Renal Masses With Equivocal Enhancement at CT: Characterization With Contrast-Enhanced Ultrasound. AJR Am J Roentgenol. 2015;204:W557-W565. [PMID: 25905962 DOI: 10.2214/ajr.14.13375]

Contrast-enhanced ultrasound of renal masses in the pre-transplant setting: literature review with case highlights

With the rising incidence of chronic kidney disease worldwide, an increasing number of patients are expected to require renal transplantation, which remains the definitive treatment of end stage renal disease. Medical imaging, primarily ultrasonography and contrast-enhanced CT and/or MRI, plays a large role in pre-transplantation assessment, especially in the characterization of lesions within the native kidneys. However, patients with CKD/ESRD often have relative contraindications to CT- and MR-contrast agents, limiting their utilization within this patient population. Contrast-enhanced ultrasound (CEUS), which combines the high temporal and spatial resolution of ultrasonography with intravascular microbubble contrast agents, provides a promising alternative. This review aims to familiarize the reader with the literature regarding the use of CEUS in the evaluation of cystic and solid renal lesions and provide case examples of its use at our institution in the pre-transplant setting.

Multifaceted Imaging of Renal Lesions With an Emphasis on Cross-Sectional Imaging

Introduction Renal lesions are common findings encountered in cross-sectional imaging. Ultrasonography (USG), computed tomography (CT), and magnetic resonance imaging (MRI) are available modalities for evaluating renal lesions. The Bosniak classification system aids in classifying a renal lesion into a particular category based on various imaging characteristics on contrast-enhanced CT (CECT).  Materials and methods The CT report archives were searched for the keyword 'Bosniak' lesions, and six illustrative cases were selected to be included in the review. Results Six cases under Bosniak categories I to IV were included in the review. Operative follow-ups were added in cases where patients underwent surgery. Discussion We have reviewed the imaging features of various renal lesions with cross-sectional modalities, namely CT and MRI, with special emphasis on the Bosniak classification system, including its amendments. Conclusion The Bosniak system is widely used to classify and characterize renal lesions. The authors have presented a scoping review of the features of renal lesions and the Bosniak system.

Associations between contrast-enhanced ultrasound features and WHO/ISUP grade of clear cell renal cell carcinoma: a retrospective study

BACKGROUND

Clear cell renal cell carcinoma (CCRCC) comprises 70%-80% of RCCs. The World Health Organization/International Society of Urology Pathology (WHO/ISUP) classification is the most important prognostic factor for CCRCC. By evaluating the variations of tumor microvascular density, contrast-enhanced ultrasound (CEUS) can noninvasively predict the WHO/ISUP grade of CCRCC, and provide the appropriate treatment plan before clinical operation.

METHODS

In this study, we used CEUS features to analyze 116 CCRCC cases and assess the value of correlation between each indicator and CCRCC WHO/ISUP grading.

RESULTS

When compared to high-grade (WHO/ISUP grade III/IV) tumors, low-grade (WHO/ISUP grade I/II) tumors had reduced relative peak intensity (ΔPI) (P = 0.021), relative area under the curve (ΔAUC) (P = 0.019). However, the frequency of incomplete pseudocapsule (P = 0.021) was significantly higher in high-grade tumors. A cut-off value of mean diameter > 5.5 cm, ΔPI > 304 × 10-3, ΔAUC > 350 × 10-3 allowed identification of high-grade tumors with an area under the curve (AUC) of 74.6%, 71.7%, 70.7%, respectively (95% confidence interval).

CONCLUSIONS

The features of CEUS are effective for differentiating high-grade tumors from low-grade tumors, thus CEUS can be considered an acceptable method for the preoperative assessment of tumor grade.

A narrative review on the application of artificial intelligence in renal ultrasound

Kidney disease is a serious public health problem and various kidney diseases could progress to end-stage renal disease. The many complications of end-stage renal disease. have a significant impact on the physical and mental health of patients. Ultrasound can be the test of choice for evaluating the kidney and perirenal tissue as it is real-time, available and non-radioactive. To overcome substantial interobserver variability in renal ultrasound interpretation, artificial intelligence (AI) has the potential to be a new method to help radiologists make clinical decisions. This review introduces the applications of AI in renal ultrasound, including automatic segmentation of the kidney, measurement of the renal volume, prediction of the kidney function, diagnosis of the kidney diseases. The advantages and disadvantages of the applications will also be presented clinicians to conduct research. Additionally, the challenges and future perspectives of AI are discussed.

The multispeciality approach to the management of localised kidney cancer

Historically, kidney cancer was approached in a siloed single-speciality way, with urological surgeons managing the localised stages of the disease and medical oncologists caring for patients if metastases developed. However, improvements in the management of localised kidney cancer have occurred rapidly over the past two decades with greater understanding of the disease biology, diagnostic options, and innovations in curative treatments. These developments are favourable for patients but provide a substantially more complex landscape for patients and clinicians to navigate, with associated challenging decisions about who to treat, how, and when. As such, the skill sets needed to manage the various aspects of the disease and guide patients appropriately outstrips the capabilities of one particular specialist, and the evolution of a multispeciality approach to the management of kidney cancer is now essential. In this Review, we summarise the current best multispeciality practice for the management of localised kidney cancer and the areas in need of further research and development.

Recent advances in imaging techniques of renal masses

Multiphasic multidetector computed tomography (CT) forms the mainstay for the characterization of renal masses whereas magnetic resonance imaging (MRI) acts as a problem-solving tool in some cases. However, a few of the renal masses remain indeterminate even after evaluation by conventional imaging methods. To overcome the deficiency in current imaging techniques, advanced imaging methods have been devised and are being tested. This review will cover the role of contrast-enhanced ultrasonography, shear wave elastography, dual-energy CT, perfusion CT, MR perfusion, diffusion-weighted MRI, blood oxygen level-dependent MRI, MR spectroscopy, positron emission tomography (PET)/prostate-specific membrane antigen-PET in the characterization of renal masses.

Contrast-Enhanced Ultrasound (CEUS) in the Evaluation of Renal Masses with Histopathological Validation—Results from a Prospective Single-Center Study

Background: To evaluate the diagnostic accuracy of contrast-enhanced ultrasound (CEUS) in characterizing between malignant and benign renal lesions confirmed by histological examination. Methods: Overall, 110 patients, for a total of 118 renal masses previously identified at CT and MRI underwent CEUS. An expert radiologist evaluated morphological, qualitative and quantitative parameters. Acquired data were analyzed to assess the value of each parameter to differentiate between malignant and benign lesions. Results: Histological results of 118 renal masses showed 88 (75%) malignant lesions and 30 (25%) benign lesions. Among morphological features, inhomogeneous echogenicity was the best predictor of malignancy depicting a sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of 76%, 76%, 88% and 57%, respectively. Among qualitative parameters, the most reliable parameter was the presence of pseudo-capsule. Here, sensitivity, specificity, positive PPV and NPV were 85%, 86%, 94% and 71%, respectively. Among quantitative parameters, the most reliable parameters were peak intensity (PI) and the area under the (AUC) with sensitivity, specificity, PPV and NPV values of 94%, 92%, 96% and 87% and 99%, 92%, 97% and 97%, respectively. Finally, the most reliable parameters were combined to distinguish between benign and malignant lesions. The best combination obtained was restricted to CEUS parameters (PI and AUC). Here, sensitivity, specificity, PPV, NPV and accuracy rate were 93%, 100%, 100%, 83% and 93%, respectively. Conclusions: CEUS increases the US accuracy to discriminate between benign and malignant renal lesions.

