Delayed CT to evaluate renal masses incidentally discovered at contrast-enhanced CT: demonstration of vascularity with deenhancement

Renal Metastasis Arising From a Pulmonary Adenoid Cystic Carcinoma: A Rare Case Report and Literature Review

Adenoid cystic carcinoma (ACC), a rare malignancy, typically originates in salivary glands and is rarely found in other locations. In this case report, we describe a 54-year-old male patient who was presented to the Urology Department of Yantai Yuhuangding hospital with right-sided waist pain. The patient underwent percutaneous ultrasound-guided biopsies of lesions in the kidney and lung, which were histologically confirmed as primary adenoid cystic carcinoma of the lung and metastatic renal adenoid cystic carcinoma, respectively. Given the presence of multiple metastases, the patient received systemic palliative chemotherapy, which was well-tolerated and effectively controlled the tumor. At the last follow-up, there was no evidence of tumor progression in the patient.

Multimodality imaging evaluation of pseudotumors in chronic renal dysfunction: exposing the masquerade!

Focal renal lesions in the background of chronic kidney disease (CKD) present a diagnostic challenge. Contrast administration is usually avoided in such a setting, undermining the usefulness of computed tomography and magnetic resonance imaging. Focal regenerating nodules may occur in the background of CKD and closely mimic renal neoplasms. The aim of the present article was to highlight the salient manifestations of such CKD pseudotumors on different imaging modalities and also to depict the differentiating features from malignancy. Radiologists must be aware of the imaging appearance of this uncommonly talked about entity so as to avoid inadvertent surgery or cause undue anxiety to the patient.

Energy-Specific Optimization of Attenuation Thresholds for Low-Energy Virtual Monoenergetic Images in Renal Lesion Evaluation

OBJECTIVE

The purpose of this study was to determine in vitro and in vivo the optimal threshold for renal lesion vascularity at low-energy (40-60 keV) virtual monoenergetic imaging.

MATERIALS AND METHODS

A rod simulating unenhanced renal parenchymal attenuation (35 HU) was fitted with a syringe containing water. Three iodinated solutions (0.38, 0.57, and 0.76 mg I/mL) were inserted into another rod that simulated enhanced renal parenchyma (180 HU). Rods were inserted into cylindric phantoms of three different body sizes and scanned with single- and dual-energy MDCT. In addition, 102 patients (32 men, 70 women; mean age, 66.8 ± 12.9 [SD] years) with 112 renal lesions (67 nonvascular, 45 vascular) measuring 1.1-8.9 cm underwent single-energy unenhanced and contrast-enhanced dual-energy CT. Optimal threshold attenuation values that differentiated vascular from nonvascular lesions at 40-60 keV were determined.

RESULTS

Mean optimal threshold values were 30.2 ± 3.6 (standard error), 20.9 ± 1.3, and 16.1 ± 1.0 HU in the phantom, and 35.9 ± 3.6, 25.4 ± 1.8, and 17.8 ± 1.8 HU in the patients at 40, 50, and 60 keV. Sensitivity and specificity for the thresholds did not change significantly between low-energy and 70-keV virtual monoenergetic imaging (sensitivity, 87-98%; specificity, 90-91%). The AUC from 40 to 70 keV was 0.96 (95% CI, 0.93-0.99) to 0.98 (95% CI, 0.95-1.00).

CONCLUSION

Low-energy virtual monoenergetic imaging at energy-specific optimized attenuation thresholds can be used for reliable characterization of renal lesions.

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.

Imaging appearance of a singular metastatic adenoid cystic carcinoma of the right kidney: A case report and literature review

Renal metastasis of a submandibular gland adenoid cystic carcinoma is clinically rare when it presents with an atypical imaging appearance of singular renal metastases. Whole-body positron emission tomography (PET)/computed tomography (CT) can determine whether the singular renal mass is benign or malignant and identify metastases in other parts of the body, particularly in uncommon sites. In the present case, the patient developed a rare partial metastasis to the right kidney three years after undergoing a surgery for submandibular gland adenoid cystic carcinoma. Based on the present case, whole-body PET/CT examination could provide an important basis for making treatment plans for singular renal metastases.

