Imaging of small renal masses: a medical success story

Which criteria can be used to predict benignity in solid renal lesions lower-equal to 2 cm?

PURPOSE

To evaluate magnetic resonance imaging (MRI) criteria of solid renal lesions lower-equal to 2 cm to differentiate benign and malignant tumors, using histopathology as gold standard.

METHODS

Three radiologists independently evaluated objective and subjective MRI criteria of focal renal lesions. A total of 105 nodules of patients who had MRI and histopathological results in our institution were included. Subjective criteria evaluated were signal on T2-weighted imaging, presence of microscopic and macroscopic fat, hemosiderin, hemorrhage, central scar, segmented inversion enhancement and enhancement type; objective criteria were gender, ADC value, heterogeneity on T2-weighted imaging and proportion of enhancement in late post-contrast phases. Finally, the readers classified the lesions in probably benign or malignant. Interobserver agreement was evaluated by the Gwet method, and the quantitative variables by intraclass correlation coefficients. To adjust the predictive model, the logistic regression model was used considering the benignity variable as outcome.

RESULTS

A total of 26 nodules (24.5%) were benign and 79 (75.2%) were malignant, with size ranging from 7 to 20 mm (median: 14 mm). The most frequent subtype was papillary renal cell carcinoma (RCC) (35.2%), followed by clear-cell RCC (24.8%) and oncocytoma (12.4%). The univariate and multivariate analysis showed, among all categories evaluated, that microscopic fat (p: 0.072), intermediate (p: 0.004) and hyper-enhancement (p: 0.031) and female sex (p: 0.0047) had the best outcome for benignity, within odds ratios of 4.29, 5.75, 4.07 and 2.86, respectively.

CONCLUSION

In small solid renal lesions lower-equal to 2 cm, microscopic fat, moderate and hyper-enhancement and female sex were associated with benignity.

Radiation dose reduction in CT-guided cryoablation of renal tumors

PURPOSE

We aimed to evaluate the effect on the radiation dose to the patient by reducing the tube current during the placement of the ablation needles (reduced dose group) compared with the patient doses delivered when scanning at the standard fully diagnostic level (full dose group) in computed tomography (CT)-guided percutaneous cryoablation.

METHODS

We conducted a retrospective study of 103 patients undergoing cryoablation in a tertiary cancer center. Overall, 62 patients were scanned with standard exposure parameters (full dose group) set on a 64-slice multidetector CT scanner, while 41 patients were scanned on a reduced dose protocol. Dose levels were retrieved from the hospital picture and archiving communication system including the volumetric CT dose index (CTDIvol), total dose length product (DLP), length of cryoablation procedure, number of cryoablation needles and patient size. Wilcoxon Mann-Whitney (rank-sum) tests were used to compare the median DLP, CTDIvol and skin dose between the two groups.

RESULTS

Median total DLP for the full dose group was 6025 mGy•cm (1909-13353 mGy•cm) compared with 3391 mGy•cm (1683-6820 mGy•cm) for the reduced dose group. The reduced dose group had a 44% reduction in total DLP and 42% reduction in total CTDIvol (p < 0.001). The estimated skin doses were 384 mGy for the full dose group and 224 mGy for the reduced dose group (42% reduction) (p < 0.001). At 12-month follow-up, the technical success for the full dose (n=62) was 97% with 2 patients requiring a further cryoablation treatment for residual tumor. The technical success for the reduced dose group (n=41) was 100%.

CONCLUSION

CT dose reduction technique during image-guided cryoablation treatment of renal tumors can achieve significant radiation dose reduction whilst maintaining sufficient image quality.

Characterizing T2 iso- and hypo-intense renal masses on MRI: Can templated algorithms improve accuracy?

PURPOSE

To assess if a templated algorithm can improve the diagnostic performance of MRI for characterization of T2 isointense and hypointense renal masses.

METHODS

In this retrospective study, 60 renal masses with histopathologic diagnoses that were also confirmed as T2 iso- or hypointense on MRI were identified (mean ± standard deviation, range: 3.9 ± 2.5, 1.0-13.7 cm). Two semi-quantitative diagnostic algorithms were created based on MRI features of renal masses reported in the literature. Three body-MRI trained radiologists provided clinical diagnoses based on their experience and separately provided semiquantitative data for each components of the two algorithms. The algorithms were applied separately by a radiology trainee without additional interpretive input. Logistic regression was used to compare the accuracy of the three methods in distinguishing malignant versus benign lesions and in diagnosing the exact histopathology. Inter-reader agreement for each method was calculated using Fleiss' kappa statistics.