Novel Imaging Methods for Renal Mass Characterization: A Collaborative Review

CONTEXT

The incidental detection of localized renal masses has been rising steadily, but a significant proportion of these tumors are benign or indolent and, in most cases, do not require treatment. At the present time, a majority of patients with an incidentally detected renal tumor undergo treatment for the presumption of cancer, leading to a significant number of unnecessary surgical interventions that can result in complications including loss of renal function. Thus, there exists a clinical need for improved tools to aid in the pretreatment characterization of renal tumors to inform patient management.

OBJECTIVE

To systematically review the evidence on noninvasive, imaging-based tools for solid renal mass characterization.

EVIDENCE ACQUISITION

The MEDLINE database was systematically searched for relevant studies on novel imaging techniques and interpretative tools for the characterization of solid renal masses, published in the past 10 yr.

EVIDENCE SYNTHESIS

Over the past decade, several novel imaging tools have offered promise for the improved characterization of indeterminate renal masses. Technologies of particular note include multiparametric magnetic resonance imaging of the kidney, molecular imaging with targeted radiopharmaceutical agents, and use of radiomics as well as artificial intelligence to enhance the interpretation of imaging studies. Among these, 99mTc-sestamibi single photon emission computed tomography/computed tomography (CT) for the identification of benign renal oncocytomas and hybrid oncocytic chromophobe tumors, and positron emission tomography/CT imaging with radiolabeled girentuximab for the identification of clear cell renal cell carcinoma, are likely to be closest to implementation in clinical practice.

CONCLUSIONS

A number of novel imaging tools stand poised to aid in the noninvasive characterization of indeterminate renal masses. In the future, these tools may aid in patient management by providing a comprehensive virtual biopsy, complete with information on tumor histology, underlying molecular abnormalities, and ultimately disease prognosis.

PATIENT SUMMARY

Not all renal tumors require treatment, as a significant proportion are either benign or have limited metastatic potential. Several innovative imaging tools have shown promise for their ability to improve the characterization of renal tumors and provide guidance in terms of patient management.

Contrast-enhanced ultrasound of the kidneys: principles and potential applications

Contrast-enhanced ultrasound (CEUS) is an extension and an enhanced form of ultrasound that allows real-time evaluation of the various structures in different vascular phases. The last decade has witnessed a widespread expansion of CEUS applications beyond the liver. It has shown fair potential in kidneys and its diagnostic efficacy is comparable to CT and MRI. Ultrasound is the well-accepted screening modality for renal pathologies, however, it underperforms in the characterization of the renal masses. CEUS can be beneficial in such cases as it can help in the characterization of such incidental masses in the same sitting. It has an excellent safety profile with no risk of radiation or contract-related nephropathy. It can aid in the correct categorization of renal cysts into one of the Bosniak classes and has proven its worth especially in complex cysts or indeterminate renal masses (especially Bosniak Category IIF and III). Few studies also describe its potential role in solid masses and in differentiating benign from malignant masses. Other areas of interest include infections, infarctions, trauma, follow-up of local ablative procedures, and VUR. Through this review, the readers shall get an insight into the various applications of CEUS in kidneys, with imaging examples.

Expanding the Role of Ultrasound for the Characterization of Renal Masses

The incidental detection of renal masses has been steadily rising. As a significant proportion of renal masses that are surgically treated are benign or indolent in nature, there is a clear need for better presurgical characterization of renal masses to minimize unnecessary harm. Ultrasound is a widely available and relatively inexpensive real-time imaging technique, and novel ultrasound-based applications can potentially aid in the non-invasive characterization of renal masses. Evidence acquisition: We performed a narrative review on novel ultrasound-based techniques that can aid in the non-invasive characterization of renal masses. Evidence synthesis: Contrast-enhanced ultrasound (CEUS) adds significant diagnostic value, particularly for cystic renal masses, by improving the characterization of fine septations and small nodules, with a sensitivity and specificity comparable to magnetic resonance imaging (MRI). Additionally, the performance of CEUS for the classification of benign versus malignant renal masses is comparable to that of computed tomography (CT) and MRI, although the imaging features of different tumor subtypes overlap significantly. Ultrasound molecular imaging with targeted contrast agents is being investigated in preclinical research as an addition to CEUS. Elastography for the assessment of tissue stiffness and micro-Doppler imaging for the improved detection of intratumoral blood flow without the need for contrast are both being investigated for the characterization of renal masses, though few studies have been conducted and validation is lacking. Conclusions: Several novel ultrasound-based techniques have been investigated for the non-invasive characterization of renal masses. CEUS has several advantages over traditional grayscale ultrasound, including the improved characterization of cystic renal masses and the potential to differentiate benign from malignant renal masses to some extent. Ultrasound molecular imaging offers promise for serial disease monitoring and the longitudinal assessment of treatment response, though this remains in the preclinical stages of development. While elastography and emerging micro-Doppler techniques have shown some encouraging applications, they are currently not ready for widespread clinical use.

Reasons why referring doctors order renal ultrasound contrast studies

PURPOSE

To determine the indications for CEUS for renal mass evaluation.

METHODS

This retrospective, single-center, IRB-approved, HIPAA compliant study analyzed data from 303 consecutive patients scheduled for a renal CEUS to determine the indications for the examination. A chart review was performed from 05/01/2020 through 05/31/2021 on all patients who received a renal CEUS. The patient demographics were extracted as well as the motivating factor for ordering the examination.

RESULTS

From the 303 patients, 114 were referred because of an indeterminate mass seen on CT and 28 were referred for long-term follow-up of a mass defined as benign or malignant was identified on CT. 9 patients were referred for a CEUS follow-up due to an indeterminate mass on MRI and 6 patients were referred for long-term follow-up of a mass defined as benign or malignant on MRI. 34 patients were referred for follow-up for characterization of a lesion seen on unenhanced ultrasound. 48 patients and 21 patients were referred for long-term follow-up of a previously observed benign or malignant lesion, respectively, seen on CEUS. CEUS was ordered in 21 patients to follow-up a partial nephrectomy and 5 patients for follow-up of a thermal ablation. 7 patients were referred because of a clinical finding.

CONCLUSION

The main reason for a renal CEUS referral is to characterize a mass which could not be characterized on CT or MRI. Another main indication is for long-term follow-up of lesions to decrease radiation dose. Referrals due to inability to receive CT or MRI contrast or renal insufficiency were minor indications.