New modalities for evaluation and surveillance of complex renal cysts

PURPOSE

The increased use of abdominal imaging has led to more frequent detection of incidental renal cysts. Since the inception of the Bosniak classification system, management of Bosniak I, III and IV cysts has been clearly defined, while evaluation and management of Bosniak II and IIF cysts have remained a clinical dilemma. Discussions of new imaging modalities are becoming increasingly prevalent in the radiological literature. In this context we performed a comprehensive review of the recent literature on complex renal cysts focusing on new imaging modalities, surveillance strategies and biopsy.

MATERIALS AND METHODS

We performed a comprehensive literature review of articles published from January 1, 1998 through December 31, 2013 via MEDLINE(®), EMBASE and the Cochrane Collection using a predetermined search strategy. All studies included were performed in humans older than 18 years, were written in English and had an abstract available for review. We grouped studies into 1 of 5 categories, ie computerized tomography, magnetic resonance imaging, ultrasound, biopsy and surveillance.

RESULTS

While computerized tomography and magnetic resonance imaging with and without contrast enhancement remain the gold standard to evaluate cystic lesions of the kidney, diffusion-weighted magnetic resonance imaging and contrast enhanced ultrasound have surfaced as new tools for assessment of complex cysts. Comparative effectiveness studies on these new imaging modalities are limited. Image guided biopsy has increasingly been shown to be useful for evaluation of intermediate (Bosniak II and IIF) complex cysts. We found few studies providing guidance on the duration and/or intensity of surveillance required for intermediate complex renal cysts.

CONCLUSIONS

Although new and enhanced techniques are in development and may be useful in the future management of complex renal cysts, there is a paucity of data regarding the value of these new techniques. Future research should focus on surveillance of intermediate complex renal cysts, particularly on the ideal frequency and type of imaging required.

Common incidental findings on MDCT: survey of radiologist recommendations for patient management

PURPOSE

The aim of this study was to evaluate for agreement with respect to how radiologists report incidental findings encountered on CT.

METHODS

A multiple-choice survey was designed to query radiologists about how they handle 12 incidental findings on body CT, assuming the patient is a 45-year-old woman with no history of malignancy. Included were a 1-cm thyroid nodule, a 5-mm noncalcified lung nodule, coronary artery calcification, a 2-cm adrenal nodule, a 2-cm pancreatic cyst, a 1-cm enhancing liver lesion, a 2-cm high-density renal cyst, short-segment small bowel intussusception, a 1-cm splenic cyst, focal gallbladder wall calcification, and a 3-cm ovarian cyst in both a premenopausal woman and a postmenopausal woman. Choices ranged from "do not report" to advising interventional procedures tailored to the organ. Surveys were administered to body CT attending radiologists at 3 academic institutions.

RESULTS

Twenty-seven radiologists completed the survey. The mean experience level was 15.7 years after training. Seventy percent or greater agreement on interpretation was identified for only 6 findings: recommend ultrasound for a 1-cm thyroid nodule, recommend ultrasound for a 3-cm cyst in postmenopausal woman, follow Fleischner Society recommendations for a 5-mm lung nodule, describe only coronary calcification, and describe as likely benign both short-segment small bowel intussusception and a 1-cm splenic cyst.

CONCLUSIONS

Agreement is lacking, both across institutions and within departments, for the management of 6 commonly encountered incidental findings on body CT. Individual departments should develop internal guidelines to ensure consistent recommendations based on existing evidence.

