Multislice computed tomography versus contrast-enhanced ultrasound in evaluation of complex cystic renal masses using the Bosniak classification system

The Predictive Power of Bosniak 3 and 4 Cystic Renal Lesion Categorization Using Contrast-Enhanced Ultrasound

OBJECTIVES

Contrast-enhanced ultrasound (CEUS) is increasingly utilized for the noninvasive assessment of renal cystic lesions, using the Bosniak grading system. Bosniak 3-4 lesions require surgical referral, which allows correlation with the histopathological outcome.

METHODS

In this single-center, retrospective study we evaluated renal CEUS exams conducted with SonoVue® with a diagnosis of a Bosniak 3 or 4 lesion between 2019 and 2022. A total of 49 patients and 50 lesions met the inclusion criteria, 31 lesions had available histopathological results. Patient demographics, cyst morphology, and dominant imaging features were registered. The histopathological diagnosis was considered a reference standard.

RESULTS

Positive predictive power (PPV) for neoplastic lesions was comparable in the Bosniak 3 and 4 categories (75 vs 93.3%, P = .33), while PPV for histopathologically malignant lesion was considerably higher in the latter group (25 vs 93.33%, P = .0002). None of the lesions which had vividly enhancing thin septa as their dominant CEUS feature were malignant. Oncocytoma, multilocular cystic renal neoplasm of low malignant potential, and cystic nephroma were the major benign entities among Bosniak 3 lesions. Localized cystic kidney disease and hemorrhagic cysts were found to be the primary mimickers leading to false positive imaging findings.

CONCLUSIONS

CEUS has a high predictive power for malignancy in the Bosniak 4 category, which is not maintained in the Bosniak 3 group due to the large proportion of benign lesions. Adherence to rigorous rule-in criteria and active surveillance strategies need to be considered for equivocal CEUS Bosniak 3 lesions.

Imaging Recommendations for Diagnosis, Staging, and Management of Renal Tumors

Renal cell carcinomas accounts for 2% of all the cancers globally. Most of the renal tumors are detected incidentally. Ultrasound remains the main screening modality to evaluate the renal masses. A multi -phase contrast enhanced computer tomography is must for characterizing the renal lesions. Imaging plays an important role in staging, treatment planning and follow up of renal cancers. In this review , we discuss the imaging guidelines for the management of renal tumors.

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

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

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.

A Comprehensive Commentary on the Multilocular Cystic Renal Neoplasm of Low Malignant Potential: A Urologist’s Perspective

Multilocular cystic renal neoplasm of low malignant potential (MCRNLMP) is a cystic renal tumor with indolent clinical behavior. In most of cases, it is an incidental finding during the examination of other health issues. The true incidence rate is estimated to be between 1.5% and 4% of all RCCs. These lesions are classified according to the Bosniak classification as Bosniak category III. There is a wide spectrum of diagnostic tools that can be utilized in the identification of this tumor, such as computed tomography (CT), magnetic resonance (MRI) or contrast-enhanced ultrasonography (CEUS). Management choices of these lesions range from conservative approaches, such as clinical follow-up, to surgery. Minimally invasive techniques (i.e., robotic surgery and laparoscopy) are preferred, with an emphasis on nephron sparing surgery, if clinically feasible.

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.

Contrast -Enhanced Ultrasound: State of the Art in North America

The Society of Radiologists in Ultrasound convened a panel of specialists in contrast-enhanced ultrasound (CEUS) to produce a white paper on noncardiac CEUS in North America. The panel met in Chicago, Illinois, on October 24 and 25, 2017. The recommendations are based on analysis of current literature and common practice strategies and are thought to represent a reasonable approach to introduce the advantages of this safe and noninvasive technique for the benefit of our patients. Characterization of liver nodules, and pediatric vascular and intravesicular applications comprise the approved indications for CEUS in the United States. They, along with the very successful off-label use of CEUS for the kidney, are included in this publication.Other off-label uses are presented with emphasis on their value and literature support in the online version.

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.

Prospective Comparison of Contrast-Enhanced Ultrasound and Magnetic Resonance Imaging to Computer Tomography for the Evaluation of Complex Cystic Renal Lesions

OBJECTIVE

To prospectively evaluate the diagnostic accuracy of contrast enhanced ultrasound (CEUS) and MRI compared to computed tomography (CT) as the current gold standard for the characterization of cystic renal lesions using the Bosniak classification.

