Assessment of cystic renal masses based on Bosniak classification: comparison of CT and contrast-enhanced US

Contrast enhanced ultrasound of the kidneys: what is it capable of?

One of the many imaging uses of contrast enhanced ultrasound (CEUS) is studying a wide variety of kidney pathology, due to its ability to detect microvascular blood flow in real time without affecting renal function. CEUS enables dynamic assessment and quantification of microvascularisation up to capillary perfusion. The objective of this paper is to briefly refresh basic knowledge of ultrasound (US) contrast agents' physical properties, to study technical details of CEUS scanning in the kidneys, and to review the commonest renal indications for CEUS, with imaging examples in comparison to baseline unenhanced US and computed tomography when performed. Safety matters and limitations of CEUS of the kidneys are also discussed.

Evaluation of indeterminate renal masses with contrast-enhanced US: a diagnostic performance study

PURPOSE

To determine the utility of contrast material-enhanced ultrasonography (US) in the characterization of indeterminate renal masses.

MATERIALS AND METHODS

This retrospective performance study was approved by the institutional review board and was HIPAA compliant, with waiver of informed consent. Patients included 721 individuals referred for contrast-enhanced US with 1018 indeterminate renal masses from 1999 to 2010, identified initially with an imaging study. Three hundred twenty patients (44.4%) were female, and 401 (55.6%) were male. Patient ages ranged from 17 to 95 years (mean ± standard deviation, 70 years ± 15). Lesion size varied from 2 to 161 mm (mean, 26.6 mm ± 19.5). Contrast-enhanced US enhancement patterns were used to characterize masses as benign or malignant. For lesions with a definitive diagnosis, 306 of 1018 (30.0%) were correlated with contrast-enhanced US findings: 167 (54.6%) were benign, and 139 (45.4%) were malignant. For lesions without a pathologic diagnosis, 712 (70.0%) were followed for as long as 10 years. Diagnostic accuracy measures were calculated by using pathologic diagnosis as the reference standard, as well as lesion stability at 3 and 5 years.

RESULTS

Contrast-enhanced US had a sensitivity of 100% (126 of 126; 95% confidence interval [CI]: 97.1%, 100%), specificity of 95.0% (132 of 139; 95% CI: 89.9%, 98.0%), positive predictive value (PPV) of 94.7% (126 of 133), and negative predictive value (NPV) of 100% (132 of 132). The five false-positive masses included three oncocytomas and two Bosniak category 3 cystic lesions. Of the 290 lesions that had follow-up of at least 36 months, none of the lesions demonstrated changes that necessitated lesion reclassification. If these lesions were included, assuming lesions classified as malignant were malignant, then of the 596 lesions, sensitivity was 100% (161 of 161), specificity was 96.6% (420 of 435), PPV was 91.5% (161 of 176), and NPV was 100% (420 of 420).

CONCLUSION

Contrast-enhanced US evaluation is a highly sensitive and specific method for characterization of indeterminate renal masses. Online supplemental material is available for this article.

Evaluation of renal masses with contrast-enhanced ultrasound

The clinical need for characterising small renal masses (SRMs) is increasing due to their rising incidental detection. This increase is especially seen in younger and older generations and concerns mainly SRMs. Diagnostics is mainly made by contrast-enhanced CT or MRI. However, these imaging methods fail to accurately distinguishing benign from malignant SRMs. Other disadvantages of CT or MRI are high costs, the use of ionizing radiation, nephrotoxicity induced by iodine contrast agents or nephrogenic systemic fibrosis (NSF) induced by gadolinium contrast agents. Contrast-enhanced ultrasound (CEUS) is based on ultrasonography and microbubbles to real-time visualize the renal blood flow without the use of nephrotoxic agents or ionizing radiation. This comprehensive review evaluates the capabilities of CEUS in the diagnostics of benign (angiomyolipomas, cysts, oncocytomas, pseudotumors) and malignant masses (renal cell carcinomas), and focuses on possible future treatment.

Evaluation of Bosniak category IIF complex renal cysts

PURPOSE

To evaluate moderately complex renal cysts of Bosniak category IIF.

MATERIALS AND METHODS

The regional ethics committee approved the study. In the period 2003-2009, radiological CT reports of 8,402 CT examinations of the kidneys were analysed retrospectively by one radiologist. All complex cystic lesions in the kidney (n = 550 in the same number of patients) were reclassified according to the Bosniak classification by two radiologists in consensus. If a patient had more than one lesion, only the highest Bosniak category was recorded. All Bosniak IIF lesions with ≥2-year follow-up were included in the study.