RESULTS

The accuracy of the two algorithms and clinical experience were similar (70%, 69%, and 64%, respectively, p = 0.22-0.32), with fair to moderate inter-reader agreement (Fleiss's kappa: r = 0.375, r = 0.308, r = 0.375, respectively, all p < 0.0001). The accuracy of the two algorithms and clinical experience in diagnosing specific histopathology were also no different from each other (34%, 29%, and 32%, respectively, p = 0.49-0.74), with fair to moderate inter-reader agreement (Fleiss's kappa: r = 0.20, r = 0.28, r = 0.375, respectively, all p < 0.0001).

CONCLUSION

Semi-quantitative templated algorithms based on MRI features of renal masses did not improve the ability to diagnose T2 iso- and hypointense renal masses when compared to unassisted interpretation by body MR trained subspecialists.

Local recurrence of renal cell carcinoma successfully treated with fusion imaging-guided percutaneous thermal ablation

Image-guided thermal ablations are increasingly applied in the treatment of renal cancers, under the guidance of ultrasound (US) or computed tomography (CT). Fusion imaging allows exploitation of the strengths of all imaging modalities simultaneously, eliminating or minimising the weaknesses of every single modality. We present a case of a 68-year-old patient treated using US/CT fusion imaging to guide radiofrequency ablation for local recurrence of renal cell carcinoma undetectable by ultrasound.

Comparative outcomes of radio frequency ablation versus partial nephrectomy for T1 renal tumors: a systematic review

Background

The role of radio frequency ablation (RFA) in small renal tumors remains controversial. This systematic review was performed to compare clinical outcomes of RFA versus partial nephrectomy (PN) for the treatment of T1 renal tumors.

Methods

A total of 11 studies including 2,397 patients were analyzed in this systematic review after searching the databases of PubMed, EMBASE and Web of Science. P value and odds ratio (OR)/hazard ratio (HR) with 95% confidence interval (CI) were used to evaluate the strength of the association.

Results

A total of six studies (2,056 patients) provided either survival curves or HR and its 95% CI, demonstrating that the majority of the patients with RFA treatment tended to exhibit a similar long-term survival rate to those with PN treatment. In addition, according to four studies, no differences were found in the overall rate of complications between the two groups. Furthermore, there were significant differences in glomerular filtration rate (GFR) change between the two methods in four studies but no differences were observed in other two.

Conclusions

Our systematic review indicated that RFA is an effective treatment option which could provide comparable oncologic outcomes to PN. Moreover, it may present obvious advantages in renal function preservation.

Diagnostic accuracy of signal loss in in-phase gradient-echo images for differentiation between small renal cell carcinoma and lipid-poor angiomyolipomas

OBJECTIVES

To assess the diagnostic accuracy of signal loss on in-phase (IP) gradient-echo (GRE) images for differentiation between renal cell carcinomas (RCCs) and lipid-poor angiomyolipomas (lpAMLs).

METHODS

We retrospectively searched our institutional database for histologically proven small RCCs (<5.0 cm) and AMLs without visible macroscopic fat (lpAMLs). Two experienced radiologists assessed MRIs qualitatively, to depict signal loss foci on IP GRE images. A third radiologist drew regions of interest (ROIs) on the same lesions, on IP and out-of-phase (OP) images to calculate the ratio of signal loss. Diagnostic accuracy parameters were calculated for both techniques and the inter-reader agreement for the qualitative analysis was evaluated using the κ test.

RESULTS

15 (38.4%) RCCs lost their signal on IP images, with a sensitivity of 38.5% (95% CI = 23.4-55.4), a specificity of 100% (71.1-100), a positive predictive value (PPV) of 100% (73.4-100), a negative predictive value (NPV) of 31.4% (26.3-37.0), and an overall accuracy of 52% (37.4-66.3%). In terms of the quantitative analysis, the signal intensity index (SII= [(SI_IP - SI_OP) / SI_OP] x 100) for RCCs was -0.132 ± 0.05, while for AMLs it was -0.031 ± 0.02, p = 0.26. The AUC was 0.414 ± -0.09 (0.237-0.592). Using 19% of signal loss as the threshold, sensitivity was 16% and specificity was 100%. The κappa value for subjective analysis was 0.63.

