Deep learning system for malignancy risk prediction in cystic renal lesions: a multicenter study

OBJECTIVES

To develop an interactive, non-invasive artificial intelligence (AI) system for malignancy risk prediction in cystic renal lesions (CRLs).

METHODS

In this retrospective, multicenter diagnostic study, we evaluated 715 patients. An interactive geodesic-based 3D segmentation model was created for CRLs segmentation. A CRLs classification model was developed using spatial encoder temporal decoder (SETD) architecture. The classification model combines a 3D-ResNet50 network for extracting spatial features and a gated recurrent unit (GRU) network for decoding temporal features from multi-phase CT images. We assessed the segmentation model using sensitivity (SEN), specificity (SPE), intersection over union (IOU), and dice similarity (Dice) metrics. The classification model's performance was evaluated using the area under the receiver operator characteristic curve (AUC), accuracy score (ACC), and decision curve analysis (DCA).

RESULTS

From 2012 to 2023, we included 477 CRLs (median age, 57 [IQR: 48-65]; 173 men) in the training cohort, 226 CRLs (median age, 60 [IQR: 52-69]; 77 men) in the validation cohort, and 239 CRLs (median age, 59 [IQR: 53-69]; 95 men) in the testing cohort (external validation cohort 1, cohort 2, and cohort 3). The segmentation model and SETD classifier exhibited excellent performance in both validation (AUC = 0.973, ACC = 0.916, Dice = 0.847, IOU = 0.743, SEN = 0.840, SPE = 1.000) and testing datasets (AUC = 0.998, ACC = 0.988, Dice = 0.861, IOU = 0.762, SEN = 0.876, SPE = 1.000).

CONCLUSION

The AI system demonstrated excellent benign-malignant discriminatory ability across both validation and testing datasets and illustrated improved clinical decision-making utility.

CRITICAL RELEVANCE STATEMENT

In this era when incidental CRLs are prevalent, this interactive, non-invasive AI system will facilitate accurate diagnosis of CRLs, reducing excessive follow-up and overtreatment.

KEY POINTS

The rising prevalence of CRLs necessitates better malignancy prediction strategies. The AI system demonstrated excellent diagnostic performance in identifying malignant CRL. The AI system illustrated improved clinical decision-making utility.

Scientific Status Quo of Small Renal Lesions: Diagnostic Assessment and Radiomics

Background: Small renal masses (SRMs) are defined as contrast-enhanced renal lesions less than or equal to 4 cm in maximal diameter, which can be compatible with stage T1a renal cell carcinomas (RCCs). Currently, 50-61% of all renal tumors are found incidentally. Methods: The characteristics of the lesion influence the choice of the type of management, which include several methods SRM of management, including nephrectomy, partial nephrectomy, ablation, observation, and also stereotactic body radiotherapy. Typical imaging methods available for differentiating benign from malignant renal lesions include ultrasound (US), contrast-enhanced ultrasound (CEUS), computed tomography (CT), and magnetic resonance imaging (MRI). Results: Although ultrasound is the first imaging technique used to detect small renal lesions, it has several limitations. CT is the main and most widely used imaging technique for SRM characterization. The main advantages of MRI compared to CT are the better contrast resolution and tissue characterization, the use of functional imaging sequences, the possibility of performing the examination in patients allergic to iodine-containing contrast medium, and the absence of exposure to ionizing radiation. For a correct evaluation during imaging follow-up, it is necessary to use a reliable method for the assessment of renal lesions, represented by the Bosniak classification system. This classification was initially developed based on contrast-enhanced CT imaging findings, and the 2019 revision proposed the inclusion of MRI features; however, the latest classification has not yet received widespread validation. Conclusions: The use of radiomics in the evaluation of renal masses is an emerging and increasingly central field with several applications such as characterizing renal masses, distinguishing RCC subtypes, monitoring response to targeted therapeutic agents, and prognosis in a metastatic context.

A pilot radiometabolomics integration study for the characterization of renal oncocytic neoplasia

Differentiating benign renal oncocytic tumors and malignant renal cell carcinoma (RCC) on imaging and histopathology is a critical problem that presents an everyday clinical challenge. This manuscript aims to demonstrate a novel methodology integrating metabolomics with radiomics features (RF) to differentiate between benign oncocytic neoplasia and malignant renal tumors. For this purpose, thirty-three renal tumors (14 renal oncocytic tumors and 19 RCC) were prospectively collected and histopathologically characterised. Matrix-assisted laser desorption/ionisation mass spectrometry imaging (MALDI-MSI) was used to extract metabolomics data, while RF were extracted from CT scans of the same tumors. Statistical integration was used to generate multilevel network communities of -omics features. Metabolites and RF critical for the differentiation between the two groups (delta centrality > 0.1) were used for pathway enrichment analysis and machine learning classifier (XGboost) development. Receiver operating characteristics (ROC) curves and areas under the curve (AUC) were used to assess classifier performance. Radiometabolomics analysis demonstrated differential network node configuration between benign and malignant renal tumors. Fourteen nodes (6 RF and 8 metabolites) were crucial in distinguishing between the two groups. The combined radiometabolomics model achieved an AUC of 86.4%, whereas metabolomics-only and radiomics-only classifiers achieved AUC of 72.7% and 68.2%, respectively. Analysis of significant metabolite nodes identified three distinct tumour clusters (malignant, benign, and mixed) and differentially enriched metabolic pathways. In conclusion, radiometabolomics integration has been presented as an approach to evaluate disease entities. In our case study, the method identified RF and metabolites important in differentiating between benign oncocytic neoplasia and malignant renal tumors, highlighting pathways differentially expressed between the two groups. Key metabolites and RF identified by radiometabolomics can be used to improve the identification and differentiation between renal neoplasms.

Virtual Non-Contrast Spectral CT in Renal Masses: Is It Time to Discard Conventional Unenhanced Phase?

Dual-layer Dual-Energy CT (dl-DECT) allows one to create virtual non-contrast (VNC) reconstructions from contrast-enhanced CT scans, with a consequent decrease of the radiation dose. This study aims to assess the reliability of VNC for the diagnostic evaluation of renal masses in comparison with true non-contrast (TNC) images. The study cohort included 100 renal masses in 40 patients who underwent dl-DECT between June and December 2021. Attenuation values and standard deviations were assessed through the drawing of regions of interest on TNC and VNC images reconstructed from corticomedullary and nephrographic phases. A Wilcoxon signed-rank test was performed in order to assess equivalence of data and Spearman's Rho correlation coefficient to evaluate correlations between each parameter. The diagnostic accuracy of VNC was estimated through the performance of receiver operating characteristic (ROC) curve analysis. Differences between attenuation values were, respectively, 74%, 18%, 5% and 3% (TNC-VNC_cort), and 74%, 15%, 9% and 2% (TNC-VNC_neph). The Wilcoxon signed-rank test demonstrated the equivalence of attenuation values between the TNC and VNC images. The diagnostic performance of VNC images in the depiction of kidney simple cysts remains high compared to TNC (VNC_cort-AUC: 0.896; VNC_neph-AUC: 0.901, TNC-AUC: 0.903). In conclusion, quantitative analysis of attenuation values showed a strong agreement between VNC and TNC images in the evaluation of renal masses.

