Case 237: Renal Cell Carcinoma with Osseous Metaplasia

History A 47-year-old man presented with palpitations and decreased exercise tolerance. A peripheral blood smear revealed anemia, thrombocytopenia, and blast cells, and a diagnosis of acute myeloid leukemia was made. Immunohistochemistry revealed positivity for cluster of differentiation (or CD) markers, which have been reported to be associated with an increased risk of extramedullary leukemic involvement. Thus, contrast material-enhanced computed tomography (CT) of the thorax, abdomen, and pelvis was requested to enable exclusion of any extramedullary extension of leukemia. Unenhanced and contrast-enhanced nephrographic phase CT was performed. Follow-up CT 3 months later showed minimal interval change in the lesion (images not shown).

Clinical significance of incidentally detected bladder wall thickening on computed tomography

PURPOSE

To evaluate the clinical significance of incidentally detected bladder wall thickening (BWT) on computed tomography (CT).

METHODS

A retrospective analysis was performed on 34,793 cystoscopy cases between January 2004 and December 2013. Among these, patients who underwent cystoscopy for the sole indication of incidentally detected BWT on CT were selected. Patients were categorized into the diffuse or focal group depending on the extent of BWT. Suspicious lesions on cystoscopy were biopsied to confirm histologic subtype. The incidence and predictive factors of bladder malignancy were examined.

RESULTS

A total of 167 (0.5%) patients received cystoscopy for incidentally detected BWT on CT, of which 11 (6.6%) patients were diagnosed with bladder malignancy. When a suspicious lesion was identified on cystoscopy, 11 of 25 (44%) patients were found to have a bladder malignancy. Of the 15 patients with diffuse BWT, 5 (33.3%) were diagnosed with bladder malignancy, consisting of carcinoma in situ in 2 patients, high-grade carcinoma in 2 patients and muscle invasive disease in 1 patient. Of the 10 patients with focal BWT, 6 (60.0%) were diagnosed with bladder malignancy, of which 3 patients had high-grade disease. On multivariate logistic regression analysis, focal BWT [95% confidence interval (CI) 1.400-25.357, P = 0.016] and atypical cells in urine cytology (95% CI 2.631-63.446, P = 0.002) were positively associated with bladder malignancy.

CONCLUSIONS

Incidentally detected BWT on CT can be suggestive of bladder malignancy. Therefore, further work-up including cystoscopy and urine cytology should be performed to assess bladder malignancy.

Visual Assessment of the Intensity and Pattern of T1 Hyperintensity on MRI to Differentiate Hemorrhagic Renal Cysts From Renal Cell Carcinoma

OBJECTIVE

The purpose of this study was to apply a visual assessment of the intensity and pattern of T1 hyperintensity at MRI to differentiate hemorrhagic renal cysts from renal cell carcinoma (RCC).

MATERIALS AND METHODS

A total of 144 T1-hyperintense renal lesions (62 cysts, all showing no enhancement on subtracted contrast-enhanced images and either 2-year stability or unenhanced CT density > 70 HU, and 82 histologically confirmed RCCs) in 144 patients were included. Two radiologists independently characterized qualitative features of the T1 hyperintensity in each lesion on unenhanced T1-weighted images. An additional radiologist placed ROIs to measure lesions' T1 signal intensity normalized to that of the psoas muscle. Chi-square and unpaired t tests were performed to compare the pattern of T1 hyperintensity between groups.

RESULTS

The T1 hyperintensity was considered marked in 62.9% of cysts and 17.1% of RCCs for reader 1 and in 46.8% of cysts and 8.5% of RCCs for reader 2 (p < 0.001). The T1 hyperintensity exhibited a diffusely homogeneous distribution in 88.7% of cysts and 7.3% of RCCs for reader 1 and in 72.6% of cysts and 4.9% of RCCs for reader 2 (p < 0.001). The combination of both diffusely homogeneous distribution and marked degree of T1 hyperintensity achieved sensitivities of 40.3-56.5%, specificities of 97.6-98.8%, and accuracies of 73.6-79.9% for the diagnosis of T1-hyperintense cysts. The two cases of RCC exhibiting this imaging pattern for at least one reader were both papillary RCCs. Normalized signal intensity was 2.39 ± 0.99 in T1-hyperintense cysts versus 2.12 ± 0.84 in T1-hyperintense RCCs (p = 0.088).

CONCLUSION

Diffuse T1 hyperintensity, particularly when marked, strongly indicates a hemorrhagic cyst rather than an RCC. Deferral of follow-up imaging may be considered when this imaging appearance is encountered at unenhanced MRI.

Diagnosis of Renal Angiomyolipomas: Classic, Fat-Poor, and Epithelioid Types

With the increasing discovery of small renal masses with cross-sectional imaging, there has been the concomitant rise in their treatment. With the intent of early curative surgery for a presumed renal cell carcinoma, many renal masses are being resected at surgery without a confirmed diagnosis. Many of them are benign, and some are angiomyolipomas. The diagnosis of renal angiomyolipoma using imaging is, therefore, is as important as ever. Although most, if not all angiomyolipomas with abundant fat are diagnosed readily, some have too little fat to be detected with imaging. This article reviews the current classification, imaging pitfalls, and diagnosis of angiomyolipoma with an emphasis on the fat-poor types. Proper imaging technique, a thorough search for fat, and the appropriate use of percutanoeus biopsy are all needed to eliminate the unnecessary treatment of these benign neoplasms.