CONCLUSION

Signal loss in "IP" images, assessed subjectively, was highly specific for distinction between RCCs and lpAMLs, although with low sensitivity. The findings can be used to improve the preoperative diagnostic accuracy of MRI for renal masses.

ADVANCES IN KNOWLEDGE

Signal loss on "IP" GRE images is a reliable sign for differentiation between RCC and lpAMLs.

[Biopsies of kidney lesions: when and how?]

The demand for image-guided renal biopsy has increased due to the better detection of renal lesions; however, despite modern imaging techniques many small renal tumors cannot be classified as benign because they cannot be differentiated from renal cell carcinoma. Ultrasound and computed tomography (CT)-guided kidney biopsy is a safe and accurate method in the diagnostics of renal lesions and can be helpful in the selection of new ablative and pharmaceutical forms of treatment and avoid unnecessary operations. This article describes the clinical indications for an image-guided biopsy and discusses factors which should be considered when performing a biopsy.

Ultrasound-guided percutaneous radiofrequency ablation for treating small renal masses

INTRODUCTION

The objective of this study was to analyse and assess the experience with radiofrequency ablation of small renal masses using a contrast-enhanced, ultrasound-guided percutaneous approach for patients who are not suitable for surgical resection and/or who refused surveillance or observation.

MATERIAL AND METHOD

From January 2007 to August 2015, 164 treatments were performed on a total of 148 patients. We present the patients' clinical-radiological characteristics, oncological and functional results in the short and medium term.

RESULTS

The overall technical success rate was 97.5%, with a successful outcome in 1 session in 100% of the lesions≤3cm and 92% in lesions measuring 3-5cm. The mean tumour diameter in the patients for whom the treatment was ultimately successful was 2.7cm, while the mean diameter of these in the unsuccessful operations was 3.9cm (P<.05). There were no statistically significant differences in the serum creatinine levels and estimated glomerular filtration rates.

CONCLUSIONS

Despite the low rate of positive renal biopsies in the series, ultrasound-guided percutaneous radiofrequency ablation for treating small renal lesions appears to be an effective and safe procedure with a minimum impact on renal function, an acceptable oncologic control in the short and medium term and a low rate of complications.

[Ablative therapy in urology: Good practice and perspective]

INTRODUCTION

To expose the main point of discussion from present ablative therapies' guidelines and propose global perspectives.

MATERIALS AND METHODS

A review of the scientific literature was performed in Medline database (http://www.ncbi.nlm.nih.gov) and Embase (http://www.embase.com/) using different associations of keywords "ablative therapy" ; "prostate cancer"; "kidney cancer"; "guidelines"; "hybrid operating room". Publications obtained were selected based on methodology, language and relevance.

RESULTS

Present guidelines on ablative therapies in urology are, considering authors and organs, either particularly prudent (EAU guidelines for prostate and kidney) or relatively optimistic (CIRSE guidelines). This discrepancy is related to a low level of proof. So, a new approach is mandatory: more homogeneous in methodology, and especially more open to a new organization sparing economic efficiency. The objective will be to get multifunctional and multidisciplinaries platforms, in facts and in minds. It will induce, in the future, a deep reflection about training and boundaries' specialties.

CONCLUSION

Ablative therapies represent a crucial stake for urology and a clear example of medicosurgical evolution in future, based on new technologies (energy, robotic, imaging). A serious and deep reflection is necessary to prepare it and be deeply involved in.

Do Incidental Hyperechoic Renal Lesions Measuring Up to 1 cm Warrant Further Imaging? Outcomes of 161 Lesions

OBJECTIVE

The purpose of this study was to determine the outcomes of hyperechoic renal lesions measuring 1 cm or less at ultrasound examination.

MATERIALS AND METHODS

This retrospective study included 161 hyperechoic renal lesions measuring 1 cm or less at ultrasound that were evaluated with follow-up ultrasound, CT, or MRI. Follow-up imaging examinations were reviewed to assess for definitive lesion characterization or size stability.