Use of lumason/sonovue in contrast-enhanced ultrasound of the kidney for characterization of renal masses-a meta-analysis

Indeterminate renal masses are a common clinical problem. CEUS has several advantages to characterize both cystic and solid renal masses including thin slice thickness, excellent background subtraction, and real-time imaging with a high frame rate. The ultrasound contrast agents are not nephrotoxic and can be used in patients with renal insufficiency and obstruction. The Bosniak classification has been developed for use in CT and MRI. A CEUS Bosniak classification has not yet been developed. This meta-analysis reviews the results of renal mass characterization using Lumason/Sonovue in characterizing renal solid and cystic masses. For complex cystic renal lesions (419 patients; 436 lesions), the pooled sensitivity and specificity of CEUS were 95% (95% CI: 91%, 99%) and 84% (95% CI: 77%, 90%) and for solid lesions (331 patients; 341 lesions), the pooled sensitivity and specificity of CEUS were 98% (95% CI: 95%, 100%) and 78% (95% CI: 68%, 88%), respectively.

Contrast-enhanced ultrasound of the kidneys and adrenals in children

Pediatric applications of contrast-enhanced ultrasound (CEUS) are growing. Evaluation of the kidneys and adrenal glands in children using intravenous administration of US contrast agents, however, is still an off-label indication. Pediatric CEUS applications for kidneys are similar to those in adults, including ischemic disorders, pseudo- versus real tumors, indeterminate lesions, complex cystic lesions, complicated pyelonephritis, and abscesses. CEUS applications for evaluation of adrenal glands in children are limited, mainly focusing on the assessment and follow-up of adrenal trauma and the differentiation between an adrenal hemorrhage and a mass. This review addresses the current experience in pediatric CEUS of the kidneys and adrenal glands. By extrapolating the established knowledge for US contrast evaluations in the adult kidney to the pediatric context we can note opportunities for CEUS clinical use in children.

Role of contrast-enhanced ultrasound in assessing indeterminate renal lesions and Bosniak ≥2F complex renal cysts found incidentally on CT or MRI

OBJECTIVE

To investigate the impact of contrast-enhanced ultrasound (CEUS) in reclassifying incidental renal findings categorized as indeterminate lesions (IL) or Bosniak ≥ 2F complex renal cysts (CRC) on CT or MRI.

METHODS

We retrospectively included 44 subjects who underwent CEUS between 2016 and 2019 to assess 48 IL (n = 12) and CRC (n = 36) incidentally found on CT or MRI. CEUS was performed by one radiologist with 10 year of experience with a sulfur hexafluoride-filled microbubble contrast agent. The same radiologist, blinded to clinical information and previous CT/MRIs, retrospectively reviewed CEUS images/videos, categorizing renal findings with Bosniak-derived imaging categories ranging from 0 (indeterminate) to 5 (solid lesion). CEUS-related reclassification rate was calculated (proportion of IL reclassified with an imaging category >0, or CRC reclassified below or above imaging category >2F). Using histological examination or a ≥ 24 months follow-up as the standard of reference, we also estimated per-lesion sensitivity/specificity for malignancy.

RESULTS

CEUS reclassified 24/48 findings (50.0%; 95% C.I. 35.2-64.7), including 12/12 IL (100%; 95% CI 73.5-100) and 12/36 CRC (33.3%; 95% C.I. 18.5-50.9), mostly above category >2F (66.7%). CEUS and CT/MRI showed 96.0% (95%CI 79.7-99.9) vs 44.0% (95%CI 24.4-65.1) sensitivity, and 82.6% (95%CI 61.2-95.1) vs 60.9% (95%CI 38.5-80.3%) specificity.

CONCLUSION

CEUS provided substantial and accurate reclassification of CT/MRI incidental findings.

ADVANCES IN KNOWLEDGE

Previous studies included Bosniak 2 incidental findings, thus possibly underestimating CEUS-induced reclassification rates. Using a more meaningful cut-off (Bosniak ≥2F), problem-solving CEUS was effective as well, with higher reclassification rates for CRC than in literature.

Predictive value of contrast-enhanced ultrasound combined with conventional ultrasound in solid renal parenchymal lesions

OBJECTIVE

This study aimed to develop a model to predict the risk of malignancy in solid renal parenchymal lesions based on the imaging features of combined conventional and contrast-enhanced ultrasound (CEUS).

METHODS

A retrospective review was performed among patients with focal solid renal parenchymal lesions on ultrasound images. Ultrasound features were characterized by two experienced radiologists independently. A multiple logistic regression analysis was performed to determine the most relevant features and to estimate the risk of malignancy. Scoring and counting methods were developed based on the most relevant features. The diagnostic performance was evaluated by the sensitivity, specificity, positive predictive value, negative predictive value and area under the receiver operating characteristic curve (AUC).

RESULTS

A total of 519 renal lesions were included in this study. The conventional ultrasound features of diameter, echogenicity, hypoechoic rim and the CEUS feature of heterogeneity were identified as the most relevant features for prediction of malignancy. The sensitivity and specificity for the logistic regression model, the scoring method and the counting method were 95.3 and 93.4%, 93.8 and 87.8%, 88.8 and 93.9%, respectively. The logistic model had the best performance for diagnosing malignant renal lesions with AUC of 0.978, compared with the scoring method and the counting method with AUCs of 0.958 and 0.965.

CONCLUSION

The combination of contrast-enhanced ultrasound with conventional ultrasound improved the diagnostic performance of solid renal lesions based on the logistic regression model.

ADVANCES IN KNOWLEDGE

In this study, we revealed that the combination of CEUS and conventional ultrasound provided higher accuracy for diagnosing malignant renal tumors.

Using Contrast-Enhanced Ultrasound in Addition to Cross-Sectional Imaging for Indeterminate Renal Cysts May Lead to Overclassification in Bosniak III Category: A Case-Control Study

INTRODUCTION

Indeterminate renal cysts may require several imaging modalities before clinical decision. The aim of this study was to investigate the effect of the imaging modality used to characterize indeterminate renal cysts on the pathological findings after surgical resection.

METHODS

From our institutional database, we identified all patients surgically treated for Bosniak III renal masses between January 2008 and January 2018. All complex renal cysts were characterized with a combination of computed tomography (CT) and/or magnetic resonance imaging (MRI), and/or contrast-enhanced ultrasound (CEUS) and discussed during a multidisciplinary tumor board. Potential association between clinical/radiological characteristics and the pathological findings were investigated, using univariate and multivariate analyses.

RESULTS

Of the 52 renal cystic lesions surgically removed, with a preoperative diagnosis of Bosniak III renal cyst, 19 (37%) were malignant and 33 (63%) were benign. The proportion of malignant lesions decreased from 47% when the renal cyst was characterized with cross-sectional imaging (CT and/or MRI) to 17% when the diagnosis required CEUS in addition to cross-sectional imaging. In multivariate analysis, prior history of renal cell carcinoma was associated with a higher risk of malignancy (p = 0.016) and diagnosis made with CEUS was associated with a lower risk of malignancy (p = 0.040).