RESULTS

Thirty-two Bosniak IIF lesions were found. Five lesions (16 %) were upgraded during follow-up and the patients were offered surgery. Pathology of three lesions showed papillary carcinoma, clear cell renal carcinoma and chronic inflammation, respectively. Due to comorbidity the remaining two patients were followed with CT without intervention. Ten lesions (31 %) with follow-up periods >5 years had no further radiological changes and clinical follow-up was stopped.

CONCLUSION

The use of Bosniak category IIF is clinically applicable, resulting in an overall surgical nephron-sparing approach to complex renal cysts.

TEACHING POINTS

• The Bosniak classification is used to categorise complex renal cystic masses • BIIF cysts behave mostly as benign lesions • Radiological progression in complexity occurs in only 16 % of cases • BIIF category seems promising for clinical application, potentially avoiding unnecessary surgery.

Office ultrasound for the urologist

Imaging of the genitourinary tract is essential in the workup of the majority of the conditions seen daily by urologists. The use of ultrasound in the office provides a safe, low cost, and efficient way for the clinician to evaluate the patient in real time. Ultrasound can allow for bedside diagnosis in many conditions and assist in treatment planning. This chapter covers the major applications of office ultrasound for the urologist as well as discusses future applications of ultrasound for the office setting.

Predicting the histology of small renal masses using preoperative dynamic contrast-enhanced magnetic resonance imaging

OBJECTIVE

To study whether magnetic resonance imaging can predict the histologic type of small renal cell carcinoma.

METHODS

Dynamic contrast-enhanced magnetic resonance imaging was performed in 63 patients with computed tomography- or ultrasonography-suspected small (≤ 4 cm) renal cell carcinoma from February 2008 to February 2010. Percentage signal intensity change, tumor-to-cortex enhancement index during precontrast phase, corticomedullary phase, and nephrogenic phase were investigated.

RESULTS

Among the 60 patients, 42 were proven to have clear cell renal cell carcinoma and 18 patients were proven to have non-clear cell renal cell carcinoma (10 patients with papillary renal cell carcinoma, 8 patients with chromophobe renal cell carcinoma). The percentage signal intensity change in the clear cell type was higher only in the corticomedullary phase (P = .002). The tumor-to-cortex enhancement index in the clear cell type was higher in the corticomedullary and nephrogenic phases (P = .007 and P = .041, respectively). The most valuable marker was percentage signal intensity change in the corticomedullary phase (area under the receiver operating characteristic curve 0.85). The cut-off value of percentage signal intensity change in the corticomedullary phase was 173%, and the sensitivity and specificity were 81% and 87.5%, respectively.

CONCLUSION

Dynamic contrast-enhanced magnetic resonance imaging could be useful for discriminating the clear cell type from non-clear cell type in small renal cell carcinoma with high sensitivity and specificity.

[The impact of ultrasound in urology]

Ultrasound is of great importance in the diagnosis of acute and chronic diseases in urology, such as kidney colic, testicular torsion, low-grade kidney trauma or for follow-up of vesicoureteral reflux, evaluation of infertility, measurement of residual urinary volume and the detection of cancer. An ultrasound examination is time and cost-effective without exposure to ionizing radiation and is routinely performed by practitioners as well as in the clinical daily routine. With technical innovations, such as contrast-enhanced ultrasound or real time elastography, it would for instance be possible to extend the application field of ultrasound. However, in some fields of investigation ultrasound still lacks accuracy and despite its many advantages the validity of ultrasound findings sometimes has to be verified with computed tomography (CT) or magnetic resonance imaging (MRI).

Contrast-enhanced ultrasound in abdominal imaging

The administration of a contrast agent is considered an essential tool to evaluate abdominal diseases using Ultrasound. The most targeted organ is the liver, especially to characterize focal liver lesions and to assess the response to percutaneous treatment. However, the expanding abdominal indications of contrast-enhanced ultrasound make this technique an important tool in the assessment of organ perfusion including the evaluation of ischemic, traumatic, and inflammatory diseases.