RESULTS

Follow-up included 11 unenhanced CT, 39 contrast-enhanced CT, 52 unenhanced and contrast-enhanced CT, two unenhanced MRI, 50 unenhanced and contrast-enhanced MRI, and 87 ultrasound examinations. At CT or MRI 58.4% of lesions were confirmed to be angiomyolipomas. At CT, one lesion represented a stone, and one a hyperdense cyst. At CT or MRI 11.8% of the lesions had no correlate; 3.1% were not visualized at follow-up ultrasound. An additional 23.6% were stable at 2-year follow-up imaging or beyond. Two lesions were evaluated with only contrast-enhanced CT less than 1 month after ultrasound, and the CT images did not show macroscopic fat or calcification or meet the criteria for a simple cyst. These lesions were considered indeterminate. One lesion in a 65-year-old man was imaged with unenhanced and contrast-enhanced CT 23 months after ultrasound, and the CT showed an increase in size, solid enhancement, and no macroscopic fat. This lesion was presumed to represent renal cell carcinoma. Overall, the one lesion presumed malignant and the two indeterminate lesions constituted 1.9% of the cohort. The other 98.1% of lesions were considered clinically insignificant.

CONCLUSION

Most hyperechoic renal lesions measuring 1 cm or smaller were clinically insignificant, suggesting that such lesions may not require additional imaging. Patient demographics, symptoms and risk factors for malignancy may help inform the decision to forgo follow-up imaging of such lesions.

Simultaneous occurrence of non-Hodgkin lymphoma, renal cell carcinoma and oncocytoma: A case report

We herein report the case of a 74 year-old woman with a diffuse large B-cell lymphoma and bilateral renal masses identified on computed tomography scans during the initial staging process. Following partial bilateral nephrectomy, histopathological examination revealed renal cell carcinoma (RCC) and oncocytoma in the left and the right kidneys, respectively. Shortly afterwards, lymphoma of the left palatine tonsil was diagnosed and the patient received chemotherapy with rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone (R-CHOP regimen), followed by radiotherapy. Due to metastasis of the RCC to the right breast, pancreas and the area of the left psoas major muscle, systemic treatment with pazopanib was commenced. To the best of our knowledge, this is the first reported case of simultaneous diagnosis of non-Hodgkin lymphoma (NHL), RCC and oncocytoma. The aim of this study was to review the related literature, discuss issues regarding the management of this unusual case and identify possible common etiopathological mechanisms underlying the simultaneous occurrence of NHL, RCC and oncocytoma.

Enhancement Threshold of Small (< 4 cm) Solid Renal Masses on CT

OBJECTIVE

The objective of our study was to determine whether small (< 4 cm) solid renal cell carcinomas (RCCs) enhance on CT below the published enhancement thresholds.

MATERIALS AND METHODS

For this retrospective study, we reviewed CT examinations of patients with pathologically characterized small solid renal masses. Patients with lipid-rich angiomyolipomas were excluded. The study included consecutive patients who had pathologically characterized small (< 4 cm) renal masses and had undergone CT during the un-enhanced phase and nephrographic phase (NP). Most CT examinations also included imaging during the corticomedullary phase (CMP); four patients did not have CMP images. The CT examinations were performed on a 64-MDCT scanner. Similar-sized ROIs were placed on each lesion on unenhanced and enhanced images and enhancement (in Hounsfield units) was calculated. Masses were considered solid with a threshold enhancement greater than either 15 or 20 HU.

RESULTS

There were 137 masses in 137 patients, 90 men and 47 women (age range, 21-91 years; median age, 65 years). The renal masses were 1.0-3.9 cm (median, 2.4 cm). Of the 137 masses, 117 (85.4%) were malignant and 20 (14.6%) were benign. One malignant mass and three benign masses did not have CMP images. Twenty of the 116 (17.2%) renal cell carcinomas (RCCs) did not reach the 15-HU threshold enhancement on CMP images, nine of 117 masses (7.7%) did not reach the 15-HU enhancement threshold on NP images, and four of 117 masses (3.4%) did not reach the 15-HU enhancement threshold on both CMP and NP images. The numbers of masses that did not reach the 20-HU enhancement threshold were 24 of 116 masses (20.7%) on CMP images, 14 of 117 masses (11.9%) on NP images, and 11 of 117 masses (9.4%) on both CMP and NP images. Depending on the phase or enhancement threshold, 13.6-59.1% of papillary RCCs did not reach the enhancement threshold.

CONCLUSION

A minority of small RCCs do not reach either a 15- or 20-HU enhancement threshold and might be misinterpreted as a hyperattenuating cyst. Most RCCs below these enhancement thresholds are papillary RCC.

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.

Local Recurrence of Renal Cancer After Surgery: Prime Time for Percutaneous Thermal Ablation?