Impact of iodinated contrast media conserving interventions and lessons for the future

INTRODUCTION

A severe shortage of iodinated contrast medium (ICM) has forced radiology departments around the world to implement strategies to reduce contrast utilization. The aim of this study was to evaluate the effect of these interventions on ordering practices and ICM consumption for computed tomography (CT).

METHODS

Our radiology department instituted several ICM-conserving interventions on 13^th May 2022, encompassing: (i) improved triage; (ii) diversion to alternative modalities and non-enhanced CT (NECT); and (iii) reduction in ICM dosing. The impact of these changes on contrast-enhanced CT (CECT) scan numbers, and ICM consumption in the first 28 days post-intervention, was quantified and compared with the preceding 12 months. Sub-analyses of CT pulmonary angiography (CTPA), abdominal and pelvic CECT (CECT AP), and 'Code stroke' CT numbers and the impact on alternative modalities was also performed. The t-test for unpaired samples was used to assess the statistical significance of change.

RESULTS

The average daily number of CECT (all), CECT (inpatient and ED), CTPA, CECT AP, and 'Code stroke' CT scans decreased significantly (P < 0.01), by 58.6%, 68.8%, 74.1%, 88.0%, and 37.5%, respectively. The number of NECT, NECT abdomen and pelvis (NECT AP), and nuclear medicine lung ventilation:perfusion (VQ) scans increased significantly (P < 0.01), by 41.6%, 608.2%, and 165.8%, respectively. ICM consumption also decreased significantly (P < 0.01), by 65.3% (75.8% for ED and inpatient scans).

CONCLUSION

Interventions in CT alone, focused on improving patient triage to CECT while avoiding deferment of any outpatient oncology studies, have achieved an approximately two-thirds reduction in ICM consumption.

Bosniak classification version 2019: a prospective comparison of CT and MRI

OBJECTIVE

To assess the diagnostic accuracy and agreement of CT and MRI in terms of the Bosniak classification version 2019 (BCv2019).

MATERIALS AND METHODS

A prospective multi-institutional study enrolled 63 patients with 67 complicated cystic renal masses (CRMs) discovered during ultrasound examination. All patients underwent CT and MRI scans and histopathology. Three radiologists independently assessed CRMs using BCv2019 and assigned Bosniak class to each CRM using CT and MRI. The final analysis included 60 histopathologically confirmed CRMs (41 were malignant and 19 were benign).

RESULTS

Discordance between CT and MRI findings was noticed in 50% (30/60) CRMs when data were analyzed in terms of the Bosniak classes. Of these, 16 (53.3%) were malignant. Based on consensus reviewing, there was no difference in the sensitivity, specificity, and accuracy of the BCv2019 with MRI and BCv2019 with CT (87.8%; 95% CI = 73.8-95.9% versus 75.6%; 95% CI = 59.7-87.6%; p = 0.09, 84.2%; 95% CI = 60.4-96.6% versus 78.9%; 95% CI = 54.4-93.9%; p = 0.5, and 86.7%; 95% CI = 64.0-86.6% versus 76.7%; 95% CI = 75.4-94.1%; p = 0.1, respectively). The number and thickness of septa and the presence of enhanced nodules accounted for the majority of variations in Bosniak classes between CT and MRI. The inter-reader agreement (IRA) was substantial for determining the Bosniak class in CT and MRI (k = 0.66; 95% CI = 0.54-0.76, k = 0.62; 95% CI = 0.50-0.73, respectively). The inter-modality agreement of the BCv219 between CT and MRI was moderate (κ = 0.58).

CONCLUSION

In terms of BCv2019, CT and MRI are comparable in the classification of CRMs with no significant difference in diagnostic accuracy and reliability.

KEY POINTS

• There is no significant difference in the sensitivity, specificity, and accuracy of the BCv2019 with MRI and BCv2019 with CT. • The number of septa and their thickness and the presence of enhanced nodules accounted for the majority of variations in Bosniak classes between CT and MRI. • The inter-reader agreement was substantial for determining the Bosniak class in CT and MRI and the inter-modality agreement of the BCv219 between CT and MRI was moderate.

Differentiating renal epithelioid angiomyolipoma from clear cell carcinoma: using a radiomics model combined with CT imaging characteristics

PURPOSE

This study aims to assess the computed tomography (CT) findings of renal epithelioid angiomyolipoma (EAML) and develop a radiomics-based model for differentiating EAMLs and clear cell renal cell carcinomas (RCCs).

METHOD

This two-center retrospective study included 28 histologically confirmed EAMLs and 56 size-matched clear cell RCCs with preoperative three-phase kidney CTs. We conducted subjective image analysis to determine the CT parameters that can distinguish EAMLs from clear cell RCCs. Training and test sets were divided by chronological order of CT scans, and radiomics model was built using ten selected features among radiomics and CT features. The diagnostic performance of the radiomics model was compared with that of the three radiologists using the area under the receiver-operating characteristic curve (AUC).

RESULTS

The mean size of the EAMLs was 6.2 ± 5.0 cm. On multivariate analysis, a snowman or ice cream cone tumor shape (OR 16.3; 95% CI 1.7-156.9, P = 0.02) and lower tumor-to-cortex (TOC) enhancement ratio in the corticomedullary phase (OR 33.4; 95% CI 5.7-197, P < 0.001) were significant independent factors for identifying EAMLs. The diagnostic performance of the radiomics model (AUC 0.89) was similar to those of genitourinary radiologists (AUC 0.78 and 0.81, P > 0.05) and superior to that of a third-year resident (AUC 0.63, P = 0.04).

CONCLUSIONS

A snowman or ice cream cone shape and lower TOC ratio were more closely associated with EAMLs than with clear cell RCCs. A CT radiomics model was useful for differentiating EAMLs from clear cell RCCs with better diagnostic performance than an inexperienced radiologist.

Imaging Tips and Tricks in Management of Renal and Urothelial Malignancies

Management of urological malignancies has evolved significantly with continually changing guidelines and treatment options which demand more centralized involvement of radiology than ever before.

Radiologists play a pivotal role in interpreting complex cancer scans and guiding clinical teams toward the best management options in the light of clinical profile. Management of complex uro-oncology cases is often discussed in multidisciplinary meetings which are essential checkpoints to evaluate an overall picture and formulate optimal treatment plans.

