRI techniques to separate benign lesions from malignancies and to predict renal cancer histologic grade and subtype. This article synthesizes the evidence regarding renal mass characterization at CT and MRI, provides diagnostic algorithms for evidence-based practice, and highlights areas of further research needed to drive imaging-based management of renal masses. Despite extensive study of morphologic and quantitative criteria at conventional imaging, no CT or MRI techniques can reliably distinguish solid benign tumors, such as oncocytoma and lipid-poor angiomyolipoma, from malignant renal tumors. Larger studies are required to validate recently developed techniques, such as diffusion-weighted imaging. Evidence-based practice includes MRI to assess renal lesions in situations where CT is limited and to help guide management in patients who are considered borderline surgical candidates.

R.E.N.A.L. Nephrometry Scoring: How Well Correlated Are Urologist, Radiologist, and Collaborator Scores?

R.E.N.A.L. Nephrometry Score (NS) is an imaging-based (CT/MRI) scoring system commonly used by urologists to standardize the reporting of renal masses by enabling quantification of anatomical characteristics. We sought to examine the inter-rater correlation of NS between urologists, radiologists, and tumor-board collaborators. We identified adult patients undergoing partial or radical nephrectomy over 10 years (n=2450). Patients with autosomal dominant polycystic kidney disease (ADPKD), metastatic disease, masses >10 cm, and studies in which the study urologists or radiologists partook in patient care were excluded. Preoperative imaging was evaluated and patients with multiphasic CT available were included. Scans were provided to the reviewers to evaluate with a R.E.N.A.L. nephrometry questionnaire. Results were analyzed using kappa correlation coefficients. One hundred twenty patients met inclusion criteria with mean age of 59.5 years. The majority of cases were partial nephrectomies (72%). Eighty-five percent of the tumors were malignant, with 26% having high-grade histology. The mean (standard deviation) overall NS was 6.8 (1.9) with fair correlation among reviewers (κ=0.222). Collaborators had the highest inter-rater correlation, ranging from 0.41 to 0.84 for NS component scores, compared with 0.42-0.85 for radiologists and 0.36-0.86 for urologists. "R" scores were best correlated (κ>0.8). NS correlation ranged between 0.16 and 0.31 for the groups while the NS complexity category correlation ranged between 0.50 and 0.61. Despite being naive to NS, inter-radiologist scoring patterns were better correlated than inter-urologist. The urologist and radiologist collaborating in tumor board showed the highest agreement, suggesting that a multidisciplinary approach in the characterization of renal masses may provide benefit to patient management.

MR imaging in the characterization of small renal masses

The aim of our study was to evaluate the effectiveness of MR imaging for the characterization of small (<2 cm) renal lesions described as indeterminate on prior US or CT. Sixty-three small renal masses in 51 patients considered indeterminate on prior ultrasound or CT scans were included in the study. A retrospective evaluation of the examinations was performed independently by two body magnetic resonance imaging (MRI) radiologists who were unaware of the final diagnosis. A 3-point confidence scale (1: benign, 2: indeterminate, and 3: malignant) was established to determine the level of suspicion for malignancy. Interobserver agreement was determined with a weighted kappa statistic. The diagnosis was verified by imaging follow-up of at least 24 months (mean 60 months) in 53 lesions and by pathology in 10 lesions. MRI detected all eight malignancies in the series. There were eight malignant lesions and two benign lesions among those with pathologic follow-up. No interval growth or evidence of malignancy in the remaining 53 lesions was found for a minimum of 24 months by repeat imaging. The sensitivity, specificity, positive predictive value, and negative predictive value of MRI for differentiating benign from malignant small renal lesions were 100% (62.9-100%, 95% CI), 94.5% (84.9-98.8%, 95% CI), 72.7% (39.1-93.6%, 95% CI), and 100% (93.1-100%, 95% CI), respectively. The kappa value for interobserver agreement was 0.77 (95% CI 0.59-0.96, p-value <0.001). MR imaging is an effective method for characterizing small (<2 cm) renal masses found to be indeterminate by US or CT.

The importance of image quality: In the eyes of the beholder?

The importance of image quality: In the eyes of the beholder?

Is The Value of FDG PET/CT in Evaluating Renal Metastasis Underestimated? A Case Report and Review of The Literature

Contrast-enhanced CT or MRI are used as a gold standard imaging modalities in the detection and characterization of renal masses. On the other hand, the role of FDG PET/CT in evaluating primary or metastatic cancers of the kidney is limited due to the excretion of FDG through urinary tract. We reported the FDG PET/CT of a lung cancer patient with multiple metastases in both kidneys which were missed in previous PET/CT, and underestimated on sequential diagnostic abdominal CT study.Conflict of interest:None declared.