Early-stage clear cell tubulopapillary renal cell carcinoma: imaging features and distinction from clear cell and papillary subtypes

PURPOSE

Clear cell tubulopapillary renal cell carcinoma (CCTPRCC) is a recently described, low-grade subtype of renal cancer. We determined if imaging features could be used to distinguish early-stage CCTPRCC from stage-matched clear cell RCC (ccRCC) and papillary RCC (pRCC).

METHODS

This IRB-approved retrospective study included 54 stage T1a patients with pathologically confirmed CCTPRCC (n = 18), ccRCC (n = 18), and pRCC (n = 18). CT (n = 48) and MRI (n = 27) exams were reviewed and imaging features compared. Continuous variables were evaluated using ANOVA and Tukey's multiple comparison tests. Categorical variables were compared using Chi-square test or Fisher's exact test.

RESULTS

Compared to pRCC, CCTPRCC had a lower mean attenuation value on unenhanced CT (p < 0.017), was more often hyperintense on T2-weighted images (p < 0.0001), showed an ill-defined margin (p = 0.003), and demonstrated nonenhancing areas (p = 0.0003). The presence of all three of these statistically significant features [hypoattenuation (unenhanced attenuation ≤25 HU), ill-defined margin, nonenhancing areas] yielded an area under the receiver operator curve (ROC) of 0.92 (95% CI 0.83-0.99) for differentiating CCTPRCC from pRCC. There were no significant differences in the imaging features of CCTPRCC and ccRCC.

CONCLUSIONS

Early-stage clear cell tubulopapillary renal cell carcinoma can be distinguished from papillary RCC based on low attenuation on unenhanced CT, high intensity on T2-weighted images, an ill-defined margin, and presence of nonenhancing areas, but cannot be distinguished from clear cell RCC.

Loss of intratumoral macroscopic fat in renal angiomyolipoma following chemoradiation therapy for pancreatic cancer

Angiomyolipoma (AML) is the most common benign mesenchymal tumour of the kidney. Classically, AML can readily be diagnosed by identifying the negatively attenuating intratumoral macroscopic fat component on non-enhanced CT scans. However, intratumoral macroscopic fat may not be visible on CT scans, mimicking renal cell carcinoma. We report a case of renal AML with CT scan evidence of macroscopic intratumoral fat that was not readily visible on subsequent CT or MRI, presumably owing to a generalized rapid loss of adipose tissue due to cachexia in a patient with pancreatic adenocarcinoma. Radiologists should be aware that AML may lose its intratumoral fat on follow-up imaging and may simulate renal cell carcinoma.

A Practical Approach to Indeterminate and Cystic Renal Masses

Cystic renal masses are a common entity with a wide differential diagnosis encountered by the radiologist in daily practice. Their characterization relies on the Bosniak classification system that has been widely accepted by radiologists and urologists as a pertinent diagnostic and communication tool. It has been designed to separate cystic lesions requiring surgery (categories III and IV) from those that can be ignored and left alone (categories I and II) or followed (category IIF). Utilization of the Bosniak classification requires, first, previous identification of the cystic nature of a renal mass with the exception of very small lesions.

Kidney, Ureter, and Bladder Biopsy

Percutaneous urologic biopsy is a safe and effective technique and can comprise a significant proportion of the daily workload of the interventional radiologist. This article discusses the indications and rationale for the performance of renal, ureter, and bladder biopsy as well as the approach to performing such biopsies, pitfalls, and potential complications.

The spectrum of renal cell carcinoma in adults

The spectrum of renal cell carcinoma (RCC) includes many neoplasms with distinct cytogenetics, biologic behaviors, and imaging appearances. The advent of molecular therapies targeting different tumor types, new insights into the relative roles of biopsy and surveillance for small incidental tumors, and a growing array of nephron-sparing interventions have altered management of RCC. Similarly, the role of the radiologist is changing, and it is becoming increasingly important for radiologists to familiarize themselves with the various types of RCC. This article introduces the reader to the common and uncommon recognized types of renal cell carcinoma and discusses how these neoplasms differ in imaging appearance and behavior.

Cystic renal masses

PURPOSE

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

CONCLUSIONS

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

Evaluation of hyperdense renal lesions incidentally detected on single-phase post-contrast CT using dual-energy CT

OBJECTIVE

To investigate the utility of dual-energy CT (DECT) for differentiating between solid and benign cystic lesions presenting as hyperdense renal lesions incidentally detected on single-phase post-contrast CT.

METHODS

90 hyperdense renal lesions incidentally detected on single-phase post-contrast CT were evaluated with follow-up DECT. DECT protocols included true non-contrast (TNC), DE corticomedullary and DE late nephrographic phase imaging. The CT numbers of hyperdense renal lesions were calculated on linearly blended and iodine overlay (IO) images, and the results were compared.

RESULTS

In total, 47 benign cystic and 43 solid renal lesions were analyzed. For differentiating between solid and benign cystic lesions on the two phases, the specificity and accuracy of all lesions and lesions <1.5 cm were statistically lower in IO images than in linearly blended images (p < 0.05), while those for lesions ≥1.5 cm were not statistically different between them (p > 0.05). For all types of lesions ≥1.5 cm, the CT numbers between linearly blended and IO images and between TNC and virtual non-contrast images were not statistically different (p > 0.05).

CONCLUSION

DECT may be useful for differentiating between solid and benign cystic lesions presenting as hyperdense renal lesions incidentally detected on single-phase post-contrast CT, particularly with the size ≥1.5 cm.