The aim of this article is to provide a radiological perspective with practical guidance to fellow radiologists participating in uro-oncology multidisciplinary meetings based on commonly encountered case scenarios, updated guidelines, and cancer pathways.

Crucial imaging tips with regards to renal and urinary tract cancers, upon which therapeutic decisions are made, have been condensed in this article after reviewing several complex cases from urology multidisciplinary meetings and European Association of Urology guidelines.

Outline of various diagnostic and management strategies, key staging features, surveillance guidelines, and, above all, what the onco-urologists want to know from radiologists have been succinctly discussed in this article.

Split-bolus CT urography after microwave ablation of renal cell carcinoma improves image quality and reduces radiation exposure

OBJECTIVE

To compare image quality and radiation dose between single-bolus 2-phase and split-bolus 1-phase CT Urography (CTU) performed immediately after microwave ablation (MWA) of clinically localized T1 (cT1) RCC.

METHODS

Forty-two consecutive patients (30 M, mean age 67.5 ± 9.0) with cT1 RCC were treated with MWA from 7/2013 to 12/2013 at two academic quaternary-care institutions. Renal parenchymal enhancement, collecting system opacification and distention and size-specific dose estimate (SSDE) were quantified and image quality subjectively assessed on single-bolus 2-phase versus split-bolus 1-phase CTU. Kruskal-Wallis and Pearson's Chi-squared tests were performed to assess differences in continuous and categorical variables, respectively. Two-sample T test with equal variances was used to determine differences in quantitative and qualitative image data.

RESULTS

Median tumor diameter was larger [2.9 cm (IQR 1.7-5.3) vs 3.6 cm (IQR 1.7-5.7), p = 0.01] in the split-bolus cohort. Mean abdominal girth (p = 0.20) was similar. Number of antennas used and unenhanced CTs obtained before and during MWA were similar (p = 0.11-0.32). Renal pelvis opacification (2.5 vs 3.5, p < 0.001) and distention (4 mm vs 8 mm, p < 0.001) were improved and renal enhancement (Right: 127 HU vs 177 HU, p = 0.001; Left: 124 HU vs 185 HU, p < 0.001) was higher for the split-bolus CTU. Image quality was superior for split-bolus CTU (3.2 vs 4.0, p = 0.004). Mean SSDE for the split-bolus CTU was significantly lower [163.9 mGy (SD ± 73.9) vs 36.3 mGy (SD ± 7.7), p < 0.001].

CONCLUSION

Split-bolus CTU immediately after MWA of cT1 RCC offers higher image quality, improved opacification/distention of the collecting system and renal parenchymal enhancement at a lower radiation dose.

Accuracy of iodine quantification using dual-energy computed tomography with focus on low concentrations

BACKGROUND

Iodine quantification using dual-energy computed tomography (DECT) is helpful in characterizing, and follow-up after treatment of tumors. Some malignant masses, for instance papillary renal cell carcinomas (p-RCC), are hard to differentiate from benign lesions because of very low contrast enhancement. In these cases, iodine concentrations might be very low, and it is therefore important that iodine quantification is reliable even at low concentrations if this technique is used.

PURPOSE

To examine the accuracy of iodine quantification and to determine whether it is also accurate for low iodine concentrations.

MATERIAL AND METHODS

Twenty-six syringes with different iodine concentrations (0-30 mg I/mL) were scanned in a phantom model using a DECT scanner with two different kilovoltage and image reconstruction settings. Iodine concentrations were measured and compared to known concentration. Absolute and relative errors were calculated.

RESULTS

For concentrations of 1 mg I/mL or higher, there was an excellent correlation between true and measured iodine concentrations for all settings (R = 0.999-1.000; P < 0.001). For concentrations <1.0 mg I/mL, the relative error was greater. Absolute and relative errors were smaller using tube voltages of 80/Sn140 kV than 100/Sn140 kV (P < 0.01). Reconstructions using a 3.0-mm slice thickness had less variance between repeated acquisitions versus 0.6 mm (P < 0.001).

CONCLUSION

Iodine quantification using DECT was in general very accurate, but for concentrations < 1.0 mg I/mL the technique was less reliable. Using a tube voltage with larger spectral separation was more accurate and the result was more reproducible using thicker image reconstructions.

Ultrasound, CT, and MR Imaging for Evaluation of Cystic Renal Masses

Cystic renal masses are often encountered during abdominal imaging. Although most of them are benign simple cysts, some cystic masses have malignant characteristics. The Bosniak classification system provides a useful way to classify cystic masses. The Bosniak classification is based on the results of a well-established computed tomography protocol. Over the past 30 years, the classification system has been refined and improved. This paper reviews the literature on this topic and compares the advantages and disadvantages of different screening and classification methods. Patients will benefit from multimodal diagnosis for lesions that are difficult to classify after a single examination.

Multimodality imaging evaluation of pseudotumors in chronic renal dysfunction: exposing the masquerade!

Focal renal lesions in the background of chronic kidney disease (CKD) present a diagnostic challenge. Contrast administration is usually avoided in such a setting, undermining the usefulness of computed tomography and magnetic resonance imaging. Focal regenerating nodules may occur in the background of CKD and closely mimic renal neoplasms. The aim of the present article was to highlight the salient manifestations of such CKD pseudotumors on different imaging modalities and also to depict the differentiating features from malignancy. Radiologists must be aware of the imaging appearance of this uncommonly talked about entity so as to avoid inadvertent surgery or cause undue anxiety to the patient.

Comparison of Bosniak Classification of cystic renal masses version 2019 assessed by CT and MRI

OBJECTIVE

To compare imaging features in cystic masses imaged with both CT and MRI using Bosniak Classification version 2019 (Bosniak.v2019) and original Bosniak Classification (Bosniak.original).

MATERIALS AND METHODS

This IRB-approved, retrospective, cross-sectional study evaluated sixty-five consecutively identified cystic (≤ 25% enhancing) masses imaged by CT and MRI between 2009 and 2019: 35 with histologic diagnosis and 30 Bosniak.v2019 Class 2 and Class 2F cystic masses verified by an expert radiologist (R1) with minimum 5-year stability. Three radiologists (R2, R3, R4) independently evaluated CT, followed by MRI and assigned Bosniak.original and Bosniak.v2019 class in two sessions separated by ≥ 1 month and assessed the following: septa number, septa/wall thickness, and protrusions. Discrepancies were resolved by consensus with R1.

RESULTS

There was 70.8% agreement (kappa = 0.60, p = 0.0146) in class assigned by CT versus MRI for Bosniak.original and 72.3% agreement (kappa = 0.63, p = 0.006) for Bosniak.v2019. Increased septa number (p < 0.001) and more protrusions (p = 0.034) were identified on MRI, with no differences in septal/wall thickness (p = 0.067, 0.855) or protrusion size (p = 0.467). For both CT and MRI, Bosniak.v2019 improved specificity (79.0% [95% confidence interval 71.0-87.0%] CT, 70% [62.0-77.0%] MRI) compared to Bosniak.original (63.0% [56.0-69.0%] CT, 66.0% [58.0-74.0%] MRI) with maintained sensitivity and higher overall accuracy. Inter-observer agreement was similar-to-slightly higher for Bosniak.v2019 (K = 0.44 CT, 0.39 MRI) versus Bosniak.original (K = 0.35 CT, 0.37 MRI).