Current and potential renal applications of contrast-enhanced ultrasound

The combination of microbubble technology and complementary ultrasound techniques has resulted in the development of contrast-enhanced ultrasound (CEUS) and, although initial clinical applications largely focussed on the liver, these are now becoming more diverse. With regard to the kidney, it is a safe, well-tolerated, and reproducible technique, and in selected cases, can obviate the need for computed tomography or magnetic resonance imaging. A clear advantage is the absence of nephrotoxicity. With respect to the current and potential renal applications, it is a useful technique in the evaluation of pseudotumours, acute pyelonephritis, renal tumours, cystic lesions, vascular insults, and renal transplantation. It may also be of value for monitoring the kidney following anti-angiogenic treatment or nephron-sparing interventional techniques for renal tumours. Assessment of microvascular perfusion using time-intensity curves is also likely to have further far-reaching applications in the kidney as well as other organs.

The current role of contrast-enhanced ultrasound (CEUS) imaging in the evaluation of renal pathology

BACKGROUND

By using a microbubble contrast agent and contrast-specific imaging software, the contrast-enhanced ultrasound (CEUS) is able to depict the micro and macrocirculation of the target organ.

METHODS

A review of the peer reviewed literature was done regarding the current role of ultrasound CEUS imaging in the evaluation of renal pathology with reference to the diagnosis of renal ischaemia, in the characterization of complex cystic lesions and in those with equivocal enhancement at CT.

RESULTS

CEUS provides information on tissue perfusion and may play a role in kidney mass characterization similar to the role of contrast-enhanced CT and MRI. In this context, the characterization of cystic lesions is probably the most consolidated field of application of contrast agents on kidney ultrasound imaging. Finally, CEUS provides a good alternative to CT, especially in patients with contraindications to iodinated contrast agents.

CONCLUSIONS

The usefulness of CEUS in these applications is confirmed by extensive literature production and this article focuses on the potential clinical applications of recent advances in CEUS technology in urology.

Contemporary imaging of the renal mass

Renal masses increasingly are detected incidentally in asymptomatic individuals. Accurate characterization of these lesions is important for clinical management, planning intervention, and avoiding unnecessary procedures. Ultrasonography, computed tomography (CT), and magnetic resonance imaging (MRI) are the mainstays of renal mass detection and characterization. Ultrasonography is useful for distinguishing cystic from solid lesions and can detect lesion vascularity, especially with use of ultrasound contrast agents, but is less sensitive, less specific, and less reproducible than CT and MRI. CT, with and without intravenous contrast, is the primary imaging test for characterization and staging of renal lesions, and is utilized more often than MRI. Current multidetector CT technology provides near isotropic acquisition, with three-dimensional reformatting capabilities. Due to lack of exposure to iodinated contrast and ionizing radiation and superior soft tissue contrast, MRI is being increasingly utilized as a problem-solving tool for diagnosis, staging, and preoperative planning for renal malignancies. Future directions for imaging of primary renal neoplasm include accurate characterization of renal cell cancer subtype, assistance with treatment planning, and evaluation of treatment response.

Renal cell carcinoma: real-time contrast-enhanced ultrasound findings

OBJECTIVE

To investigate the findings of renal cell carcinomas (RCCs) on contrast-enhanced ultrasound (CEUS).

METHODS

CEUS features of 84 RCCs confirmed by pathologic examination in 81 patients were retrospectively analyzed. A contrast-specific mode and a sulfur hexafluoride-filled microbubble contrast agent were used for CEUS. The enhancement pattern, extent, and dynamic change in the cortical, corticomedullary, and late phases were evaluated.

RESULTS

On CEUS, the emergence of tumor enhancement was earlier in two nodules (2.4%), simultaneous in 71 (84.5%), and later in 11 (13.1%), in comparison with the adjacent renal cortex. Seventy-four RCC nodules (88.1%) showed hyper-enhancement (n = 2) or iso-enhancement (n = 72) during the cortical phase, and the remaining 10 (11.9%) showed hypo-enhancement. Twenty-three nodules (27.4%) showed homogeneous enhancement and 61 (72.6%) inhomogeneous enhancement. In the corticomedullary phase, the nodules showed hypo-enhancement in 68 (81.0%) and iso-enhancement in 16 (19.0%). In the late phase, all RCCs showed the same enhancement pattern as that shown in the corticomedullary phase. Seventy-two (85.7%) nodules showed a clear perilesional rim-like enhancement in late phase.

CONCLUSIONS

Hyper- or iso-enhancement during the cortical phase, subsequent washout in late phase, inhomogeneous enhancement, and perilesional rim-like enhancement are clues for RCCs, which might be useful for characterization of RCCs.