ADVANCES IN KNOWLEDGE

DECT may be used to characterize hyperdense renal lesions ≥1.5 cm incidentally detected on single-phase post-contrast CT, without the use of TNC images.

The role of Bosniak classification in malignant tumor diagnosis: A single institution experience

PURPOSE

To evaluate the clinical reliability of the Bosniak classification in Korea, and to identify independent predictors of malignancy in complicated renal cysts.

MATERIALS AND METHODS

We reviewed the records of 368 patients with renal cysts between January 2001 and December 2014; 14 patients were excluded, due to interobserver variability in Bosniak classification between the radiologist and urologist. Clinical characteristics and radiologic findings of malignant cystic masses were analyzed, retrospectively.

RESULTS

In 324 surgically excised lesions from patients (n=312) with renal cysts, the percentages of malignancy in the different Bosniak classifications were as follows: category I, 1.0% (1 of 103); II, 3.8% (2 of 53); IIF, 17.1% (7 of 41); III, 38.0% (27 of 71); and IV, 82.1% (46 of 56). Mean age and lesion size were 59.88±11.9 years (180 men, 144 women) and 5.47±3.51 cm, respectively. Univariate analysis identified hypertension (p=0.011), a history of smoking (p=0.038), and obesity (p=0.015) as the strongest risk factors of malignancy. In a study of Bosniak category III patients, hypertension (p=0.018), lesion size (p<0.001), and difference of Hounsfield Unit (HU) (p=0.027) were the strongest risk factors of malignancy. Multivariate analysis identified lesion size as the strongest potential predictor of malignancy, followed by hypertension and difference of HU.

CONCLUSIONS

Risk factors of malignancy in complicated renal cyst patients were not different from those published previously. In Bosniak category III lesions, hypertension and lesion size were the strongest predictors of malignancy. Characteristically, the lesion size was smaller than in benign complicated renal cysts, in contrast with other categories.

Management of incidental renal masses: Time to consider contrast-enhanced ultrasonography

Proliferation of imaging studies for different clinical purposes and continuous improvement of imaging technology have led to an increasing number of incidental findings of renal masses. It is estimated that over 50% of patients older than 50 years have at least one renal mass. The majority of incidental renal masses are simple cysts that can be easily diagnosed by conventional ultrasonography. However, some incidental renal masses are not simple cysts, and differentiation between benign and malignant entities requires further imaging modalities. In the past, multiphase contrast-enhanced computed tomography and magnetic resonance imaging were considered the primary imaging modalities used to characterize and stage complex cystic and solid renal lesions. Currently, contrast-enhanced ultrasonography represents a novel alternative to contrast-enhanced computed tomography and magnetic resonance imaging. Contrast-enhanced ultrasonography employs microbubble contrast agents that allow the study of different enhancement phases of the kidney without risk of nephrotoxicity and radiation exposure. The diagnostic accuracy of contrast-enhanced ultrasonography in the characterization of complex renal cysts is comparable to that of computed tomography and magnetic resonance imaging, and several studies have demonstrated its reliability also in identifying solid lesions such as pseudotumors, typical angiomyolipomas, and clear cell renal carcinomas. Considering the high incidence of incidental renal masses and the need for rapid and reliable diagnosis, contrast-enhanced ultrasonography could be proposed as the first step in the diagnostic work-up of renal masses because of its safety and cost effectiveness. In this paper, we propose a diagnostic algorithm for the characterization of cystic and solid renal masses.

Assessing Strength of Evidence of Appropriate Use Criteria for Diagnostic Imaging Examinations

OBJECTIVE

For health information technology tools to fully inform evidence-based decisions, recommendations must be reliably assessed for quality and strength of evidence. We aimed to create an annotation framework for grading recommendations regarding appropriate use of diagnostic imaging examinations.

METHODS

The annotation framework was created by an expert panel (clinicians in three medical specialties, medical librarians, and biomedical scientists) who developed a process for achieving consensus in assessing recommendations, and evaluated by measuring agreement in grading the strength of evidence for 120 empirically selected recommendations using the Oxford Levels of Evidence.

RESULTS

Eighty-two percent of recommendations were assigned to Level 5 (expert opinion). Inter-annotator agreement was 0.70 on initial grading (κ = 0.35, 95% CI, 0.23-0.48). After systematic discussion utilizing the annotation framework, agreement increased significantly to 0.97 (κ = 0.88, 95% CI, 0.77-0.99).

CONCLUSIONS

A novel annotation framework was effective for grading the strength of evidence supporting appropriate use criteria for diagnostic imaging exams.

Optimization of non-contrast-enhanced MR angiography of the renal artery with three-dimensional balanced steady-state free-precession and time-spatial labeling inversion pulse (time-SLIP) at 3T MRI, in relation to age and blood velocity

PURPOSE

To determine the optimal inversion time (TI) value of three-dimensional (3D) balanced steady-state free-precession time-spatial labeling inversion pulse (time-SLIP) technique for visualization of the renal artery at 3T MRI, and to assess whether the optimal TI is affected by the subject's age and blood velocity.

MATERIALS AND METHODS

Forty-two healthy volunteers (range 20-67 years) were enrolled in the study and subjected to non-contrast-enhanced renal MR angiography. Five different TI values (1200, 1400, 1600, 1800, and 2000 ms) were selected for evaluation. For quantitative evaluation, the relative signal intensity (SI) of the main renal artery was compared with that of the renal medulla (Vessel-to-Kidney ratio; VKR). Blood velocity of the abdominal aorta was measured using 2D phase contrast technique. For qualitative evaluation, two radiologists scored the depiction of the renal pelvis and the quality of visualization of the renal artery.