CONCLUSION

Class assignment differs in cystic masses evaluated by CT versus MRI for original and v2019 Bosniak Classification with similar-to-slightly higher agreement and improved specificity and higher overall accuracy on both CT and MRI with Bosniak version 2019.

Bosniak classification of cystic renal masses, version 2019: interpretation pitfalls and recommendations to avoid misclassification

The purpose of this review is to describe the potential sources of variability or discrepancy in interpretation of cystic renal masses under the Bosniak v2019 classification system. Strategies to avoid these pitfalls and clinical examples of diagnostic approaches are also presented. Potential pitfalls in the application of Bosniak v2019 are divided into three categories: interpretative, technical, and mass related. An organized, comprehensive review of possible discrepancies in interpreting Bosniak v2019 cystic masses is presented with pictorial examples of difficult clinical cases and proposed solutions. The scheme provided can guide readers to consistent, precise application of the classification system. Radiologists should be aware of the possible sources of misinterpretation of cystic renal masses when applying Bosniak v2019. Knowing which features and types of cystic masses are prone to interpretive errors, in addition to the inherent trade-offs between the CT and MR techniques used to characterize them, can help radiologists avoid these pitfalls.

Imaging Manifestations of Genitourinary Tuberculosis

The genitourinary region is one of the most common sites of extrapulmonary tuberculosis (TB) involvement. The imaging features of genitourinary TB are protean and can mimic other entities, including malignancy, and pose a diagnostic dilemma. Hematogenous seeding and lymphatic spread of mycobacteria from pulmonary, tonsillar, and nodal TB are implicated in the pathogenesis of genitourinary TB. In addition, contiguous extension from the urinary tract and sexual transmission are described as sources of genital TB. Genitourinary TB can be indolent and results in nonspecific signs and symptoms; thus, imaging has a vital role in the working diagnosis for these cases. Classic uroradiologic signs of genitourinary TB are primarily described from the era of intravenous urography and conventional radiography. Now, CT, CT urography, MRI, and US are used in the diagnosis and management. Familiarity with the imaging features of genitourinary TB may help guide the diagnosis and, in turn, lead to timely management. US has a vital role in the evaluation of scrotal and female genital TB. MRI offers superior soft-tissue contrast resolution and excellent depiction of anatomic detail. The various imaging manifestations of genitourinary TB are highlighted. ^©RSNA, 2021.

The role of imaging in the management of renal masses

The wide availability of cross-sectional imaging is responsible for the increased detection of small, usually asymptomatic renal masses. More than 50 % of renal cell carcinomas (RCCs) represent incidental findings on noninvasive imaging. Multimodality imaging, including conventional US, contrast-enhanced US (CEUS), CT and multiparametric MRI (mpMRI) is pivotal in diagnosing and characterizing a renal mass, but also provides information regarding its prognosis, therapeutic management, and follow-up. In this review, imaging data for renal masses that urologists need for accurate treatment planning will be discussed. The role of US, CEUS, CT and mpMRI in the detection and characterization of renal masses, RCC staging and follow-up of surgically treated or untreated localized RCC will be presented. The role of percutaneous image-guided ablation in the management of RCC will be also reviewed.

EFSUMB 2020 Proposal for a Contrast-Enhanced Ultrasound-Adapted Bosniak Cyst Categorization - Position Statement

The well-established Bosniak renal cyst classification is based on contrast-enhanced computed tomography determining the malignant potential of cystic renal lesions. Ultrasound has not been incorporated into this pathway. However, the development of ultrasound contrast agents coupled with the superior resolution of ultrasound makes it possible to redefine the imaging of cystic renal lesions. In this position statement, an EFSUMB Expert Task Force reviews, analyzes, and describes the accumulated knowledge and limitations and presents the current position on the use of ultrasound contrast agents in the evaluation of cystic renal lesions.

CT and MR imaging of acute adrenal disorders

The adrenal glands may be overlooked when evaluating acutely ill patients. Acute adrenal disorders may result from complications of an underlying systemic disease, which may be unsuspected clinically. Various acute adrenal emergencies including trauma, spontaneous hemorrhage, infarction and infection can be diagnosed using CT and MRI; however, in uncertain cases follow-up to resolution of imaging findings or histological sampling may be required for diagnosis.

Routes to diagnosis and missed opportunities in the detection of renal cancer

AIM

To determine the proportion of renal cancers for which incidental detection was the route to diagnosis, the characteristics of tumours identified in this way, and the frequency with which opportunities to make this diagnosis were missed.

MATERIALS AND METHODS

Consecutive patients with renal cancers treated at Royal Cornwall Hospitals NHS Trust (April 2011 and July 2018 inclusive) were identified from the Trust's cancer registry database, and a retrospective review of the imaging and electronic case notes was undertaken. Mann-Whitney U-tests for comparison of patient age and tumour size at diagnosis, and chi-squared tests for comparing cell type distribution and grade were performed. Logistic regression was then used to identify the characteristics of patients in whom a renal tumour was missed initially.

RESULTS

Of 327 patients, 194 (63%) presented incidentally, and 133 (37%) symptomatically. Incidentally detected cancers were found in younger patients, (median of 65 years versus 69 p=0.01) and were smaller at presentation (median of 5.5 versus 7.2 cm, p<0.00001). Thirty-six different reporters missed opportunities to diagnose renal cancer in 50 (16%) patients on 78 occasions, 28 lesions (35%) being missed more than once. Thirty were imaged incompletely; four were visible only on a single image and three on a scout view at magnetic resonance imaging.

CONCLUSION

The commonest route to diagnosis of renal cancer is by incidental detection of a mass. In 16% of patients in whom renal cancer is diagnosed, there is at least one prior examination on which the lesion is visible at an earlier date. The clinical impact of these missed diagnostic opportunities remains uncertain.

