Evaluation of renal masses with contrast-enhanced ultrasound: initial experience

Comparative diagnostic performance of contrast-enhanced ultrasound and dynamic contrast-enhanced magnetic resonance imaging for differentiating clear cell and non-clear cell renal cell carcinoma

OBJECTIVE

To compare the diagnostic efficiency of contrast-enhanced ultrasound (CEUS) with that of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) for the differential diagnosis of clear and non-clear cell renal cell carcinoma, as confirmed by subsequent pathology.

METHODS

A total of 181 patients with 184 renal lesions diagnosed by both CEUS and DCE-MRI were enrolled in the study, including 136 clear cell renal cell carcinoma (ccRCC) and 48 non-clear cell renal cell carcinoma (non-ccRCC) tumors. All lesions were confirmed by histopathologic diagnosis after surgical resection. Interobserver agreement was estimated using a weighted kappa statistic. Diagnostic efficiency in evaluating ccRCC and non-ccRCC was compared between CEUS and DCE-MRI.

RESULTS

The weighted kappa value for interobserver agreement was 0.746 to 0.884 for CEUS diagnosis and 0.764 to 0.895 for DCE-MRI diagnosis. Good diagnostic performance in differential diagnosis of ccRCC and non-ccRCC was displayed by both CEUS and DCE-MRI: sensitivity was 89.7% and 91.9%, respectively; specificity was 77.1% and 68.8%, respectively; and area under the receiver operating curve was 0.834 and 0.803, respectively. No statistically significant differences were present between the two methods (p = 0.54).

CONCLUSIONS

Both CEUS and DCE-MRI imaging are effective for the differential diagnosis of ccRCC and non-ccRCC. Thus, CEUS could be an alternative to DCE-MRI as a first test for patients at risk of renal cancer, particularly where DCE-MRI cannot be carried out.

KEY POINTS

• CEUS and DCE-MRI features can help differentiate ccRCC and non-ccRCC. • The differential diagnosis of ccRCC and non-ccRCC by CEUS is comparable to that of DCE-MRI. • Interobserver agreement is generally high using CEUS and DCE-MRI.

Gray-Scale, Color Doppler, Spectral Doppler, and Contrast-Enhanced Renal Artery Ultrasound: Imaging Techniques and Features

Renal artery stenosis (RAS) is increasingly being detected in elderly patients as life expectancy increases. RAS induces hypertension or reduces renal function. Computed tomography or magnetic resonance angiography are objective in detecting RAS but may cause iodine-induced nephrotoxicity or nephrogenic systemic fibrosis in patients with RAS. Ultrasound (US) is, by contrast, a noninvasive and real-time imaging modality useful in patients with reduced renal function. Renal US is not as sensitive for detecting RAS because this technique indirectly assesses the renal artery by analyzing intrarenal hemodynamic changes. Although, ideally, US would be used to directly evaluate the renal artery, its current utility for RAS detection remains unclear. The purpose of this review is to introduce how to assess renal artery with US, to describe imaging features of renal artery US, to compare renal artery US and renal US, and to show how to perform work-up in patients in whom RAS is suspected.

Ultrasonography findings for the diagnosis of renal oncocytoma

Renal oncocytomas are rare benign epithelial tumors of the kidney. However, they are easily misdiagnosed as renal cancers, resulting in unnecessary radical nephrectomy. This review summarizes the use of ultrasound for the diagnosis of renal oncocytomas. On two-dimensional grayscale ultrasound, renal oncocytomas appear as solid, well-defined, round or oval, and relatively isoechoic or slightly hyperechoic masses. On color Doppler flow imaging, the "spoke-wheel" sign is evident. On power Doppler flow imaging, renal oncocytomas show mixed penetrating and peripheral patterns. Renal oncocytomas usually appear as highly enhanced on contrast-enhanced ultrasound images, and irregular nonenhanced areas in larger tumors. This review will help sonographers recognize renal oncocytomas.

Solid renal masses in adults

With the ever increasing trend of using cross-section imaging in today's era, incidental detection of small solid renal masses has dramatically multiplied. Coincidentally, the number of asymptomatic benign lesions being detected has also increased. The role of radiologists is not only to identify these lesions, but also go a one step further and accurately characterize various renal masses. Earlier detection of small renal cell carcinomas means identifying at the initial stage which has an impact on prognosis, patient management and healthcare costs. In this review article we share our experience with the typical and atypical solid renal masses encountered in adults in routine daily practice.

Utility of contrast-enhanced ultrasound for solid mass surveillance and characterization in children with tuberous sclerosis complex: an initial experience

BACKGROUND

Patients with tuberous sclerosis complex (TSC) can develop solid kidney masses from childhood. Imaging surveillance is done to detect renal cell carcinoma (RCC) and angiomyolipomas (AML), including AMLs at risk for hemorrhage. Intravenous contrast-enhanced ultrasound (CEUS) may be useful for screening as ultrasound is well tolerated by children and ultrasound contrast agents (UCA) are not nephrotoxic.

METHODS

Retrospective review of kidney CEUS exams of pediatric TSC patients. Qualitative CEUS analysis by consensus of 3 radiologists assessed rate, intensity, and pattern of lesion enhancement. Quantitative CEUS analysis was performed using Vuebox®. Where available, abdominal MRI was analyzed qualitatively for the same features and quantitatively by in-house-developed software. Time-intensity curves were generated from both CEUS and MRI where possible. Appearance of lesions were compared between CEUS and MRI and histology where available.

RESULTS

Nine masses in 5 patients included one histologically proven RCC and 8 AMLs diagnosed by imaging. Quantitative CEUS of RCC showed malignant features including increased peak enhancement 162%, rapid wash-in rate 162%, and elevated washout rate 156% compared to normal kidney tissue; versus AML which was 68%, 105%, and 125%, respectively. All masses were hypoenhancing on MRI compared to normal kidney tissue; MR dynamic contrast study offered no distinction between RCC and AML. The only MRI feature differentiating RCC from AML was absence of fat.

CONCLUSION

Temporal resolution afforded by CEUS was useful to distinguish malignant from benign kidney masses. CEUS may prove useful for screening, characterizing, and follow-up of kidney lesions in pediatric TSC patients.

