Renal imaging for diagnosis and staging of renal cell carcinoma

Biomarkers for the Detection and Surveillance of Renal Cancer

Renal cell carcinoma (RCC) is a heterogeneous disease characterized by a broad spectrum of disorders in terms of genetics, molecular and clinical characteristics. There is an urgent need for noninvasive tools to stratify and select patients for treatment accurately. In this review, we analyze serum, urinary, and imaging biomarkers that have the potential to detect malignant tumors in patients with RCC. We discuss the characteristics of these numerous biomarkers and their ability to be used routinely in clinical practice. The development of biomarkers continues to evolve with promising prospects.

Prognostic evaluation based on radiological morphological characteristic for tumors larger than 7 cm in renal cell carcinoma

PURPOSE

To predict survival prognosis of renal cell carcinoma (RCC) patients with tumors larger than 7 cm by preoperative radiological morphological features.

METHODS

We reviewed the medical records of RCC patients with tumors larger than 7 cm from 2007 to 2017 in Zhongshan Hospital, Fudan University. A total of 251 patients' clinical data were collected. 25 and 9 patients were excluded due to loss of follow-up and lack of imaging data, respectively. PFS and OS from date of surgery were evaluated. We defined the irregularity of the tumor as the morphological feature studied and quantified it according to a theorem of the ellipse: the length from the midpoint of the ellipse to any point on the ellipse is shorter than or equal to 1/2 of the long axis. The cutoff value of irregularity was calculated based on the ROC curve. Cox proportional hazards regression models were used to test associations between features and outcome.

RESULTS

Of all the 217 patients included in the study, 67 patients had disease progression and 30 patients died. The cutoff value of the irregularity was selected to be 0.5335. Adrenal invasion, presence of distant metastasis and irregularity of tumors were significantly associated with PFS, and presence of distant metastasis and irregularity of tumors were significantly associated with OS.

CONCLUSIONS

For patients with tumors larger than 7 cm in RCC, we found a radiological index that is closely related to the prognosis: irregularity. This is an unreported independent prognostic risk factor that can be quantified before surgery.

Clinical Influences in the Multidisciplinary Management of Small Renal Masses at a Tertiary Referral Center

INTRODUCTION

We designed a multidisciplinary Small Renal Mass Center to help patients decide among treatment options and individualize therapy for small renal masses. In this model physicians and support staff from multiple specialties work as a team to evaluate and devise a treatment plan for patients at the same organized visit.

METHODS

We retrospectively reviewed the records of 263 patients seen from 2009 to 2014. Monitored patient characteristics included age, Charlson comorbidity index, body mass index, nephrometry score, tumor size and estimated glomerular filtration rate. Univariate and multivariate analyses were performed to identify patient characteristics associated with each treatment choice.

RESULTS

Of the cohort 88 patients elected active surveillance, 64 underwent ablation and 111 were treated with surgery, including partial and radical nephrectomy in 74 and 37, respectively. There were significant associations between treatment modality and age, Charlson comorbidity index, tumor size and estimated glomerular filtration rate. Mean patient age at presentation was 61.1 years. Patients with a high Charlson comorbidity index score (greater than 5) or a decreased estimated glomerular filtration rate (less than 60 ml/minute/1.73 m2) were more likely to undergo active surveillance (41.6% and 35%) and ablative therapy (29.6% and 34%) vs partial nephrectomy (10.6% and 9%, respectively, each p <0.001). On multivariable analysis age, tumor size and estimated glomerular filtration rate remained significantly associated with modality after adjustment for all other factors (each p <0.001).

CONCLUSIONS

The Small Renal Mass Center enables patients to assess the various treatment modalities for a small renal mass in a single setting. By providing simultaneous access to the various specialists it provides an invaluable opportunity for informed patient decision making.

Diagnostic Utility of Diffusion-weighted Magnetic Resonance Imaging in Differentiating Small Solid Renal Tumors (≤ 4 cm) at 3.0T Magnetic Resonance Imaging

BACKGROUND

The aim of this study was to assess the performance of apparent diffusion coefficient (ADC) measurement obtained with diffusion-weighted magnetic resonance imaging (DW-MRI) to distinguish renal cell carcinomas (RCCs) from small benign solid renal tumors (≤ 4 cm).

METHODS

In this cross-sectional study, 49 consecutive patients with histopathologically confirmed small solid renal tumors, and seven healthy volunteers were imaged using nonenhanced MRI and DW-MRI. The ADC map was calculated using the b values of 0, 50, 400, and 600 s/mm 2 and values compared via the Kruskal-Wallis and Mann-Whitney tests. The utility of ADC for differentiating RCCs and benign lesions was assessed using a receiver operating characteristic curve. Multiple nonenhanced MRI features were analyzed by Logistic regression.

RESULTS

The tumors consisted of 33 cases of clear-cell RCCs (ccRCCs) and 16 cases of benign tumors, including 14 cases of minimal fat angiomyolipomas and 2 cases of oncocytomas. The ADCs showed significant differences among benign tumors ([0.90 ± 0.52] × 10-3 mm 2 /s), ccRCCs ([1.53 ± 0.31] × 10-3 mm 2 /s) and the normal renal parenchyma ([2.22 ± 0.12] × 10-3 mm 2 /s) (P < 0.001). Moreover, there was statistically significant difference between high and low-grade ccRCCs (P = 0.004). Using a cut-off ADC of 1.36 × 10-3 mm 2 /s, DW-MRI resulted in an area under the curve (AUC), sensitivity, and specificity equal to 0.839, 75.8%, and 87.5%, respectively. Nonenhanced MRI alone and the combination of imaging methods led to an AUC, sensitivity and specificity equal to 0.919, 93.9%, and 81.2%, 0.998, 97%, and 100%, respectively. The Logistic regression showed that the location of the center of the tumor (inside the contour of the kidney) and appearance of stiff blood vessel were significantly helpful for diagnosing ccRCCs.