Differentiation of Bosniak categories IIF and III cystic masses: what radiologists should know

Based on a review of the literature, we describe old and new features that both old and new radiologists should be aware of (a) to determine which imaging features affect the differentiation of categories IIF and III masses, (b) to show imaging features of benign cystic renal masses preoperatively diagnosed as category III, and (c) to introduce imaging techniques that help to differentiate categories IIF and III masses without requiring the use of CT or magnetic resonance contrast material.

Characterization of complex renal cysts: a critical evaluation of the Bosniak classification

OBJECTIVE

Complex renal cysts represent a major clinical problem, since it is often difficult to exclude malignancy. The Bosniak classification system, based on computed tomography (CT), is widely used to categorize cystic renal lesions. The aim of this study was to evaluate critically available data on the Bosniak classification.

MATERIAL AND METHODS

All publications from an Entrez Pubmed search were reviewed, focusing on clinical applicability and the use of imaging modalities other than CT to categorize complex renal cysts.

RESULTS

Fifteen retrospective studies were found. Most series were small, with only six studies comprising more than 30 patients. When the results of these six studies were pooled the percentage of malignancy was: category I, 0%; category II, 15.6%; category IIF, 0%; category III, 65.3%; and category IV, 91.7%. Category IIF was included in only three studies. Both magnetic resonance imaging and contrast-enhanced ultrasonography (US) seemed to have reasonable agreement with CT, although both modalities had a tendency to upgrade lesions.

CONCLUSIONS

The main problem with the Bosniak classification is in separating category II and III lesions, which is of major importance, since decisions on intervention are based on this separation. The use of category IIF seems promising to detect those category II lesions that eventually will develop into malignancy and reduce overtreatment of lesions originally classified as category III. The scientific basis of this "new" classification strategy is, however, still missing. Data on other imaging modalities are too limited for conclusions to be drawn.

Contrast-enhanced ultrasound using a time-intensity curve for the diagnosis of renal cell carcinoma

OBJECTIVE

• To evaluate the usefulness of contrast-enhanced ultrasound (CEUS) for the diagnosis of renal cell carcinoma by employing a time-intensity curve (TIC).

PATIENTS AND METHODS

• From May 2008 to October 2009, CEUS was performed prior to surgery in 30 patients with renal masses. • In all, 10 of the 30 patients had cystic renal masses. The final diagnoses of all patients were pathologically confirmed. Contrast enhancement as a function of time was measured in two (tumour or solid component of cystic lesions and normal parenchyma) regions of interest (ROI) and TICs were obtained. • The time to the contrast enhancement peak (TTP), intensity change from the baseline to peak (ΔI) and ΔI/TTP of the tumour and the normal parenchyma were measured from the TIC.

RESULTS

• Pathological diagnoses were renal cell carcinoma in 30 patients. • The TTP of the cancer was shorter than that of the normal parenchyma in all cases (6.0 ± 2.0 vs 10.4 ± 3.0 s; P < 0.0001). • The ΔI did not differ between the cancer and normal parenchyma [21.3 ± 5.9 vs 20.9 ± 7.0 decibels (db); P= 0.68]; the ΔI/TTP of the cancer was significantly higher than that of the normal parenchyma (3.9 ± 1.4 vs 2.2 ± 0.94 db/s; P < 0.0001). • TIC patterns of solid cancer and cystic cancer were very similar.

CONCLUSIONS

• An objective and quantitative diagnosis of renal cell carcinoma by CEUS using a second-generation ultrasound contrast agent can be made by employing a TIC. • The TIC patterns of solid and cystic cancers were very similar, despite their morphological and vascular differences. • CEUS using TIC is a promising tool in the diagnosis of cystic renal cancer.

Microbubble-enhanced US in body imaging: what role?

Contrast agents for ultrasonography (US) comprise microscopic bubbles of gas in an encapsulating shell. They are unique in that they interact with the imaging process, oscillating in response to a low-intensity ultrasound field and disrupting in response to a high-intensity field. New contrast-specific imaging modes allow US to show exquisite vascularity and tissue perfusion in real time and with excellent spatial resolution. In Europe, Asia, and Canada, to name only the most obvious, characterization of focal liver masses is the first and best established use of contrast-enhanced (CE) US, allowing for the noninvasive diagnosis of commonly encountered liver masses with comparable accuracy to that of computed tomography and magnetic resonance studies. CE US is a preferred modality for the difficult task of diagnosis of liver nodules detected on surveillance scans in those at risk for hepatocellular carcinoma. Newer body applications include the guidance of ablative intervention, monitoring activity of bowel inflammation in Crohn disease, characterization of kidney masses, especially cystic renal cell carcinoma, diagnosis of prostate cancer, and monitoring the response of tumors to antivascular drug therapies. Microbubble contrast agents are easy to use and robust; their use poses no risk of nephrotoxicity and requires no ionizing radiation. CE US plays a vital and expanding role that improves management and patient care.