PURPOSE

The purpose of the study was to retrospectively assess the safety and efficacy of radiofrequency thermal ablation (RFA) for retroperitoneal relapse following surgery for renal cell carcinoma (RCC).

PATIENTS AND METHODS

After open radical nephrectomy or nephron-sparing surgery, eight patients with no evidence of distant metastases were treated for retroperitoneal relapse of RCC with RFA. A total of 16 lesions were ablated. Technical success, tumor response, follow-up duration, and complications were retrospectively analyzed.

RESULTS

Disease progression after surgery occurred within a mean time of 57 months (range 9-120). Recurrent tumor size varied from 5 to 34 mm. Five patients previously underwent surgical resection of retroperitoneal recurrent lesions. Six patients were treated with percutaneous approach, while two with recurrent nodes located on the anterior pancreatic surface underwent laparotomic RFA approach. All lesions were completely ablated and patients were followed up with CT at 30 days, after 3 and every 6 months. There was no residual enhancement after a mean follow-up of 12 months (range 7-17). Both patients treated with laparotomic approach had a grade 2 complication according to the Clavien-Dindo classification.

CONCLUSIONS

In our small series, RFA after relapse of surgically removed RCC was safe and effective. Percutaneous and laparotomic thermal ablation should be assessed as first line loco-regional treatment on a larger patient group.

Four-dimensional MRI of renal function in the developing mouse

The major roles of filtration, metabolism and high blood flow make the kidney highly vulnerable to drug-induced toxicity and other renal injuries. A method to follow kidney function is essential for the early screening of toxicity and malformations. In this study, we acquired high spatiotemporal resolution (four dimensional) datasets of normal mice to follow changes in kidney structure and function during development. The data were acquired with dynamic contrast-enhanced MRI (via keyhole imaging) and a cryogenic surface coil, allowing us to obtain a full three-dimensional image (isotropic resolution, 125 microns) every 7.7 s over a 50-min scan. This time course permitted the demonstration of both contrast enhancement and clearance. Functional changes were measured over a 17-week course (at 3, 5, 7, 9, 13 and 17 weeks). The time dimension of the MRI dataset was processed to produce unique image contrasts to segment the four regions of the kidney: cortex (CO), outer stripe (OS) of the outer medulla (OM), inner stripe (IS) of the OM and inner medulla (IM). Local volumes, time-to-peak (TTP) values and decay constants (DC) were measured in each renal region. These metrics increased significantly with age, with the exception of DC values in the IS and OS. These data will serve as a foundation for studies of normal renal physiology and future studies of renal diseases that require early detection and intervention.

Radiofrequency thermal ablation of renal tumors

Percutaneous radiofrequency ablation (PRFA) of renal malignancies is currently a therapeutic option for patients who are not able to undergo surgery. Some authors consider PRFA as the therapeutic standard in the treatment of renal neoplasms in non-operable patients due to comorbid conditions and in patients with mild-moderate renal failure, to preserve residual renal functionality. The use of PRFA has become more and more widespread due to a rise in the incidental detection of renal cell carcinomas with the ever-increasing use of Imaging for the study of abdominal diseases. Clinical studies indicate that RF ablation is an effective therapy with a low level of risk of complications, which provides good results in selected patients over short and medium term periods of time, however up to now few long-term studies have been carried out which can confirm the effectiveness of PRFA.

Role of percutaneous needle biopsy for renal masses

The role of percutaneous renal mass biopsy has expanded considerably in the past 10 years. The incidence of incidentally detected small (< 4 cm) solid renal masses is on the rise, and despite a commensurate increase in nephron-sparing treatment, the mortality rate from renal cell carcinoma remains the same. Earlier detection and treatment have not had dramatic effects on population outcome, implying that not all small renal masses will grow to be life-limiting. Indeed, many small solid renal masses are benign, and among those that are malignant, not all share the same malignant behavior. Percutaneous biopsy provides a minimally invasive method for discriminating benign from malignant renal masses, and portends the potential for stratifying malignant risk. With recent improvements in image-guided equipment and technique, percutaneous renal mass biopsy can be performed safely and effectively, with a low complication rate (< 5%) and a high diagnostic yield (> 90%).