Papillary renal cell carcinoma: radiologic-pathologic correlation and spectrum of disease

Papillary renal cell carcinoma (pRCC) is the second most common type of renal cell carcinoma (RCC). pRCC has unique imaging and clinical features that may allow differentiation from clear cell RCC (cRCC). There have been significant advances in our knowledge of the natural history and treatment of pRCC, with data suggesting that it may be best to manage pRCC differently from the other subtypes of RCC. At contrast material-enhanced computed tomography, pRCC enhances less than does cRCC in all phases of contrast-enhanced imaging. The difference in the degree of enhancement between pRCC and cRCC is due to differences in their intratumoral vascularity. In general, if a heterogeneous mass enhances to a degree similar to that manifested by the renal cortex, it is likely to be a cRCC. A mass that enhances to a lesser degree is likely to be a non-clear cell RCC. It is common for metastatic lesions from pRCC to show enhancement characteristics similar to those of the primary tumor and be hypovascular.

Radiologic evaluation of small renal masses (I): pretreatment management

When characterizing a small renal mass (SRM), the main question to be answered is whether the mass represents a surgical or nonsurgical lesion or, in some cases, if followup studies are a reasonable option. Is this a task for a urologist or a radiologist? It is obvious that in the increasing clinical scenario where this decision has to be made, both specialists ought to work together. This paper will focus on the principles, indications, and limitations of ultrasound, CT, and MRI to characterize an SRM in 2008 with a detailed review of relevant literature. Special emphasis has been placed on aspects regarding the bidirectional information between radiologists and urologists needed to achieve the best radiological approach to an SRM.

Renal-adrenal fusion: instance of an adrenal adenoma mimicking a solid renal mass at CT--case report

The authors report an unusual case of unilateral renal-adrenal fusion with a concurrent adrenal adenoma. At computed tomography, this abnormality appeared as a solid enhancing lesion in the upper pole of the kidney, mimicking a renal mass. The ambiguous characteristics of this lesion at cross-sectional imaging, along with alternative diagnostic possibilities, are discussed.

Hyperattenuating renal masses: etiologies, pathogenesis, and imaging evaluation

Some renal masses have higher attenuation than the surrounding renal parenchyma at computed tomography (CT). Their hyperattenuation is usually the result of proteinaceous fluid or densely packed cells. Most hyperattenuating renal masses are benign hemorrhagic or proteinaceous cysts. However, solid enhancing hyperattenuating renal masses may have malignant as well as benign causes. Possible malignant causes include renal cell carcinoma and lymphoma; benign causes include angiomyolipoma with minimal fat. It is important to identify the cause of a hyperattenuating renal mass so as to avoid unnecessary surgical resection or ablation. CT may be useful for diagnosing benign hyperattenuating renal cysts, hematomas, and vascular anomalies that appear masslike. However, some solid, enhancing, hyperattenuating masses cannot be diagnosed confidently with CT alone: Small (< or = 3-cm-diameter), homogeneously enhancing, hyperattenuating renal masses depicted on CT images may be either benign angiomyolipomas with minimal fat or renal cell carcinomas. Magnetic resonance (MR) imaging may be helpful for differentiating between angiomyolipomas with minimal fat and clear cell renal cell carcinomas; however, differentiation between angiomyolipomas with minimal fat and papillary renal cell carcinomas often is not possible on the basis of MR imaging. In such cases, a percutaneous biopsy may be useful for diagnosis. If the results of MR imaging and percutaneous biopsy are not definitive, surgery is warranted.

Differentiation of Renal Neoplasms From High-Density Cysts

PURPOSE

The current study evaluated attenuation changes for proven renal neoplasms between the corticomedullary and the nephrographic phases of a contrast-enhanced computed tomographic (CT) scan as a possible means for differentiating these tumors from the cysts of the kidney when high-density renal masses are detected on a CT scan that does not include a noncontrast baseline.

METHODS

We retrospectively reviewed the CT scans performed on 20 patients with 21 biopsy-proven renal neoplasms, which had been done using standard contrast-enhanced computed tomography only. Attenuation values for the 21 renal neoplasms and for 23 simple cysts, used as an internal control, were measured and recorded from the 2 phases of enhancement. The difference in attenuation between the 2 phases of enhancement for each mass was calculated. Data for the neoplasms and cysts were compared with published data for enhancement changes for proven high-density renal cysts.