CONCLUSION

We found that using CEUS in addition to cross-sectional imaging to characterize indeterminate renal cysts tends to redefine Bosniak III as lesions with a lower risk of malignancy and can lead to overclassification.

Role of Contrast-Enhanced Ultrasound (CEUS) in Native Kidney Pathology: Limits and Fields of Action

Gray scale ultrasound has an important diagnostic role in native kidney disease. Low cost, absence of ionizing radiation and nephrotoxicity, short performance time, and repeatability even at the bedside, are the major advantages of this technique. The introduction of contrast enhancement ultrasound (CEUS) in daily clinical practice has significantly reduced the use of contrast enhancement computed tomography (CECT) and contrast enhancement magnetic resonance (CEMR), especially in patients with renal disease. Although there are many situations in which CECT and CEMRI are primarily indicated, their use may be limited by the administration of the contrast medium, which may involve a risk of renal function impairment, especially in the elderly, and in patients with acute kidney injury (AKI) and moderate to severe chronic kidney disease (CKD). In these cases, CEUS can be a valid diagnostic choice. To date, numerous publications have highlighted the role of CEUS in the study of parenchymal micro-vascularization and renal pathology by full integration with second level imaging methods (CECT and CEMRI) both in patients with normal renal function and with diseased kidneys. The aim of this review is to offer an updated overview of the limitations and potential applications of CEUS in native kidney disease.

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.

Evaluation of Cystic and Solid Renal Lesions with Contrast-Enhanced Ultrasound: A Retrospective Study

Purpose Renal lesions are frequent random findings on CT, MRI, and conventional ultrasound. Since they are usually found accidentally, the respective examinations have not been performed optimally to provide a conclusive diagnosis, making additional multiphase contrast-enhanced examinations necessary. The aim of the study is to correlate CEUS findings with the final diagnosis and to determine whether it is a suitable method for the conclusive characterization of undetermined renal lesions. Materials and Methods All CEUS examinations of focal renal lesions performed at our institute between 2007 and 2014 were retrospectively examined. 437 patients with a total of 491 lesions and 543 examinations were included. 54 patients had bilateral lesions. One patient had three lesions in one kidney. Histology was available in 49 cases and follow-ups in 124 cases. The sensitivity, specificity, positive and negative predictive value as well as positive and negative likelihood ratios were calculated. Results There were 54 malignant and 437 benign lesions. The sensitivity and specificity were 0.981/0.954 overall, 1.000/0.956 for cystic lesions, 0.977/0.906 for solid lesions, and 0.971/0.071 for the histologically confirmed lesions. Bosniak classification was consistent in 289 of 301 lesions (96%). Only 12 lesions (3.9%) were falsely assessed as malignant. Conclusion CEUS is an appropriate method for the clarification of undetermined renal lesions. The characterization of cystic lesions according to Bosniak is adequately possible, especially for potentially malignant lesions (types III and IV).

Structured Reporting in the Characterization of Renal Cysts by Contrast-Enhanced Ultrasound (CEUS) Using the Bosniak Classification System-Improvement of Report Quality and Interdisciplinary Communication

BACKGROUND

This study aims to evaluate the potential benefits of structured reporting (SR) compared to conventional free-text reporting (FTR) in contrast-enhanced ultrasound (CEUS) of cystic renal lesions, based on the Bosniak classification.

METHODS

Fifty patients with cystic renal lesions who underwent CEUS were included in this single-center study. FTR created in clinical routine were compared to SR retrospectively generated by using a structured reporting template. Two experienced urologists evaluated the reports regarding integrity, effort for information extraction, linguistic quality, and overall quality.

RESULTS

The required information could easily be extracted by the reviewers in 100% of SR vs. 82% of FTR (p < 0.001). The reviewers trusted the information given by SR significantly more with a mean of 5.99 vs. 5.52 for FTR (p < 0.001). SR significantly improved the linguistic quality (6.0 for SR vs. 5.68 for FTR (p < 0.001)) and the overall report quality (5.98 for SR vs. 5.58 for FTR (p < 0.001)).

CONCLUSIONS

SR significantly increases the quality of radiologic reports in CEUS examinations of cystic renal lesions compared to conventional FTR and represents a promising approach to facilitate interdisciplinary communication in the future.

Contrast-enhanced ultrasound after successful cryoablation of benign and malignant renal tumours: how long does tumour enhancement persist?

INTRODUCTION

To investigate how long successfully ablated tumours take to become completely avascular at CEUS after cryoablation.

METHODS

Ninety-five patients had percutaneous cryoablation of 103 renal tumours investigated at CEUS on post-operative day one. If the lesion was avascular, a contrast-CT/MR was scheduled six months after the procedure, while CEUS was repeated if the lesion still displayed enhancement, until the disappearance of intralesional vascularity. Technical success was defined when the tumour was covered completely by the ablation zone. Technique efficacy was assessed at six months of follow-up.

RESULTS

Technical efficacy was obtained for 101/103 cryoablations, 56% of which (57/101) were avascular on post-operative day one. After one week, two weeks, one month 83%, 91% and 100% of these 101 lesions, respectively, were avascular. Two tumours were unsuccessfully treated. They displayed persistent intralesional vascularity at CEUS one month after the procedure.

CONCLUSIONS

After cryoablation, obtaining CEUS before one month may be misleading. When technical efficacy is obtained, disappearance of intralesional enhancement is observed within two weeks in the majority of cases (91%), but can persist until one month. Identification of tumour enhancement after one month may be concerning for residual viable tumour.

Contrast-enhanced ultrasound (CEUS) imaging for active surveillance of small renal masses

PURPOSE

To assess the safety and efficacy of contrast-enhanced ultrasound (CEUS) imaging for monitoring small (< 4 cm) renal masses (SRM) in patients undergoing active surveillance (AS).

METHODS

We retrospectively selected all consecutive patients with SRMs who underwent AS for at least 6 months at our Institution between January 2014 and December 2018. CEUS imaging was performed by two experienced genitourinary radiologists at established time points. The accuracy of CEUS for monitoring SRM size was compared with that of CT scan. For solid SRMs, four enhancement patterns (EP) were recorded. Radiological progression was defined as SRM growth rate ≥ 5 mm/year.

RESULTS

Overall, 158/1049 (15.1%) patients with SRMs underwent AS. At a median follow-up of 25 months (IQR 13-39), no patient died due to renal cell carcinoma (RCC). No patients experienced CEUS-related adverse events. There was a large variability in the pattern of growth of SRMs (overall median growth rate: 0.40 mm/year), with 9.5% of SRMs showing radiological progression. The median SRM size was comparable between CEUS and CT scan examinations at all time points. The vast majority (92.7%) of SRMs did not show a change in their EP over time; and there was no association between the SRM's EP and radiological progression or SRM size. Overall, 43 (27.2%) patients underwent delayed intervention (DI); median SRM size, and median growth rate were significantly higher in these patients as compared to those continuing AS.