Evaluation of Indeterminate Renal Masses with Contrast-enhanced US: A Diagnostic Performance Study

To determine the utility of contrast material-enhanced ultrasonography (US) in the characterization of indeterminate renal masses. This retrospective performance study was approved by the institutional review board and was HIPAA compliant, with waiver of informed consent. Patients included 721 individuals referred for contrast-enhanced US with 1018 indeterminate renal masses from 1999 to 2010, identified initially with an imaging study. Three hundred twenty patients (44.4%) were female, and 401 (55.6%) were male. Patient ages ranged from 17 to 95 years (mean ± standard deviation, 70 years ± 15). Lesion size varied from 2 to 161 mm (mean, 26.6 mm ± 19.5). Contrast-enhanced US enhancement patterns were used to characterize masses as benign or malignant. For lesions with a definitive diagnosis, 306 of 1018 (30.0%) were correlated with contrast-enhanced US findings: 167 (54.6%) were benign, and 139 (45.4%) were malignant. For lesions without a pathologic diagnosis, 712 (70.0%) were followed for as long as 10 years. Diagnostic accuracy measures were calculated by using pathologic diagnosis as the reference standard, as well as lesion stability at 3 and 5 years. Contrast-enhanced US had a sensitivity of 100% (126 of 126; 95% confidence interval [CI]: 97.1%, 100%), specificity of 95.0% (132 of 139; 95% CI: 89.9%, 98.0%), positive predictive value (PPV) of 94.7% (126 of 133), and negative predictive value (NPV) of 100% (132 of 132). The five false-positive masses included three oncocytomas and two Bosniak category 3 cystic lesions. Of the 290 lesions that had follow-up of at least 36 months, none of the lesions demonstrated changes that necessitated lesion reclassification. If these lesions were included, assuming lesions classified as malignant were malignant, then of the 596 lesions, sensitivity was 100% (161 of 161), specificity was 96.6% (420 of 435), PPV was 91.5% (161 of 176), and NPV was 100% (420 of 420). Contrast-enhanced US evaluation is a highly sensitive and specific method for characterization of indeterminate renal masses. Online supplemental material is available for this article.

Modern imaging of kidney tumors

If a renal mass is suspected on clinical examination or ultrasound the finding has to be confirmed by cross-sectional imaging. Methods that are used include multidetector-row computed tomography (MDCT) and magnetic resonance imaging (MRI). Also contrast-enhanced ultrasound has been successfully implemented in renal imaging and now plays a major role in the differentiation of benign from malignant renal masses. In expert hands it can be used to show very faint vascularization and subtle enhancement. The MDCT technique benefits from the recently introduced dual energy technology that allows superior characterization of renal masses in a single-phase examination, thereby greatly reducing radiation exposure. For young patients and persons allergic to iodine MRI should be used and it provides excellent soft tissue contrast and visualizes contrast enhancement kinetics in multiphase examinations.This article aims at giving a comprehensive overview of these different imaging modalities, their clinical indications and contraindications, as well as a description of imaging findings of various renal masses.

Arterial Spin-labeling MR Imaging of Renal Masses: Correlation with Histopathologic Findings

To assess the value of arterial spin-labeling (ASL) perfusion magnetic resonance (MR) imaging in the characterization of solid renal masses by using histopathologic findings as the standard of reference. This prospective study was compliant with HIPAA and approved by the institutional review board. Informed consent was obtained from all patients before imaging. Forty-two consecutive patients suspected of having renal masses underwent ASL MR imaging before their routine 1.5-T clinical MR examination. Mean and peak tumor perfusion levels were obtained by one radiologist, who was blinded to the final histologic diagnosis, by using region of interest analysis. Perfusion values were correlated with histopathologic findings by using analysis of variance. A linear correlation model was used to evaluate the relationship between tumor size and perfusion in clear cell renal cell carcinoma (RCC). P < .05 was considered indicative of a statistically significant difference. Histopathologic findings were available in 34 patients (28 men, six women; mean age ± standard deviation, 60.4 years ± 11.7). The mean perfusion of papillary RCC (27.0 mL/min/100 g ± 15.1) was lower than that of clear cell RCC (171.6 mL/min/100 g ± 61.2, P = .001), chromophobe RCC (152.9 mL/min/100 g ± 80.7, P = .04), unclassified RCC (208.0 mL/min/100 g ± 41.1, P = .001), and oncocytoma (373.9 mL/min/100 g ± 99.2, P < .001). The mean and peak perfusion levels of oncocytoma (373.9 mL/min/100 g ± 99.2 and 512.3 mL/min/100 g ± 146.0, respectively) were higher than those of papillary RCC (27.0 mL/min/100 g ± 15.1 and 78.2 mL/min/100 g ± 39.7, P < .001 for both), chromophobe RCC (152.9 mL/min/100 g ± 80.7 and 260.9 mL/min/100 g ± 61.9; P < .001 and P = .02, respectively), and unclassified RCC (208.0 mL/min/100 g ± 41.1 and 273.3 mL/min/100 g ± 83.4; P = .01 and P = .03, respectively). The mean tumor perfusion of oncocytoma was higher than that of clear cell RCC (P < .001). ASL MR imaging enables distinction among different histopathologic diagnoses in renal masses on the basis of their perfusion level. Oncocytomas demonstrate higher perfusion levels than RCCs, and papillary RCCs exhibit lower perfusion levels than other RCC subtypes.