Characterization of intra-abdominal lesions of undetermined origin by contrast-enhanced harmonic EUS (with videos)

BACKGROUND

The diagnosis of intra-abdominal lesions of undetermined origin is often a challenge for endoscopists and radiologists.

OBJECTIVE

To evaluate the microvasculature of benign and malignant intra-abdominal lesions by contrast-enhanced harmonic EUS (CEH-EUS) and to investigate its usefulness for discriminating between malignant and benign lesions.

DESIGN

The vascularity of intra-abdominal lesions of undetermined origin was observed by using CEH-EUS. The lesions were classified according to their vascular patterns. The effectiveness of CEH-EUS in differentiating malignant from benign lesions was evaluated.

SETTING

Kinki University School of Medicine, Osaka, Japan.

PATIENTS

Forty-three patients, each with a lesion of undetermined origin, were evaluated prospectively by CEH-EUS between March 2007 and March 2009.

INTERVENTIONS

CEH-EUS was performed by using a prototype echoendoscope and the extended pure harmonic detection mode (a specific mode for contrast harmonic imaging).

MAIN OUTCOME MEASUREMENTS

The lesions were categorized by 2 physicians as having no, homogeneous, or heterogeneous enhancement. A consensus was reached for each case offline. How the benign and malignant groups differed in terms of their enhancement patterns was examined.

RESULTS

The kappa coefficient of the interobserver agreement test was 0.953 (P < .001). Of the 27 malignant lesions, 26 (96.3%) exhibited heterogeneous enhancement. The 1 remaining malignant lesion (3.7%) showed homogeneous enhancement. Of the 16 benign lesions, none displayed heterogeneous enhancement, and 12 (75%) and 4 (25%) exhibited homogeneous and no enhancement, respectively. The malignant and benign lesion groups differed significantly in terms of homogeneous and heterogeneous enhancement (P < .001). The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy with which CEH-EUS differentiated malignant from benign lesions were 96.3%, 100%, 100%, 94.1%, and 97.6%, respectively.

LIMITATIONS

A single medical unit with a limited number of patients.

CONCLUSIONS

CEH-EUS depicted the microvasculature of intra-abdominal lesions of undetermined origin very clearly and may be useful for characterizing such lesions.

Assessment of cystic renal masses in children: comparison of multislice computed tomography and ultrasound imaging using the Bosniak classification system

To retrospectively compare contrast-enhanced multislice computed tomography (MSCT) and ultrasound (US) imaging for the assessment of cystic renal masses in children using the Bosniak classification system. Twenty-two consecutive patients (age 1 month to 5.2 years, mean 2.4 years) with 24 cystic renal masses (7 benign, 17 malignant) pathologically confirmed after surgical resection underwent both MSCT and US imaging, and were retrospectively analyzed using the Bosniak classification. A senior and a junior radiologist retrospectively and independently reviewed imaging findings. The sensitivity, specificity, positive predictive value and negative predictive values of MSCT and US were assessed using diagnostic statistics. The statistical significance of differences was determined by the McNemar test. Both radiologists accurately predicted lesions of categories I and IV with the Bosniak classification using MSCT and US. All masses classified as Bosniak classes I and II were proven to be benign, and all malignant lesions were correctly characterized in all cases both on ultrasound images and on the contrast-enhanced CT (CECT) images. Two benign multilocular cystic nephromas and one multicystic dysplastic kidney were classified into category III or even IV based on the classification scheme because of their multilocular nature and thick septation. The diagnostic accuracy of CECT was slightly better than ultrasound (CECT vs. US: senior reader, 92% vs. 88%; junior reader, 88% vs. 83%). However, there was no statistically significant difference between the two sets (p>0.05). The two radiologists had perfect inter-observer agreement on the two modalities. Both MSCT and US provide highly accurate diagnosis for the malignant renal cystic masses in children using the Bosniak classification system, but assessment of benign masses still needs improvement. We would recommend US is the best screening modality in Bosniak I and II, In Bosniak III and IV, MSCT are first the choice.