CONCLUSION

In experienced hands, CEUS is a safe and effective strategy for active monitoring of SRMs in well-selected patients undergoing AS.

Imaging Characterization of Renal Masses

The detection of a renal mass is a relatively frequent occurrence in the daily practice of any Radiology Department. The diagnostic approaches depend on whether the lesion is cystic or solid. Cystic lesions can be managed using the Bosniak classification, while management of solid lesions depends on whether the lesion is well-defined or infiltrative. The approach to well-defined lesions focuses mainly on the differentiation between renal cancer and benign tumors such as angiomyolipoma (AML) and oncocytoma. Differential diagnosis of infiltrative lesions is wider, including primary and secondary malignancies and inflammatory disease, and knowledge of the patient history is essential. Radiologists may establish a possible differential diagnosis based on the imaging features of the renal masses and the clinical history. The aim of this review is to present the contribution of the different imaging techniques and image guided biopsies in the diagnostic management of cystic and solid renal lesions.

Contrast-Enhanced Ultrasound (CEUS) for the Evaluation of Bosniak III Complex Renal Cystic Lesions-A 10-Year Specialized European Single-Center Experience with Histopathological Validation

Background and objectives: The aim of the present retrospective single-center study is to evaluate the diagnostic performance of contrast-enhanced ultrasound (CEUS) for assessing Bosniak III complex renal cystic lesions with histopathological validation. Materials and Methods: 49 patients with CEUS-categorized Bosniak III renal cystic lesions were included in this retrospective study. All patients underwent native B-mode, Color Doppler, contrast-enhanced ultrasound (CEUS) between 2010-2020. Eight and five patients underwent computed tomography (CT) and magnetic resonance imaging (MRI), respectively. Twenty-nine underwent (partial) nephrectomy allowing for histopathological analysis. The applied contrast agent for CEUS was a second-generation blood pool agent. Ultrasonography examinations were performed and interpreted by a single experienced radiologist with more than 15 years of experience (EFSUMB Level 3). Results: CEUS examinations were successfully performed in all included patients without registering any adverse effects. The malignancy rate of CEUS-categorized Bosniak III renal lesions accounted for 66%. Initially, cystic complexity was visualized in native B-mode. In none of the renal lesions hypervascularization was detected in Color Doppler. CEUS allowed for detection of contrast enhancement patterns in all included Bosniak III renal lesions. Delayed wash-out could be detected in 6/29 renal lesions. In two cases of histopathologically confirmed clear-cell RCC, appropriate up-grading from Bosniak IIF to III was achieved by CEUS. Conclusions: CEUS depicts a promising imaging modality for the precise diagnostic workup and stratification of renal cystic lesions according to the Bosniak classification system, thereby helping guidance of adequate clinical management in the future.

Superb Microvascular Imaging Improves Detection of Vascularity in Indeterminate Renal Masses

OBJECTIVES

Vascular assessment of indeterminate renal masses (iRMs) remains a crucial element of diagnostic imaging, as the presence of blood flow within renal lesions suggests malignancy. We compared the utility of Superb Microvascular Imaging (SMI; Canon Medical Systems, Tustin, CA), a novel Doppler technique, to standard color Doppler imaging (CDI) and power Doppler imaging (PDI) for the detection of vascularity within iRMs.

METHODS

Patients undergoing contrast-enhanced ultrasound (CEUS) evaluations for iRMs first underwent a renal ultrasound examination with the following modes: CDI, PDI, color Superb Microvascular Imaging (cSMI), and monochrome Superb Microvascular Imaging (mSMI), using an Aplio i800 scanner with an i8CX1 transducer (Canon Medical Systems). After image randomization, each mode was assessed for iRM vascularity by 4 blinded readers on a diagnostic confidence scale of 1 to 5 (5 = most confident). The results were compared to CEUS as the reference standard.

RESULTS

Forty-one patients with 50 lesions met inclusion criteria. Relative to the other 3 modalities, mSMI had the highest sensitivity (63.3%), whereas cSMI had the highest specificity (62.1%). Both cSMI and mSMI also had the highest diagnostic accuracy (0.678 and 0.680, respectively; both P < 0.001) compared to CDI (0.568) and PDI (0.555). Although the reader-reported confidence interval of mSMI (mean ± SD, 3.6 ± 1.1) was significantly lower than CDI (4.1 ± 1.0) and PDI (4.0 ± 1.0; P < 0.001), the confidence level of cSMI (4.1 ± 0.9) was not (P > 0.173).

CONCLUSIONS

Preliminary data suggest that SMI is a potentially useful modality in detecting microvasculature in iRMs compared to standard Doppler techniques. Future studies should aim to compare the efficacy of both SMI and CEUS and to assess the ability of SMI to characterize malignancy in iRMs.

Contrast-Enhanced Ultrasound (CEUS) for Follow-Up of Bosniak 2F Complex Renal Cystic Lesions-A 12-Year Retrospective Study in a Specialized European Center

Bosniak 2F renal cystic lesions feature morphologic characteristics between Bosniak I and III categories, the majority of which remain benign. However, a minor part of Bosniak 2F lesions may progress to malignancy. The purpose of this study was to assess Bosniak 2F cystic lesions during follow-up examinations by CEUS. One-hundred-and-twelve out of 364 patients with Bosniak 2F lesions underwent follow-up CEUS examinations between February 2008 and February 2020. Twelve out of 364 patients underwent renal surgery without follow-up CEUS. The progression rate of Bosniak 2F renal lesions detected by CEUS accounted for 7.1% (8/112 patients) after a mean of 12.9 months. The first follow-up CEUS revealed 75% of progressions (6/8), the remaining 25% (2/8) of progressions were detected during second follow-up CEUS. Underlying clear-cell renal cell carcinoma was histopathologically validated in 5/8 progressive complex cystic renal lesions. Stable sonomorphologic features were observed in 92.1% (104/112 patients). CEUS depicts a promising diagnostic imaging modality in the diagnostic work-up and follow-up of complex renal cystic lesions at higher spatial and temporal resolutions than CT or MRI. Its excellent safety profile, its easy and repeatable accessibility, and low financial costs render CEUS an attractive and powerful alternative imaging tool for monitoring complex renal cystic lesions.

Multi-energy computed tomography and material quantification: Current barriers and opportunities for advancement

Computed tomography (CT) technology has rapidly evolved since its introduction in the 1970s. It is a highly important diagnostic tool for clinicians as demonstrated by the significant increase in utilization over several decades. However, much of the effort to develop and advance CT applications has been focused on improving visual sensitivity and reducing radiation dose. In comparison to these areas, improvements in quantitative CT have lagged behind. While this could be a consequence of the technological limitations of conventional CT, advanced dual-energy CT (DECT) and photon-counting detector CT (PCD-CT) offer new opportunities for quantitation. Routine use of DECT is becoming more widely available and PCD-CT is rapidly developing. This review covers efforts to address an unmet need for improved quantitative imaging to better characterize disease, identify biomarkers, and evaluate therapeutic response, with an emphasis on multi-energy CT applications. The review will primarily discuss applications that have utilized quantitative metrics using both conventional and DECT, such as bone mineral density measurement, evaluation of renal lesions, and diagnosis of fatty liver disease. Other topics that will be discussed include efforts to improve quantitative CT volumetry and radiomics. Finally, we will address the use of quantitative CT to enhance image-guided techniques for surgery, radiotherapy and interventions and provide unique opportunities for development of new contrast agents.