RESULTS

VKR is the highest at TI = 1600 ms. A strong negative correlation between age and blood velocity was demonstrated. Regarding the qualitative evaluation, the overall image scores of renal arteries were the highest at a TI = 1800 ms for both readers. The optimal TI values in subjects below 50 years of age were 1600 and 1800 ms, whereas in subjects above 50 years of age, the optimal TI value was 1800 ms.

CONCLUSION

The optimal TI value for the visualization of renal arteries using time-SLIP technique at 3T MRI was 1800 ms. Subjects' age affected optimal TI and this is likely due to differences in the blood velocity of the abdominal aorta.

ACR Appropriateness Criteria indeterminate renal mass

Renal masses are increasingly detected in asymptomatic individuals as incidental findings. An indeterminate renal mass is one that cannot be diagnosed confidently as benign or malignant at the time it is discovered. CT, ultrasonography, and MRI of renal masses with fast-scan techniques and intravenous (IV) contrast are the mainstays of evaluation. Dual-energy CT, contrast-enhanced ultrasonography, PET/CT, and percutaneous biopsy are all technologies that are gaining traction in the characterization of the indeterminate renal mass. In cases in which IV contrast cannot be used, whether because of IV contrast allergy or renal insufficiency, renal mass classification with CT is markedly limited. In the absence of IV contrast, ultrasonography, MRI, and biopsy have some advantages. Owing to the low malignant and metastatic potential of small renal cell carcinomas (≤4 cm in diameter), active surveillance is additionally emerging as a diagnostic strategy for patients who have high surgical risk or limited life expectancy. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every 3 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and application by the panel of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

CT and MR imaging for evaluation of cystic renal lesions and diseases

Cystic renal lesions are commonly encountered in abdominal imaging. Although most cystic renal lesions are benign simple cysts, complex renal cysts, infectious cystic renal disease, and multifocal cystic renal disease are also common phenomena. The Bosniak classification system provides a useful means of categorizing cystic renal lesions but places less emphasis on their underlying pathophysiology. Cystic renal diseases can be categorized as focal, multifocal, or infectious lesions. Diseases that manifest with focal lesions, such as cystic renal cell carcinoma, mixed epithelial and stromal tumor, and cystic nephroma, are often difficult to differentiate but have differing implications for follow-up after resection. Multifocal cystic renal lesions can be categorized as acquired or heritable. Acquired entities, such as glomerulocystic kidney disease, lithium-induced nephrotoxicity, acquired cystic kidney disease, multicystic dysplastic kidney, and localized cystic renal disease, often have distinct imaging and clinical features that allow definitive diagnosis. Heritable diseases, such as autosomal dominant polycystic kidney disease, von Hippel-Lindau disease, and tuberous sclerosis, are usually easily identified and have various implications for patient management. Infectious diseases have varied imaging appearances, and the possibility of infection must not be overlooked when assessing a cystic renal lesion. A thorough understanding of the spectrum of cystic renal disease will allow the radiologist to make a more specific diagnosis and provide the clinician with optimal recommendations for further diagnostic testing and follow-up imaging.

Comparison between computed tomography multislice and high-field magnetic resonance in the diagnostic evaluation of patients with renal masses

BACKGROUND

Renal masses are a common finding in diagnostic imaging; these lesions usually are solid or cystic, benign or malignant, and the correct diagnosis may be difficult. The aim of our study was the comparison of multi-slice computed tomography (MSCT) and high-field magnetic resonance (MR) in the diagnostic evaluation of renal masses.

METHODS

We studied 29 patients, 16 men and 13 women aged 8-85 years (mean 61±17 years) with histo-cytological diagnosis of renal masses (n=31), of which the majority (74%; n=23) was represented by malignant lesions [renal cell carcinoma (Ca) =16, chromophobe renal cell Ca =2, squamous cell Ca =1, urothelial Ca =2, lymphoma =1, Wilms tumor =1]; the remaining 8 masses (26%) were benign (pyelonephritis =2, simple cyst =1, hematic cyst =1, lipoma =1 and oncocytoma =3). All patients underwent MSCT and MR (3.0 Tesla) before and after contrast injection; the images were evaluated in double-blind by two expert radiologists. The results of the images were then compared with the histo-cytological data to calculate the values of diagnostic accuracy for both methods in the identification and characterization of renal masses. The benign or malignant nature of the lesions was established according to the regularity of the margins, presence or absence of significant contrast enhancement, infiltration of perirenal fat and vascular invasion. The concordance of the results of the two imaging techniques was then calculated using the coefficient Kappa Cohen.

RESULTS

For both identification and characterization of renal masses, MSCT and MR showed comparable values of diagnostic accuracy with a significant concordance (k=1); in particular, the diagnostic accuracy of MSCT/MR was 100%/100% for lesion identification, 90%/90% for lesion characterization in terms of benign or malignant nature, 97%/97% for the evaluation of lesion edges, 90%/90% for the assessment of lesion contrast enhancement, 93%/93% for the evaluation of peri-renal fat infiltration and 96%/96% for the evaluation of vascular infiltration. Only in three cases of oncocytoma the two imaging methods were both inaccurate for diagnosis of benignity classifying the lesions as probably malignant on the basis of the absence of central scar and of dynamic contrast enhancement pattern.

CONCLUSIONS

The results of our study show comparable diagnostic accuracy of computed tomography (CT) and MR for the identification and characterization of expansive renal lesions. High-field MR is, therefore, a valid alternative to MSCT in the evaluation of renal masses avoiding exposure to ionizing radiation.