Contrast-enhanced US for the Interventional Radiologist: Current and Emerging Applications

US is a powerful and nearly ubiquitous tool in the practice of interventional radiology. Use of contrast-enhanced US (CEUS) has gained traction in diagnostic imaging given the recent approval by the U.S. Food and Drug Administration (FDA) of microbubble contrast agents for use in the liver, such as sulfur hexafluoride lipid-type A microspheres. Adoption of CEUS by interventional radiologists can enhance not only procedure guidance but also preprocedure patient evaluation and assessment of treatment response across a wide spectrum of oncologic, vascular, and nonvascular procedures. In addition, the unique physical properties of microbubble contrast agents make them amenable as therapeutic vehicles in themselves, which can lay a foundation for future therapeutic innovations in the field in drug delivery, thrombolysis, and vascular flow augmentation. The purpose of this article is to provide an introduction to and overview of CEUS aimed at the interventional radiologist, highlighting its role before, during, and after frequently practiced oncologic and vascular interventions such as biopsy, ablation, transarterial chemoembolization, detection and control of hemorrhage, evaluation of transjugular intrahepatic portosystemic shunts (TIPS), detection of aortic endograft endoleak, thrombus detection and evaluation, evaluation of vascular malformations, lymphangiography, and percutaneous drain placement. Basic physical principles of CEUS, injection and scanning protocols, and logistics for practice implementation are also discussed. Early adoption of CEUS by the interventional radiology community will ensure rapid innovation of the field and development of future novel procedures. Online supplemental material is available for this article. ^©RSNA, 2020.

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.

Contrast-Enhanced Ultrasound for the Evaluation of Renal Transplants

Contrast-enhanced ultrasound has emerged as a useful imaging modality for the evaluation of the transplant kidney. Advantages over traditional imaging modalities such as computed tomography and magnetic resonance imaging include the ability to visualize a lesion's enhancement pattern in real time, the lack of nephrotoxicity, and relatively low cost. Potential uses of contrast-enhanced ultrasound include characterization of solid and cystic transplant renal masses, assessment for pyelonephritis and identification of its complications, and evaluation of transplant complications in immediate and delayed settings. Contrast-enhanced ultrasound will likely play an increasing role for evaluating the transplant kidney, as an accurate diagnosis based on imaging can direct treatment and prevent unnecessary interventions.

Diagnostic Performance of Contrast-Enhanced Ultrasound (CEUS) in the Evaluation of Solid Renal Masses

Background: The present study aims to evaluate the diagnostic performance of contrast-enhanced ultrasound (CEUS) for discriminating between benign and malignant solid renal masses. Methods: 18 patients with histopathologically confirmed benign solid renal masses (11 oncocytomas, seven angiomyolipomas) as well as 96 patients with confirmed renal cell carcinoma (RCC) who underwent CEUS followed by radical or partial nephrectomy were included in this single-center study. CEUS examinations were performed by an experienced radiologist (EFSUMB Level 3) and included the application of a second-generation contrast agent. Results: Renal angiomyolipomas, oncocytomas, and renal cell carcinomas showed varying sonomorphological characteristics in CEUS. Angiomyolipomas showed heterogeneous echogenicity (57% hypo-, 43% hyperechoic), while all lesions showed rapid contrast-enhancement with two lesions also showing venous wash-out (29%). Notably, 9/11 oncocytomas could be detected in conventional ultrasound (64% hypo-, 9% hyper-, 9% isoechoic) and 2/11 only demarcated upon intravenous application of contrast agent (18%). All oncocytomas showed hyperenhancement in CEUS, venous wash-out was registered in 7/11 lesions (64%). Conclusions: In line with the current state of knowledge, no specific sonomorphological characteristics allowing for accurate distinction between benign and malignant solid renal masses in CEUS could be detected in our study.

Use of Contrast Ultrasound for Renal Mass Evaluation

An introduction to the expanding modality of contrast-enhanced ultrasound is provided, along with basics on contrast agents and technique. The contrast ultrasound findings of multiple renal tumors are reviewed with examples, including clear cell renal cell carcinoma, papillary renal cell carcinoma, chromophobe renal cell carcinoma, other rare renal cell carcinoma subtypes, oncocytoma, upper tract urothelial carcinoma, lymphoma, and angiomyolipoma, followed also by brief discussions of renal infections and pseudolesions.

Comparison of computed tomography (CT), magnetic resonance imaging (MRI) and contrast-enhanced ultrasound (CEUS) in the evaluation of unclear renal lesions

PURPOSE

 To compare the sensitivity and specificity of contrast-enhanced ultrasound (CEUS), computed tomography (CT) and magnetic resonance imaging (MRI) in the evaluation of unclear renal lesions to the histopathological outcome.

MATERIALS AND METHODS

 A total of 255 patients with a single unclear renal mass with initial imaging studies between 2005 and 2015 were included. Patient ages ranged from 18 to 86 with (mean age 62 years; SD ± 13). CEUS (255 patients), CT (88 out of 255 patients; 34.5 %) and MRI (36 out of 255 patients; 14.1 %) were used for determining malignancy or benignancy and initial findings were correlated with the histopathological outcome.

RESULTS

 CEUS showed a sensitivity of 99.1 % (95 % confidence interval (CI): 96.7 %, 99.9 %), a specificity of 80.5 % (95 % CI: 65.1 %, 91.2 %), a positive predictive value (PPV) of 96.4 % (95 % CI: 93.0 %, 98.4 %) and a negative predictive value (NPV) of 94.3 % (95 % CI: 80.8 %, 99.3 %). CT showed a sensitivity of 97.1 % (95 % CI: 89.9 %, 99.6 %), a specificity of 47.4 % (95 % CI: 24.4 %, 71.1 %), a PPV of 87.0 % (95 % CI: 77.4 %, 93.6 %) and a NPV of 81.8 % (95 % CI: 48.2 %, 97.7 %). MRI showed a sensitivity of 96.4 % (95 % CI: 81.7 %, 99.9 %), a specificity of 75.0 % (95 % CI: 34.9 %, 96.8 %), a PPV of 93.1 % (95 % CI: 77.2 %, 99.2 %) and a NPV of 85.7 % (95 % CI: 42.1 %, 99.6 %). Out of the 212 malignant lesions a total of 130 clear cell renal carcinomas, 59 papillary renal cell carcinomas, 7 chromophobe renal cell carcinomas, 4 combined clear cell and papillary renal cell carcinomas and 12 other malignant lesions, e. g. metastases, were diagnosed. Out of the 43 benign lesions a total 10 angiomyolipomas, 3 oncocytomas, 8 benign renal cysts and 22 other benign lesions, e. g. renal adenomas were diagnosed. Using CEUS, 10 lesions were falsely identified as malignant or benign, whereas 8 lesions were false positive and 2 lesions false negative.

CONCLUSION

 CEUS is an useful method which can be additionally used to clinically differentiate between malignant and benign renal lesions. CEUS shows a comparable sensitivity, specificity, PPV and NPV to CT and MRI. In daily clinical routine, patients with contraindications for other imaging modalities can particularly benefit using this method.