Percutaneous ablation of the small renal mass-techniques and outcomes

An increasing number of T1a renal cell carcinomas are being diagnosed in recent years, in part due to incidental detection from the increased use of cross-sectional imaging. Although partial nephrectomy is still considered the primary treatment for these small renal masses, percutaneous ablation is now being performed as a standard therapeutic, nephron-sparing approach in patients who are poor surgical candidates. Clinical studies to date have demonstrated that percutaneous ablation is an effective therapy with acceptable outcomes and low risk in the appropriate clinical settings. This article will review various clinical aspects regarding the percutaneous ablation of small renal masses, including patient selection, preprocedural preparations, and the procedural considerations of commonly employed ablative technologies. Specific techniques such as radiofrequency ablation, cryoablation, microwave ablation, irreversible electroporation, and high-intensity focused ultrasound will be addressed in detail. In addition, the technical and oncologic outcomes of percutaneous ablation will be discussed and referenced to that of partial nephrectomy.

Radiofrequency ablation (RFA) of renal cell carcinoma (RCC): experience in 200 tumours

Objectives

Patients and Methods

Results

Conclusions

Renal cell carcinoma: value of multiphase MDCT with multiplanar reformations in the detection of pseudocapsule

OBJECTIVE

The purpose of this study was to assess the diagnostic performance of four-phase (unenhanced, arterial, portal, and nephrographic-excretory) MDCT with multiplanar reformations in the detection of pseudocapsule of renal cell carcinoma (RCC).

MATERIALS AND METHODS

In a retrospective study of 29 histologically proven RCCs in 29 patients (17 men, 12 women; mean age, 59 years), examinations were performed with a 16-MDCT scanner. The protocol included unenhanced and three-phase (arterial, portal, and nephrographic-excretory) contrast-enhanced CT. The data were analyzed by two reviewers blinded to the histopathologic results. Any discrepancy was resolved by consensus. The presence of a regular, high- or low-attenuation halo surrounding a renal neoplasm was considered to represent renal pseudocapsule. The accuracy of MDCT in the detection of pseudocapsule with the histopathologic results as the standard of reference was evaluated. Unenhanced transverse images and multiplanar reformations in the transverse, coronal, and sagittal planes of each contrast-enhanced phase were separately analyzed. The chi-square two-way test was used to compare each CT phase and multiplanar reformation with histologic results.

RESULTS

The mean diameter of RCCs on CT scans was 5.6 cm (range, 2.8-15 cm), in accordance with the pathologic result. MDCT enabled detection of renal pseudocapsule in 20 of 29 RCCs with 83% sensitivity, 80% specificity, 95% positive predictive value, 50% negative predictive value, and 83% overall accuracy. Imaging in the portal and nephrographic phases with coronal and sagittal reformations proved more accurate in the detection of pseudocapsule (p < 0.05).

CONCLUSION

Multiphase MDCT with multiplanar reformations had satisfactory results in the detection of renal pseudocapsule in RCC.

CT urography for hematuria

Hematuria can signify serious disease such as bladder cancer, upper urinary tract urothelial cell carcinoma (UUT-UCC), renal cell cancer or urinary tract stones. CT urography is a rapidly evolving technique made possible by recent advances in CT technology. CT urography is defined as CT examination of the kidneys, ureters and bladder with at least one series of images acquired during the excretory phase after intravenous contrast administration. The reasoning for using CT urography to investigate hematuria is based on its high diagnostic accuracy for urothelial cell carcinoma (UCC) and favorable comparison with other imaging techniques. The optimum diagnostic imaging strategy for patients with hematuria at high-risk for UCC involves the use of CT urography as a replacement for other imaging tests (ultrasonography, intravenous urography, or retrograde ureteropyelography) and as a triage test for cystoscopy, resulting in earlier diagnosis and improved prognosis of bladder cancer, UUT-UCC, renal cell cancer and stones. Current problems with CT urography for investigating hematuria might be solved with a formative educational program simulating clinical reporting to reduce reader error, and a new technique for image-guided biopsy of UUT-UCC detected by CT urography for histopathological confirmation of diagnosis and elimination of false-positive results. CT urography is recommended as the initial imaging test for hematuria in patients at high-risk for UCC.