Imaging features of haematological malignancies of kidneys

Haematological malignancies are relatively uncommon neoplasms of kidneys. Nevertheless, the incidence of these neoplasms is increasing, partly due to more widespread use of computed tomography and magnetic resonance imaging. This article discusses the clinical and imaging features of renal lymphoma, leukaemia, extra-osseous multiple myeloma, and post-transplant lymphoproliferative disorder. Although there is overlap of imaging features with other more common malignancies, such as transitional and renal cell cancers, the combination of imaging findings and the appropriate clinical picture should allow the radiologist to raise a provisional diagnosis of a haematological neoplasm. This has management implications including the preference for image-guided core biopsies and a shift towards medical rather than surgical therapy.

Renal Masses: Imaging Evaluation

This article illustrates the imaging characteristics of cystic and solid renal masses, along with a summary of identified imaging criteria that may be of use to differentiate masses that are more likely to be benign from those that are more likely to be malignant. In addition, important features of known or suspected renal cancers that should be identified before treatment are summarized, including staging of renal cancer and RENAL nephrometry. Finally, the imaging appearance of patients following treatment of renal cancer, including after partial or total nephrectomy, thermal ablation, or chemotherapy for metastatic disease, is reviewed.

Utility of MRI in the Characterization of Indeterminate Small Renal Lesions Previously Seen on Screening CT Scans of Potential Renal Donor Patients

OBJECTIVE

The purpose of this study was to determine whether MRI could more confidently characterize indeterminate small renal lesions (< 15 mm) previously seen on CT scans of potential renal donor patients and whether such characterization could impact surgical management and donor candidate status.

MATERIALS AND METHODS

After dedicated contrast-enhanced renal CT examinations of a population of renal donor patients identified indeterminate small renal lesions (< 15 mm), dedicated renal MRI examinations were performed for 55 of those patients. Two radiologists used consensus reading of established MRI characteristics to characterize indeterminate small lesions as simple cysts, hemorrhagic cysts, angiomyolipomas, or solid renal masses.

RESULTS

A total of 94 indeterminate small renal lesions were detected on CT. MRI was able to confidently diagnose 93 of those lesions, including 83 cysts, eight hemorrhagic cysts, and two angiomyolipomas. MRI directly affected the surgical management of four of the patients (7%).

CONCLUSION

For potential renal donor patients, MRI can be an effective means of characterizing lesions that are deemed to be too small to characterize by CT. MRI can also potentially alter the surgical management and donor status of this group of patients.

Fat-poor angiomyolipoma with cyst-like changes mimicking a cystic renal cell carcinoma: a case report

Angiomyolipoma is a common benign renal tumor. It is typically composed of adipose tissue and hence is easily diagnosed by using imaging methods such as ultrasonography, computed tomography, and magnetic resonance imaging. However, it is difficult to differentiate an atypical angiomyolipoma such as a fat-poor angiomyolipoma from a malignant tumor by using these imaging methods. We report a case of a fat-poor angiomyolipoma with cyst-like changes in a 35-year-old man. The angiomyolipoma was initially suspected to be a cystic renal cell carcinoma according to preoperative imaging studies. A 5-cm cystic tumor with an enhanced septal wall and exophytic formation was present in the middle section of the left kidney. The patient underwent partial nephrectomy. Pathological findings showed necrosis and hematoma in almost the entire lesion, with a small amount of adipose and muscle tissue. Finally, a fat-poor angiomyolipoma was diagnosed.

Outcomes and complications related to the management of Bosniak cystic renal lesions

OBJECTIVE

The objective of our study was to evaluate outcomes and complications related to the management of Bosniak category IIF, III, and IV renal cysts.

MATERIALS AND METHODS

For this multiinstitutional retrospective study, a Web-based Research Electronic Data Capture (REDCap) data registry was used to record data of 286 adult patients with 312 prospectively classified Bosniak IIF, III, and IV renal cysts diagnosed between January 2000 and October 2011. Included patients were managed by surgery (n = 86), percutaneous ablation (n = 19), or imaging surveillance of 1 year or more (n = 181). The median number of years of clinical surveillance was 2.4 years (range, 0-11.7 years), 2.6 years (range, 0.4-11.4 years), and 3.2 years (range, 1.1-11.6 years) for patients managed by surgery, ablation, and imaging surveillance, respectively. Pathologic and survival outcomes and complications related to management were evaluated.

RESULTS

The malignancy rate at surgical pathology was 38% (3/8) for Bosniak IIF, 40% (29/72) for Bosniak III, and 90% (18/20) for Bosniak IV renal cysts. There were no metastases or deaths (0/144) directly related to Bosniak IIF renal cysts. There were no deaths (0/113) directly related to Bosniak III renal cysts, although one patient (1/113) developed local progression and lung metastases after thermal ablation. One patient with a Bosniak IV renal cyst (1/29) presented with and died of metastatic disease. Moderate to severe complications occurred in 19% (16/86), 5% (1/19), and 0% (0/181) of patients managed by surgery, ablation, and imaging surveillance, respectively (p < 0.0001). Severe complications occurred in 7% (6/86) of surgical patients and included multiorgan failure (n = 2), acute myocardial infarction (n = 1), acute ischemic stroke (n = 1), conversion to hemodialysis-dependent chronic kidney disease (n = 1), and postoperative severe hemorrhage (n = 1).

CONCLUSION

There were no deaths from Bosniak IIF or III renal cysts regardless of management approach. Moderate to severe complications are frequent in patients managed by surgery.