METHODS

Between July 2014 and October 2017 we prospectively enrolled patients with cystic renal lesions. Based on the Bosniak classification of complex renal lesions (≥BII-F) we evaluated the accuracy of observed agreement by Cohen's Kappa coefficient and calculated sensitivity, specificity, positive and negative predictive values (PPV/NPV) between the three imaging modalities CT, MRI and CEUS.

RESULTS

We evaluated 65 cystic renal lesions in 48 patients (median age 63 years, range 36-91 years; 18 females, 30 males). According to CT 29 (47%) of the cystic renal lesions were classified as complex. The agreement between CEUS and CT in the classification of complex cystic lesions was fair (agreement 50.8%, Kappa 0.31), and was excellent between MRI and CT (agreement 93.9%, Kappa 0.88). Compared to CT, CEUS and MRI had a sensitivity of 100% and 96.6%, a specificity of 33.3% and 91.7%, a PPV of 54.7% and 90.3%, and a NPV of 100% and 97.1% with an accuracy of 63.1% and 93.8% respectively.

CONCLUSION

CEUS has an excellent sensitivity and NPV and represents a promising non-invasive screening tool for renal cystic lesions. The classification of complex renal cysts based on MRI and CT scans correlated closely.

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).

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.

Diagnostic Performance of Contrast-Enhanced Ultrasound in Renal Cancer: A Meta-Analysis

Background

Contrast-enhanced ultrasound (CEUS) is an examination mode for detecting blood vessels in tissues, and it has been gradually used in the diagnosis of kidney cancer in recent years. This study explores the value of contrast-enhanced ultrasound in the clinical diagnosis of renal cancer, and provides an accurate and effective method for clinical diagnosis of renal cancer.

Methods

CEUS and RCC were selected as the keywords. Searching the PubMed and Embase from 2007 to 2020, the original data were abstracted and performed heterogeneity test with the Meta-Disc software. The weighted sensitivity, specificity, positive likelihood ratio and negative likelihood ratio were calculated, as well as the summary receiver operating characteristic (SROC) curve. Further estimated the diagnostic value of CEUS in the research of renal cancer by calculating the area under the curve (AUC). The quality of evidence in researches was evaluated by QUADAS items. Meta-disc, Review Manager 5.3, and STATA 13 were used.

Results

A total of 20 studies were adopted for Meta-analysis. The weighted sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and diagnostic odds ratio were 0.97, 0.86, 6.8, 0.04 and 171, respectively; and AUC was 0.97. The results showed that there was high heterogeneity.

Conclusion

CEUS technology has a good diagnostic value for RCC.

Contrast-enhanced ultrasound (CEUS) of cystic renal lesions in comparison to CT and MRI in a multicenter setting

PURPOSE

Contrast-enhanced-ultrasound (CEUS) has been frequently used in assessment of cystic renal lesions.

OBJECTIVE

The aim of this study was to investigate the Bosniak classification in CEUS compared to CT and MRI in a multi-center setting.

METHODS

Bosniak classification in CEUS examinations of cystic renal lesions were compared to imaging findings in computed-tomography (ceCT) and magnetic-resonance-imaging (ceMRI). Imaging results were correlated to histopathological reports. All examinations were performed by experts (EFSUMB level 3) using up-to-date CEUS examination-protocols.

RESULTS

Overall, 173 cystic renal lesions were compared to subgroups CT (n = 87) and MRI (n = 86). Using Bosniak-classification 64/87 renal cysts (73.6%) were rated equal compared to CT with upgrade of four lesions (4.6%) and downgrade of 19 lesions (21.8%) by CT (Intra-class-correlation [ICC] coefficient of 0.824 [p < 0.001]). CEUS compared to MRI, presenting different scoring especially in classes Bosniak IIF (n = 16/31) and Bosniak III (n = 16/28) with an ICC coefficient of 0.651 (p < 0.001).