CONCLUSIONS

DW-MRI has potential in distinguishing ccRCCs from benign lesions in human small solid renal tumors (≤ 4 cm), and in increasing the accuracy for diagnosing ccRCCs when combined with nonenhanced MRI.

Current status of renal biopsy for small renal masses

Small renal masses (SRMs) are defined as radiologically enhancing renal masses of less than 4 cm in maximal diameter. The incidence of renal cell carcinoma (RCC) has increased in recent years, which is mainly due to the rise in incidental detection of localized SRMs. However, the cancer-specific mortality rate is not increasing. This discrepancy may be dependent on the indolent nature of SRMs. About 20% of SRMs are benign, and smaller masses are likely to have pathologic characteristics of low Fuhrman grade and clear cell type. In addition, SRMs are increasingly detected in elderly patients who are likely to have comorbidities and are a high-risk group for active treatment like surgery. As the information about the nature of SRMs is improved and management options for SRMs are expanded, the current role of renal mass biopsy for SRMs is also expanding. Traditionally, renal mass biopsy has not been accepted as a standard diagnostic tool in the clinical scenario because of several issues about safety and accuracy. However, current series on SRM biopsy have reported high diagnostic accuracy with rare complications. Studies of modern SRM biopsy have reported diagnostic accuracy greater than 90% with very high specificity. Also, current series have shown very rare morbid cases caused by renal mass biopsy. Currently, renal biopsy of SRMs can be recommended in most cases except when patients have imaging or clinical characteristics indicative of pathology and in cases in which conservative management is not considered.

FDG in Urologic Malignancies

Kidney, bladder, and prostate cancer account for more than one-eighth of new cancer cases worldwide. Imaging in kidney cancer is dominated by computed tomography (CT). Positron emission tomography (PET) imaging of bladder cancer is hampered by the urinary excretion of the most common PET tracer, 18F-fluoro-deoxy-glucose (FDG). PET imaging has been applied more often in prostate cancer. FDG-PET/CT is claimed to have a high frequency of false-negative results in urologic cancers; however, this finding may instead reflect correctly the state of disease being due to slow-growing cancers with a good prognosis and without a need of therapy.

Iodine quantification using dual-energy multidetector computed tomography imaging: phantom study assessing the impact of iterative reconstruction schemes and patient habitus on accuracy

PURPOSE

The aim of this study was to assess the accuracy of iodine quantification based on spectral dual-energy computed tomography (DECT) extraction with additional noise reduction using iterative reconstruction in simulated optimal and obese patient environments.

MATERIALS AND METHODS

Two custom-designed DECT phantoms were containing 10 vials with iodine concentrations representing arterial/parenchymal enhancement ranging from water isodensity to -150 Hounsfield units and, in addition, 40 vials simulating enhancement seen in nondiluted thoracic inlet vasculature and urinary bladder/renal collecting systems of up to -2000 Hounsfield units.Dual-energy computed tomography acquisition was performed using a dual-source scanner at 140 kVp/90 mAs and 80 kVp/495 mAs. Backprojection-based soft tissue kernels and corresponding iteratively reconstructed kernels generated dual-energy series used for iodine extraction.Fractional variations between known and spectrally determined iodine concentration were calculated for each concentration step; paired t tests evaluated variations between backprojected and iteratively reconstructed data sets for small and obese phantoms. Bland-Altman plots with regression analyses assessed concentration differences observed in backprojected and iteratively reconstructed data.

RESULTS

For backprojected data, mean concentration variations of 8.7% ± 8.4 and 12.2% ± 6.3 were detected in small and large phantoms, respectively, compared with significantly less variation observed in iteratively reconstructed data with 6.1% ± 6.2 and 11.0% ± 6.5, respectively. Dual-energy quantification systematically overestimated concentrations in lower concentration ranges and underestimated concentrations in higher concentration ranges. Regression analyses showed cubic distribution of concentration differences for backprojected (R = 0.697) and linear distribution for iteratively reconstructed data (R = 0.701).

CONCLUSION

Spectral DECT-based iodine quantification is able to accurately quantify iodine in phantoms simulating optimal and large patients; iterative reconstruction improves the accuracy of iodine detection. Systematic deviations of the spectrally determined iodine concentrations could potentially be corrected with weighting curves.

The expanding role of imaging in the management of renal cell carcinoma

The management of renal cell carcinoma (RCC) is evolving owing to the increasing detection of small renal masses, greater understanding of the metabolic pathways involved, new targeted medical treatments for metastatic RCC, and evolving surgical and minimally invasive image-guided treatment techniques. Consequently, the role of imaging and radiology has expanded, with new challenges encompassing all aspects of management, including diagnosis, predicting cell type, staging, preoperative vascular mapping, image-guided treatment and biopsy, detection of recurrence and the use of imaging as a biomarker to assess response to treatment. This article is a comprehensive review of RCC, outlining the etiology of the disease, RCC histological subtypes and their imaging characteristics, imaging modality techniques for evaluation of RCC, treatment strategies and the management of small renal masses.

Characterization of small renal masses less than 4 cm with quadriphasic multidetector helical computed tomography: differentiation of benign and malignant lesions

Purpose

To identify the characteristic quadriphasic (unenhanced, corticomedullary, nephrographic, and excretory phase) helical multidetector computed tomography (MDCT) features of renal masses less than 4 cm to distinguish benign from malignant renal masses.