RESULTS

The mean absolute value change in attenuation between the corticomedullary and the nephrographic phases for renal neoplasms was 22 Hounsfield units (HU) (range, 1.0-48 HU) and 1 HU (range, 0.1-3.3 HU) for simple cysts. Only one renal neoplasm (5%) changed to less than 10 HU.

CONCLUSIONS

Almost all renal neoplasms studied had an attenuation change of more than 10 HU, either increased or decreased, between 2 phases of a contrast-enhanced CT scan separated by 50 seconds. The results suggest that if the attenuation of a renal tumor changes by more than 10 HU between phases of a contrast-enhanced computed tomography, then the diagnosis of renal neoplasm is very likely. High-attenuation renal masses which change less than 10 HU between the corticomedullary and tubular phases are most likely high-density cysts, but neoplasm is possible.

Results of computerized tomography guided percutaneous ablation of renal masses with nondiagnostic pre-ablation pathological findings

PURPOSE

Ablative therapy for renal masses has been criticized because the entire tumor cannot be evaluated pathologically after the procedure. Diagnosis depends on imaging findings and the results of percutaneous needle biopsies, which may be nondiagnostic in up to 21% of cases. We determined outcomes in patients undergoing ablation who had nondiagnostic biopsies at the time of the procedure.

MATERIALS AND METHODS

A total of 79 patients (88 renal masses) underwent percutaneous computerized tomography guided biopsy and ablation of a renal mass under conscious sedation. Patients with nondiagnostic biopsies were identified and the medical records were reviewed retrospectively. All patients had an enhancing renal mass on preoperative computerized tomography or magnetic resonance imaging and all underwent postoperative contrast imaging to evaluate persistent viable tumor.

RESULTS

A total of 19 patients (20 tumors) with nondiagnostic percutaneous biopsy (22.7% or 20 of 88) were included in the study. No serious complications occurred. Tumors were treated with frequency ablation (12) or cryoablation (7). In 17 patients (89.5%) post-procedure imaging confirmed the absence of contrast enhancement at a median followup of 27.3 months (range 3 weeks to 56 months). In 2 cases (10.5%) post-procedure imaging showed a residual renal mass or recurrence with enhancement, suggesting that the original percutaneous biopsy result was false negative. In 1 patient residual tumor was identified on initial post-ablation imaging and the patient underwent laparoscopic partial nephrectomy. In another patient recurrence was diagnosed 30 months after ablation and the patient underwent laparoscopic radical nephrectomy. Although there was a nondiagnostic percutaneous biopsy in each case, pathological findings in the subsequent surgical specimen confirmed renal cell carcinoma.

CONCLUSIONS

Nondiagnostic percutaneous biopsy at renal tumor ablation does not obviate the need for standard post-procedure imaging followup. Of patients with nondiagnostic biopsies in this series 10.5% still harbored viable renal cell carcinoma after percutaneous ablation.

Maximizing clinical information obtained by CT

CT scanning is an integral part of the urologist's practice today. It is the most commonly used imaging modality and the one with which urologists are most familiar. CT urography, CT angiography, and 3D reconstruction enable the urologist to perform comprehensive evaluations of patients who have different urologic diseases, using a single imaging modality. It is thus prudent that urologists become familiar with CT applications, to maximize the clinical information available from them.

Value of Delayed Imaging in MDCT of the Abdomen and Pelvis

OBJECTIVE

Our objective was to illustrate the benefits of obtaining delayed CT images.

CONCLUSION

There are several clinical scenarios in which delayed CT images may improve diagnostic specificity.

Kidney cancer: identification of novel targets for therapy

Kidney cancer, although relatively rare when compared to other malignancies, occurs not uncommonly in patients with renal disease and is often discovered incidentally during the initial nephrologic work-up, or by the savvy clinician who is familiar with the paraneoplastic signs. While surgical approaches are generally curative when the disease is confined to the kidney, one-third of the cases that present in the metastatic form and require conventional medical therapy are associated with a truly dismal patient survival rate. In light of the emerging knowledge of the molecular mechanisms of kidney cancer oncogenesis, several novel and promising therapeutic approaches are emerging. In this review, we summarize the current state of kidney cancer diagnosis and therapy, as well as some of the novel treatments that capitalize on those newly elucidated molecular pathways that are deranged in this disease.