Active surveillance of small renal masses

Most renal masses incidentally detected by cross-sectional images are benign, being mainly cysts, and if they are malignant, they are indolent in nature with limited metastatic potential. Enhanced renal masses less than 4 cm in size are known as small renal masses (SRMs), and their growth rate (GR) and the possibility of developing metastasis are extremely low. Delayed intervention of SRMs by closed and routine imaging follow-up known as active surveillance (AS) is now an option according to urological guidelines. Radiologists have a key position in AS management of SRMs even unifocal and multifocal (sporadic or associated with genetic syndromes) and also in the follow-up of complex renal cysts by Bosniak cyst classification system. Radiologists play a key role in the AS of both unifocal and multifocal (sporadic or associated with genetic syndromes) SRMs as well as in the follow-up of complex renal cysts using the Bosniak cyst classification system. Indeed, radiologists must determine which patients with SRMs or complex renal cysts can be included in AS, establish the follow-up radiological test algorithm to be used in different scenarios, perform measurements in follow-up tests, and decide when AS should be discontinued. The purpose of this article is to review the indications and management of AS in SRMs, especially focused on specific scenarios, such as complex renal cysts and multifocal renal tumors (sporadic or hereditary). In this work, the authors aimed to provide a thorough review of imaging in the context of active surveillance of renal masses.

Contrast enhanced ultrasound: A review of radiology applications

Ultrasound contrast agents have been used for decades in Europe and Asia for cardiac and abdominal imaging and are now being more commonly utilized in the United States for radiology applications. Our article reviews the basics of contrast-enhanced ultrasound including how the contrast agent works, advantages and disadvantages, as well as pearls and pitfalls to help the radiologist efficiently integrate this technology into day-to-day clinical practice. We also discuss the diagnosis of focal hepatic lesions as well as off-label applications such as evaluation of renal masses.

Usefulness of contrast-enhanced ultrasonography for diagnosis of renal cell carcinoma in dialysis patients: Comparison with computed tomography

AIMS

To investigate the usefulness of contrast-enhanced ultrasonography for diagnosing renal cell carcinoma (RCC) in dialysis patients.

MATERIAL AND METHODS

Of 1301 dialysis patients who underwent abdominal computed tomography (CT) between January 2012 and March 2017, 19 were suspected to have solid renal lesions; of these patients, 18 gave consent for and underwent contrast-enhanced ultrasonography with perflubutane in addition to CT; 13 underwent dynamic contrast-enhanced CT, and 5, who could not be administered iodinated contrast media, underwent unenhanced CT. The final diagnoses were based on histopathological findings or the presence/absence of enlargement of the lesion during follow-up.

RESULTS

Of the 19 lesions in 18 patients, 14 were diagnosed as RCC and 5 as benign cysts. CT facilitated accurate diagnosis in 10/19 lesions (52.6%) with obvious enhancement (≥20 Hounsfield units [HU]), while definitive diagnosis by CT was difficult in 9 lesions: 2 lesions showed ambiguous enhancement (10-20 HU), 1 lesion was an inflammatory cyst with obvious enhancement, and 6 lesions were assessed by unenhanced CT. Compared with CT, contrast-enhanced ultrasonography allowed more accurate diagnosis (McNemar test, P = .02) in 17/19 lesions (89.5%, 14 RCC and 3 cysts; including all lesions assessed by unenhanced CT and 2 with ambiguous enhancement on CT), with 1 false-positive (inflammatory cyst with hyper-enhancement) and 1 false-negative result due to deep location of the lesion.

CONCLUSIONS

Contrast-enhanced ultrasonography was useful for the diagnosis of RCC in dialysis patients with suspected solid renal lesions especially when contrast enhancement was not obvious on CT or contrast-enhanced CT could not be performed.

Application of contrast-enhanced ultrasound for scar pregnancy cases misdiagnosed as other diseases

OBJECTIVE

To demonstrate the feasibility of utilizing contrast-enhanced ultrasound (CEUS) in scar pregnancies misdiagnosed by transvaginal ultrasound (TVS).

METHODS

CEUS was performed in three patients with clinically suspected abnormal pregnancy, and the diagnosis were inconclusive by TVS. Clinical manifestations and features of TVS and CEUS in these cases were analyzed.

RESULTS

Three cases included an intramural pregnancy (IMP) after hysteromyomectomy, and two mass-based cesarean scar pregnancy (CSP), the mass was caused by curettage and spontaneous abortion, respectively. In all these cases, early enhancement with high intensity was observed by CEUS at the site of implantation. Moreover, prominently enhanced signal was detected inside the mass, with or without peritrophoblastic ring. No enhancement was detected in clots or masses after effective treatment.

CONCLUSION

CEUS can be used as a supplementary method to diagnose scar pregnancy and evaluate the treatment efficacy, especially in cases with ambiguous results by TVS.

Comparative Diagnostic Accuracy of Contrast-Enhanced Ultrasound and Shear Wave Elastography in Differentiating Benign and Malignant Lesions: A Network Meta-Analysis

Background: We performed a network meta-analysis to compare the diagnostic accuracy of contrast-enhanced ultrasound (CEUS) and shear wave elastography (SWE) in differentiating benign and malignant lesions in different body sites.

Methods: A computerized literature search of Medline, Embase, SCOPUS, and Web of Science was performed using relevant keywords. Following data extraction, we calculated sensitivity, specificity, positive likelihood ratio (LR), negative LR, and diagnostic odds ratio (DOR) for CEUS, and SWE compared to histopathology as a reference standard. Statistical analyses were conducted by MetaDiSc (version 1.4) and R software (version 3.4.3).

Results: One hundred and fourteen studies (15,926 patients) were pooled in the final analyses. Network meta-analysis showed that CEUS had significantly higher DOR than SWE (DOR = 27.14, 95%CI [2.30, 51.97]) in breast cancer detection. However, there were no significant differences between CEUS and SWE in hepatic (DOR = −6.67, 95%CI [−15.08, 1.74]) and thyroid cancer detection (DOR = 3.79, 95%CI [−3.10, 10.68]). Interestingly, ranking analysis showed that CEUS achieved higher DOR in detecting breast and thyroid cancer, while SWE achieved higher DOR in detecting hepatic cancer. The overall DOR for CEUS in detecting renal cancer was 53.44, 95%CI [29.89, 95.56] with an AUROC of 0.95, while the overall DOR for SWE in detecting prostate cancer was 25.35, 95%CI [7.15, 89.89] with an AUROC of 0.89.