Materials and Methods

In total, 84 patients were retrospectively analyzed to determine the characteristic features for the prediction of subtypes of small renal masses. The patients' age, gender, and tumor size and CT features, including the presence of intra-tumor degenerative changes, septation, calcification, and wall irregularity, were evaluated. In addition, the degree and pattern of enhancement obtained during four phases were analyzed. The relationship between the subtype of the small renal masses and the gender, morphological features, and pattern of contrast enhancement on the CT was analyzed by using the chi-square test. Tumor size and degree of contrast enhancement were compared by the Mann-Whitney U test. The predictive value of each of the CT features was determined by multivariate logistic regression analysis.

Results

Of the 84 small renal masses, 17 (20%) were benign and 67 (80%) were malignant. Univariate analysis revealed that renal cell carcinoma lesions showed heterogeneous enhancement (p=0.002) and higher mean attenuation value on the corticomedullary and nephrographic phases (135.1±53.9, p=0.000, and 132.4±43.6, p=0.006). The multivariate analysis with logistic regression model showed that only the mean attenuation value on the corticomedullary phase had a statistically significant correlation (p=0.021).

Conclusions

For the characterization of small renal masses, the degree of enhancement on the corticomedullary phase is a valuable parameter. Furthermore, the heterogeneous enhancement pattern and degree of enhancement on the nephrographic phase can provide information for differentiating small renal masses.

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.

The growth rate of large renal masses opposes active surveillance

OBJECTIVE

To retrospectively determine the growth rate of renal masses with a diameter of > or =4 cm at the time of surgery, as the average growth rate of untreated small (<4 cm) renal masses is assumed to be 0.1-0.7 cm/year, but little is known about the progression of large masses.

PATIENTS AND METHODS

Of 256 patients who had their renal tumour surgically removed between January and December 2008, we identified nine (five men and four women; median age 65.2 years, range 29.2-74.2) with solitary large renal masses (>4 cm) who had abdominal imaging with identification of renal masses >6 months before admission. In none of the patients had the initial imaging led to admission, either by accident or because the masses were overlooked. The tumour growth rate was calculated based on images taken > or =6 months before admission and actual imaging, as well as histological results.

RESULTS

All patients had surgical resection of their renal masses in 2008. The median (range) follow-up from initial diagnosis to surgery was 14.6 (6.5-58.4) months. The median observed tumour growth rate was 6.41 (2.47-8.66) cm/year. The histological diagnosis was clear cell renal cell carcinoma (RCC) in seven patients, papillary in one and clear cell RCC with portions of sarcomatoid de-differentiation in one; two patients had lymph node metastases and one had pulmonary metastases, and five had tumours of > or =T3.

CONCLUSIONS

The growth rate of large tumours is much higher than of small renal masses and most patients present with advanced disease. Thus, tumours of > or =4 cm seem not to be candidates for active surveillance but require immediate therapy. Further studies are warranted to determine the clinical relevance of progressive tumour growth and the underlying mechanisms.

Renal lesions: characterization with diffusion-weighted imaging versus contrast-enhanced MR imaging

PURPOSE

To compare the diagnostic performance of diffusion-weighted (DW) magnetic resonance (MR) imaging with that of contrast material-enhanced (CE) MR imaging and to assess the performance of these examinations combined for the characterization of renal lesions, with MR follow-up and histopathologic analysis as the reference standards.

MATERIALS AND METHODS

The institutional review board waived the requirement of informed patient consent for this retrospective HIPAA-compliant study. One hundred nine renal lesions in 64 patients (46 men, 18 women; mean age, 60.7 years) were evaluated with CE MR imaging and breath-hold DW imaging performed with various b values. Renal lesions were characterized with use of CE MR criteria, and apparent diffusion coefficients (ADCs) were measured. The ADCs of benign and malignant lesions were compared at Mann-Whitney testing. Receiver operating characteristic (ROC) analysis was performed to assess the accuracy of DW imaging and CE MR imaging in the diagnosis of renal cell carcinoma (RCC).

RESULTS

The 109 renal lesions--81 benign lesions and 28 RCCs--had a mean diameter of 4.2 cm +/- 2.5 (standard deviation). The mean ADC for RCCs (1.41 x 10(-3) mm(2)/sec +/- 0.61) was significantly lower (P < .0001) than that for benign lesions (2.23 x 10(-3) mm(2)/sec +/- 0.87) at DW imaging performed with b values of 0, 400, and 800 sec/mm(2). At a cutoff ADC of less than or equal to 1.92 x 10(-3) mm(2)/sec, the area under the ROC curve (AUC), sensitivity, and specificity of DW imaging for the diagnosis of RCCs (excluding angiomyolipomas) were 0.856, 86%, and 80%, respectively. The corresponding AUC, sensitivity, and specificity of CE MR imaging were 0.944, 100%, and 89%, respectively. Combined DW and CE MR imaging had 96% specificity. The AUC for the DW imaging-based diagnosis of solid RCC versus oncocytoma was 0.854. Papillary RCCs had lower ADCs than nonpapillary RCCs.

CONCLUSION

DW imaging can be used to characterize renal lesions; however, compared with CE MR imaging, it is less accurate. DW imaging can be used to differentiate solid RCCs from oncocytomas and characterize the histologic subtypes of RCC.

Association of gadolinium based magnetic resonance imaging contrast agents and nephrogenic systemic fibrosis

PURPOSE

We investigated the recently discovered association between gadolinium based magnetic resonance imaging contrast agents and the development of nephrogenic systemic fibrosis in patients with chronic kidney disease or acute kidney injury.