Re: Arterial Spin Labeling MR Imaging for Characterisation of Renal Masses in Patients With Impaired Renal Function: Initial Experience

Re: Arterial Spin Labeling MR Imaging for Characterisation of Renal Masses in Patients With Impaired Renal Function: Initial Experience

Characterization of Small Renal Masses Less than 4 cm with Quadriphasic Multidetector Helical Computed Tomography: Differentiation of Benign and Malignant Lesions

PurposeTo identify the characteristic quadriphasic (unenhanced, corticomedullary, nephrographic, and excretory phase) helical multidetector computed tomography (MDCT) features of renal masses less than 4 cm to distinguish benign from malignant renal masses.Materials and MethodsIn total, 84 patients were retrospectively analyzed to determine the characteristic features for the prediction of subtypes of small renal masses. The patients' age, gender, and tumor size and CT features, including the presence of intra-tumor degenerative changes, septation, calcification, and wall irregularity, were evaluated. In addition, the degree and pattern of enhancement obtained during four phases were analyzed. The relationship between the subtype of the small renal masses and the gender, morphological features, and pattern of contrast enhancement on the CT was analyzed by using the chi-square test. Tumor size and degree of contrast enhancement were compared by the Mann-Whitney U test. The predictive value of each of the CT features was determined by multivariate logistic regression analysis.ResultsOf the 84 small renal masses, 17 (20%) were benign and 67 (80%) were malignant. Univariate analysis revealed that renal cell carcinoma lesions showed heterogeneous enhancement (p=0.002) and higher mean attenuation value on the corticomedullary and nephrographic phases (135.1±53.9, p=0.000, and 132.4±43.6, p=0.006). The multivariate analysis with logistic regression model showed that only the mean attenuation value on the corticomedullary phase had a statistically significant correlation (p=0.021).ConclusionsFor the characterization of small renal masses, the degree of enhancement on the corticomedullary phase is a valuable parameter. Furthermore, the heterogeneous enhancement pattern and degree of enhancement on the nephrographic phase can provide information for differentiating small renal masses.

Utility of Iodine Overlay Technique and Virtual Unenhanced Images for the Characterization of Renal Masses by Dual-Energy CT

The objective of our study was to assess the utility of dual-energy CT for characterizing renal masses using iodine overlay techniques and virtual unenhanced images and to measure the potential radiation dose reduction for two-phase kidney CT compared with a standard three-phase protocol. Sixty patients with suspected renal masses underwent dual-energy CT including true unenhanced, dual-energy corticomedullary, and dual-energy late nephrographic phase imaging. Iodine overlay and virtual unenhanced images were derived from the corticomedullary and late nephrographic phases, respectively. The CT numbers of renal masses were calculated using the iodine overlay images superimposed on the virtual unenhanced images. The overall imaging quality of the true unenhanced images and of the virtual unenhanced images was also evaluated. The effective radiation doses for dual-energy CT and for true unenhanced imaging were calculated. For overlay or enhancement values on iodine overlay images, 36 simple cysts and 10 hemorrhagic cysts had an attenuation value of less than 20 HU, whereas 21 renal cell carcinomas showed an attenuation value of 20 HU or greater. Eleven angiomyolipomas contained macroscopic fat tissue. All renal masses were accurately classified on the basis of dual-energy CT. The imaging quality of the virtual unenhanced images from the corticomedullary and late nephrographic phases was inferior to the image quality of the true unenhanced images (p < 0.01). The mean effective doses for the three-phase protocol and for true unenhanced images were 12.6 and 2.4 mSv, respectively. Our results show that dual-energy CT using iodine overlay techniques and virtual unenhanced images may be useful for characterizing renal masses.

Arterial spin labeling MR imaging for characterisation of renal masses in patients with impaired renal function: initial experience

To retrospectively evaluate the feasibility of arterial spin labeling (ASL) magnetic resonance imaging (MRI) for the assessment of vascularity of renal masses in patients with impaired renal function. Between May 2007 and November 2008, 11/67 consecutive patients referred for MRI evaluation of a renal mass underwent unenhanced ASL-MRI due to moderate-to-severe chronic or acute renal failure. Mean blood flow in vascularised and non-vascularised lesions and the relation between blood flow and final diagnosis of malignancy were correlated with a 2-sided homogeneous variance t-test and the Fisher Exact Test, respectively. A p value <0.05 was considered statistically significant. Seventeen renal lesions were evaluated in 11 patients (8 male; mean age = 70 years) (range 57-86). The median eGFR was 24 mL/min/1.73 m(2) (range 7-39). The average blood flow of 11 renal masses interpreted as ASL-positive (134 +/- 85.7 mL/100 g/min) was higher than that of 6 renal masses interpreted as ASL-negative (20.5 +/- 8.1 mL/100 g/min)(p = 0.015). ASL-positivity correlated with malignancy (n = 3) or epithelial atypia (n = 1) at histopathology or progression at follow up (n = 7). ASL detection of vascularity in renal masses in patients with impaired renal function is feasible and seems to indicate neoplasia although the technique requires further evaluation. Arterial spin labeling may help to characterise renal masses in patients with renal failure Detection of blood flow on ASL in a renal mass supports the presence of a neoplasm Renal masses with high blood-flow levels on ASL seem to progress rapidly.