Imaging renal cell carcinoma with ultrasonography, CT and MRI

The increased use of abdominal imaging techniques for a variety of indications has contributed to more-frequent detection of renal cell carcinoma (RCC). Ultrasonography has been used to characterize the solid versus cystic nature of renal masses. This modality has limitations, however, in further characterization of solid tumors and in staging of malignancy, although contrast-enhanced ultrasonography has shown promise. Cross-sectional imaging with multiplanar reconstruction capability via CT or MRI has become the standard-bearer in the diagnosis, staging and surveillance of renal cancers. The use of specific protocols and the exploitation of different imaging characteristics of RCC subtypes, including variations in contrast agent timing, MRI weighting and digital subtraction, have contributed to this diagnostic capability. Cystic renal masses are a special case, evaluation of which can require multiple imaging modalities. Rigorous evaluation of these lesions can provide information that is crucial to prediction of the likelihood of malignancy. Such imaging is not without risk, however, as radiation from frequent CT imaging has been implicated in the development of secondary malignancies, and contrast agents for CT and MRI can pose risks, particularly in patients with compromised renal function.

Renal cell carcinoma and renal angiomyolipoma: differential diagnosis with real-time contrast-enhanced ultrasonography

OBJECTIVE

The purpose of this study was to evaluate the usefulness of contrast-enhanced ultrasonography (CEUS) in differentiating renal cell carcinoma (RCC) from renal angiomyolipoma (RAML).

METHODS

One hundred nineteen patients with 126 renal lesions (33 RAMLs and 93 RCCs) who had undergone CEUS were retrospectively studied. All of the lesions were histopathologically or clinical proved. Contrast-enhanced ultrasonography was performed using low-acoustic power modes and a sulfur hexafluoride-filled microbubble contrast agent. The baseline sonograms and CEUS images were retrospectively analyzed in consensus by 2 radiologists. The tumor echogenicity, enhancement patterns, and degree of enhancement at different phases were evaluated. The diagnostic efficacy of CEUS in differentiating the two diseases was computed and compared.

RESULTS

On CEUS, the features of wash-out from hyperenhancement or isoenhancement to hypoenhancement over time (observed in 3.0% of RAMLs and 71.0% of RCCs; P < .001), heterogeneous enhancement (observed in 12.1% of RAMLs and 74.2% of RCCs; P < .001), and an enhanced perilesional rim (observed in 3.0% of RAMLs and 79.6% of RCCs; P < .001) achieved significant difference between RCCs and RAMLs. Early wash-out and heterogeneous enhancement or peritumoral rim enhancement yielded the highest diagnostic capability in differentiating RCC from RAML. The corresponding sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 88.2% (82 of 93), 97.0% (32 of 33), 98.8% (82 of 83), 74.4% (32 of 43), and 90.5% (114 of 126), respectively.

CONCLUSIONS

The CEUS features of early wash-out, heterogeneous enhancement, and an enhanced peritumoral rim highly suggest RCC, whereas homogeneous enhancement and prolonged enhancement are characteristic manifestations of RAML. Contrast-enhanced ultrasonography is valuable in differentiating RCC from RAML.

Imaging angiogenesis of genitourinary tumors

Angiogenesis is a key process in the growth and metastasis of cancer, and genitourinary tumors are no exception. The evolution of angiogenesis as an important target for novel anticancer therapeutics has brought with it new challenges for in vivo imaging. Most imaging techniques quantify physiological parameters, such as blood volume and capillary endothelial permeability. Although CT, PET and ultrasonography have shown promise, MRI is the most common method used to evaluate angiogenesis in clinical trials of genitourinary tumors. Pilot studies of MRI, CT and ultrasonography in patients with renal cancer have produced promising results; reductions in vascular permeability and blood flow have been correlated with progression-free survival. The vascular characteristics of prostate cancer have been evaluated by MRI, and this has been suggested as a means of assessing tumor response to hormone deprivation therapy. Current evidence highlights the potential of angiogenesis imaging in the diagnosis, staging and possibly response monitoring of bladder cancer. In the future, assessment of the angiogenic process at the structural, functional and molecular levels, before, during and after antiangiogenic therapy will undoubtedly be integrated into wider clinical practice.