Update on MRI of Cystic Renal Masses Including Bosniak Version 2019

Incidental cystic renal masses are common, usually benign, and almost always indolent. Since 1986, the Bosniak classification has been used to express the risk of malignancy in a cystic renal mass detected at imaging. Historically, magnetic resonance imaging (MRI) was not included in that classification. The proposed Bosniak v.2019 update has formally incorporated MRI, included definitions of imaging terms designed to improve interobserver agreement and specificity for malignancy, and incorporated a variety of masses that were incompletely defined or not included in the original classification. For example, at unenhanced MRI, homogeneous masses markedly hyperintense at T₂ -weighted imaging (similar to cerebrospinal fluid) and homogeneous masses markedly hyperintense at fat suppressed T₁ -weighted imaging (approximately ≥2.5 times more intense than adjacent renal parenchyma) are classified as Bosniak II and may be safely ignored, even when they have not been imaged with a complete renal mass MRI protocol. MRI has specific advantages and is recommended to evaluate masses that at computed tomography (CT) 1) have abundant thick or nodular calcifications; 2) are homogeneous, hyperattenuating, ≥3 cm, and nonenhancing; or 3) are heterogeneous and nonenhancing. Although MRI is generally excellent for characterizing cystic renal masses, there are unique weaknesses of MRI that bear consideration. These details and others related to MRI of cystic renal masses are described in this review, with an emphasis on Bosniak v.2019. A website (https://bosniak-calculator.herokuapp.com/) and mobile phone apps named "Bosniak Calculator" have been developed for ease of assignment of Bosniak classes. LEVEL OF EVIDENCE: 5 TECHNICAL EFFICACY STAGE: 3.

Mimics and Pitfalls in Renal Imaging

There are several potential pitfalls that radiologists face when interpreting images of the kidneys. Some result from image acquisition and can arise from the imaging equipment or imaging technique, whereas others are patient related. Another category of pitfalls relates to image interpretation. Some difficulties stem from methods to detect enhancement after contrast administration, whereas others are benign entities that can mimic a renal tumor. Finally, interpretation and diagnosis of fat-containing renal masses may be tricky due to the complexities discerning the pattern of fat within a mass and how that translates to an accurate diagnosis.

Imaging of Renal Infections and Inflammatory Disease

Acute pyelonephritis is a bacterial infection of the renal parenchyma and collecting system. Diagnosis is based on clinical findings of fever, flank pain, and urinary tract infection. Computed tomography findings include renal enlargement with wedge-shaped heterogeneous areas of decreased enhancement, known as a "striated nephrogram." Imaging is primarily used to diagnose complications such as emphysematous pyelonephritis, renal abscess, and pyonephrosis. Chronic pyelonephritis can have varying appearances on imaging ranging from xanthogranulomatous pyelonephritis or, in extreme cases, renal replacement lipomatosis.

Imaging guided percutaneous renal biopsy: do it or not?

Since its first reported application, renal biopsy became an important part of the diagnostic algorithm, considered advantages and risks, to better manage therapeutic options. The biopsy can be performed with different techniques (open, laparoscopic, transjugular, transurethral and percutaneous). Currently, the percutaneous approach is the modality of choice. Percutaneous biopsy can be performed under CT or US guidance, but critical benefits and disadvantages have to be considered. Core needle biopsy is usually preferred to fine-needle aspiration because of the sample quality, usually obtaining multiple cores, especially in heterogeneous tumors. Principal complications are hematuria (1-10%), perinephric hematoma (10-90%), pneumothorax (0,6%), clinically significant pain (1,2%).

Small (< 4 cm) Bosniak renal cysts: association of initial fluid percentage and enhancing solid volume thresholds with future lesion behavior

PURPOSE

Evaluate the fluid percentage (FP) and enhancing solid volume (SV) of small (< 4 cm) Bosniak 2F, 3 and 4 renal lesions and the association with Bosniak category at baseline and follow-up.

METHODS

Hospital database was searched from 1/1/2010 to 8/3/2018 for small (< 4 cm) Bosniak 2F, 3 and 4 lesions studied with initial and follow-up C+CT/MRI. Two radiologists blindly assigned Bosniak categories to first and last available studies. One radiologist performed volumetric analysis of each lesion, calculating the FP and SV. Association with Bosniak category was explored.

RESULTS

121 patients (84:37 M:F) were identified with 136 renal lesions (84, 37 and 15 Bosniak category 2F, 3 and 4) and followed for 1-12.3 years (mean 3.5 years). 87% (73/84) of 2F lesions were downgraded or remained stable. 48% (25/52) of 3/4 lesions were downgraded. Higher FP was associated with a lower Bosniak category (p value = 0.0042). Increase in FP was associated with the probability of being downgraded on follow-up (OR 1.03, p value = 0.0036), while increase in fluid volume of lesion was directly associated with change in overall lesion size among lesions that were downgraded (b-estimate = 0.03, p value = 0.0003). All Bosniak 3/4 lesions with initial SV less than 0.05 cc were downgraded.

CONCLUSION

FP and SV are useful quantitative surrogates for Bosniak category and future behavior, respectively. Growth of small renal lesions by an increase in fluid volume and FP leads to a downgrade in Bosniak category. Initial SV less than 0.05 cc in Bosniak 3/4 lesions suggests possible future downgrade.

Renal abscesses refractory to treatment: Have you thought of tuberculosis?

Urogenital tuberculosis is the commonest extrapulmonary tuberculosis after lymphadenitis, with the kidneys being the most frequently affected organ. The clinical manifestation of renal tuberculosis is frequently nonspecific, leading to many overlooked cases especially in a developed country. Herein, we report a case of renal tuberculosis in a 79-year-old Caucasian lady who presented with recurrent renal abscess refractory to antibiotics.

Level of evidence: Level 5

Imaging Manifestations of Acute and Chronic Renal Infection That Mimics Malignancy: How to Make the Diagnosis Using Computed Tomography and Magnetic Resonance Imaging

PURPOSE

To review the computed tomography and magnetic resonance imaging manifestations of acute and chronic renal infections that may mimic malignancy and to provide useful tips to establish an imaging diagnosis.

CONCLUSION

Acute and chronic bacterial pyelonephritis are usually readily diagnosed clinically and on imaging when the diagnosis is suspected based upon clinical presentation. When unsuspected, focal, extensive or mass-like, acute and chronic bacterial pyelonephritis may mimic infiltrative tumours such as urothelial cell carcinoma (UCC), lymphoma, and metastatic disease. Infection may be suspected when patients are young and otherwise healthy when there is marked associated perinephric changes and in the absence of metastatic adenopathy or disease elsewhere in the abdomen and pelvis. Renal abscesses, from bacterial or atypical microbial agents, can appear as complex cystic renal masses mimicking cystic renal cell carcinoma. Associated inflammatory changes in and around the kidney and local invasion favour infection. Emphysematous pyelonephritis can mimic necrotic or fistulizing tumour; however, infection is more likely and should always be considered first. Xanthogranulomatous pyelonephritis can mimic malignancy when focal or multifocal and in cases without associated renal calculi. Malacoplakia is an inflammatory process that may mimic malignancy and should be considered in patients with chronic infection. Bacillus Calmette-Guerin (BCG)-induced pyelonephritis is rare but can mimic renal malignancy and should be considered in patients presenting with a renal mass when being treated with BCG for urinary bladder UCC.