CONCLUSION

CEUS can visualize even finest septal and small nodular wall enhancement, which may result in an upgrade of cystic lesions into a higher Bosniak class compared to CT or MRI. Thus, a modification of the Bosniak classification on CEUS may reduce unnecessary biopsies and surgery.

[Kidney Cysts and Cystic Nephropathies in Children - A Consensus Guideline by 10 German Medical Societies]

This consensus-based guideline was developed by all relevant German pediatric medical societies. Ultrasound is the standard imaging modality for pre- and postnatal kidney cysts and should also exclude extrarenal manifestations in the abdomen and internal genital organs. MRI has selected indications. Suspicion of a cystic kidney disease should prompt consultation of a pediatric nephrologist. Prenatal management must be tailored to very different degrees of disease severity. After renal oligohydramnios, we recommend delivery in a perinatal center. Neonates should not be denied renal replacement therapy solely because of their age. Children with unilateral multicystic dysplastic kidney do not require routine further imaging or nephrectomy, but long-term nephrology follow-up (as do children with uni- or bilateral kidney hypo-/dysplasia with cysts). ARPKD (autosomal recessive polycystic kidney disease), nephronophthisis, Bardet-Biedl syndrome and HNF1B mutations cause relevant extrarenal disease and genetic testing is advisable. Children with tuberous sclerosis complex, tumor predisposition (e. g. von Hippel Lindau syndrome) or high risk of acquired kidney cysts should have regular ultrasounds. Even asymptomatic children of parents with ADPKD (autosomal dominant PKD) should be monitored for hypertension and proteinuria. Presymptomatic diagnostic ultrasound or genetic examination for ADPKD in minors should only be done after thorough counselling. Simple cysts are very rare in children and ADPKD in a parent should be excluded. Complex renal cysts require further investigation.

The use of contrast enhancement in the diagnosis of simple and complex cysts kidneys

In developed countries, the main methods of research and dynamic monitoring of cystic kidney formations are CT and MRI, but their use is impossible in patients with severe concomitant diseases, as well as in the presence of metal structures, pacemakers, etc. Additionally, taking into account the high dose of radiation exposure when using CT obtained by the patient during dynamic observation, the development of alternative methods is relevant. These include, but not limited to, ultrasound using contrast enhancement, which can be used as an alternative or additional method in primary diagnosis or in the dynamic observation of cystic kidney formations. In the article, the authors provide their own experience with the use of an ultrasound contrast medium for the diagnosis and dynamic observation of complex kidney cysts, as well as the introduction of ultrasound observation using a contrast medium to classify patients according to Bosniak M.A.

The study included the results of the use of contrast enhanced ultrasound (CEUS) in 28 patients with various cystic formations of the kidneys. The patients were previously divided into two groups: the first consisted of 13 patients with simple cysts, the second – 15 with suspected complex cysts. As a result of the study, the patients were distributed as follows: 15 patients were classified as Bosniak type I, 7 patients – as type II, 3 - type III, 3 - type IV. The studied CEUS method is simple and effective. The specificity of the method was 78.57%, the accuracy of the method was 85.71%, the predictive value of the positive result was 81.25%, and the predictive value of the negative result was 91.66%. CEUS helps to quickly and accurately conduct differential diagnosis between a simple cyst and a complex one, as well as classify cysts according to M.A. Bosniak.

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.

European Society of Paediatric Radiology abdominal imaging task force: recommendations for contrast-enhanced ultrasound and diffusion-weighted imaging in focal renal lesions in children

Contrast-enhanced ultrasound (CEUS) and diffusion-weighted imaging (DWI) are safe, repeatable imaging techniques. The aim of this paper is to discuss the advantages, technical factors and possible clinical applications of these imaging tools in focal renal lesions in children.

Contrast-Enhanced Ultrasound in Renal Imaging and Intervention

PURPOSE OF REVIEW

In recent years, there has been renewed interest in the use of contrast-enhanced ultrasound (CEUS) in abdominal imaging and intervention. The goal of this article is to review the practical applications of CEUS in the kidney, including renal mass characterization, treatment monitoring during and after percutaneous ablation, and biopsy guidance.