Renal Masses With Equivocal Enhancement at CT: Characterization With Contrast-Enhanced Ultrasound

OBJECTIVE

The purpose of this article is to retrospectively investigate in two radiology centers the role of contrast-enhanced ultrasound in the characterization of renal masses with equivocal enhancement at CT (i.e., with a density increase of 10-20 HU between unenhanced and contrast-enhanced scans) not characterized with conventional ultrasound modes.

MATERIALS AND METHODS

Forty-seven renal lesions (range, 0.8-7.7 cm; average, 2.6 cm) with equivocal enhancement at CT underwent contrast-enhanced ultrasound using sulfur hexafluoride-filled microbubbles. Examinations were digitally recorded for retrospective blinded evaluation by two radiologists with 20 and 10 years' experience in urologic imaging. Histologic results were available for 30 of 47 (64%) lesions (25 primary malignant tumors, two metastases, and three primary benign lesions). Two lesions increased in size and complexity during the follow-up and were considered malignant. One Bosniak category III and 14 category IIF cysts were stable after a follow-up of at least 3 years and were considered benign. ROC curve analysis was used to assess the capability of contrast-enhanced ultrasound to differentiate benign from malignant lesions.

RESULTS

Twelve likely complex cystic lesions at gray-scale ultrasound were cystic also on contrast-enhanced ultrasound and reference procedures. Eleven of 34 lesions that appeared solid at gray-scale ultrasound were cystic on contrast-enhanced ultrasound and reference procedures. One lesion considered likely solid by one radiologist and possibly cystic by the other was a solid tumor at contrast-enhanced ultrasound and histologic analysis. The diagnostic performance of contrast-enhanced ultrasound to characterize the lesions as benign or malignant was high for both readers (AUC, 0.958 and 0.966, respectively).

CONCLUSION

Contrast-enhanced ultrasound is effective for characterizing renal lesions presenting with equivocal enhancement at CT.

Radiation exposure from CT-guided ablation of renal masses: effects on life expectancy

OBJECTIVE. The purpose of this article is to project the effects of radiation exposure on life expectancy (LE) in patients who opt for CT-guided radiofrequency ablation (RFA) instead of surgery for renal cell carcinoma (RCC). MATERIALS AND METHODS. We developed a decision-analytic Markov model to compare LE losses attributable to radiation exposure in hypothetical 65-year-old patients who undergo CT-guided RFA versus surgery for small (≤ 4 cm) RCC. We incorporated mortality risks from RCC, radiation-induced cancers (for procedural and follow-up CT scans), and all other causes; institutional data informed the RFA procedural effective dose. Radiation-induced cancer risks were generated using an organ-specific approach. Effects of varying model parameters and of dose-reduction strategies were evaluated in sensitivity analysis. RESULTS. Cumulative RFA exposures (up to 305.2 mSv for one session plus surveillance) exceeded those from surgery (up to 87.2 mSv). In 65-year-old men, excess LE loss from radiation-induced cancers, comparing RFA to surgery, was 11.7 days (14.6 days for RFA vs 2.9 days for surgery). Results varied with sex and age; this difference increased to 14.6 days in 65-year-old women and to 21.5 days in 55-year-old men. Dose-reduction strategies that addressed follow-up rather than procedural exposure had a greater impact. In 65-year-old men, this difference decreased to 3.8 days if post-RFA follow-up scans were restricted to a single phase; even elimination of RFA procedural exposure could not achieve equivalent benefits. CONCLUSION. CT-guided RFA remains a safe alternative to surgery, but with decreasing age, the higher burden of radiation exposure merits explicit consideration. Dose-reduction strategies that target follow-up rather than procedural exposure will have a greater impact.

[Incidental radiological findings]

All findings which arise in the context of radiological diagnostics, potentially affect the health of a subject but with no intention to detect the corresponding finding are considered to be incidental radiological findings (IF). The prevalence of IFs is increasing due to the wider use of modern imaging techniques, such as magnetic resonance imaging (MRI) and computed tomography (CT) in routine clinical practice and the inclusion of imaging, such as whole body MRI in large population-based cohorts. The reporting of radiological IFs can lead to further diagnostics and treatment. The management of IFs in the clinical routine is regulated by the guidelines of the various academic societies. The management of IFs in the setting of research studies differs depending on various factors, such as study design and health status of enrolled subjects. In general, IFs must be disclosed to the subject if the radiological IFs are potentially clinically relevant; however, subjects must also be protected from the consequences of false positive findings. This review article discusses radiological IFs in the setting of the clinical routine and research studies and provides a basic summary of the management recommendations for commonly occurring IFs.

[Ultrasound of the urinary system]

Ultrasound techniques are able to provide a fairly complete examination of the urinary system, achieving a high sensitivity in relevant-pathology detection, especially in the kidney, bladder and prostate. Early detection of pathologies such as tumors or urinary tract obstructions, sometimes even before their clinical manifestation, has improved their management and prognosis in many cases. This, added to its low cost and harmlessness, makes ultrasound ideal for early approaches and follow-up of a wide number of urinary system pathologies. In this article, the ultrasound characteristics of the main urinary system pathologies that can be diagnosed by this technique, are reviewed.

Diagnostic potential of multidetector computed tomography for characterizing small renal masses

OBJECTIVES

To assess the potential of CT for characterizing small renal tumors.

METHODS

76 patients with <4 cm renal tumors underwent CT examination. The following parameters were assessed: presence of calcifications, densitometry on unenhanced and enhanced scans, washout percentage, urinary tract infiltration, star-shaped scar, and paradoxical effect.