Comparison of enhancement quantification from virtual unenhanced images to true unenhanced images in multiphase renal Dual-Energy computed tomography: A phantom study

Multiphase computed tomography (CT) exams are a commonly used imaging technique for the diagnosis of renal lesions and involve the acquisition of a true unenhanced (TUE) series followed by one or more postcontrast series. The difference in CT number of the mass in pre- and postcontrast images is used to quantify enhancement, which is an important criterion used for diagnosis. This study sought to assess the feasibility of replacing TUE images with virtual unenhanced (VUE) images derived from Dual-Energy CT datasets in renal CT exams. Eliminating TUE image acquisition could reduce patient dose and improve clinical efficiency. A rapid kVp-switching CT scanner was used to assess enhancement accuracy when using VUE compared to TUE images as the baseline for enhancement calculations across a wide range of clinical scenarios simulated in a phantom study. Three phantoms were constructed to simulate small, medium, and large patients, each with varying lesion size and location. Nonenhancing cystic lesions were simulated using distilled water. Intermediate (10-20 HU [Hounsfield units]) and positively enhancing masses (≥20 HU) were simulated by filling the spherical inserts in each phantom with varied levels of iodinated contrast mixed with a blood surrogate. The results were analyzed using Bayesian hierarchical models. Posterior probabilities were used to classify enhancement measured using VUE compared to TUE images as significantly less, not significantly different, or significantly higher. Enhancement measured using TUE images was considered the ground truth in this study. For simulation of nonenhancing renal lesions, enhancement values were not significantly different when using VUE versus TUE images, with posterior probabilities ranging from 0.23-0.56 across all phantom sizes and an associated specificity of 100%. However, for simulation of intermediate and positively enhancing lesions significant differences were observed, with posterior probabilities < 0.05, indicating significantly lower measured enhancement when using VUE versus TUE images. Positively enhancing masses were categorized accurately, with a sensitivity of 91.2%, when using VUE images as the baseline. For all scenarios where iodine was present, VUE-based enhancement measurements classified lesions with a sensitivity of 43.2%, a specificity of 100%, and an accuracy of 78.1%. Enhancement calculated using VUE images proved to be feasible for classifying nonenhancing and highly enhancing lesions. However, differences in measured enhancement for simulation of intermediately enhancing lesions demonstrated that replacement of TUE with VUE images may not be advisable for renal CT exams.

Update on Gadolinium-Based Contrast Agent-Enhanced Imaging in the Genitourinary System

OBJECTIVE. The purpose of this article is to review gadolinium-based contrast agent (GBCA)-enhanced MRI applications in the genitourinary system. CONCLUSION. Nephrogenic systemic fibrosis is rare or nonexistent with standard dosing of group II GBCAs. Gadolinium retention, cost, and examination times are emerging considerations affecting GBCA use. GBCA is unnecessary to diagnose adrenal adenomas, simple cysts, and some Bosniak category II cysts; however, it is required to determine solid or septal renal mass enhancement. Biparametric prostate MRI requires high-quality and reproducible DWI; therefore, dynamic contrast-enhanced MRI remains valuable in selected prostate MRI examinations.

Diagnostic Accuracy of Attenuation Difference and Iodine Concentration Thresholds at Rapid-Kilovoltage-Switching Dual-Energy CT for Detection of Enhancement in Renal Masses

OBJECTIVE. The objective of our study was to evaluate iodine concentration and attenuation change in Hounsfield unit (ΔHU) thresholds to diagnose enhancement in renal masses at rapid-kilovoltage-switching dual-energy CT (DECT). MATERIALS AND METHODS. We evaluated 30 consecutive histologically confirmed solid renal masses (including nine papillary renal cell carcinomas [RCCs]) and 27 benign cysts (17 simple and 10 hemorrhagic or proteinaceous cysts) with DECT December 2016 and May 2018. A blinded radiologist measured iodine concentration (in milligrams per milliliter) and ΔHU (attenuation on enhanced CT - attenuation on unenhanced CT) using 70-keV corticomedullary (CM) phase virtual monochromatic and 120-kVp nephrographic (NG) phase images. The accuracies of previously described enhancement thresholds were compared by ROC curve analysis. RESULTS. An iodine concentration of ≥ 2.0 mg/mL and an iodine concentration of ≥ 1.2 mg/mL achieved sensitivity, specificity, and the area under the ROC curve (AUC) of 73.3%, 100.0%, and 0.87 and 86.7%, 100.0%, and 0.93, respectively. On 70-keV CM phase images, ΔHU ≥ 20 HU and ΔHU ≥ 15 HU yielded sensitivity, specificity, and AUC of 80.0%, 100.0%, and 0.90 and 90.0%, 100.0%, and 0.95, respectively. The numbers of incorrectly classified papillary RCCs were as follows: iodine concentration of ≥ 2.0 mg/mL, 77.8% (7/9; range, 0.7-1.6 mg/mL); iodine concentration of ≥ 1.2 mg/mL, 44.4% (4/9; range, 0.7-0.9 mg/mL); ΔHU ≥ 20 HU on 70-keV CM phase images, 66.7% (6/9; range, 4-17 HU); and ΔHU ≥ 15 HU on 70-keV DECT images, 33.3% (3/9; 4-12 HU). No cyst pseudoenhancement occurred on DECT. For 120-kVp NG phase DECT, ΔHU ≥ 20 HU and ΔHU ≥ 15 HU yielded sensitivity, specificity, and AUC of 93.3%, 96.3%, and 0.95 and 100.0%, 88.9%, and 0.94, respectively. With ΔHU ≥ 20 HU, 22.2% (2/9) (range, 15-18 HU) of papillary RCCs were misclassified and there was one pseudoenhancing cyst. With ΔHU ≥ 15 HU, no papillary RCCs were misclassified but 11.1% (3/27) of cysts showed pseudoenhancement. Only an iodine concentration of ≥ 2.0 mg/mL showed significantly lower accuracy than other measures (p = 0.031-0.045). CONCLUSION. DECT applied in the CM phase performed best using an iodine concentration of ≥ 1.2 mg/mL or a 70-keV ΔHU ≥ 15 HU; these parameters improved sensitivity for the detection of enhancement in renal masses without instances of cyst pseudoenhancement.

Evaluation of a free-breathing respiratory-triggered (Navigator) 3-D T1-weighted (T1W) gradient recalled echo sequence (LAVA) for detection of enhancement in cystic and solid renal masses

OBJECTIVES

To evaluate free-breathing Navigator-triggered 3-D T1-weighted MRI (NAV-LAVA) compared to breath-hold (BH)-LAVA among cystic and solid renal masses.