RECENT FINDINGS

Current evidence suggests that CEUS allows accurate differentiation of solid and cystic renal masses and is an acceptable alternative to either computed tomography (CT) or magnetic resonance imaging (MRI) for characterization of indeterminate renal masses. CEUS is sensitive and specific for diagnosing residual or recurrent renal cell carcinoma (RCC) following percutaneous ablation. Furthermore, given its excellent spatial and temporal resolution, CEUS is well suited to demonstrate tumoral microvascularity associated with malignant renal masses and is an effective complement to conventional grayscale ultrasound (US) for percutaneous biopsy guidance. Currently underutilized, CEUS is an important problem-solving tool in renal imaging and intervention whose role will continue to expand in coming years.

Comparison of the Diagnostic Performance of Contrast-enhanced Ultrasound with That of Contrast-enhanced Computed Tomography and Contrast-enhanced Magnetic Resonance Imaging in the Evaluation of Renal Masses: A Systematic Review and Meta-analysis

CONTEXT

Contrast-enhanced ultrasound (CEUS) has the potential to be a valuable alternative to contrast-enhanced computed tomography (CECT) and contrast-enhanced magnetic resonance imaging (CEMR), the current gold standards in characterisation of renal masses.

OBJECTIVE

To systematically review all available evidence on the qualitative diagnostic performance of CEUS versus that of CECT and CEMR in the evaluation of benign and malignant cystic and solid renal masses.

EVIDENCE ACQUISITION

The review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement.

EVIDENCE SYNTHESIS

After screening 1483 articles, six cohort studies and 10 descriptive studies were included. Pooling data from included studies with final diagnosis of benign or malignant renal masses by pathology showed a significant difference in the sensitivity of CEUS (0.96; 95% confidence interval [CI] 0.94-0.98) versus that of CECT (0.90; 95% CI 0.86-0.93). Pooling data from included studies with final diagnosis by pathology report or reaffirmed diagnosis by follow-up imaging without pathology report showed significant difference in the sensitivity of CEUS (0.98; 95% CI 0.94-1.0) versus that of CEMR (0.78; 95% CI 0.66-0.91).

CONCLUSIONS

Preliminary data imply that CEUS may perform at least as well as or better than CECT and CEMR in the diagnosis of renal masses. However, the evidence base is limited, and more high-quality, well-designed, adequately powered, and sampled studies are needed to reach definitive conclusions.

PATIENT SUMMARY

Early data suggest that contrast-enhanced ultrasound is a promising option for the evaluation of renal masses, but more reliable evidence is required.

[Reliable diagnosis of cystic renal lesions]

CLINICAL/METHODICAL ISSUE

Cystic renal lesions are commonly seen during routine ultrasound examinations of the abdomen.

STANDARD RADIOLOGICAL METHODS

Some cystic renal lesions cannot be sufficiently characterized using native ultrasound. In these cases additional imaging might be necessary.

METHODICAL INNOVATIONS

Contrast-enhanced ultrasound (CEUS) is a reliable imaging modality to characterize cystic renal lesions. Contrast enhancement of septations and the cystic wall are visualized in high resolution. This information helps to categorize the cystic renal lesions applying the CEUS Bosniak classification. This classification helps to estimate the probability of a malignant etiology of cystic renal lesions.

PERFORMANCE

Using CEUS, cystic renal lesions can be characterized with a high sensitivity and specificity.

ACHIEVEMENTS

The advantages of CEUS include that there is no effect on the function of the kidneys or the thyroid gland and no radiation exposure. In some cases, additional cross-sectional imaging is necessary to optimize diagnostic accuracy.

PRACTICAL RECOMMENDATIONS

CEUS is a helpful imaging modality to characterize cystic renal lesions, to avoid unnecessary follow-ups and to detect malignant cystic renal lesions.

[CEUS-diagnostic workup of cystic renal lesions]

CLINICAL/METHODICAL ISSUE

Cystic renal lesions are common incidental findings in radiological imaging and they should be adequately examined to be able to characterize them as benign or malignant.

STANDARD RADIOLOGICAL METHODS

It is not always possible to sufficiently characterize cystic renal lesion solely using native B‑mode sonography and color-Doppler sonography.

METHODICAL INNOVATIONS

Using contrast-enhanced ultrasound (CEUS), it is possible to dynamically evaluate the perfusion of cystic renal lesions and to characterize the potential malignancy of these lesions using the Bosniak classification in order to give recommendations regarding further work-up. CEUS can also be used in patients with contraindications for other radiological imaging modalities as it uses a contrast agent with almost no side effects.