MATERIALS AND METHODS

A systematic review of the PubMed database and publicly available patient databases was performed to characterize nephrogenic systemic fibrosis and its possible association with exposure to gadolinium based magnetic resonance imaging contrast agents.

RESULTS

Data from case series reports, nephrogenic systemic fibrosis patient databases, nephrogenic systemic fibrosis case reporting to the Food and Drug Administration after gadolinium contrast agent exposure and retrospective case control studies suggest a strong association between the use of gadolinium based magnetic resonance imaging contrast agents and the subsequent development of nephrogenic systemic fibrosis in patients with renal disease. These data also suggest that the risk of nephrogenic systemic fibrosis depends on the degree of renal dysfunction, dose of contrast agent, gadolinium contrast agent stability and severity of concomitant illness. Thus, the occurrence of nephrogenic systemic fibrosis after gadolinium contrast agent exposure may vary from negligible up to 2% to 5% in select high risk clinical situations.

CONCLUSIONS

Magnetic resonance imaging using gadolinium based contrast agents must be performed judiciously in patients with renal dysfunction, carefully weighing on a case by case basis the benefits of magnetic resonance imaging and the risk of nephrogenic systemic fibrosis as well as the disadvantages of undergoing alternative or foregoing imaging studies.

Apparent wall thickening of cystic renal lesions on MRI

PURPOSE

To show that cystic renal lesions that would otherwise meet criteria for simple cysts can demonstrate perceptible walls or increased wall thickness on MRI, sometimes causing these lesions to be "upgraded." It was hypothesized that thickening of cyst walls on MRI can be artifactual, due to data truncation, applied filtering, and low signal-to-noise ratio (SNR).

MATERIALS AND METHODS

k-Space data for a 4-cm cyst were created in a 40-cm field of view (FOV) (512 x 512 matrix). Additional data sets were created using the central 512 x 256 and 512 x 128 points. Noise was simulated so that the cyst SNR was approximately 7, 14, and 20, respectively. Actual wall thickness was set at 0.25 mm, and cyst:wall signal at 1:4. An inverse two-dimensional (2D) fast Fourier transform (FFT) yielded simulated images. A Fermi filter was applied to reduce ringing. Images/projections were examined for wall thickening. Seven patients with initially thick-walled cysts on fat-saturated spoiled gradient-echo (FS-SPGR) images were scanned with increasing resolution (256 x 128 and 256 x 256; four patients were also scanned with 512 x 512). Average wall thickness at each resolution was compared using a two-tailed paired Student's t-test.

RESULTS

Simulations showed apparent wall thickening at low resolution, improving with higher resolutions. Low SNR and application of the Fermi filter made it difficult to identify ringing as the cause of this thickening. The simulation results were confirmed on seven patients, whose cyst walls proved to be artifactually thickened (P < 0.01).

CONCLUSION

Thickening of cyst walls on MRI can be artifactual. Upon encountering thick-walled cystic renal lesions, high-resolution images can be acquired to exclude apparent thickening.

Characterization of radiologists' search strategies for lung nodule detection: slice-based versus volumetric displays

The goal of this study was to assess whether radiologists' search paths for lung nodule detection in chest computed tomography (CT) between different rendering and display schemes have reliable properties that can be exploited as an indicator of ergonomic efficiency for the purpose of comparing different display paradigms. Eight radiologists retrospectively viewed 30 lung cancer screening CT exams, containing a total of 91 nodules, in each of three display modes [i.e., slice-by-slice, orthogonal maximum intensity projection (MIP) and stereoscopic] for the purpose of detecting and classifying lung nodules. Radiologists' search patterns in the axial direction were recorded and analyzed along with the location, size, and shape for each detected feature, and the likelihood that the feature is an actual nodule. Nodule detection performance was analyzed by employing free-response receiver operating characteristic methods. Search paths were clearly different between slice-by-slice displays and volumetric displays but, aside from training and novelty effects, not between MIP and stereographic displays. Novelty and training effects were associated with the stereographic display mode, as evidenced by differences between the beginning and end of the study. The stereo display provided higher detection and classification performance with less interpretation time compared to other display modes tested in the study; however, the differences were not statistically significant. Our preliminary results indicate a potential role for the use of radiologists' search paths in evaluating the relative ergonomic efficiencies of different display paradigms, but systematic training and practice is necessary to eliminate training curve and novelty effects before search strategies can be meaningfully compared.

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.

Imaging in genitourinary cancer from the urologists' perspective

It is well established that advances in imaging may lead to early cancer detection, more accurate tumour staging and consequently adequate treatment, better monitoring of the disease and enhanced surveillance for recurrences after treatment. This manuscript reviews the current use of imaging in genitourinary cancer and explores the impact of imaging findings in clinical management. Additionally, an effort has been made to present the emerging imaging modalities and also their possible role in diagnosis and treatment of these cancers.

Ultrasonography of Renal Masses Using Contrast Pulse Sequence Imaging: A Pilot Study

BACKGROUND AND PURPOSE

The use of contrast-enhanced ultrasonography for imaging of renal masses was first described in 1994. Since then, many new techniques for visualization of the effect of microbubble contrast agents have been developed. In this pilot study, a small number of patients was investigated with contrast pulse sequence imaging (CPS), and the characteristics of this perfusion imaging technique were evaluated subjectively and judged against the clinical diagnosis and histology findings when available. The purpose of this pilot study was to describe CPS imaging in several cases.

PATIENTS AND METHODS

Eighteen patients with 20 previously identified renal masses were examined with CPS. Perfusion imaging was compared with clinical diagnosis and with histologic findings when available.