Percutaneous ablation in the kidney

Percutaneous ablation in the kidney is now performed as a standard therapeutic nephron-sparing option in patients who are poor candidates for resection. Its increasing use has been largely prompted by the rising incidental detection of renal cell carcinomas with cross-sectional imaging and the need to preserve renal function in patients with comorbid conditions, multiple renal cell carcinomas, and/or heritable renal cancer syndromes. Clinical studies to date indicate that radiofrequency ablation and cryoablation are effective therapies with acceptable short- to intermediate-term outcomes and with a low risk in the appropriate setting, with attention to pre-, peri-, and postprocedural detail. The results following percutaneous radiofrequency ablation and cryoablation in the treatment of renal cell carcinoma are reviewed in this article, including those of several larger scale studies of ablation of T1a tumors. Clinical and technical considerations unique to ablation in the kidney are presented, and potential complications are discussed.

Diagnosis of renal angiomyolipoma with hounsfield unit thresholds: effect of size of region of interest and nephrographic phase imaging

PURPOSE

To retrospectively determine the optimal Hounsfield unit threshold and region of interest (ROI) size required to accurately diagnose renal angiomyolipoma (AML) and differentiate it from renal cell carcinoma (RCC).

MATERIALS AND METHODS

This retrospective study was institutional review board approved and HIPAA compliant, and the requirement for written informed patient consent was waived. The radiologic reports on 4502 dual-phase abdominal computed tomography (CT) examinations (nonenhanced and nephrographic phases, 5-mm collimation, 120-140 kVp, variable milliampere-second settings) performed in 2872 patients from June 2002 through October 2007 were reviewed. Solid-component masses reported as suspicious for RCC or AML were correlated with histologic and/or follow-up imaging findings. ROIs of three different sizes-tiny (8-13 mm(2)), small (19-24 mm(2)), and medium (30-35 mm(2))-were drawn in the lowest-attenuation focus on images obtained during both phases. The test characteristics (sensitivity, specificity, positive predictive value, negative predictive value, false-positive rate, false-negative rate) of multiple attenuation thresholds at each combination of ROI size and contrast enhancement phase were calculated, and receiver operating characteristic (ROC) curves were derived. Areas under the ROC curve were calculated.

RESULTS

There were 217 RCCs and 65 AMLs. With an attenuation threshold of -10 HU or lower at nonenhanced CT, RCC would be misdiagnosed as AML in 11 (5.1%) cases, one (0.5%) case, and one (0.5%) case with use of the tiny, small, and medium ROIs, respectively. With use of the tiny, small, and medium ROIs, misdiagnosis rates would be 2.3%, 0.5%, and 0.5%, respectively, at a threshold of -15 HU or lower and 1.8%, 0%, and 0%, respectively, at a threshold of -20 HU or lower. Areas under the ROC curve for the nonenhanced phase images (range, 0.874-0.889) were superior to those for the nephrographic phase images (range, 0.790-0.826).

CONCLUSION

Nonenhanced CT images were superior to nephrographic phase CT images for the diagnosis of AML. An attenuation threshold of -10 HU or lower with an ROI of at least 19-24 mm(2) is optimal for the diagnosis of AML. This threshold is not accurate with use of smaller (8-13-mm(2)) ROIs.

Evaluation and management of the renal mass

The evaluation and management of renal cell carcinoma (RCC) has evolved in recent decades in response to the changing clinical presentation of the disease. Traditional teaching suggested that RCC usually presents with signs or symptoms. However, RCC discovered this way was usually locally advanced and often metastatic, requiring radical nephrectomy in most cases but often having a poor prognosis. As contemporary general medical practice began routinely using axial body imaging in the evaluation of many nonspecific abdominal complaints, today more than 70% of RCC cases identified are "screen-detected" as incidental findings having no attributable symptoms. This change has prompted a significant RCC stage migration over the past 20 years, with most kidney tumors seen in 2010 being smaller, organ-confined, and appropriate for nephron-sparing approaches with the anticipation of a favorable outcome. The approach to addressing patients with these incidentally detected, often localized, small renal masses raises different concerns than those for traditional patients presenting with symptomatic RCC. This article reviews the modern epidemiology of RCC, outlines the components of the evaluation of the incidental renal mass, details the current options of management, and discusses the long-term expectations for these patients.