MATERIALS AND METHODS

With an IRB waiver, 44 patients with 105 renal masses (71 non-enhancing cysts and 14 cystic and 20 solid renal masses) underwent MRI between 2016 and 2017 where BH-LAVA and NAV-LAVA were performed. Subtraction images were generated for BH-LAVA and NAV-LAVA using pre- and 3-min post-gadolinium-enhanced images and were evaluated by two blinded radiologists for overall image quality, image sharpness, motion artifact, and quality of subtraction (using 5-point Likert scales) and presence/absence of enhancement. Percentage signal intensity change (Δ%SI) = ([SI.post-gadolinium-SI.pre-gadolinium]/SI.pre-gadolinium)*100, was measured on BH-LAVA and NAV-LAVA. Likert scores were compared using Wilcoxon's sign-rank test and accuracy for detection of enhancement compared using receiver operator characteristic (ROC) analysis.

RESULTS

Overall image quality (p = 0.002-0.141), image sharpness (p = 0.002-0.031), and motion artifact were better (p = 0.002) comparing BH-LAVA to NAV-LAVA for both radiologists; however, quality of image subtraction did not differ between groups (p = 0.09-0.14). Sensitivity/specificity/area under ROC curve for enhancement in cystic and solid renal masses using subtraction and %SIΔ were (1) BH-LAVA: 64.7%/98.6%/0.82 (radiologist 1), 61.8%/95.8%/0.79 (radiologist 2), and 70.6%/81.7%/0.76 (%SIΔ) versus 2) NAV-LAVA: 58.8%/95.8%/0.79 (radiologist 1, p = 0.16), 58.8%/88.7%/0.73 (radiologist 2, p = 0.37), and 73.5%/76.1%/0.75 (%SIΔ, p = 0.74).

CONCLUSIONS

NAV-LAVA showed similar quality of subtraction and ability to detect enhancement compared to BH-LAVA in renal masses albeit with lower image quality, image sharpness, and increased motion artifact. NAV-LAVA may be considered in renal MRI for patients where BH is suboptimal.

KEY POINTS

• Free-breathing Navigator (NAV) 3-D subtraction MRI is comparable to breath-hold (BH) images. • Accuracy for subjective and quantitative diagnosis of enhancement in renal masses on NAV 3-D T1W is comparable to BH MRI. • NAV 3-D T1W renal MRI is useful in patients who may not be able to adequately BH.

Contemporary update on imaging of cystic renal masses with histopathological correlation and emphasis on patient management

This article presents an updated review of cystic renal mass imaging. Most cystic renal masses encountered incidentally are benign and can be diagnosed confidently on imaging and require no follow-up. Hyperattenuating masses discovered at unenhanced or single-phase enhanced computed tomography (CT) measuring between 20-70 HU are indeterminate and can be further investigated first by using ultrasound and, then with multi-phase CT or magnetic resonance imaging (MRI); as the majority represent haemorrhagic/proteinaceous cysts (HPCs). Dual-energy CT may improve differentiation between HPCs and masses by suppressing unwanted pseudo-enhancement observed with conventional CT. HPCs can be diagnosed confidently when measuring >70 HU at unenhanced CT or showing markedly increased signal on T1-weighted imaging. Although the Bosniak criteria remains the reference standard for diagnosis and classification of cystic renal masses, histopathological classification and current management has evolved: multilocular cystic renal cell carcinoma (RCC) has been reclassified as a cystic renal neoplasm of low malignant potential, few Bosniak 2F cystic masses progress radiologically during follow-up; RCC with predominantly cystic components are less aggressive than solid RCC; and Bosniak III cystic masses behave non-aggressively. These advances have led to an increase in non-radical management or surveillance of cystic renal masses including Bosniak 3 lesions. Tubulocystic RCC is a newly described entity with distinct imaging characteristics, resembling a pancreatic serous microcystadenoma. Other benign cystic masses including: mixed epithelial stromal tumours (MEST) are now considered in the spectrum of cystic nephroma and angiomyolipoma (AML) with epithelial cysts (AMLEC) resemble a fat-poor AML with cystic components.

Renal cancer at unenhanced CT: imaging features, detection rates, and outcomes

PURPOSE

To describe and quantify the rate of detection of renal cancer on unenhanced CT.

METHODS

This retrospective, HIPAA-compliant study was approved by the Institutional Review Board. Electronic health records for all patients who underwent unenhanced abdominal CT at our institution between 2000 and 2005 were reviewed to identify patients subsequently diagnosed with renal cancer during a follow-up period of up to 12 years. Images were reviewed to determine if the cancer was visible at index (first) unenhanced CT and their findings recorded. Original radiology reports were reviewed to determine whether the renal cancer was reported; Fisher's Exact Test compared imaging features of detected and missed cancers. Clinical outcomes including time until diagnosis and stage at diagnosis were used to assess the potential impact of missed cancers.

RESULTS

Of 15,695 patients, 82 (0.52%) were diagnosed with renal cancer. Of these, 43/82 (52%) cancers were retrospectively detectable on index unenhanced CT. Among retrospectively detectable cancers, 63% (27/43) were originally detected and reported on index CT and 37% (16/43) were missed. Size was the only feature associated with detection; 83% (20/24) of cancers > 3.0 cm were detected versus 37% (7/19) of cancers ≤ 3.0 cm (p = 0.0036). Although none of the 16 missed renal cancers developed metastases between index CT and time of diagnosis (median 33.5 months), 4 (25%) progressed in stage.

CONCLUSIONS

Renal cancer was rare in patients undergoing unenhanced abdominal CT. Over one-third of potentially detectable cancers were missed prospectively. However, missed cancers did not metastasize and infrequently progressed in stage before being diagnosed.

Two in One: Epithelioid angiomyolipoma within a classic kidney angiomyolipoma - a case report

Background

Epithelioid angiomyolipoma is defined as potentially malignant mesenchymal neoplasm, characterized by proliferating epithelioid cells, whereas classic angiomyolipoma, composed of fat, smooth muscle cells and dysmorphic vessels, is defined as a potentially benign. The usual or classic angiomyolipoma is often found incidentally on imaging studies, relatively easily identified due to the presence of fat, in contrast to the epithelioid angiomyolipoma that can pose diagnostic challenges.

Case presentation

We report a 51-year-old female patient in which an ultrasonography examination showed a solid mass close to the right renal pelvis with hypoechoic and hyperechoic areas. A differential diagnosis of atypical sinus lipomatosis, lipoma and a transitional cell carcinoma was postulated whereas in a subsequent computed tomography a classic angiomyolipoma was postulated. A re-examination by contrast enhanced ultrasound revealed a striking perfusion difference of the hypoechoic and hyperechoic areas. The hypoechoic area showed homogenous and prolonged enhancement whereas the hypoechoic area displayed a marked slower contrast material flooding and a relatively rapid wash out. The histological analysis from the biopsy of the hyperechoic area showed a classic angiomyolipoma, whereas the sample of the hypoechoic central portion revealed an epithelioid angiomyolipoma. A nephrectomy was performed because of the malignant potential of the epithelioid variant of the angiomyolipoma.