RESULTS

Calcifications were found in 7/56 (12.5%) carcinomas. Clear cell carcinomas were as follows: mean density 183.5 HU (arterial phase), 136 HU (portal phase), and 94 HU (delayed phase), washout 34.3%; chromophobe carcinomas were as follows: mean density 135 HU (arterial phase), 161 HU (portal phase), and 148 HU (delayed phase), washout 28%; papillary carcinomas were as follows: mean density 50.3 HU (arterial phase), 60 HU (portal phase), and 58.1 HU (delayed phase), washout 2.7%. In 2/56 (3.6%) cases urinary tract infiltration was found. Oncocytomas were as follows: mean density 126.5 HU (arterial phase), 147.5 HU (portal phase), and 115.5 HU (delayed phase), washout 28.6%. On unenhanced scans, angiomyolipomas were as follows: density values <30 HU in 12/12 (100%) of cases and on enhanced scans: mean density 78 HU (arterial phase), 128 HU (portal phase), and 80 HU (delayed phase), washout 50%.

CONCLUSIONS

Intralesional calcifications and urinary tract infiltration are suggestive for malignancy, with the evidence of adipose tissue for angiomyolipomas and a modest increase in density with a reduced washout for papillary carcinomas. The intralesional density on enhanced scans, peak enhancement, and washout do not seem significant for differentiating clear cell, chromophobe carcinomas, angiomyolipomas, and oncocytomas.

Accuracy of Contrast-enhanced US for Differentiating Benign from Malignant Solid Small Renal Masses

PURPOSE

To test the hypothesis that qualitative and quantitative features of contrast material-enhanced ultrasonography (US) can be used to differentiate benign from malignant small renal masses.

MATERIALS AND METHODS

This is an institutional review board approved, HIPAA-compliant prospective study with written informed consent. Patients with histologically characterized solid small renal masses, excluding lipid-rich angiomyolipomas, underwent qualitative contrast-enhanced US with a combination of three different US machines. A subgroup of patients underwent quantitative contrast-enhanced US. Patients received a bolus injection of 0.2 mL of contrast material for qualitative and quantitative evaluations and were followed for 3 minutes. Two radiologists independently reviewed videotaped qualitative contrast-enhanced US examinations and were blinded to the final diagnoses. Features that were evaluated included lesion vascularity relative to the adjacent cortex in the arterial phase, the presence of a capsule, homogeneity, the pattern of vascularity, and washout. One radiologist separately reviewed a subset of contrast-enhanced US examinations that were performed with all three machines. Parameters of a first-pass time intensity curve were calculated for quantitative analysis. The Mann-Whitney test was used for quantitative parameters, the χ(2) or Fisher exact test was used for qualitative parameters, and κ statistics and Fleiss methodology were used to determine interobserver and intermachine agreement.

RESULTS

The study population consisted of 91 patients (35 women and 56 men) with 94 lesions. The mean age was 62 years ± 14 (range, 21-91). Three patients had two lesions each, which were evaluated at two different sessions. There were 26 benign small renal masses (including 18 oncocytomas, seven lipid-poor angiomyolipomas, and one hemangioblastoma) and 68 malignant masses (including 41 clear cell, 20 papillary, and seven chromophobe renal cell carcinomas [RCCs[) that were 1.1-4.0 cm in diameter (mean, 2.7 cm ± 0.9). All patients underwent contrast-enhanced US on the same one machine, and 68 patients were imaged on all three machines. Vascularity was present in all lesions (n = 94) at contrast-enhanced US. Lesion hypovascularity relative to the adjacent cortex in the arterial phase was seen in only malignant lesions by both reviewers; reviewer 1 saw hypovascularity in 24 of 94 lesions (P = .0001), and reviewer 2 saw hypovascularity in 21 of 94 lesions (P = .0006), for a specificity of 100% (95% confidence interval [CI]: 84, 100). This feature had κ values of 0.91 (95%CI: 0.82, 1.00) between the two reviewers and 0.85 (95% CI: 0.72, 0.99) between the three machines. Eighteen of 20 papillary RCCs were hypovascular. Quantitative parameters of area under the receiver operating characteristics curve, peak intensity, wash-in slope of 10%-90% and 5%-45%, and washout slope of 100%-10% and 50%-10% were significantly higher in malignant renal masses (P = .018, P = .002, P = .036, P = .016, P = .001, and P = .005, respectively) than in benign lesions.

CONCLUSION

Excluding lipid-rich angiomyolipoma, hypovascularity-which has high interobserver and intermachine agreement-of solid small renal masses relative to the cortex in the arterial phase has 100% specificity (95% CI: 84, 100) for detecting malignancy, most often papillary RCC.

CT Hounsfield numbers of soft tissues on unenhanced abdominal CT scans: variability between two different manufacturers' MDCT scanners

OBJECTIVE

The purpose of this study is to determine whether Hounsfield numbers of soft tissues on unenhanced abdominal CT of the same patient vary on repeat scans done on two different manufacturers' MDCT scanners.

MATERIALS AND METHODS

A database search was performed to identify patients older than 18 years who underwent unenhanced CT of the abdomen and pelvis performed both on a Volume CT (GE Healthcare) and a Definition AS Plus (Siemens Healthcare) 64-MDCT scanner within 12 months of each other. After excluding those patients for whom Hounsfield unit measurements would be affected by mitigating factors, 48 patients (mean age, 58.8 years) were identified. Hounsfield unit measurements were obtained in nine different soft-tissue anatomic locations on each scan, and the location of these sites was kept identical on each scan pair. Data were analyzed to evaluate Hounsfield unit differences between these scanners.