KEY POINTS

  · Wide availability. · Safe applicability in patients with known renal insufficiency or allergies to iodine or gadolinium. · Comparable sensitivity, specificity, PPV and NPV to CT and MRT. · May lead to a reduction in interventional radiological or surgical interventions.

CITATION FORMAT

· Marschner CA, Ruebenthaler J, Schwarze V et al. Comparison of computed tomography (CT), magnetic resonance imaging (MRI) and contrast-enhanced ultrasound (CEUS) in the evaluation of unclear renal lesions. Fortschr Röntgenstr 2020; 192: 1053 - 1058.

Single-center study: the diagnostic performance of contrast-enhanced ultrasound (CEUS) for assessing renal oncocytoma

Purpose: The aim of the present retrospective single-center study is to evaluate the diagnostic performance of contrast-enhanced ultrasound (CEUS) in the evaluation of renal oncocytoma.Method: Thirteen patients with histopathologically confirmed renal oncocytoma and 26 patients with histopathologically confirmed renal cell carcinoma were included in this retrospective single-center study on whom CEUS was performed between 2005 and 2015. The applied contrast agent was a second-generation blood pool agent. CEUS examinations were performed and interpreted by a single radiologist with more than 15 years of experience (EFSUMB Level 3).Results: CEUS examinations were successfully performed in all included patients without any adverse effects. Renal oncocytomas showed varying echogenicity (46% hypoechoic, 23% hyperechoic, 8% iso-/hyperechoic, 8% isoechoic). In two cases renal oncocytoma only demarcated upon i.v. application of contrast medium. In bilateral oncocytosis, lesions presented as hyperechoic. Only 23% of renal oncocytomas showed slight vascularization using Color Doppler. No oncocytoma-specific pattern of microperfusion could be elucidated: 85% of the oncocytomas presented hyperenhancing, of whom 50% also showed delayed venous wash-out; 8% of renal oncocytomas showed venous wash-out without early arterial hyperenhancement.Conclusions: Within the frame of the present study and in line with the recent state of knowledge, no specific sonomorphological feature - including CEUS - could be detected allowing for adequate discrimination between oncocytoma and renal cell carcinoma.

How does contrast-enhanced ultrasonography influence Bosniak classification for complex cystic renal mass compared with conventional ultrasonography?

To analyze the degree and pattern of influence of contrast-enhanced ultrasonography (CEUS) on the Bosniak classification system for complex renal cystic mass as compared with conventional ultrasonography (US). One hundred two consecutive patients with complex renal cystic masses were retrospectively analyzed. The diagnostic performance of the Conventional US and CEUS were evaluated separately for malignant and benign lesions. The diagnostic concordance rates were calculated according to pathologic diagnoses. ROC curve analysis determined the confidence in the diagnostic accuracy by calculating the area under each ROC curve. Compared to the Conventional US, septae number, wall and/or septae thickness, solid component and the Bosniak classification changed in 17 (16.7%), 39 (38.2%), 31 (30.4%), and 67 (65.7%) patients as compared with 0 (0.0%), 21 (20.6%), 31 (30.4%), and 37 (36.3%) of the treatment strategy that changed after CEUS respectively. The diagnostic performance of CEUS showed overall higher in terms of sensitivity (100.0 vs 97.2%); specificity (90.9 vs 62.1%); positive predictive value (PPV) (85.7 vs 58.3%); negative predictive value (NPV) (100.0 vs 97.6%); and the concordance with pathology (kappa = 0.876 vs 0.515). CEUS had a higher diagnostic confidence (P < .05) according to the area under the ROC curve (AUC = 0.968 vs 0.799).CEUS performed better than the Conventional US in the diagnosis of complex renal cystic mass, and it might be considered as the first tool to evaluate a complex cystic renal mass, especially for these Bosniak III masses displaying the presence of hemorrhage or infection.

Retrospective Analysis of Contrast-enhanced Ultrasonography Effectiveness in Reducing Time to Diagnosis and Imaging-related Expenditures at a Single Large United States County Hospital

Hepatic and renal lesions detected during ultrasound examinations frequently require subsequent contrast-enhanced computed tomography (CT) or magnetic resonance imaging (MRI) for characterization, delaying time to imaging diagnosis and increasing overall health care expenditures. Contrast-enhanced ultrasonography (CEUS) is a comparatively low-cost diagnostic tool that is underutilized in the evaluation of such indeterminate or suspicious hepatic and renal lesions. A retrospective chart review of CEUS examinations performed in our department demonstrated significantly shorter time to imaging diagnosis with CEUS compared to CT or MRI, largely due to the ability to perform the CEUS examination at the time of initial examination. For example mean time to completion for outpatient examinations was 5.2, 52.3, and 123.5 days for CEUS, CT, and MRI, respectively. The majority (78.4%) of CEUS examinations were completed the same day as the initial examination. Additionally, 66.7% of CEUS examinations were deemed diagnostic, abrogating further workup with CT or MRI in most cases. Annual imaging cost reduction of up to US $117,000 is anticipated in our institution based on projected reductions in follow-up CT and MRI examinations. These results indicate when CEUS was used as a first step to characterize both incidental lesions in patients without known risk factors for malignancy as well as suspicious lesions in patients with risk factors it can greatly reduce time to diagnosis and health care expenditures.

Untargeted Contrast-Enhanced Ultrasound Versus Contrast-Enhanced Computed Tomography: A Differential Diagnostic Performance (DDP) Study for Kidney Lesions

OBJECTIVES

Histopathology is the 'gold standard' for diagnosing renal cell carcinoma but is limited by sample size. Contrast-enhanced ultrasound can differentiate malignant and benign lesions, but the Chinese guidelines on the management of renal cell carcinoma do not include this method. The purpose of this study was to compare the diagnostic parameters of contrast-enhanced ultrasound against those of contrast-enhanced computed tomography for detecting kidney lesions, with histopathology considered the reference standard.

METHODS

Patients with suspected kidney lesions from prior grayscale ultrasonography and computed tomography were included in the analysis (n=191). The contrast-enhanced ultrasound, contrast-enhanced computed tomography, and histopathology data were collected and analyzed. A solid, enhanced mass was considered a malignant lesion, and an unenhanced mass or cyst was considered a benign lesion. The Bosniak criteria were used to characterize the lesions.

RESULTS

Contrast-enhanced ultrasound and contrast-enhanced computed tomography both detected that 151 patients had malignant tumors and 40 patients had benign tumors. No significant differences in the tumors and their subtypes were reported between contrast-enhanced ultrasound and histopathology (p=0.804). Chromophobe renal cell carcinoma was detected through contrast-enhanced computed tomography (n=1), but no such finding was reported by contrast-enhanced ultrasound. A total of 35 cases of papillary renal cell carcinoma were reported through contrast-enhanced ultrasound while 32 were reported through histopathology.