Conclusions

A solid kidney mass with two sharply defined parts, one-part compatible with a classical angiomyolipoma and the other being suspected of carcinoma, is rare, but also illustrative and instructive. The combination of different imaging modalities in the work up of a solid renal mass facilitated to discriminate benign from malignant areas.

Comparison of MDCT, MRI and MRI with diffusion-weighted imaging in evaluation of focal renal lesions: The defender, challenger, and winner!

Purpose:

To compare the diagnostic performance of multidetector computed tomography (MDCT), magnetic resonance imaging (MRI), and MRI with diffusion-weighted imaging (DWI) in the characterization of focal renal lesions. We also compared MDCT and MRI in the staging of renal cell carcinoma (RCC).

Materials and Methods:

One hundred and twenty adult patients underwent MDCT (40-row and 128-row scanners), MRI (at 1.5 T), and DWI (at b-values of 0 and 500 s/mm²) for characterization of 225 renal lesions. There were 65 malignant neoplasms (44 RCCs), 25 benign neoplasms, 25 abscesses, 45 pseudotumors, 15 hemorrhagic cysts, and 50 benign cysts. A composite gold standard including histology, typical imaging criteria, and follow-up imaging was employed. To determine the diagnostic performance of imaging modalities, area-under-curve (AUC) was calculated by receiver-operating-characteristic analysis and compared. Fisher's exact test was used to compare the diagnostic accuracies and confidence levels with MDCT, MRI, and MRI + DWI. Cross-tabulation was used to assess the precision of MDCT and MRI in RCC staging.

Results:

AUC for MDCT (0.834) and MRI (0.841) in the classification of benign and malignant lesions were within corresponding 95% confidence interval (CI) (P = 0.88) whereas MRI + DWI had significantly better performance (AUC 0.968, P = 0.0002 and 0.0004, respectively). Both CT and MRI had low specificity (66.9% and 68.8%, respectively), which increased substantially with DWI (93.8%) owing to correct diagnosis of pseudotumors. MRI was superior to CT in diagnosing necrotic RCC and hemorrhagic cysts. MRI + DWI had the highest accuracy (94.2%) in assigning the definitive diagnosis and 97.6% lesions were diagnosed with very high confidence, significantly better than CT and MRI. Both CT and MRI had the same accuracy (86.1%) in RCC staging and evaluation of intravascular thrombi.

Conclusions:

Characterization of renal lesions was most accurate with MRI + DWI. The latter is also the most suitable modality in diagnosing pseudotumors and evaluating patients with renal dysfunction. CT and MRI were equivalent in RCC staging.

Characterization of small (<4cm) solid renal masses by computed tomography and magnetic resonance imaging: Current evidence and further development

Diagnosis of renal cell carcinomas (RCC) subtypes on computed tomography (CT) and magnetic resonance imaging (MRI) is clinically important. There is increased evidence that confident imaging diagnosis is now possible while standardization of the protocols is still required. Fat-poor angiomyolipoma show homogeneously increased unenhanced attenuation, homogeneously low signal on T2-weighted MRI and apparent diffusion coefficient (ADC) map, may contain microscopic fat and are classically avidly enhancing. Papillary RCC are also typically hyperattenuating and of low signal on T2-weighted MRI and ADC map; however, their gradual progressive enhancement after intravenous administration of contrast material is a differentiating feature. Clear cell RCC are avidly enhancing and may show intracellular lipid; however, these tumors are heterogeneous and are of characteristically increased signal on T2-weighted MRI. Oncocytomas and chromophobe tumors (collectively oncocytic neoplasms) show intermediate imaging findings on CT and MRI and are the most difficult subtype to characterize accurately; however, both show intermediately increased signal on T2-weighted with more gradual enhancement compared to clear cell RCC. Chromophobe tumors tend to be more homogeneous compared to oncocytomas, which can be heterogeneous, but other described features (e.g. scar, segmental enhancement inversion) overlap considerably between tumors. Tumor grade is another important consideration in small solid renal masses with emerging studies on both CT and MRI suggesting that high grade tumors may be separated from lower grade disease based upon imaging features.

Solid Renal Tumors Isoenhancing to Kidneys on Contrast-Enhanced Sonography: Differentiation From Pseudomasses

OBJECTIVES

To estimate the prevalence of solid renal tumors isoenhancing to kidneys in all vascular phases on contrast-enhanced sonography and to investigate whether they can be differentiated from pseudomasses.

METHODS

A computer search of the databases of 3 institutions identified 31 patients with pseudomasses and 380 patients with solid tumors investigated with contrast-enhanced sonography. Nineteen of 380 (5%) patients had tumors isoenhancing in all phases. Images and clips of these 19 tumors and the 31 pseudomasses were blindly assessed by 2 radiologists. They were asked to differentiate tumors from pseudomasses based on echogenicity, vascular architecture, and the presence of the medulla.

RESULTS

Isoenhancing tumors were clear cell carcinomas (n = 7), angiomyolipomas (n = 3), papillary tumors (n = 3), metastasis (n = 1), and oncocytoma (n = 1). In the 4 nonoperated tumors, the diagnosis was confirmed by progression during the follow-up. There were 3 markedly hyperechoic, 11 mildly hypo/hyperechoic, and 5 isoechoic masses. Most pseudomasses were isoechoic to kidneys (23 of 31), with the medulla identified in 22 of 31 and 15 of 31 by radiologists 1 and 2, respectively. One and 2 pseudomasses were considered tumors by radiologists 1 and 2, respectively. One isoechoic isoenhancing tumor was not identified on contrast-enhanced sonography. Isoenhancing tumors in all phases were differentiated from pseudomasses by combining grayscale and contrast-enhanced sonography (areas under the receiver operating characteristic curve, 0.997 for reader 1; 0.969 for reader 2), with very good inter-reader agreement (weighted κ = 0.81).

CONCLUSIONS

In our retrospective study, 5% of solid renal lesions were isoenhancing to kidneys in all phases. Differentiation from pseudomasses was possible by looking at baseline sonographic features and vascular characteristics.

SEOM clinical guideline for treatment of kidney cancer (2017)

The goal of this article is to provide recommendations about the management of kidney cancer. Based on pathologic and molecular features, several kidney cancer variants were described. Nephron-sparing techniques are the gold standard of localized disease. After a randomized trial, sunitinib could be considered in adjuvant treatment in high-risk patients. Patients with advanced disease constitute a heterogeneous population. Prognostic classification should be considered. Both sunitinib and pazopanib are the standard options for first-line systemic therapy in advanced renal cell carcinoma. Based on the results of two randomized trials, both nivolumab and cabozantinib should be considered the standard for second and further lines of therapy. Response evaluation for present therapies is a challenge.