Renal Multidector Row CT

Multidetector row CT is the most recent advance in CT technology. An increased number of detector rows and more powerful x-ray tubes result in faster scanning time, increased volume coverage, and improved spatial and temporal resolution. MDCT technology allows superior image quality, decreased examination time, and the ability to perform complex multiphase vascular and three-dimensional examinations.

The management of indeterminate incidental findings detected at abdominal CT

Abdominal computed tomography (CT) scans often have findings that are incidental to the reason the study was ordered. Several recent studies and reviews have addressed how these findings should be managed. This article summarizes current management strategies for several types of lesions that are commonly encountered. Some of these findings can be characterized without additional imaging (including simple renal cyst, angiomyolipoma, hepatic steatosis). Other findings are indeterminate. While some of these indeterminate incidental findings can be ignored based on statistical arguments (for example, a sharply circumscribed homogeneous low-attenuation renal lesion under 1 cm in patients without a predisposition to develop renal cell carcinoma), many may need additional imaging studies to either characterize them or demonstrate stability over time. Adhering to these strategies will hopefully reduce overutilization of imaging services while directing attention to those findings which need diagnostic or therapeutic interventions.

Decreases in free cholesterol and fatty acid unsaturation in renal cell carcinoma demonstrated by breath-hold magnetic resonance spectroscopy

Increased utilization of cross-sectional imaging has resulted in increased detection of incidental renal tumors. The noninvasive characterization of renal tissue has important implications for the diagnosis of renal malignancies and treatment monitoring. Recently, multiple breath-hold averaged proton magnetic resonance spectroscopy (1H-MRS) performed at high field has enabled the use of this noninvasive metabolic profiling technique for the investigation of the abdomen. Multiple breath-hold averaged 1H-MRS at high field (3T) was obtained in the kidneys of 10 healthy volunteers and in renal cell carcinoma tumors of 14 patients. The spectra of normal kidneys showed four main groups of resonances: 1) at 5.4–5.6 ppm, attributed to C6 of cholesterol and the unsaturated parts of the olefinic region of fatty acids; 2) at 4.7 ppm, attributed to the residual water signal; 3) at 3.2 ppm, attributed to trimethylamine moiety of choline metabolites; and 4) at 1.3 and 0.9 ppm, attributed to the methylenes and terminal methyls of lipids. The ratio of the signal at 5.4 ppm to that of 1.3 ppm was 19-fold lower in renal cell carcinomas than in healthy kidneys, tied P = 0.0003 Mann-Whitney U-test, suggesting a decrease in both free cholesterol and the degree of unsaturation of fatty acids in the malignant tissue. This metabolic shift is in agreement with previous ex vivo studies of human renal cell carcinoma. The ability to detect renal metabolic shifts noninvasively may improve the specificity of preoperative renal tissue characterization and may provide a new modality for treatment monitoring.

From the RSNA Refresher Courses

The pathologic and imaging features of the renal cyst have been well described. A fluid-filled lesion is considered a cystic mass (ie, not a simple cyst) when it has any of the following features: calcification, high attenuation (>20 HU) at computed tomography, signal intensity not typical of water at magnetic resonance imaging, septations, multiple locules, enhancement, wall thickening, or nodularity. There are two important causes of a cystic renal mass: a complicated simple cyst (eg, one with hemorrhage, infection, or ischemia) and cystic renal cell carcinoma. At radiologic evaluation of such masses, it is imperative that optimal imaging techniques be used. Masses with calcification, high attenuation or high signal intensity, or septations can be categorized as benign (no further evaluation required), as requiring follow-up (probably benign), or as requiring surgery. Lesions requiring surgery can be benign or malignant at microscopic examination. Lesions that are multiloculated or demonstrate enhancement, wall thickening, or nodularity usually require surgery. When multiple features are present (eg, calcification and enhancement), the mass should be managed according to its most aggressive feature. Likewise, when there are conflicting findings at evaluation with different imaging modalities, the mass should be managed according to the most aggressive finding.