CONCLUSIONS

Contrast-enhanced ultrasound might be safe and as accurate as histopathology in diagnosing kidney lesions, especially renal cell carcinoma. Additionally, this study provides additional information over histopathology and has an excellent safety profile.

LEVEL OF EVIDENCE

III.

Contrast-enhanced ultrasound findings of adult renal cell carcinoma associated with Xp11.2 translocation/TFE3 gene fusion: comparison with clear cell renal cell carcinoma and papillary renal cell carcinoma

BACKGROUND

To investigate the contrast-enhanced ultrasound (CEUS) findings of renal cell carcinoma (RCC) associated with Xp11.2 translocation/TFE3 gene fusion (Xp11.2/TFE3) in adult patients by comparison with those of clear cell RCC (ccRCC) and papillary RCC (pRCC).

METHODS

In total, 110 patients (110 renal masses) who underwent CEUS examinations were enrolled in this study. The cases included 18 Xp11.2/TFE3 RCCs, 60 ccRCCs and 32 pRCCs. All masses were confirmed by operative pathology. The CEUS imaging data of these patients were retrospectively analysed by two readers. The conventional US and CEUS features of Xp11.2/TFE3 RCC were compared with those of ccRCC and pRCC.

RESULTS

The age of the patients with Xp11.2/TFE3 RCC ranged from 20 to 68 years, with a mean age of 38.3 ± 16.3 years and a slight female predominance. The weighted kappa value that interprets the concordance between the interobserver agreement of the US and CEUS features ranged from 0.61 to 0.89. On conventional US and CEUS imaging of Xp11.2/TFE3 RCCs, the tumours were hypoechoic (6/18, 33.3%), isoechoic (8/18, 44.4%), and hyperechoic (4/18, 22.2%). The cystic component was present in 5 cases (27.8%), calcification was present in 9 cases (50.0%), and colour flow signal was present in 7 cases (38.9%). Most cases showed simultaneous wash-in (11/18, 61.1%); the peak enhancement showed hypoenhancement (6/18, 33.3%), isoenhancement (10/18, 55.6%), and hyperenhancement (2/18, 11.1%); most cases exhibited heterogeneous enhancement (12/18, 66.7%) and fast- or simultaneous-out (16/18, 88.9%); and a pseudocapsule was present in 6 cases (33.3%). In the multivariate logistic regression analysis, calcification and lower peak enhancement were more likely to be present in Xp11.2/TFE3 RCC than in ccRCC (P < 0.05), and younger age and relatively high peak enhancement were more likely to be present in Xp11.2/TFE3 RCC than in pRCC (P < 0.05). The calcification combined peak enhancement model differentiated Xp11.2/TFE3 RCC from ccRCC, and the age combined peak enhancement model differentiated Xp11.2/TFE3 RCC from pRCC with an AUC, a sensitivity and a specificity of 0.896, 94.4% and 73.3% and 0.786, 50.0% and 100.0%, respectively.

CONCLUSIONS

The specific CEUS features combined with demographic information and clinical symptoms may be helpful for differentiating Xp11.2/TFE3 RCC from ccRCC and pRCC.

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.

Relationship between plasma Atherogenic index and final pathology of Bosniak III-IV renal masses: a retrospective, single-center study

Background

There is an increased incidence of renal cell carcinoma (RCC) in patients with metabolic syndrome who usually have high levels of serum triglyceride (TG) and low high-density lipoprotein-cholesterol (HDL-C). Plasma atherogenic index (PAI) is the logarithmic ratio of serum TG level to HDL-C and related to cardiovascular diseases. In this study, we aimed to determine the accuracy of PAI in determining renal malignancy in localized renal masses preoperatively.

Methods

Totally 169 patients who were diagnosed with Bosniak III-IV lesions by imaging modalities and treated in our hospital with partial or radical nephrectomy were retrospectively analyzed using institutional renal cancer database between 2013 and 2018. Preoperative images were evaluated by two experienced radiologists. The patients were divided into two groups according to their postoperative pathological diagnosis as malignant or benign tumors. The PAI of each patient was calculated and the statistical significance of PAI in predicting malignancy for renal masses was analyzed using uni- and multivariable analyses.

Results

Of patients, 109 (64.5%) were males and 60 (35.5%) were females with a median age of 61 (33–84) years. Median tumor size was 6.5 (2–18) cm. Pathological diagnosis was malignant in 145 (85.8%) and benign in 24 (14.2%) patients. There was no statistically significant difference in serum TG levels between malignant and benign cases (p > 0.05). The HDL-C levels were significantly lower in malignant cases (p = 0.001). Median PAI value was 0.63 (0.34–1.58) and significantly higher in malignant cases (p = 0.003). The PAI cut-off value for malignancy was ≥0.34. The sensitivity was calculated as 88.2% and specificity as 45.8%, the positive predictive value as 90.8, negative predictive value as 39.3, and odds ratio as 6.37 (95% CI: 2.466–16.458). In multivariable analysis, gender, smoking status, and hypertension had no effect on malignancy, whereas PAI and HDL-C were independent risk factors (p = 0.003 and p = 0.003, respectively). The risk of malignancy was 5.019 times higher, when PAI was > 0.34 (95% CI: 1.744–14.445) in multivariable logistic regression analysis.

Conclusions

The PAI can be used as a predictive tool in suspicion of malignant renal masses. In case of a benign pathology, PAI levels may be encouraging for surgeons for nephron-sparing surgery.

Renal Masses: Evaluation with Contrast-Enhanced Ultrasound, with a Special Focus on the Pseudocapsule Sign

The aim of this study was to analyze the diagnostic performance of contrast-enhanced ultrasound (CEUS) in differentiating between benign and malignant renal masses, with a special emphasis on the value of the pseudocapsule sign. A total of 163 consecutive patients with 163 renal masses were involved. The conventional ultrasonography and CEUS features were assessed. Sensitivity, specificity and the area under the receiver operating characteristic curve (Az) were calculated for qualitative CEUS, and a multivariate analysis was performed to analyze the correlation between the sonographic features and malignancy. Time to peak (TTP) and peak intensity (PI) were compared between benign and malignant renal masses for quantitative CEUS analysis in 72 of 163 patients. Intraclass correlations were calculated for variability in intensity and time parameters between qualitative and quantitative evaluation. Among all qualitative CEUS features, the pseudocapsule sign showed the highest Az (0.777; 95% confidence interval: 0.701-0.853) and yielded the highest sensitivity (67.4%) and specificity (88.0%); multivariate logistic regression analysis showed that the pseudocapsule sign and color Doppler flow imaging patterns were the two strongest independent predictors for malignancy. For quantitative CEUS analysis, higher PI and shorter TTP were found in malignant renal masses than those in benign ones. The Intraclass correlation coefficient values among qualitative and the quantitative assessments were 0.00 for time and 0.03 for intensity. The pseudocapsule sign offered the most efficient performance among all the qualitative and quantitative CEUS features.