Contrast enhanced ultrasound of renal masses

Contrast enhanced ultrasound (CEUS) has gained clinical importance over the last years for the characterization of hepatic masses. Its role in extrahepatic indications has been investigated repeatedly but has been less comprehensively studied. Currently more than 50% of renal masses are incidentally diagnosed, mostly by B-mode ultrasound. The method of choice for characterization of renal lesions is contrast enhanced computed tomography (CECT). In the case of cystic lesions CECT refers to the Bosniak classification for cystic lesions to assess the risk of malignant behavior. The majority of masses are renal cell carcinoma, but the exact proportion is controversial. Disadvantages of CECT are a significant risk for patients with impaired renal function, allergic reactions and hyperthyroidism due to iodinated contrast agents. Several studies concerning CEUS for the characterization of both solid and cystic renal lesions have been published, but prospective multicenter studies are missing, the presented data being mainly descriptive. The aim of the this manuscript is to review the current literature for CEUS in renal masses, to summarize the available data and focus on possible concepts for studies in the future.

[Usefulness of contrast-enhanced ultrasonography in daily clinical practice: a multicenter study in Spain]

OBJECTIVES

We aimed to determine whether the use of ultrasonographic contrast agents improves the diagnostic performance of ultrasonography (US).

MATERIAL AND METHODS

We carried out a prospective multicenter study in 42 hospitals. We included 1786 patients with inconclusive US; 84.9% of the inconclusive studies were abdominal US (including studies of the liver, kidneys, spleen, and other sites), 6.2% were studies of the peripheral vessels, 4.3% were breast studies, and 4.6% were other studies. We evaluated the type of contrast-enhanced US (color Doppler or contrast-specific method), type of contrast agent, dose and number of doses, and type of administration (bolus or infusion). We evaluated whether the findings at contrast-enhanced US improved the diagnostic performance of unenhanced US and whether they enabled a conclusive diagnosis to be reached.

RESULTS

The contrast agent SonoVue was used in 99.9% of the studies; a single dose of contrast agent was used in 84.8%, and the contrast agent was administered in bolus in 98.5%. Contrast-enhanced US improved the diagnostic performance in 91.6% of cases and enabled the conclusive diagnosis in 69.2%. The best diagnostic performance was obtained in the supraaortic trunks, where a definitive diagnosis was reached in 95.4% of cases, followed by the abdominal area, with a conclusive diagnosis in 72.6% of cases.

CONCLUSIONS

The use of contrast-enhanced US significantly improved the diagnostic performance of US and enabled a conclusive diagnosis in most cases.

Renal cell carcinoma originating in a renal cyst in a 12-year-old girl

We report a 12-year-old girl with renal cell carcinoma originating in a cyst of the left kidney. Ultrasonography revealed 2 small hyperechoic masses in the luminal side of a cyst. Although hypervascularity was not detected in the cyst by computed tomography, the possibility of malignancy could not be ruled out because of the presence of 2 solid masses. Therefore, partial left nephrectomy was performed. On histopathologic examination, the 2 solid masses within the cyst were found to be renal cell carcinoma. This patient remains disease-free at 4 years after partial nephrectomy.

Differential diagnosis of complex cystic renal mass using multiphase computerized tomography

PURPOSE

We evaluated the additional usefulness of multiphase computerized tomography for improving the differential diagnosis of cystic renal masses by the Bosniak classification.

MATERIALS AND METHODS

We reviewed the records of 104 patients with Bosniak class II (29 or 27.8%), III (38 or 36.5%) and IV (37 or 35.7%) cystic renal masses managed surgically between 1997 and 2007. On preoperative multiphase computerized tomography enhancement differences in HU between the precontrast and corticomedullary phases were measured at the highest enhancement area to correlate with pathological findings.

RESULTS

Renal cell carcinoma was diagnosed in 56 patients (53.8%). Of the tumors 35 (62.5%) showed clear cell histology. According to Bosniak class 3 (11.5%), 21 (55.2%) and 32 (86.4%) class II to IV lesions, respectively, were diagnosed as renal cell carcinoma. For renal cell carcinoma and benign cysts mean HU at the precontrast phase was similar (31.5 and 32.4 HU, respectively), while renal cell carcinoma showed a significantly higher measurement at the corticomedullary phase (112.9 vs 59.8 HU, p <0.0001). To differentiate renal cell carcinoma a corticomedullary phase minus precontrast phase value of greater than 42 HU was predictive with 97.1% sensitivity and 85.7% specificity (area under the ROC curve 0.966). In a multiple regression model the corticomedullary phase minus precontrast phase value and the Bosniak classification independently determined malignant pathological findings (corticomedullary phase minus precontrast phase greater than 42 HU HR 31.541, 95% CI 8.320-119.563 and Bosniak class HR 5.545, 95% CI 2.153-14.279, each p <0.0001).