Image-guided ablation of renal cell carcinoma

An increasing number of small asymptomatic renal cell carcinomas (RCCs) are being detected by cross-sectional imaging. Because of the nonaggressive biologic behavior of many of these tumors, there is increasing interest in minimally invasive treatment modalities,particularly for the elderly, infirm, and patients with comorbid conditions. Radiofrequency(RF) ablation, cryoablation, microwave ablation, and laser ablation have all shown promise for the treatment of RCC, with high local control and low complication rates for RF ablation and cryoablation. However, the clinical trial data remain early, and survival data are not yet available for a definitive comparison with conventional surgical techniques for removal 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.

Technical considerations in renal CT

CT is a robust, rapid means of evaluation for a wide spectrum of urologic disorders. The evaluation of renal trauma, urologic malignancy, urolithiasis, and vascular anatomy is well suited to CT techniques. Subtle adjustments in the technical parameters and timing of the study, however, can optimize the evaluation based on the clinical setting. As CT is more widely used, often repeatedly on an individual patient, radiation exposure must be minimized while still obtaining diagnostic image quality.

Distinction of renal cell carcinomas from high-attenuation renal cysts at portal venous phase contrast-enhanced CT

PURPOSE

To determine if renal cell carcinomas can be distinguished from high-attenuation renal cysts on portal venous phase contrast material-enhanced computed tomographic (CT) scans.

MATERIALS AND METHODS

Fifty-seven renal cell carcinomas and 37 high-attenuation (>20 HU) renal cysts that were at least 1 cm in diameter were retrospectively identified in 90 patients who underwent portal venous phase contrast-enhanced CT. Two independent readers recorded the CT number and degree of internal heterogeneity (uniform or mildly, moderately, or markedly heterogeneous) of all lesions. Logistic regression analysis with adjustment for the two readers was used to examine the association between clinical and CT parameters and the final diagnosis. Stepwise logistic regression analysis was used to identify independent distinguishing variables, which were then incorporated in a classification and regression tree analysis to construct the most efficient classification algorithm.

RESULTS

Renal cell carcinomas were of significantly greater size (5.10 cm vs 2.84 cm, P <.001), mean attenuation (101.2 HU vs 55.3 HU, P <.001), and internal heterogeneity (P <.001) than high-attenuation renal cysts. Stepwise logistic regression showed attenuation and internal heterogeneity were both independent variables associated with final diagnosis, but lesion size was not an independent distinguishing variable after adjustment for internal heterogeneity. Classification and regression tree analysis demonstrated that an attenuation greater than 70 HU or the presence of moderate or marked internal heterogeneity was an accurate sign of renal cell carcinoma, with a sensitivity of 91% (52 of 57) for both readers and a specificity of 92% (34 of 37) for reader 1 and 84% (31 of 37) for reader 2.

CONCLUSION

On portal venous phase contrast-enhanced CT scans, attenuation greater than 70 HU or moderate or marked internal heterogeneity favor a diagnosis of renal cell carcinoma over a diagnosis of high-attenuation renal cyst.

Imaging-guided percutaneous radiofrequency ablation of solid renal masses: techniques and outcomes of 38 treatment sessions in 32 consecutive patients

OBJECTIVE

The purpose of this study was to describe the treatment techniques and results of 38 consecutive imaging-guided percutaneous radiofrequency ablations of solid renal masses performed in 32 patients.