Value of Contrast-Enhanced Ultrasound in the Diagnosis of Renal Cancer and in Comparison With Contrast-Enhanced Computed Tomography: A Meta-analysis

OBJECTIVES

The purpose of this meta-analysis was to assess the diagnostic accuracy of contrast-enhanced ultrasound (CEUS) in renal cancer and to compare it with contrast-enhanced computed tomography (CECT).

METHODS

A systematic search was performed to recruit eligible original studies published until December 2017. Two reviewers independently extracted data. A meta-analysis was performed, and the pooled sensitivity, specificity, positive and negative likelihood ratios, positive and negative predictive values, diagnostic odds ratio, summary receiver operating characteristic curve, and area under the curve were calculated. The extent and potential sources of heterogeneity were further explored. Moreover, a head-to-head comparison was also performed to compare the diagnostic value between CEUS and CECT in renal cancer.

RESULTS

Twenty-two studies were included in this meta-analysis. The summary sensitivity and specificity of CEUS for detecting renal cancer were 0.96 (95% confidence interval [CI], 0.94-0.97) and 0.82 (95% CI, 0.74-0.88), respectively. The summary diagnostic odds ratio was 102.04 (95% CI, 49.55-210.13). The area under the summary receiver operating characteristic curve was 0.97 (95% CI, 0.95-0.98). In the head-to-head comparison, CEUS showed higher diagnostic sensitivity than CECT (0.94 versus 0.85) for renal cancer, whereas the specificities were comparable between CEUS and CECT (0.77 versus 0.75).

CONCLUSIONS

Contrast-enhanced US has high sensitivity and moderate specificity in the differential diagnosis of renal cancer. The diagnostic sensitivity of CEUS in renal cancer was higher than that of CECT, suggesting that CEUS could be used as a preferred diagnostic tool for renal cancer.

A fast scheme for renal microvascular perfusion functional imaging: Assessed by an imaging quality evaluation model

PURPOSE

This study aimed to develop a fast scheme of multiparametric perfusion functional imaging (PFI) based on dynamic contrast-enhanced ultrasound (DCEUS) for assessing renal microvascular hemodynamics.

METHOD

The flow process in the DCEUS-based PFI was modified step-by-step to improve its operational efficiency, which was validated through in vivo renal perfusion experiments. A multiparametric model with a comprehensive coefficient of imaging quality (CIQ) was then built on four terms of the average information entropy, contrast, gray, and noise coefficient of PFIs to evaluate the sacrifice of imaging quality during modifications of DCEUS-based PFI.

RESULTS

The multiparametric model successfully evaluated modifications of DCEUS-based PFI from multiple perspectives (R²  = 0.73, P < 0.01). Compared with the raw scheme in the renal sagittal and coronal planes, the fast PFI scheme significantly improved its operational efficiency by 62.82 ± 1.07% (P < 0.01) and the nine PFIs simultaneously maintained a similar CIQ of 0.26 ± 0.06.

CONCLUSIONS

The inhomogeneous hemodynamic distributions with a ring-like feature in the renal microvasculature were accurately and efficiently characterized by the fast PFI scheme. The fast PFI scheme can be applied for early diagnosis, follow-up evaluation and monitoring treatment of chronic kidney disease.

Time-intensity curve analysis of contrast-enhanced ultrasound is unable to differentiate renal dysfunction in the early post-transplant period - a prospective study

Background

Contrast enhanced ultrasonography (CEUS) assessment of kidney allografts mainly focuses on graft rejection. However, studies on delayed graft function (DGF) without acute rejection are still lacking. The aim of this study was to build a time-intensity curve (TIC) using CEUS in non-immunological DGF to understand the utility of CEUS in early transplantation.

Methods

Twenty-eight patients in the short-term postoperative period (<14 days) were divided according to the need for dialysis (early graft function [EGF] and [DGF]) and 37 subjects with longer than 90 days follow-up were divided into creatinine tertiles. Time to peak [TTP] and rising time [RT were compared between groups.

Results

EGF and DGF were similar, except for creatinine. In comparison to the late group, medullary TTP and RT were shorter in the early group as well as the delay regarding contrast arrival in the medulla (in relation to cortex) and reaching the medullary peak (in relation to artery and cortex). In the late group, patients with renal dysfunction showed shorter temporal difference to reach medullary peak in relation to artery and cortex.

Conclusions

Although it was not possible to differentiate EGF and DGF using TIC, differences between early and late groups point to blood shunting in renal dysfunction.

RETRACTED: Recommandations françaises du Comité de Cancérologie de l’AFU – Actualisation 2018–2020 : prise en charge du cancer du reinFrench ccAFU guidelines – Update 2018–2020: Management of kidney cancer

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). Cet article est retiré de la publication à la demande des auteurs car ils ont apporté des modifications significatives sur des points scientifiques après la publication de la première version des recommandations. Le nouvel article est disponible à cette adresse: DOI:10.1016/j.purol.2019.01.004. C’est cette nouvelle version qui doit être utilisée pour citer l’article. This article has been retracted at the request of the authors, as it is not based on the definitive version of the text because some scientific data has been corrected since the first issue was published. The replacement has been published at the DOI:10.1016/j.purol.2019.01.004. That newer version of the text should be used when citing the article.

Quantitative analysis of thyroid tumors vascularity: A comparison between 3-D contrast-enhanced ultrasound and 3-D Power Doppler on benign and malignant thyroid nodules

PURPOSE

To perform a comparative quantitative analysis of Power Doppler ultrasound (PDUS) and Contrast-Enhancement ultrasound (CEUS) for the quantification of thyroid nodules vascularity patterns, with the goal of identifying biomarkers correlated with the malignancy of the nodule with both imaging techniques.

METHODS

We propose a novel method to reconstruct the vascular architecture from 3-D PDUS and CEUS images of thyroid nodules, and to automatically extract seven quantitative features related to the morphology and distribution of vascular network. Features include three tortuosity metrics, the number of vascular trees and branches, the vascular volume density, and the main spatial vascularity pattern. Feature extraction was performed on 20 thyroid lesions (ten benign and ten malignant), of which we acquired both PDUS and CEUS. MANOVA (multivariate analysis of variance) was used to differentiate benign and malignant lesions based on the most significant features.