RESULTS

Nineteen masses were visible. Various enhancement patterns could be observed, and interpretations of CPS characteristics are described. In carcinomas, inhomogeneous enhancement patterns were observed, and areas without enhancement inside the inhomogeneous lesions corresponded to necrotic areas in histologic specimens. All simple cysts and complex benign cysts showed absence of enhancement inside or in the wall of the lesion and a regular shape.

CONCLUSION

To our knowledge, this is the first study in which the characteristics of CPS imaging of renal masses have been related to clinical diagnoses and histologic features. From the results of this pilot project, we conclude that CPS is a promising technique to determine perfusion patterns in the kidney.

Assessment of the kidney tumor vascular supply by two-phase MDCT-angiography

PURPOSE

Current kidney surgery uses less invasive laparoscopic and nephron-sparring procedures. Thus, perfect imaging of the renal vasculature is essential for surgery planning. The aim of our retrospective study was to evaluate the accuracy of 16-detector-row CT-angiography in assessing the vascular anatomy of the kidney with a tumor.

SUBJECTS AND METHODS

Referred for computed tomography (CT) because of a suspected renal tumor, 50 consecutive patients (mean age 58.6 years; range 43-82) were enrolled into our retrospective study. All examinations were performed with 16x0.75 mm collimation after the intravenous application of 80 ml of a non-ionic contrast material. The imaging protocol contained two-phase scanning in the arterial and then in the venous phase. The vascular anatomy of the kidney with tumor was evaluated using volume rendered (VRT) and maximum intensity images (MIP). Findings were compared with the anatomy found during surgery.

RESULTS

Forty-seven patients underwent nephrectomy, with an advanced clinical stage (IV) found in the three remaining ones. Correct topography of the renal hilus, including a number of arteries and veins, and the anatomy of their branching, was described in 46 patients. A very small upper polar artery was overlooked in one patient. The accuracy for the only-arterial was 97.9% and only-venous anatomy was 100%. The parasitic vasculature of the tumor was discovered in 10 cases and all of them were confirmed by surgery (100% accuracy). Macroscopic intravenous spread of the tumor was discovered in two cases, but microscopic intravenous invasion was confirmed during histology of the kidney specimens in another two cases, the overall tumor staging accuracy reaching 95.7%.

CONCLUSION

Two-phase multidetector CT is a valuable tool for assessing vascular supply of the kidney before surgery due to the tumor and can fully replace catheter-based angiography.

Imaging of kidney cancer

Advances in molecular genetics have expanded the understanding of renal cell tumors. Now it is understood that renal cortical tumors are a family of neoplasms with distinct cytogenetics and molecular defects, unique histopathologic features, and different malignant potentials. Imaging contributes to clinical management of patients with renal tumors in providing diagnostic information for tumor detection, characterization, staging, treatment planning, and follow-up.

Staging of Renal Cell Carcinoma: Past, Present, and Future

Tumor stage, which describes the anatomic extent of disease, is a powerful determinant of prognosis and survival for patients with renal cell carcinoma (RCC). Stratification of patients based on prognostic outcomes derived from staging systems facilitates therapeutic decision-making, disease surveillance, and clinical research. Staging for RCC has evolved from the Robson classification into the TNM system, developed by the International Union Against Cancer and the American Joint Committee on Cancer. The most recent revisions of the TNM system for RCC introduced in 1997 and 2002 further subdivided organ-confined tumors, reclassified tumors with venous involvement, and clarified the staging of tumors that invade the perisinus fat. Most studies suggest that these revisions have substantially improved prognostication for RCC. Nevertheless, additional modifications have been proposed that would alter the subclassification of organ-confined disease, integrate various levels of venous involvement with other aspects of local tumor aggressiveness, and upgrade the classification of adrenal involvement. The data in support of each of these proposals will be discussed, and the current limitations of clinical and radiographic staging for RCC will be reviewed. Finally, a glimpse into the future of staging of RCC will be offered with a discussion of integrated staging and prognostic systems.

Detection, staging and surveillance in renal cell carcinoma

This article discusses the computed tomography (CT) and magnetic resonance (MR) scanning techniques used for the detection and staging of renal cell carcinoma and their pitfalls. Comparison between the Robson and recent modifications to the TNM classifications is also addressed. The accuracy of CT and MR in the staging of renal cell carcinoma and the role of positron emission tomography (PET) scanning is outlined and finally the surveillance of patients who have had curative treatment of renal cell carcinoma is briefly addressed.

The Role of Imaging in the Surveillance of Urologic Malignancies

Urologic malignancies are common, accounting for approximately 25% of all new cancer cases in the United States. Patients with urologic malignancies require long-term surveillance to detect progression or recurrence as early as possible. The urologist is faced with the task of balancing patient safety and cost-effectiveness, while finding the most practical follow-up regimen. For each urologic malignancy, this article reviews the commonly used radiologic techniques for surveillance and offers recommended follow-up schedules.

Magnetic Resonance Imaging of Renal Disease: Recent Developments and Future Applications

Magnetic resonance imaging (MRI) offers the ability to non-invasively assess parenchymal and vascular renal disease. Indications for renal MRI include the evaluation of renal masses, urinary obstruction and infection, renal vasculature, and the health of transplant kidneys. The potential of MR angiography to replace invasive conventional x-ray angiography has been recognized for many years. Recent developments in MRI resulting from fast MR systems with faster gradients, new surface coil designs and the latest sequence developments coupled with innovative contrast agent administration strategies have prompted substantial progress of MRI in the diagnosis of renal disease. The goal of this article is to present the current state of MRI in diagnosing renal disease, with an emphasis on the latest developments in the evaluation of renal vascular disease.