Conclusion: Both diagnostic tests showed relatively high sensitivity and specificity in detecting malignant tumors in different organs. Network meta-analysis showed that CEUS had higher diagnostic accuracy than SWE in detecting breast and thyroid cancer, while SWE had higher accuracy in detecting hepatic cancer. However, the results were not statistically significant in hepatic and thyroid malignancies. Further head-to-head comparisons are needed to confirm the optimal imaging technique to differentiate each cancer type.

A Pilot Study on Diagnostic Performance of Contrast-Enhanced Ultrasonography for Detection of Early Cervical Cancer

In this cohort study of 49 women with all stages of cervical cancer and 21 healthy controls, we compared contrast-enhanced ultrasonography (CEUS) filling pattern and semi-quantitative parameters in the two groups. Participants were examined with conventional grayscale and power Doppler ultrasound (US) followed by CEUS, using a 2.5 mL bolus of intravenous contrast agent. CEUS video clips were analyzed with regard to contrast distribution (focal or global) and semi-quantitative parameters. Focal contrast distribution was found in 3% (1/32) of the women with no tumor versus 89% (34/38) of women with histologically detectable tumor. A semi-quantitative analysis showed that the amount of contrast over a period of the whole tumor (area under the curve [AUC[ 0.92, 95% confidence interval [CI] 0.87-1.0), and the maximal intensity area (AUC 0.94, 95% CI 0.84-1.0) could accurately distinguish tumors from healthy tissue. In conclusion, the CEUS parameters differ significantly between tumors and healthy cervical tissue.

Contrast-enhanced ultrasound for characterizing renal masses

On cross-sectional imaging studies performed for other indications, incidental discovery of renal lesions is not uncommon. In daily use, grey-scale ultrasonography (US) and conventional Doppler modes are often the modality of choice for the initial assessment. While simple cysts are fully characterized with US, other lesions require further characterization, which is traditionally obtained by multiphase imaging, such as contrast-enhanced CT and MRI. Contrast-enhanced ultrasound (CEUS) has become a powerful additional tool for imaging renal lesions. With its lack of nephrotoxicity, the absence of ionizing radiation, and the ability to evaluate the enhancement pattern of renal lesions quickly and in real- time, CEUS has unique advantages over traditional modes. Established applications are differentiation between solid tumours, pseudolesions, and complex cysts; characterization of complex cysts with different malignant potential, and evaluation of tumor ablation. Microbubble contrast agents are safe. Adverse reactions are rare. This article provides an overview of the current clinical applications of CEUS in characterizing renal masses, discussing advantages and limitations. The aim is to provide the framework for sonologists to make informed decisions regarding this emerging imaging test in appropriate circumstances.

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.

Perioperative Acute Kidney Injury: Risk Factors and Predictive Strategies

Acute kidney injury (AKI) is a common complication in surgical patients and is associated with increases in mortality, an increased risk for chronic kidney disease and hemodialysis after discharge, and increased cost. Better understanding of the risk factors that contribute to perioperative AKI has led to improved AKI prediction and will eventually lead to improved prevention of AKI, mitigation of injury when AKI occurs, and enhanced recovery in patients who sustain AKI. The development of advanced clinical prediction scores for AKI, new imaging techniques, and novel biomarkers for early detection of AKI provides new tools toward these ends.

Contrast-Enhanced Ultrasound Classification of Previously Indeterminate Renal Lesions

OBJECTIVES

To determine the utility of contrast-enhanced ultrasound (US) for characterizing renal lesions that were indeterminate on prior imaging.

METHODS

This Institutional Review Board-approved retrospective diagnostic accuracy study evaluated all patients who underwent renal contrast-enhanced US examinations from 2006 to 2015 at our tertiary care hospital. We compared the number of lesions definitively characterized by contrast-enhanced US with the indeterminate lesions by prior imaging. The accuracy of contrast-enhanced US was compared with the final diagnosis by histologic examination and follow-up (mean, 3.63 years). Accuracy and agreement estimates were compared with the exact binomial distribution to assess statistical significance.

RESULTS

A total of 134 lesions were evaluated with contrast-enhanced US, and 106 were indeterminate by preceding computed tomography, magnetic resonance imaging, or US. Only the largest lesion per patient was included in analysis. A total of 95.7% (90 of 94) of the previously indeterminate lesions were successfully classified with contrast-enhanced US. The sensitivity was 100% (20 of 20; 95% confidence interval [CI], 83%-100%; P < .0001); specificity was 85.7% (18 of 21; 95% CI, 62%-97%; P = .0026); positive predictive value was 87.0% (20 of 23; 95% CI, 66%-97%; P = .0005); negative predictive value was 100% (18 of 18; 95% CI, 81%-100%; P < .001); and accuracy was 90.2% (37 of 41; 95% CI, 80%-98%; P < .0001).

CONCLUSIONS

Contrast-enhanced US has a high likelihood of definitively classifying a renal lesion that is indeterminate by computed tomography, magnetic resonance imaging, or conventional US.

Diagnostic accuracy of contrast-enhanced ultrasound for characterization of kidney lesions in patients with and without chronic kidney disease

BACKGROUND

Patients with chronic kidney disease are at increased risk of cystic kidney disease that requires imaging monitoring in many cases. However, these same patients often have contraindications to contrast-enhanced computed tomography and magnetic resonance imaging. This study evaluates the accuracy of contrast-enhanced ultrasound (CEUS), which is safe for patients with chronic kidney disease, for the characterization of kidney lesions in patients with and without chronic kidney disease.

METHODS

We performed CEUS on 44 patients, both with and without chronic kidney disease, with indeterminate or suspicious kidney lesions (both cystic and solid). Two masked radiologists categorized lesions using CEUS images according to contrast-enhanced ultrasound adapted criteria. CEUS designation was compared to histology or follow-up imaging in cases without available tissue in all patients and the subset with chronic kidney disease to determine sensitivity, specificity and overall accuracy.

RESULTS

Across all patients, CEUS had a sensitivity of 96% (95% CI: 84%, 99%) and specificity of 50% (95% CI: 32%, 68%) for detecting malignancy. Among patients with chronic kidney disease, CEUS sensitivity was 90% (95% CI: 56%, 98%), and specificity was 55% (95% CI: 36%, 73%).

CONCLUSIONS

CEUS has high sensitivity for identifying malignancy of kidney lesions. However, because specificity is low, modifications to the classification scheme for contrast-enhanced ultrasound could be considered as a way to improve contrast-enhanced ultrasound specificity and thus overall performance. Due to its sensitivity, among patients with chronic kidney disease or other contrast contraindications, CEUS has potential as an imaging test to rule out malignancy.

TRIAL REGISTRATION

This trial was registered in clinicaltrials.gov, NCT01751529 .