RESULTS

The analysis of the extracted features showed a significant difference between the benign and malignant nodules for both PDUS and CEUS techniques for all the features. Furthermore, by using a linear classifier on the significant features identified by the MANOVA, benign nodules could be entirely separated from the malignant ones.

CONCLUSIONS

Our early results confirm the correlation between the morphology and distribution of blood vessels and the malignancy of the lesion, and also show (at least for the dataset used in this study) a considerable similarity in terms of findings of PDUS and CEUS imaging for thyroid nodules diagnosis and classification.

Evaluation of renal lesions using contrast-enhanced ultrasound (CEUS); a 10-year retrospective European single-centre analysis

OBJECTIVE

To investigate the usefulness of contrast-enhanced ultrasound (CEUS) in the evaluation of renal masses.

METHODS

This study included 255 patients with renal masses. Ages ranged from 18-86 years. CEUS was used for determining malignancy or benignancy and findings were correlated with the histopathological outcome. Out of 255 lesions, 212 lesions were malignant (83.1%) and 43 were benign (16.9%). Diagnostic accuracy was tested using the histopathological diagnosis as the gold standard.

RESULTS

CEUS showed a sensitivity of 99.1% [95% confidence interval (CI): 96.7%, 99.9%], a specificity of 80.5% (CI: 65.1%, 91.2%), a positive predictive value of 96.4% (CI: 93.0%, 98.4%) and a negative predictive value of 94.3% (CI: 80.8%, 99.3%). Kappa for diagnostic accuracy was κ = 0.85 (CI: 0.75, 0.94). Of 212 malignant lesions, 200 renal cell carcinomas and 12 other malignant lesions were diagnosed. Out of 43 benign lesions, 10 angiomyolipomas, 3 oncocytomas, 8 renal cysts and 22 other benign lesions were diagnosed.

CONCLUSION

CEUS is an useful method to differentiate between malignant and benignant renal lesions. To date, to our knowledge, this is the largest study in Europe for the evaluation of renal lesions using CEUS with a histopathological validation.

KEY POINTS

• CEUS helps clinicians detect and characterise unclear solid and cystic renal lesions • CEUS shows a high diagnostic accuracy in the characterization of these lesions • Proper surgical treatment or follow-up can be given with better diagnostic confidence.

Applications of contrast-enhanced ultrasound in the kidney

Incidental discovery of renal lesions on cross-sectional imaging studies performed for other indications is not uncommon. With the increased reliance on medical imaging, the number of incidentally detected renal lesions has also grown over time. While simple cysts account for the majority of these lesions, the presence of complex features within a cystic lesion, such as septations and solid components, can present a confusing picture. Solid lesions, too, can be indeterminate, and distinguishing between benign solid masses (like lipid-poor angiomyolipomas and oncocytomas) and renal cell carcinoma affects patient management and can prevent unnecessary interventions. Indeterminate renal lesions are traditionally further characterized by multiphase imaging, such as contrast-enhanced computed tomography and magnetic resonance imaging. Contrast-enhanced ultrasound (CEUS) is a new, relatively inexpensive technique that has become increasingly employed in the diagnostic workup of indeterminate 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 imaging modalities. This article provides an overview of the current clinical applications of CEUS in characterizing renal lesions, both cystic and solid. Additional applications of CEUS in the kidney, including its roles in renal transplant evaluation and guidance for percutaneous biopsy, will also be briefly discussed.

Superb Microvascular Imaging: Added Value and Novel Applications

Determining the presence and characteristics of vascular flow is an essential part of sonography interrogation. However, small vessels and low velocities are not always possible to depict with conventional color and power Doppler ultrasound. This can be frustrating, especially when the diagnosis depends mainly on the existence of vascular flow, the sonographic examination will be inconclusive, further imaging examinations will be required and diagnosis delayed. Superb microvascular imaging (SMI) is a novel vascular imaging mode, which provides visualization of low velocity and microvascular flow. SMI uses a clutter suppression algorithm to extract flow signals and depicts this information as a color overlay image or as a monochrome or color map of flow. By using SMI, high frame rates and high-resolution images remain maintained. With SMI, it is possible to visualize small vessels including their branches that, until now, it is possible to demonstrate only using contrast-enhanced ultrasound. Availability of this additional technology on all ultrasound machines may make some of the computed tomography scans unnecessary. In our paper, we describe six patients, aged 16-73 years, in which final diagnosis was achieved only with SMI and where conventional color and power Doppler failed. All these examinations were performed using Aplio 500 Platinum ultrasound unit (Toshiba Medical Systems, Tokyo, Japan).

Contrast-enhanced ultrasound of the kidney: a single-institution experience

BACKGROUND

Focal renal masses are typically evaluated by means of triphasic contrast-enhanced CT or MRI scan but use of iodinated contrast or gadolinium is unsuitable for some patients. Contrast-enhanced ultrasound (CEUS) is an imaging alternative in this scenario but has limited availability in Ireland.

AIM

The aim of the study was to retrospectively evaluate experience with selective use of CEUS for non-invasive characterization of focal renal masses in a tertiary referral institution in Ireland, with a particular focus on cystic renal lesions and the influence of CEUS on final Bosniak classification and treatment outcomes.

METHODS

All cases of renal CEUS between 2009 and 2017 were identified. Imaging history, patient records, histopathology reports, urology conference notes, clinical follow-up details, details of lesion progression or stability on surveillance, biopsy and/or resection details and pre- and post-CEUS Bosniak scores were recorded.

RESULTS

Thirty-one patients underwent renal CEUS (7 solid renal lesions, 21 cystic renal lesions and 3 'indeterminate' renal lesions). After CEUS, the CEUS-modified Bosniak score was upgraded in nine patients and downgraded in two patients. All three lesions upgraded from Bosniak III to IV were renal cell carcinomas. One of two lesions downgraded from Bosniak IV to III was resected (cystic nephroma) and the other showed no progression after 19 months of surveillance.

CONCLUSION

CEUS is a valuable alternative to CT in assessing complex cystic or solid renal lesions where iodinated CT contrast or gadolinium is inappropriate. CEUS can also refine the Bosniak category of atypical cystic renal lesions and help facilitate treatment decisions.