The natural history of observed enhancing renal masses: meta-analysis and review of the world literature

PURPOSE

Standard therapy for an enhancing renal mass is surgical. However, operative treatment may not be plausible in all clinical circumstances. Data on the natural history of untreated enhancing renal lesions is limited but could serve as a decision making resource for patients and physicians. We examined available data on the natural history of observed solid renal masses.

MATERIALS AND METHODS

A Medline review of the literature was performed from 1966 to the present regarding untreated, observed, localized solid renal masses. To these data we added our institutional experience with a total of 61 lesions observed in 49 patients for a minimum of 1 year. Variables examined were initial lesion size at presentation, growth rate, duration of followup, pathological findings and progression to metastatic disease. Overall weighted mean estimates were calculated for lesion size at presentation, growth rate and followup based upon combining single institutional series with complete information.

RESULTS

We identified 10 reports from 9 single institutional series in the world literature regarding the natural history of untreated solid localized renal lesions. The series included 6 to 40 patients (mean 25) with a mean followup of 30 months (range 25 to 39). When combined with our institutional data, a total of 286 lesions were analyzed, of which 234 could be included in the meta-analysis. Mean lesion size at presentation was 2.60 cm (median 2.48, range 1.73 to 4.08). Meta-analysis revealed a mean growth rate of 0.28 cm yearly (median 0.28, range 0.09 to 0.86) at a mean followup of 34 months (median 32, range 26 to 39) in all series combined. Pathological confirmation was available in 46% of the cases (131 of 286) and it confirmed 92% (120 of 131) as RCC variants. Evaluable data in this subset of confirmed RCC demonstrated a mean growth rate of 0.40 cm yearly (median 0.35, range 0.42 to 1.6). Lesion size at presentation did not predict the overall growth rate (p = 0.46). Progression to metastatic disease was identified in only 1% of lesions (3 of 286) during followup.

CONCLUSIONS

The majority of small enhancing renal masses grow at a slow rate when observed. Although metastatic and cancer specific death are low, serial radiographic data alone are insufficient to predict the true natural history of these lesions. Therefore, physicians and patients assume a calculated risk when following these tumors. Basic biological data are needed to assess the natural history of untreated renal masses.

Genitourinary malignancies in solid organ transplant recipients

Malignancy is a recognized complication of transplantation. Genitourinary cancers are the second most common tumors in transplant recipients with prostate cancer and renal cell carcinoma the most common. Unlike the more common skin malignancies, genitourinary tumors have a significant impact on both graft and patient survival. Surgical and radiation treatments need to consider the location of heterotopic transplants and administration of chemotherapy may need alteration in light of immunosuppression being used. The major genitourinary malignancies and their management will be reviewed in this article with emphasis on the concerns that arise in a transplant recipient.

Multidetector computed tomography vs magnetic resonance imaging for defining the upper limit of tumour thrombus in renal cell carcinoma: a study and review

OBJECTIVE

To compare the findings of multidetector computed tomography (CT) with surgical pathology and magnetic resonance imaging (MRI), to determine the accuracy of delineating the superior extent of inferior vena cava (IVC) thrombotic involvement in renal cell cancer (RCC).

PATIENTS AND METHODS

A prospective database was examined of 11 patients (median age 65 years, range 45-77) being assessed for suspected IVC extension of RCC tumour thrombus with both multidetector CT and MRI. All had pathology confirming RCC, and eight of those undergoing surgery had pathological confirmation of tumour thrombus extent. All images were analysed originally, then re-analysed by two independent radiologists, an experienced urologist and a urological trainee unaware of the original reports and other imaging results, with a final determination on tumour thrombus level by consensus.

RESULTS

The multidetector CT results were completely accurate when compared with surgical specimens and were in agreement with MRI on all but one occasion, where MRI determined the renal vein to be clear when it was involved on CT and at surgery, giving MRI an accuracy of seven of eight samples.

CONCLUSIONS

Whilst there were few patients and further studies are needed, multidetector CT was comparable with MRI in determining tumour thrombus level. More importantly, in the eight patients with surgical pathological confirmation, multidetector CT was accurate in all. Ultimately, it may replace MRI as the 'gold standard' for imaging to delineate the upper limit of tumour thrombosis in RCC.

[Survival prognostic factors valuation on a series of 202 patients with surgical treatment of renal cell carcinoma]

OBJECTIVES

To describe renal cell carcinoma prognostic factors and set up the relationship with survival rates in this neoplasm. Likewise we show epidemiologic, clinical, diagnosis and therapeutic facts.

MATERIAL AND METHOD

We review 202 patients underwent surgical treatment for renal cell carcinoma and the following features were recorded: gender, age and presenting symptoms, especially incidentally discovered tumors; tumor-related factors like TNM tumor stage, tumor grade and venous involvement: therapy-related recorded were surgical techniques and cytokine-based therapy.

RESULTS

60% of the patients showed organ-confined disease, 10% of patients with renal cell carcinoma presented with nodal positive disease and 7% with systemic metastases. 42% of patients presenting incidental tumor, with survival rates substantially better than that for symptomatic patients. 42% of patients with nodal positive disease presented systemic metastases at diagnosis, and 30% at surveillance. Systemic metastases presented a particularly poor prognosis for patients with renal cell carcinoma, with 12-months survival rates that 0%. Patients with cytokine-related therapy for metastatic disease presented 24-months survival rates that 20%.

CONCLUSIONS

Renal cell carcinoma remains a major source of mortality, basically at advanced disease (nodal positive disease or systemic disease), without a clear improvement of survival rates despite the newer therapy modalities.