CONCLUSIONS

In cases of complex cystic renal masses diagnostic accuracy can be improved to differentiate renal cell carcinoma by combining Bosniak class and enhancement differences measured on multiphase computerized tomography between precontrast and maximal enhancement phases. This would help determine the need for and the method of surgical treatment.

Comparison of contrast-enhanced sonography with unenhanced sonography and contrast-enhanced CT in the diagnosis of malignancy in complex cystic renal masses

OBJECTIVE

The objective of our study was to evaluate contrast-enhanced sonography in the diagnosis of malignancy in complex cystic renal masses.

MATERIALS AND METHODS

We analyzed a series of 40 cystic renal masses (diameter, 2-8 cm) with a complex pattern at contrast-enhanced CT in 40 consecutive subjects (18 men, 22 women; mean age +/- SD, 62 +/- 11 years). Each renal mass was scanned using sonography without contrast material and after IV injection of sulfur hexafluoride-filled microbubbles during the arterial (15-40 seconds) and venous (40-120 seconds from injection) phases. Two radiologists in consensus assessed onsite the enhancement patterns in the peripheral wall and intracystic septa and the evidence of solid endocystic components. Three blinded readers with 2, 6, and 10 years of experience in renal imaging performed a retrospective off-site interpretation of unenhanced sonography, contrast-enhanced sonography, and CT images and made a benign or malignant diagnosis according to refer ence diagnostic criteria for contrast-enhanced sonography and to the Bosniak classification for CT.

RESULTS

Final diagnoses comprised two multilocular cystic nephromas, two inflammatory and seven hemorrhagic cysts, and eight uncomplicated benign cysts and 21 cystic renal cell carcinomas. The overall diagnostic accuracy of contrast-enhanced sonography was better than unenhanced sonography and CT (contrast-enhanced sonography vs unenhanced sonography vs CT: reader 1, 83% vs 30% vs 75%; reader 2, 83% vs 30% vs 63%; reader 3, 80% vs 30% vs 70%; p < 0.05, McNemar test).

CONCLUSION

Contrast-enhanced sonography was found to be better than unenhanced sonography and CT in the diagnosis of malignancy in complex cystic renal masses.

Contrast-enhanced ultrasound for diagnosis of prostate cancer and kidney lesions

PURPOSE OF REVIEW

Conventional ultrasonography of both, kidney and prostate, is limited due to the poor contrast of B-mode imaging for parenchymal disease and limited sensitivity of colour Doppler for the detection of capillaries and deep pedicular vessels. Contrast-enhanced ultrasound (CEUS) overcomes these limitations.

RECENT FINDINGS

CEUS investigates the blood flow of the prostate, allows for prostate cancer visualization and for targeted biopsies. Comparisons between systematic and CEUS-targeted biopsies have shown that the targeted approach detects more cancers with a lower number of biopsy cores and with higher Gleason scores compared with the systematic approach. Also the kidney offers promising applications as CEUS improves the detection of abnormal microvascular and macrovascular disorders.

SUMMARY

In recent literature CEUS has shown its value for diagnosis of both, prostate cancer and kidney lesions. This paper describes recent improvements and future perspectives of CEUS.

Renal cell carcinoma: imaging and therapy

PURPOSE OF REVIEW

The increasing use of ultrasound and computerized tomography has led to over 50% of renal cell carcinomas being incidentally detected. With an increasing number of small and asymptomatic tumors being identified it is particularly important for an accurate diagnosis to be reached via available imaging modalities to permit selection of patients for surgical treatment. The identification of patients suitable for management via nephron-sparing surgery is a key issue.

RECENT FINDINGS

Advances in imaging have focused on the ability to distinguish malignant from nonmalignant tumors. Advanced assessments have aimed to identify the cancer subtype preoperatively in order to limit the requirement for surgery in carcinomas with low metastatic potential. Improved staging of renal tumors with magnetic resonance imaging and positron emission tomography has allowed more accurate preoperative assessment and planning of treatment for both organ-confined and extensive renal tumors. Radioimmunoscintigraphy and radioimmunotherapy also offer potential for therapeutic intervention at an antigen-directed level.

SUMMARY

More accurate matching of therapeutic options to newly diagnosed renal carcinomas is now possible with contemporary imaging techniques in order to limit morbidity of surgical treatment. The potential for urologists to progress to treatment of renal malignancies via advanced radiographic techniques is fast approaching.