MATERIALS AND METHODS

Solid renal masses in 32 patients underwent 38 treatment sessions using imaging-guided percutaneous radiofrequency ablation. During 36 sessions, radiofrequency ablation was performed using CT guidance, and two, using sonographic guidance. The average patient age was 76 years (range, 52-87 years), and the average renal mass size was 2.6 cm (range, 1-5 cm). The average number of radiofrequency treatments per solid mass at each session was 2.4 (range, 1-6 treatments), and the average time per treatment was 9.2 min (range, 3-14 min). A single electrode was used in 12 sessions, and a cluster electrode was used in 26 sessions. The average follow-up time was 9 months (range, 1-36 months).

RESULTS

Twenty-six of 32 patients had successful treatment of the solid renal mass using percutaneous imaging-guided radiofrequency ablation after one treatment session. Successful treatment was defined as lack of enhancement of the treated region on follow-up CT. Six of 32 patients had residual enhancing tissue after the first treatment session and returned for a second session. Five of these six retreatments were successful. Masses requiring a second treatment session were significantly larger than masses treated in a single session (3.5 vs 2.4 cm, respectively; p = 0.0013). Two patients had perinephric hematomas (which did not require transfusion), and one patient developed a 5-mm skin metastasis at the electrode insertion site, which was resected without recurrence.

CONCLUSION

Percutaneous imaging-guided radiofrequency ablation shows promise in the treatment of solid renal malignancies.

Imaging for renal tumors

PURPOSE OF REVIEW

The present review summarizes current developments in the imaging of renal tumors.

RECENT FINDINGS

Computed tomography (CT), magnetic resonance imaging, and ultrasound are used for diagnosing, characterizing, and staging renal tumors. Recent advances have been made in many areas, but the most significant changes have occurred in helical CT. The traditional roles for CT and magnetic resonance imaging have been expanded to include the use of three-dimensional CT and magnetic resonance imaging as surgical planning tools. Three-phase CT scans are commonly performed for detection, characterization, and staging of renal lesions, but pelvic CT is probably not needed for preoperative staging. Three-phase CT scans are more sensitive for characterization and for identifying the renal vasculature. Enhancement characteristics on these scans can help to distinguish between different tumor types. Finally, CT urography is a promising alternative to conventional excretory urography, with the potential to simplify the imaging evaluation of patients with hematuria.

SUMMARY

Although ultrasound and magnetic resonance imaging have many indications for imaging renal tumors, CT, with new uses and improved diagnostic capabilities, remains the gold standard in renal imaging.

Enhancement characteristics of papillary renal neoplasms revealed on triphasic helical CT of the kidneys

OBJECTIVE

The purpose of this study was to determine whether renal tumor enhancement or heterogeneity on triphasic helical CT scans is predictive of the papillary cell subtype or nuclear grade of renal cell carcinoma.

MATERIALS AND METHODS

We reviewed the CT scans of 90 consecutive patients with renal masses who had undergone triphasic renal helical CT before a complete or partial nephrectomy (12 with papillary renal cell carcinomas, 66 with nonpapillary renal cell carcinomas, and 12 with benign lesions). Three radiologists who were unaware of the patients' diagnoses retrospectively and independently measured the attenuation of each patient's tumor, abdominal aorta, and normal renal parenchyma on the scans obtained during all three phases. Ratios of tumor-to-aorta enhancement and tumor-to-normal renal parenchyma enhancement were calculated for both of the phases performed after contrast material had been administered. Tumor heterogeneity was calculated as the difference between the highest and lowest attenuation values divided by the value of the enhancement of the aorta. Values were correlated with cell type and nuclear grade found at surgical pathology.

RESULTS

Low tumor-to-aorta enhancement and low tumor-to-normal renal parenchyma enhancement ratios on the vascular phase scans significantly correlated (p < 0.001) with papillary renal cell type carcinoma. Homogeneity and tumor-to-parenchyma enhancement ratios on the parenchymal phase scans also significantly correlated (p < 0.001) with papillary renal cell type carcinoma. Heterogeneity and tumor enhancement ratios did not correlate with the nuclear grade of the carcinoma.