Renal magnetic resonance imaging

PURPOSE OF REVIEW

Current magnetic resonance imaging systems allow the visualization of normal and diseased kidney, with exquisite resolution of renal structures. Dynamic contrast magnetic resonance imaging has the potential, unique among all noninvasive modalities, to differentiate diseases that affect different portions of the vascular-nephron system. This article reviews the most important recently published studies in selected topics chosen because of their clinical relevance or potential for technical developments.

RECENT FINDINGS

Magnetic resonance imaging is used increasingly to evaluate renal masses, the prenatal genitourinary system, urinary obstruction and infection, renal vasculature, and the kidneys of transplant donors and recipients. Dynamic contrast magnetic resonance renography based on gadolinium chelated to diethylenetriamine pentaacetic acid, a safe (non-nephrotoxic) paramagnetic agent, emerges as the functional renal imaging modality of choice. Both perfusion and filtration rates can be assessed in individual kidney.

SUMMARY

Magnetic resonance imaging has the potential to provide a complete anatomic, physiologic, kidney-specific evaluation. With future advances in automated image analysis methods we can expect functional renal magnetic resonance imaging to play an influential role in management of renal disease.

Radiologic-pathologic correlations of intratumoral tissue components in the most common solid and cystic renal tumors. Pictorial review

This paper describes the correlation between US-CT images and pathologic findings in the most common solid and cystic renal tumors, to better differentiate malignant and benign renal masses. Several intratumoral tissue components present correlation with US-CT images. Macroscopic components, corresponding to necrotic, hemorrhagic and cystic changes, are identified by visual analysis of the gross specimen, while microscopic components are identified by histopathologic analysis. Microscopic components are classified as cellular [(1) high cellularity with poor extracellular stroma, +/-high nucleus-cytoplasm ratio+/-high uniformity in tumoral cells dimensions; (2) low cellularity with large extracellular stroma+/-low nucleus-cytoplasm ratio+/-low uniformity in tumoral cells dimensions], stromal [(1) fibrotic; (2) fibrovascular; (3) fibromyxoid], vascular related to neoangiogenesis, necrotic [(1) coagulative; (2) colliquative; (3) hemorrhagic], calcific, and adipose.

Preoperative imaging in renal cell cancer

Renal cell cancer (RCC) represents the fifth most common cancer in men, with a rising incidence. Radical cancer surgery remains the only curative treatment in localized and advanced RCC. Therefore, preoperative imaging is most important for the planning of the surgical approach and strategy. The aim of any preoperative imaging in RCC is to differentiate benign from malignant lesions, to adequately assess tumor size, localization and organ confinement, to identify lymph node and/or visceral metastases, and to reliably predict the presence and extent of any thrombus of the vena cava. It is our aim to review the current status of preoperative imaging modalities in RCC. Computed tomography (CT) remains the most appropriate imaging modality to differentiate benign from malignant lesions. Although RCC can appear as iso-, hyper- or hypodense lesions on native CT scans, it usually demonstrates a significant contrast enhancement of about 115 HU and intratumoral areas of necrosis following the intravenous application of contrast medium. Benign masses such as renal oncocytoma are most often homogenous lesions exhibiting hypodensity compared to the normal renal parenchyma following the i.v. application of contrast dye. CT accurately predicts the tumor size with only a 0.5 cm difference as compared to the pathological size of the lesion. The identification of lymph node metastases still remains a problem since the limiting size is 4 mm and CT will result in a false negative rate of about 10%, especially in the presence of micrometastases; the false positive rate of 3-43% is mainly due to reactive hyperplasia. New technologies, such as the multidetector CT with thin collimation and multiplanar reformatting, might result in a diagnostic improvement. The involvement of the adrenal gland can be accurately predicted by CT scans or MRI, allowing an adrenal sparing approach in the case of unsuspicious findings. The detection of visceral metastases appears to be crucial since it has been shown that even patients with metastatic disease might benefit from radical nephrectomy followed by systemic immunotherapy in the case of a good performance status, and the presence of lymph node and pulmonary metastases only. Involvement of the renal vein and the vena cava with tumor thrombus formation will change the surgical strategy. Preoperatively, the presence and the cranial extent of the thrombus need to be known in order to plan the surgical approach. With regard to the extent of renal vein thrombi, a three phase helical CT scan is most appropriate; for vena caval thrombi only a MRI examination is able to accurately identify any infra- or suprahepatic as well as intracardial extension of the thrombus. The identification of multifocal lesions remains another unsolved problem in preoperative imaging techniques for RCC. Compared to the pathohistological analysis of nephrectomy specimens, neither ultrasonography, color duplex sonography nor regular CT scans are able to identify multifocal lesions with acceptable sensitivity and specificity. The evaluation of unenhanced CT scans together with the enhanced corticomedullary and the nephrogenic phase result in a 100% sensitivity and might represent a valuable option. Angiography has basically been abandoned from the armory of routine imaging techniques. It has, however, a current role in terms of the embolization of large tumors to reduce intraoperative blood loss, and in the palliative management of pain and bleeding due to RCC not amenable to surgery. Finally, we present a diagnostic algorithm for the most informative imaging techniques in the evaluation of RCC.