Single-antenna microwave ablation under contrast-enhanced ultrasound guidance for treatment of small renal cell carcinoma: preliminary experience

The purpose of this study was to determine the safety, effectiveness, and feasibility of microwave ablation (MWA) of small renal cell carcinomas (RCCs) in selected patients. Institutional review board and informed consent were obtained. From December 2007 to January 2009, 12 patients (8 male, 4 female) were enrolled in a treatment group, in which percutaneous MWA of small RCCs was performed under contrast-enhanced ultrasound guidance. The tumors were 1.7-2.9 cm in diameter (mean diameter, 2.0 cm).Therapeutic effects were assessed at follow-up with computed tomography. All patients were followed up for 3-14 months (mean, 6 months) to observe the therapeutic effects and complications (according to SIR classification). Assessment was carried out with CT imaging. No severe complications or unexpected side effects were observed after the MWA procedures. In all cases technical success was achieved. Clinical effectiveness was 100%; none of the patients showed recurrence on imaging. In conclusion, our preliminary results support the use of MWA for the treatment of small renal tumors. This technology can be applied in select patients who are not candidates for surgery, as an alternative to other ablative techniques.

Biopsy of renal masses: when and why

Percutaneous image-guided biopsy of renal masses is a safe and accurate procedure. Although once reserved for the diagnosis of unresectable renal cell carcinoma, metastases, lymphoma, and infection, today percutaneous image-guided biopsy has an expanded role. There is increasing awareness that a substantial proportion of small, solid renal masses are benign neoplasms. Although imaging can be used to diagnose most of them, some are incorrectly believed to represent renal cell carcinoma and unnecessary surgery may be performed. Based largely on advances in cytological techniques, percutaneous biopsy can be now be used to diagnose benign neoplasms and thus prevent them from being treated unnecessarily. Concurrent advances in percutaneous ablation have also promoted its use. As a result, there are 8 established indications for percutaneous biopsy, and reason to believe that the number of indications will expand further in the future.

[Multi-detector computed tomography in non-traumatic urologic emergencies]

Today's modern multi-detector computer tomography (MDCT) with its fast gantry rotation enables scanning of large body volumes with high temporal and spatial resolution. The fast acquisition of data and subsequent data reconstruction enables multiphase protocols with short time gaps between consecutive scan series so that large numbers of scans within one respiratory pause are possible and even in cases of non-cooperative patients acceptable quality of image data is provided. The acquired thin-slice raw data with isotropic submillimeter voxels can be visualized with different reconstruction algorithms. The advantages of imaging for diagnostics in urologic emergencies are the excellent visualization of acute arterial and venous pathologies, detailed assessment of renal parenchyma and the precise depiction of the urinary tract. In non-trauma settings this enables detailed visualization of inflammatory diseases and differentiation of obstructive or post-therapeutic pathologies along the upper and lower urinary tract. Based on these MDCT findings adequate therapy planning and planning of interventional or surgical procedures can be carried out.

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.

Thermal ablation: update and technique at a high-volume institution

In the era of nephron-sparing surgery for small renal tumors, thermal ablation is gaining popularity. Both cryoablation and radiofrequency ablation have well-demonstrated short-term oncologic efficacy and safety. This article shares the current literature and the radiofrequency ablation technique at a high-volume institution. Cases are presented that illustrate solutions to obstacles frequently encountered during percutaneous ablation of renal masses.

Ultrasound guided percutaneous microwave ablation for small renal cancer: initial experience

PURPOSE

We evaluated the feasibility, safety and efficacy of ultrasound guided percutaneous microwave ablation for small renal cell cancers.

MATERIALS AND METHODS

A total of 12 patients with a pathologically proven renal cell cancer 1.3 to 3.8 cm in diameter were treated with microwave ablation. A cooled shaft needle antenna was percutaneously inserted into the tumor under ultrasound guidance. One antenna was used for tumors 2 cm or smaller and antennae were used for tumors larger than 2 cm. One thermocouple was placed about 0.5 cm away from the tumor to monitor temperature in real time during ablation. Microwaves were emitted at 50 W for 500 seconds and prolonged as necessary to attain temperatures sufficient to ensure tumor kill. Immediate treatment efficacy was assessed by contrast enhanced ultrasound 1 day after ablation. Short-term efficacy was assessed by contrast enhanced computerized tomography and/or contrast enhanced ultrasound at 1, 3 and 6 months, and every 6 months thereafter.

RESULTS

All tumors were completely ablated at a single session and no complications occurred. No residual tumor or recurrence was observed at a median followup of 11 months (range 4 to 20). The ablation zone was well defined on contrast enhanced imaging and it gradually shrank with time.

CONCLUSIONS

Ultrasound guided percutaneous microwave ablation appears to be a safe and effective technique for small renal cell cancer in select patients.