PERFORMANCE

Using CEUS, cystic renal lesions can be reliably characterized with a diagnostic accuracy greater than 90%.

ACHIEVEMENTS

CEUS is a useful method in diagnosing and characterizing unclear cystic renal lesions and should always be considered as a viable diagnostic tool.

PRACTICAL RECOMMENDATIONS

CEUS should always be performed in initially unclear cases and is a useful additional tool for the diagnosis and characterization of unclear cystic renal lesions.

Active Surveillance Versus Nephron-Sparing Surgery for a Bosniak IIF or III Renal Cyst: A Cost-Effectiveness Analysis

OBJECTIVE

The objective of our study was to evaluate the cost-effectiveness of active surveillance (AS) versus nephron-sparing surgery (NSS) in patients with a Bosniak IIF or III renal cyst.

MATERIALS AND METHODS

Markov models were developed to estimate life expectancy and lifetime costs for 60-year-old patients with a Bosniak IIF or III renal cyst (the reference cases) managed by AS versus NSS. The models incorporated the malignancy rates, reclassification rates during follow-up, treatment effectiveness, complications and costs, and short- and long-term outcomes. An incremental cost-effectiveness analysis was performed to identify management preference under an assumed $75,000 per quality-adjusted life-year (QALY) societal willingness-to-pay threshold, using data from studies in the literature and the 2015 Medicare Physician Fee Schedule. The effects of key parameters were addressed in a multiway sensitivity analysis.

RESULTS

The prevalence of malignancy for Bosniak IIF and III renal cysts was 26% (25/96) and 52% (542/1046). Under base case assumptions for Bosniak IIF cysts, the incremental cost-effectiveness ratio of NSS relative to AS was $731,309 per QALY for women, exceeding the assumed societal willingness-to-pay threshold, and AS outperformed NSS for both life expectancy and cost for men. For Bosniak III cysts, AS yielded greater life expectancy (24.8 and 19.4 more days) and lower lifetime costs (cost difference of $12,128 and $11,901) than NSS for men and women, indicating dominance of AS over NSS. Superiority of AS held true in sensitivity analyses for men 46 years old or older and women 57 years old or older even when all parameters were set to favor NSS.

CONCLUSION

AS is more cost-effective than NSS for patients with a Bosniak IIF or III renal cyst.

Classification and Diagnosis of Cystic Renal Tumors: Role of MR Imaging Versus Contrast-Enhanced Ultrasound

Superior soft tissue and contrast resolution of MR imaging benefits sensitivity to kidney cyst features and classification, which may have an impact on patient management and outcomes. Contrast-enhanced ultrasound (CEUS) may have nearly similar sensitivity for detection of cyst features yet is dependent on patient body habitus and adequacy of visualization windows for the kidneys, which does not have the same impact on MR imaging results. Both MR imaging and CEUS may provide superior kidney cyst assessment compared with contrast-enhanced CT; however, further research is needed, particularly for the identification of role of CEUS.

Comparison of contrast-enhanced ultrasound with MRI in the diagnosis of complex cystic renal masses: a meta-analysis

Background The differential diagnosis of cystic renal masses still faces great challenges. There has been no systematically assessment to compare the value of contrast-enhanced ultrasound (CEUS) with magnetic resonance imaging (MRI) in the diagnosis of cystic renal masses. Purpose To perform a meta-analysis to compare the diagnostic efficacy of CEUS with that of MRI for cystic renal masses. Material and Methods A systematic search was performed for literature evaluating the diagnostic performance of CEUS or MRI in cystic renal masses. Quality assessment of diagnostic studies 2 (QUADAS-2) was used to evaluate the quality of each study included. The pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and the areas under the summary receiver operating characteristic (AUCs-SROC) curve for CEUS and MRI were calculated, respectively. Results Seventeen studies with 1142 lesions were included. The pooled sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio for CEUS /MRI were 0.95/0.92, 0.84/0.91, 5.62/6.74, and 0.09/0.13, respectively. The AUCs-SROC curves for the two methods were 95.66% and 94.65%. The subgroup analysis indicated that the scanning slice thickness may influence the diagnostic efficacy of MRI. Conclusion Both CEUS and MRI have good diagnostic performance for cystic renal masses and can provide the reference for clinicians. CEUS is more sensitive but less specific than MRI.