Preoperative imaging in renal cell cancer

Renal cell cancer (RCC) represents the fifth most common cancer in men, with a rising incidence. Radical cancer surgery remains the only curative treatment in localized and advanced RCC. Therefore, preoperative imaging is most important for the planning of the surgical approach and strategy. The aim of any preoperative imaging in RCC is to differentiate benign from malignant lesions, to adequately assess tumor size, localization and organ confinement, to identify lymph node and/or visceral metastases, and to reliably predict the presence and extent of any thrombus of the vena cava. It is our aim to review the current status of preoperative imaging modalities in RCC. Computed tomography (CT) remains the most appropriate imaging modality to differentiate benign from malignant lesions. Although RCC can appear as iso-, hyper- or hypodense lesions on native CT scans, it usually demonstrates a significant contrast enhancement of about 115 HU and intratumoral areas of necrosis following the intravenous application of contrast medium. Benign masses such as renal oncocytoma are most often homogenous lesions exhibiting hypodensity compared to the normal renal parenchyma following the i.v. application of contrast dye. CT accurately predicts the tumor size with only a 0.5 cm difference as compared to the pathological size of the lesion. The identification of lymph node metastases still remains a problem since the limiting size is 4 mm and CT will result in a false negative rate of about 10%, especially in the presence of micrometastases; the false positive rate of 3-43% is mainly due to reactive hyperplasia. New technologies, such as the multidetector CT with thin collimation and multiplanar reformatting, might result in a diagnostic improvement. The involvement of the adrenal gland can be accurately predicted by CT scans or MRI, allowing an adrenal sparing approach in the case of unsuspicious findings. The detection of visceral metastases appears to be crucial since it has been shown that even patients with metastatic disease might benefit from radical nephrectomy followed by systemic immunotherapy in the case of a good performance status, and the presence of lymph node and pulmonary metastases only. Involvement of the renal vein and the vena cava with tumor thrombus formation will change the surgical strategy. Preoperatively, the presence and the cranial extent of the thrombus need to be known in order to plan the surgical approach. With regard to the extent of renal vein thrombi, a three phase helical CT scan is most appropriate; for vena caval thrombi only a MRI examination is able to accurately identify any infra- or suprahepatic as well as intracardial extension of the thrombus. The identification of multifocal lesions remains another unsolved problem in preoperative imaging techniques for RCC. Compared to the pathohistological analysis of nephrectomy specimens, neither ultrasonography, color duplex sonography nor regular CT scans are able to identify multifocal lesions with acceptable sensitivity and specificity. The evaluation of unenhanced CT scans together with the enhanced corticomedullary and the nephrogenic phase result in a 100% sensitivity and might represent a valuable option. Angiography has basically been abandoned from the armory of routine imaging techniques. It has, however, a current role in terms of the embolization of large tumors to reduce intraoperative blood loss, and in the palliative management of pain and bleeding due to RCC not amenable to surgery. Finally, we present a diagnostic algorithm for the most informative imaging techniques in the evaluation of RCC.

Preoperative imaging in renal cell cancer

Renal cell cancer (RCC) represents the fifth most common cancer in men, with a rising incidence. Radical cancer surgery remains the only curative treatment in localized and advanced RCC. Therefore, preoperative imaging is most important for the planning of the surgical approach and strategy. The aim of any preoperative imaging in RCC is to differentiate benign from malignant lesions, to adequately assess tumor size, localization and organ confinement, to identify lymph node and/or visceral metastases, and to reliably predict the presence and extent of any thrombus of the vena cava. It is our aim to review the current status of preoperative imaging modalities in RCC. Computed tomography (CT) remains the most appropriate imaging modality to differentiate benign from malignant lesions. Although RCC can appear as iso-, hyper- or hypodense lesions on native CT scans, it usually demonstrates a significant contrast enhancement of about 115 HU and intratumoral areas of necrosis following the intravenous application of contrast medium. Benign masses such as renal oncocytoma are most often homogenous lesions exhibiting hypodensity compared to the normal renal parenchyma following the i.v. application of contrast dye. CT accurately predicts the tumor size with only a 0.5 cm difference as compared to the pathological size of the lesion. The identification of lymph node metastases still remains a problem since the limiting size is 4 mm and CT will result in a false negative rate of about 10%, especially in the presence of micrometastases; the false positive rate of 3-43% is mainly due to reactive hyperplasia. New technologies, such as the multidetector CT with thin collimation and multiplanar reformatting, might result in a diagnostic improvement. The involvement of the adrenal gland can be accurately predicted by CT scans or MRI, allowing an adrenal sparing approach in the case of unsuspicious findings. The detection of visceral metastases appears to be crucial since it has been shown that even patients with metastatic disease might benefit from radical nephrectomy followed by systemic immunotherapy in the case of a good performance status, and the presence of lymph node and pulmonary metastases only. Involvement of the renal vein and the vena cava with tumor thrombus formation will change the surgical strategy. Preoperatively, the presence and the cranial extent of the thrombus need to be known in order to plan the surgical approach. With regard to the extent of renal vein thrombi, a three phase helical CT scan is most appropriate; for vena caval thrombi only a MRI examination is able to accurately identify any infra- or suprahepatic as well as intracardial extension of the thrombus. The identification of multifocal lesions remains another unsolved problem in preoperative imaging techniques for RCC. Compared to the pathohistological analysis of nephrectomy specimens, neither ultrasonography, color duplex sonography nor regular CT scans are able to identify multifocal lesions with acceptable sensitivity and specificity. The evaluation of unenhanced CT scans together with the enhanced corticomedullary and the nephrogenic phase result in a 100% sensitivity and might represent a valuable option. Angiography has basically been abandoned from the armory of routine imaging techniques. It has, however, a current role in terms of the embolization of large tumors to reduce intraoperative blood loss, and in the palliative management of pain and bleeding due to RCC not amenable to surgery. Finally, we present a diagnostic algorithm for the most informative imaging techniques in the evaluation of RCC.