RESULTS

In general, there was a low consistency in the Hounsfield unit measurements for each of these sites on scans obtained by the two scanners, with the subcutaneous fat in the left posterolateral flank showing the lowest correlation (intraclass correlation coefficient, 0.198). There were differences in the Hounsfield unit measurements obtained in all anatomic sites on scans obtained by both scanners. Mean Hounsfield unit measurements obtained on the Definition AS Plus scanner were lower than those obtained on the Volume CT scanner, with the intriguing exception of the anterior midline subcutaneous fat Hounsfield unit measurements, which were higher on the Definition AS Plus scanner. All differences were statistically significant (p < 0.05).

CONCLUSION

Hounsfield unit measurements for unenhanced abdominal soft tissues of the same patient vary between scanners of two common MDCT manufacturers.

Renal angiomyolipoma: a radiological classification and update on recent developments in diagnosis and management

Angiomyolipoma is the most common benign solid renal neoplasm observed in clinical practice. Once thought to be a hamartoma and almost always diagnosed by the imaged-based detection of fat, angiomyolipomas are now known to consist of a heterogeneous group of neoplasms. Although all are considered perivascular epithelioid cell tumors, many display different pathology, imaging features, and clinical behavior. The importance of understanding this group of neoplasms is emphasized by the fact that many types of angiomyolipoma contain little to no fat, and despite being benign, sometimes escape a pre-operative diagnosis. These types of angiomyolipomas can all be considered when encountering a renal mass that is both hyperattenuating relative to renal parenchyma on unenhanced CT and T2-hypointense, features that reflect their predominant smooth muscle component. We review recent developments and provide a radiological classification of angiomyolipomas that helps physicians understand the various types and learn how to both diagnose and manage them.

Imaging the renal mass: a historical review

A matter of months after Roentgen's landmark discovery in 1895, Roentgen's rays were focused on diseases and disorders of the urinary tract, specifically the kidney. At the dawn of the 20th century, urologists in the United States and around the world quickly recognized that by using a variety of metal stylets and radiopaque contrast agents, such as silver salts, the upper urinary tract, namely the ureter, pelvis, and calyces, could be depicted with radiography. Renal cysts and tumors were diagnosed on the basis of deformities in the kidney. Retrograde pyelography dominated the imaging evaluation of the kidney until the discovery of a safe intravenous method for urinary tract imaging (ie, intravenous pyelography). Pioneers and pathfinders in the field of contrast media development and radiologic procedures helped give radiologists the lead role in the work-up of renal masses, an area where urologists once held forth. The subspecialty of uroradiology was born in the middle of the 20th century. Intravenous urography, nephrotomography, and diagnostic angiography with pharmacologic manipulation followed by cyst or mass puncture and biopsy yielded unrivaled specificity for the diagnosis and staging of benign and malignant renal masses. The advent of cross-sectional and multiplanar imaging and the profound effects they had and continue to have on the discovery and characterization of renal masses has been detailed in the pages of Radiology since the 1920s. Ultrasonography, nuclear imaging, computed tomographic scanning, magnetic resonance imaging, and positron emission tomography each have made a claim to a part of the imaging algorithm of modern uroradiologic practice.

Imaging findings of common benign renal tumors in the era of small renal masses: differential diagnosis from small renal cell carcinoma: current status and future perspectives

The prevalence of small renal masses (SRM) has risen, paralleling the increased usage of cross-sectional imaging. A large proportion of these SRMs are not malignant, and do not require invasive treatment such as nephrectomy. Therefore, differentation between early renal cell carcinoma (RCC) and benign SRM is critical to achieve proper management. This article reviews the radiological features of benign SRMs, with focus on two of the most common benign entities, angiomyolipoma and oncocytoma, in terms of their common imaging findings and differential features from RCC. Furthermore, the role of percutaneous biopsy is discussed as imaging is yet imperfect, therefore necessitating biopsy in certain circumstances to confirm the benignity of SRMs.

DNA methylation profiling reveals novel diagnostic biomarkers in renal cell carcinoma

BACKGROUND

Renal cell carcinoma (RCC) is the tenth most commonly diagnosed cancer in the United States. While it is usually lethal when metastatic, RCC is successfully treated with surgery when tumors are confined to the kidney and have low tumor volume. Because most early stage renal tumors do not result in symptoms, there is a strong need for biomarkers that can be used to detect the presence of the cancer as well as to monitor patients during and after therapy.

METHODS

We examined genome-wide DNA methylation alterations in renal cell carcinomas of diverse histologies and benign adjacent kidney tissues from 96 patients.

RESULTS

We observed widespread methylation differences between tumors and benign adjacent tissues, particularly in immune-, G-protein coupled receptor-, and metabolism-related genes. Additionally, we identified a single panel of DNA methylation biomarkers that reliably distinguishes tumor from benign adjacent tissue in all of the most common kidney cancer histologic subtypes, and a second panel does the same specifically for clear cell renal cell carcinoma tumors. This set of biomarkers were validated independently with excellent performance characteristics in more than 1,000 tissues in The Cancer Genome Atlas clear cell, papillary, and chromophobe renal cell carcinoma datasets.

CONCLUSIONS

These DNA methylation profiles provide insights into the etiology of renal cell carcinoma and, most importantly, demonstrate clinically applicable biomarkers for use in early detection of kidney cancer.