CONCLUSION

Papillary renal cell carcinomas are typically hypovascular and homogeneous. A high tumor-to-parenchyma enhancement ratio (> or = 25%) essentially excludes the possibility of a tumor being papillary renal cell carcinoma. A low tumor-to-aorta enhancement ratio or tumor-to-normal renal parenchyma enhancement ratio is more likely to indicate papillary renal cell carcinoma.

Current concepts in the diagnosis and management of renal cell carcinoma: role of multidetector ct and three-dimensional CT

Renal cell carcinoma is the most common primary tumor of the kidney, with more than 30,000 new cases diagnosed in the United States each year. With the widespread use of cross-sectional imaging, many tumors are detected incidentally. Single- and multidetector computed tomography (CT) have helped refine the diagnostic work-up of renal masses by allowing image acquisition in various phases of renal enhancement after intravenous administration of a single bolus of contrast material. The scanning protocol should include unenhanced CT followed by imaging during the corticomedullary and nephrographic phases of enhancement. The nephrographic phase is the most sensitive for tumoral detection, while the corticomedullary phase is essential for imaging the renal veins for possible tumoral extension and the parenchymal organs for potential metastases. Knowledge of the tumoral stage at the time of diagnosis is essential for prognosis and surgical planning. The accuracy of CT for staging has been reported to reach 91%, with most staging errors related to the diagnosis of perinephric extension of tumor. Three-dimensional CT provides the urologist with an interactive road map of the relationships among the tumor, the major vessels, and the collecting system. This information is particularly critical if the tumor extends into the inferior vena cava and if nephron-sparing surgery is being planned.

Renal scars masquerading as complex masses in a patient with vesicoureteral reflux nephropathy

Vesicoureteral reflux can lead to chronic pyelonephritis, renal scarring, and renal failure. We present a case of renal scarring masquerading as bilateral, complex renal masses. A 35-year old woman who was diagnosed with vesicoureteral reflux as a child presented for evaluation of recently developed hypertension and an abnormal renal ultrasound. Her serum creatinine level was 2.5 mg/dL and she had subnephrotic-range proteinuria. A renal sonogram showed small, echogenic kidneys and bilateral complex renal masses of 3.8 (right) and 4.4 (left) cm in greatest dimensions. CT scan of the kidneys revealed slightly contrast-enhancing masses with irregular walls. Renal angiogram showed decreased blood supply to the areas coinciding with the masses consistent with renal scarring. There was no increased vascularity. This case demonstrates that renal scarring may masquerade as renal masses. A step-wise, comprehensive approach is necessary to rule out potentially malignant lesions in these patients.

Imaging renal masses

Imaging plays a crucial role in the detection, characterization, and post-operative follow-up of renal masses. With rapidly advancing technology, imaging techniques are continuously evolving. This review will discuss the current modalities and techniques available for renal imaging, and recent developments.

Cystic renal masses: accurate Bosniak classification requires adequate renal CT

OBJECTIVE

The objective of this study was to assess the practical usefulness of the Bosniak classification system for separating surgical from nonsurgical cystic renal masses in a large number of patients examined with properly performed renal CT. The study included only patients whose scans were technically adequate to allow proper assignment of the lesion to a category.

MATERIALS AND METHODS

The scans of 109 patients were gathered from two large teaching institutions both prospectively and retrospectively, yielding a total of 116 analyzable renal cystic lesions. Eighty-two masses were resected from 77 of these patients, retrospectively categorized by two experienced uroradiologists using the Bosniak classification system, and correlated with pathology reports. A second group of 34 lesions in 32 patients with atypical cysts was followed up prospectively for periods ranging from 3 months to 10 years.

RESULTS

The results were similar for the two institutions: 15 resected categories I and II lesions were correctly identified as benign, and all 18 category IV lesions were malignant. Twenty-nine (59%) of 49 pooled category III masses were malignant. No malignancies have been identified in the prospectively monitored group of patients.

CONCLUSION

Our results are compared with earlier, smaller series and support those that show that the Bosniak classification system is useful in separating lesions requiring surgery from those that can be safely followed up, provided proper CT techniques are used.