Ultrasound-Stimulated Drug Delivery Using Therapeutic Reconstituted High-Density Lipoprotein Nanoparticles

The abnormal tumor vasculature and the resulting abnormal microenvironment are major barriers to optimal chemotherapeutic drug delivery. It is well known that ultrasound (US) can increase the permeability of the tumor vessel walls and enhance the accumulation of anticancer agents. Reconstituted high-density lipoproteins (rHDL) nanoparticles (NPs) allow selective delivery of anticancer agents to tumor cells via their overexpressed scavenger receptor type B1 (SR-B1) receptor. The goal of this study is to investigate the potential of noninvasive US therapy to further improve delivery and tumor uptake of the payload from rHDL NPs, preloaded with an infrared dye (IR-780), aimed to establish a surrogate chemotherapeutic model with optical localization. Athymic nude mice were implanted orthotopically with one million breast cancer cells (MDA-MB-231/Luc). Three weeks later, animals were divided into seven groups with comparable mean tumor size: control, low, moderate, and high concentration of rHDL NPs alone groups, as well as these three levels of rHDL NPs plus US therapy groups (N = 7 to 12 animals per group), where low, moderate and high denote 5, 10, and 50 µg of the IR-780 dye payload per rHDL NP injection, respectively. The US therapy system included a single element focused transducer connected in series with a function generator and power amplifier. A custom 3D printed cone with an acoustically transparent aperture and filled with degassed water allowed delivery of focused US energy to the tumor tissue. US exposure involved a pulsed sequence applied for a duration of 5 min. Each animal in the US therapy groups received a slow bolus co-injection of MB contrast agent and rHDL NPs. Animals were imaged using a whole-body optical system to quantify intratumoral rHDL NP accumulation at baseline and again at 1 min, 30 min, 24 h, and 48 h. At 48 h, all animals were euthanized and tumors were excised for ex vivo analysis. We investigated a noninvasive optical imaging method for monitoring the effects of US-stimulated drug delivery of IR-780 dye-loaded rHDL NPs in living animals. No change in optical imaging data was found in the control animals. However, there was considerable dye accumulation (surrogate drug) within 48 h in the low (5 µg), moderate (10 µg), and high (50 µg) rHDL NP concentration-dosed group animals (p < 0.09). With US therapy added to the experimental protocol, there was an additional and significant increase in local tumor drug uptake at 48 h (p < 0.02). Optical image data collected from ex vivo tumor samples confirmed tumor retention of the IR-780 dye-loaded rHDL NPs and correlated positively with in vivo optical imaging results (R² > 0.69, p < 0.003). IR-780 dye extraction from the tumor tissue samples confirmed the in vivo and ex vivo US therapy findings. Overall, the addition of US therapy considerably improved local rHDL NP accumulation in tumor tissue. This study concludes that US-mediated drug delivery can facilitate tumor uptake of rHDL NPs and more research is warranted to optimize the drug dosing schedule and the respective therapeutic protocols.

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.

Contrast-enhanced ultrasound for differentiating benign from malignant solid small renal masses: comparison with contrast-enhanced CT

PURPOSE

The study aimed to compare the diagnostic efficiency of contrast-enhanced ultrasound (CEUS) with that of contrast-enhanced computed tomography (CECT) in the evaluation of benign and malignant small renal masses (SRMs) (<4 cm) confirmed by pathology.

METHODS

A total of 118 patients with 118 renal masses smaller than 4 cm diagnosed by both CEUS and CECT were enrolled in this study, including 25 benign lesions and 93 malignant lesions. All lesions were confirmed by histopathologic diagnosis after surgical resection. The diagnostic imaging studies of the patients were retrospectively reviewed by two independent ultrasonologists and two independent radiologists blinded to the CT or ultrasound findings and final histological results. All lesions on both CEUS and CECT were independently scored on a 3-point scale (1: benign, 2: equivocal, and 3: malignant). The concordance between interobserver agreement was interpreted using a weighted kappa statistic. The diagnostic efficiency of the evaluation of benign and malignant lesions was compared between CEUS and CECT.

RESULTS

All the 118 included lesions were detected by both CEUS and CECT. In CEUS and CECT imaging evaluation of the 118 lesions, the weighted kappa value interpreting the concordance between interobserver agreement was 0.89 (95% CI 0.79-0.98) and 0.93 (95% CI 0.87-0.99), respectively. Both CEUS and CECT demonstrated good diagnostic performance in differential diagnosis of benign and malignant SRMs with sensitivity of 93.5% and 89.2%, specificity of 68% and 76%, PPV of 91.6% and 93.3%, NPV of 73.9% and 65.5%, and AUC of 0.808 and 0.826, respectively. There was no statistically significant difference in any of the diagnostic performance indices between these two methods (P > 0.05). However, the qualitative diagnosis of small papillary renal cell carcinoma (RCC) by CEUS was significantly better than that by CECT (P < 0.05), while there was no significant difference in qualitative diagnostic accuracy on other histotypes of SRMs between CEUS and CECT (P > 0.05).

CONCLUSIONS

Both CEUS and CECT imaging modalities are effective for the differential diagnosis of benign and malignant SRMs. Furthermore, CEUS may be more effective than CECT for the qualitative diagnosis of small papillary RCC.

Imaging of Renal Medullary Carcinoma

Renal medullary carcinoma (RMC) is a rare, highly aggressive tumor recognized as an independent pathological entity. African-descent adolescents and young adults with sickle cell hemoglobinopathy are the most affected groups. This rare subtype of renal cell carcinoma has its own morphogenetic and pathological characteristics. The major clinical manifestations include gross hematuria, abdominal or flank pain, and weight loss. The prognosis is very poor, with 95% of cases diagnosed at an advanced stage of the disease. In this review, we summarize the morphologic and dynamic characteristics of RMC under various imaging modalities such as ultrasound, computed tomography, and magnetic resonance. Differential diagnosis and management strategies are also discussed.

A Pilot Clinical Study in Characterization of Malignant Renal-cell Carcinoma Subtype with Contrast-enhanced Ultrasound

Malignant renal cell carcinoma (RCC) is a diverse set of diseases, which are independently difficult to characterize using conventional MRI and CT protocols due to low temporal resolution to study perfusion characteristics. Because different disease subtypes have different prognoses and involve varying treatment regimens, the ability to determine RCC subtype non-invasively is a clinical need. Contrast-enhanced ultrasound (CEUS) has been assessed as a tool to characterize kidney lesions based on qualitative and quantitative assessment of perfusion patterns, and we hypothesize that this technique might help differentiate disease subtypes. Twelve patients with RCC confirmed pathologically were imaged using contrast-enhanced ultrasound. Time intensity curves were generated and analyzed quantitatively using 10 characteristic metrics. Results showed that peak intensity ( p = 0.001) and time-to-80% on wash-out ( p = 0.004) provided significant differences between clear cell, papillary, and chromophobe RCC subtypes. These results suggest that CEUS may be a feasible test for characterizing RCC subtypes.