CT imaging of solid renal masses: pitfalls and solutions

Computed tomography (CT) remains the first-line imaging test for the characterisation of renal masses; however, CT has inherent limitations, which if unrecognised, may result in errors. The purpose of this manuscript is to present 10 pitfalls in the CT evaluation of solid renal masses. Thin section non-contrast enhanced CT (NECT) is required to confirm the presence of macroscopic fat and diagnosis of angiomyolipoma (AML). Renal cell carcinoma (RCC) can mimic renal cysts at NECT when measuring <20 HU, but are usually heterogeneous with irregular margins. Haemorrhagic cysts (HC) may simulate solid lesions at NECT; however, a homogeneous lesion measuring >70 HU is essentially diagnostic of HC. Homogeneous lesions measuring 20-70 HU at NECT or >20 HU at contrast-enhanced (CE) CT, are indeterminate, requiring further evaluation. Dual-energy CT (DECT) can accurately characterise these lesions at baseline through virtual NECT, iodine overlay images, or quantitative iodine concentration analysis without recalling the patient. A minority of hypo-enhancing renal masses (most commonly papillary RCC) show indeterminate or absent enhancement at multiphase CT. Follow-up, CE ultrasound or magnetic resonance imaging (MRI) is required to further characterise these lesions. Small (<3 cm) endophytic cysts commonly show pseudo-enhancement, which may simulate RCC; this can be overcome with DECT or MRI. In small (<4 cm) solid renal masses, 20% of lesions are benign, chiefly AML without visible fat or oncocytoma. Low-dose techniques may simulate lesion heterogeneity due to increased image noise, which can be ameliorated through the appropriate use of iterative reconstruction algorithms.

The radiologist's role in the management of papillary renal cell carcinoma

Papillary carcinoma is the second most common renal cell carcinoma. It has a better prognosis than the more frequent clear cell carcinoma, although this does not hold true for advanced cases, because no specific treatment exists. It presents as a circumscribed peripheral tumor (small and homogeneously solid or larger and cystic/hemorrhagic) or as an infiltrating lesion that invades the veins, which has a worse prognosis. Due to their low vascular density, papillary renal cell carcinomas enhance less than other renal tumors, and this facilitates their characterization. On computed tomography, they might not enhance conclusively, and in these cases they are impossible to distinguish from hyperattenuating cysts. Contrast-enhanced ultrasonography and magnetic resonance imaging are more sensitive for detecting vascularization. Other characteristics include a specific vascular pattern, hypointensity on T2-weighted images, restricted water diffusion, and increased signal intensity in opposed phase images. We discuss the genetic, histologic, clinical, and radiological aspects of these tumors in which radiologists play a fundamental role in management.

Cryotherapy of Renal Lesions: Enhancement on Contrast-Enhanced Sonography on Postoperative Day 1 Does Not Imply Viable Tissue Persistence

OBJECTIVES

To investigate whether persistent enhancement detected on contrast-enhanced sonography at postoperative day 1 (early contrast-enhanced sonography) after cryoablation of renal tumors implies the presence of residual viable tumor tissue, defined as residual enhancing tissue on reference imaging (computed tomography or magnetic resonance imaging) performed 6 months after the procedure.

METHODS

Seventy-four patients with percutaneous cryoablation of renal tumors had early contrast-enhanced sonography from November 2011 to August 2015. Two independent readers evaluated early contrast-enhanced sonographic findings and contrast-enhanced sonographic investigations performed 1 month after cryoablation of lesions that displayed enhancement on early contrast-enhanced sonography. They scored intralesional enhancement in 4 groups: no enhancement, few intralesional vessels, focal enhancing areas, and diffuse enhancement. Inter-reader agreement in evaluating lesion vascularity on early contrast-enhanced sonography was assessed with weighted κ statistics. Computed tomography or magnetic resonance imaging performed 6 months after the treatment was the reference procedure for assessing the absence or presence of residual disease.

RESULTS

Inter-reader agreement in assessing intratumoral vascularization on early contrast-enhanced sonography was very good (κ = 0.90). Enhancement was absent for both readers in 33 of 74 cases; only a few intralesional vessels were visible in 21; whereas diffuse or focal enhancement was present in 13. In the remaining 7 patients, there were differences. Four lesions with focal enhancement on early contrast-enhanced sonography and 1 that was considered avascular had residual tumors on reference imaging. Ablation was successful in the remaining 69 of 74 patients (93%).

CONCLUSIONS

After cryoablation, intratumoral enhancement on early contrast-enhanced sonography does not imply tumor cell viability.

Impact of contrast-enhanced ultrasound in patients with renal function impairment

AIM

To investigate the role of contrast enhanced ultrasound (CEUS) in evaluating patients with renal function impairment (RFI) showing: (1) acute renal failure (ARF) of suspicious vascular origin; or (2) suspicious renal lesions.

METHODS

We retrospectively evaluated patients addressed to CEUS over an eight years period to rule-out vascular causes of ARF (first group of 50 subjects) or assess previously found suspicious renal lesions (second group of 41 subjects with acute or chronic RFI). After preliminary grey-scale and color Doppler investigation, each kidney was investigated individually with CEUS, using 1.2-2.4 mL of a sulfur hexafluoride-filled microbubble contrast agent. Image analysis was performed in consensus by two readers who reviewed digital clips of CEUS. We calculated the detection rate of vascular abnormalities in the first group and performed descriptive statistics of imaging findings for the second group.

RESULTS

In the first group, CEUS detected renal infarction or cortical ischemia in 18/50 patients (36%; 95%CI: 23.3-50.9) and 1/50 patients (2%; 95%CI: 0.1-12), respectively. The detection rate of infarction was significantly higher (P = 0.0002; McNemar test) compared to color Doppler ultrasonography (10%). No vascular causes of ARF were identified in the remaining 31/50 patients (62%). In the second group, CEUS detected 41 lesions on 39 patients, allowing differentiation between solid lesions (21/41; 51.2%) vs complex cysts (20/41; 48.8%), and properly addressing 15/39 patients to intervention when feasible based on clinical conditions (surgery and cryoablation in 13 and 2 cases, respectively). Cysts were categorized Bosniak II, IIF, III and IV in 8, 5, 4 and 3 cases, respectively. In the remaining two patients, CEUS found 1 pseudolesion and 1 subcapsular hematoma.

CONCLUSION

CEUS showed high detection rate of renal perfusion abnormalities in patients with ARF, influencing the management of patients with acute or chronic RFI and renal masses throughout their proper characterization.

Correlating Preoperative Imaging with Histologic Subtypes of Renal Cell Carcinoma and Common Mimickers

Renal cell carcinoma (RCC) consists of distinct subtypes that have unique pathologic and imaging features as well as specific cytogenetic and molecular characteristics. As the prognosis and therapeutic strategies may differ for each subtype, correlation of the preoperative imaging with the pathologic findings is of great clinical relevance. In addition, differentiation of RCC from benign entities is ideal in order to prevent overtreatment. However, a noninvasive diagnosis with imaging alone is not always straightforward due to the overlapping appearance of RCC with benign lesions such as fat-poor angiomyolipoma and oncocytoma. With new imaging modalities, there have been significant improvements in correlating preoperative imaging with pathologic characteristics. These new discoveries are able to aid in a more specific, noninvasive, diagnosis that in turn helps direct patient management.