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.

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.

MRI and contrast enhanced ultrasound (CEUS) image fusion of renal lesions

Ultrasound is a common and established imaging method for the initial characterization of renal lesions. The widespread used Bosniak classification (I-IV) classifies renal lesions in five individual groups using contrast-enhanced computer tomography (CE-CT), magnetic resonance imaging (MRI) and/or contrast-enhanced ultrasound (CEUS) imaging criteria. For complex pathologies, CEUS/MRI image fusion is a novel imaging technique for the differentiation of benign and malignant renal lesions. Compared to CE-CT and MRI alone, ultrasound image fusion offers the additional possibility of being a real-time imaging technique that can be used together with other cross-sectional imaging techniques.This article describes the newest possibilities of image fusion with CEUS and MRI in detection and characterization of unclear renal lesions.

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.

Effectiveness of contrast-enhanced ultrasound and serum liver enzyme measurement in detection and classification of blunt liver trauma

Objective

This study was performed to identify the correlation between contrast-enhanced ultrasound (CEUS) and contrast-enhanced multidetector computed tomography (CE-MDCT) as well as the correlation between serum liver enzyme concentrations and CE-MDCT in classification of the severity of blunt hepatic trauma using CE-MDCT as a reference standard.

Materials and methods

A blunt liver trauma model was created using 20 rabbits, and CE-MDCT, CEUS, and serum liver enzyme assays were performed. A radiologist and an ultrasound physician independently evaluated the degree of liver trauma. The diagnostic performance of CEUS and serum liver enzyme measurements was compared with that of CE-MDCT using Spearman’s correlation analysis and Pearson’s correlation analysis, respectively.

Results

Spearman’s rank correlation coefficient between the CEUS-based classification and CE-MDCT was 0.888. The aspartate aminotransferase and lactate dehydrogenase concentrations and the aspartate aminotransferase/alanine aminotransferase ratio were positively correlated with the grade of liver injury; Pearson’s correlation coefficients were 0.664, 0.704, and 0.503, respectively. The gamma-glutamyltransferase concentration had a significantly negative correlation with the grade of liver injury (r = −0.467).

Conclusions

CEUS and serum liver enzyme measurement exhibited high consistency with CE-MDCT for both detection and grading of intraparenchymal lesions in blunt liver trauma. These techniques may permit more accurate diagnosis of liver trauma.

Bosniak classification system: a prospective comparison of CT, contrast-enhanced US, and MR for categorizing complex renal cystic masses

Background The Bosniak classification was originally based on computed tomographic (CT) findings. Magnetic resonance (MR) and contrast-enhanced ultrasonography (CEUS) imaging may demonstrate findings that are not depicted at CT, and there may not always be a clear correlation between the findings at MR and CEUS imaging and those at CT. Purpose To compare diagnostic accuracy of MR, CEUS, and CT when categorizing complex renal cystic masses according to the Bosniak classification. Material and Methods From February 2011 to June 2012, 46 complex renal cysts were prospectively evaluated by three readers. Each mass was categorized according to the Bosniak classification and CT was chosen as gold standard. Kappa was calculated for diagnostic accuracy and data was compared with pathological results. Results CT images found 27 BII, six BIIF, seven BIII, and six BIV. Forty-three cysts could be characterized by CEUS, 79% were in agreement with CT (κ = 0.86). Five BII lesions were upgraded to BIIF and four lesions were categorized lower with CEUS. Forty-one lesions were examined with MR; 78% were in agreement with CT (κ = 0.91). Three BII lesions were upgraded to BIIF and six lesions were categorized one category lower. Pathologic correlation in six lesions revealed four malignant and two benign lesions. Conclusion CEUS and MR both up- and downgraded renal cysts compared to CT, and until these non-radiation modalities have been refined and adjusted, CT should remain the gold standard of the Bosniak classification.