Comparison of magnetic resonance imaging (MRI) and contrast-enhanced ultrasound (CEUS) in the evaluation of unclear solid renal lesions

PURPOSE

To compare the sensitivity and specificity of contrast-enhanced ultrasound (CEUS) and magnetic resonance imaging (MRI) in the evaluation of unclear renal lesions to the histopathological outcome.

MATERIALS AND METHODS

A total of 36 patients with a single unclear solid renal lesion with initial imaging studies between 2005 and 2015 were included. CEUS and MRI were used for determining malignancy or benignancy and initial findings were correlated with the histopathological outcome. Out of the 36 renal masses a total of 28 lesions were malignant (77.8%) and 8 were found to be benign (22.2%). Diagnostic accuracy was testes by using the histopathological diagnosis as the gold standard.

RESULTS

CEUS showed a sensitivity of 96.4%, a specificity of 100.0%, a positive predictive value (PPV) of 100.0% and a negative predictive value (NPV) of 88,9%. MRI showed a sensitivity of 96.4%, a specificity of 75.0%, a PPV of 93.1% and a NPV of 85.7%. Out of the 28 malignant lesions a total of 18 clear cell renal carcinomas, 6 papillary renal cell carcinomas and 4 other malignant lesions, e.g. metastases, were diagnosed. Out of the 8 benign lesions a total 3 angiomyolipomas, 2 oncocytomas, 1 benign renal cyst and 2 other benign lesions, e.g. renal adenomas were diagnosed. Using CEUS, 1 lesion was falsely identified as benign. Using MRI, 2 lesions were falsely identified as benign and 1 lesion was falsely identified as malignant.

CONCLUSION

CEUS is an useful method which can be additionally used to clinically differentiate between malignant and benign renal lesions. CEUS shows a comparable sensitivity, specificity, PPV and NPV to MRI. In daily clinical routine, patients with contraindications for other imaging modalities can particularly benefit using this method.

Characterization of histological subtypes of clear cell renal cell carcinoma using contrast-enhanced ultrasound (CEUS)

INTRODUCTION

The aim of this study was to analyze the histological subtypes of clear cell renal cell carcinoma (RCC) examined by means of contrast-enhanced ultrasound (CEUS) and a second generation blood pool agent (SonoVue®, Bracco, Milan, Italy) during the pre-operative phase.

MATERIALS AND METHODS

29 patients with histologically proven subtypes of clear cell RCC were examined. A total of three patients were diagnosed with highly differentiated clear cell RCC, 21 out of 29 cases with moderately differentiated clear cell RCC and five out of 29 patients had insufficiently differentiated clear cell RCC. An experienced radiologist examined the patients with CEUS. The following parameters were analyzed: maximum signal intensity (PEAK), time elapsed until PEAK is reached (MTT), local blood flow (RBF), area under the time intensity curve (AUC) and the signal intensity (SI) during the course of time. For the groups all comparisons are made based on healthy renal parenchyma.

RESULTS

In the clear cell RCC significant differences (significance level p < 0.05) between cancerous tissue and the healthy renal parenchyma were noticed in all four parameters. Therefore, the clear cell RCC stands out due to its reduced blood volume. However, it reached the PEAK reading relatively rapidly and its signal intensity was always lower than that of the healthy renal parenchyma. In the arterial phase retarded absorption of the contrast agent was observed, followed by fast washing out of the contrast agent bubbles.In all three histological subgroups no significant differences were noticed in PEAK and SI. However, the diagrams showed the possible bias, that the group of the insufficiently differentiated clear cell RCC had the highest PEAK-value and the highest signal intensity when compared with highly and moderately differentiated clear cell RCC.

CONCLUSION

Our study suggests that CEUS may be an additional tool for non-invasive characterisation and differentiation of the three histological subtypes of clear cell RCC. Furthermore, it seems to have an additional diagnostic value in daily clinical.

Differentiation of subtypes of renal cell carcinoma with contrast-enhanced ultrasonography

We aimed to assess the difference of enhancement patterns among the three RCC subtypes with contrast-enhanced ultrasound (CEUS). Two hundreds cases of pathologically proved clear cell renal cell carcinomas (ccRCC), 58 papillary renal cell carcinomas (pRCC) and 51 chromophobe renal cell carcinomas (chRCC) underwent preoperative conventional ultrasound and CEUS. The wash-in and wash-out pattern, peak enhancement degree and homogeneity, and the presence of pseudocapsule were evaluated by two blinded observers respectively. The interreader agreement in the characterization of CEUS features between two observers was good (κ  = 0.649-0.775). Compared with pRCCs and chRCCs, ccRCCs demonstrated higher frequency of simultaneous wash-in pattern, hyperenhancement and heterogeneity with necrotic areas. Most pRCCs and chRCCs manifested hypoenhancement, homogeneity, fast wash-out and presence of pseudocapsule. The only difference we obtained between pRCC and chRCC was the wash-in pattern, with slow wash-in in pRCC and simultaneous wash-in in chRCC. In small lesions with long diameter≤3 cm, the majority of the three subtypes of RCC showed homogeneous enhancement and there was no difference among them. CEUS was a useful method to preoperatively differentiate the ccRCC from non-ccRCC subtypes. There were no distinguishing features identifid on CEUS that allowed reliable differentiation of pRCC from chRCC.

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.

Ultrasound-based imaging methods of the kidney-recent developments

In recent years, several novel ultrasound (US)-based techniques have emerged for kidney diagnostic imaging, including tissue stiffness assessment with elastography, Ultrasensitive Doppler techniques, and contrast-enhanced ultrasonography to assess renal microvascularization. Renal elastography has become available with the development of noninvasive quantitative techniques, following the rapidly growing field of liver fibrosis diagnosis. With the increased incidence of chronic kidney disease, noninvasive diagnosis of renal fibrosis can be of critical value. However, it is difficult to simply extend the application of US elastography from one organ to the other due to anatomic and technical issues. Today, renal elastography appears to be a promising application that, however, still requires optimization and validation. New ultrasensitive Doppler techniques improve the detection of slow blood flow and can be used alone or after administration of US contrast agents. These microbubble-based agents are extremely well tolerated and can be administered even in cases of impaired renal function. Despite the lack of approval, they improve the characterization of atypical renal masses, complex cystic renal masses, and peripheral vascular disorders. Dynamic contrast-enhanced US is based on quantification of the signal intensity from region of interest and mathematical fits of the time-intensity curves. Perfusion-related parameters can be extracted for the monitoring of vascular changes in the renal parenchyma and in tumors in order to evaluate drug response. This estimation of renal perfusion depends on many parameters that should be kept constant for follow-up studies, and, when possible, an internal reference should be used to normalize the measurements.