Malignancy rates and diagnostic performance of the Bosniak classification for the diagnosis of cystic renal lesions in computed tomography - a systematic review and meta-analysis

Objective

To systematically review the literature on the Bosniak classification system in CT to determine its diagnostic performance to diagnose malignant cystic lesions and the prevalence of malignancy in Bosniak categories.

Methods

A predefined database search was performed from 1 January 1986 to 18 January 2016. Two independent reviewers extracted data on malignancy rates in Bosniak categories and several covariates using predefined criteria. Study quality was assessed using QUADAS-2. Meta-analysis included data pooling, subgroup analyses, meta-regression and investigation of publication bias.

Results

A total of 35 studies, which included 2,578 lesions, were investigated. Data on observer experience, inter-observer variation and technical CT standards were insufficiently reported. The pooled rate of malignancy increased from Bosniak I (3.2 %, 95 % CI 0–6.8, I² = 5 %) to Bosniak II (6 %, 95 % CI 2.7–9.3, I² = 32 %), IIF (6.7 %, 95 % CI 5–8.4, I² = 0 %), III (55.1 %, 95 % CI 45.7–64.5, I² = 89 %) and IV (91 %, 95 % CI 87.7–94.2, I² = 36). Several study design-related influences on malignancy rates and subsequent diagnostic performance indices were identified.

Conclusion

The Bosniak classification is an accurate tool with which to stratify the risk of malignancy in renal cystic lesions.

Key points

• The Bosniak classification can accurately rule out malignancy.

• Specificity remains moderate at 74 % (95 % CI 64–82).

• Follow-up examinations should be considered in Bosniak IIF and Bosniak II cysts.

• Data on the influence of reader experience and inter-reader variability are insufficient.

• Technical CT standards and publication year did not influence diagnostic performance.

Electronic supplementary material

The online version of this article (doi:10.1007/s00330-016-4631-9) contains supplementary material, which is available to authorized users.

The role of contrast-enhanced ultrasound in the classification of CT-indeterminate renal lesions

OBJECTIVE

Focal renal lesions are common incidental findings on computed tomography (CT). For lesions with a cystic appearance, the Bosniak classification system has enabled an important separation of benign and (potentially) malignant cysts, giving a practical guide for management. The purpose of this study was to evaluate contrast-enhanced ultrasound (CEUS) as a problem-solving modality for classification of indeterminate renal lesions detected with CT.

MATERIALS AND METHODS

In total, 140 consecutive patients with 148 indeterminate renal lesions were examined with ultrasound combined with CEUS (81 men and 59 women with mean age 63.8 years).

RESULTS

Altogether, 146 lesions were classified by CEUS in categories according to the Bosniak classification system, or as solid lesions. Mean lesion diameter was 30 mm (range 5-166 mm). Nine lesions were classified as category I, 32 as category II and 59 as category IIF ("non-surgical lesions"). 48 IIF cysts were followed for a minimum of 2 years (mean 4 years and 8 months): three lesions were upgraded to category III (6%) and 45 were stable category. 19 lesions had a more complex cystic appearance: 12 were classified as category III and seven as category IV cysts. 27 lesions were diagnosed as solid, enhancing tumors. In total, 25 patients with lesions of category III, IV and solid ("surgical lesions") underwent renal surgery, with malignancy diagnosed in 18.

CONCLUSION

In the common setting of indeterminate renal lesions incidentally detected with a CT exam, CEUS has the potential to classify lesions into "non-surgical" and "surgical" categories, providing a platform for urological decision making, while avoiding radiation exposure.

Cystic renal masses

PURPOSE

The purpose of the study is to provide an update on the imaging evaluation of cystic renal masses, to review benign and malignant etiologies of cystic renal masses, and to review current controversies and future directions in the management of these lesions.

CONCLUSIONS

Cystic renal masses are relatively common in daily practice. The Bosniak classification is a time-proven method for the imaging classification and management of these lesions. Knowledge of the pathognomonic features of certain benign Bosniak 2F/3 lesions is important to avoid surgery on these lesions (e.g., localized cystic disease, renal abscess). For traditionally surgical Bosniak lesions (Classes 3 and 4), there are evolving data that risk stratification based on patient demographics, imaging size, and appearance may allow for expanded management options including tailored surveillance or ablation, along with the traditional surgical approach.