How I Do It: Evaluating Renal Masses

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.

Imaging of renal cell carcinoma

Renal cell carcinoma (RCC) is the most common kidney cancer in adults. Early and accurate imaging plays an important role in the detection, staging, and follow-up of RCC. Patient care and case management revolves heavily around diagnostic imaging so it is imperative that appropriate and adequate imaging is acquired. There are well-established standard imaging protocols available to patients and their providers, although at the same time, there is also extensive ongoing research on improving the various modalities. Ultrasound has been the most commonly used imaging technique for renal imaging in general. However, computed tomography (CT) is the first choice for imaging of renal masses, and has been the mainstay for several decades. High resolution, reproducibility, reasonable preparation and acquisition time, and acceptable cost allow CT to remain as the primary choice for radiologic imaging. Magnetic resonance imaging (MRI) is considered as an important alternative in patients requiring further imaging or in cases of allergies, pregnancy, or surveillance. With increasing concern over radiation exposure, there has been a trend toward the higher use of MRI. It is important to understand the various imaging options available, as well as the current status of and results from recent RCC imaging studies. In this review we discuss these modalities, including the current state of ultrasound, CT, and MRI in RCC.

Synchronous malignant renal mass in patient with a Lung cancer: case report and literature review

The finding on imaging (computed tomography scan or magnetic resonance imaging) of synchronous malignant renal mass in patient with an active nonrenal malignancy without renal specific symptoms is not frequent and diagnostic evaluation can be challenging. We describe a 54-year-old Moroccan male former chronic smoker who presented to our hospital with dry cough and impairment of the performance status. The imaging found a tumor mass in the left upper lobe of the lung associated to mediastinal lymph node and a scanno-guided biopsy of this tumor showed a non small cell lung cancer. The radiological staging revealed a solitary renal mass in the right kidney. The patient received firstly two cycles of a lung cancer chemotherapy with a partial response in the lung and a stability of the renal mass. Consequently, he underwent a scanno-guided biopsy of this mass which confirmed a synchronous clear cell renal carcinoma. The patient got chemo radiotherapy for the lung cancer and then after that he got a partial nephrectomy. He is still under a good control with more than 2 years after the initial diagnosis.

Accuracy of preoperative CT T staging of renal cell carcinoma: which features predict advanced stage?

AIMS

To characterise CT findings in renal cell carcinoma (RCC), and establish which features are associated with higher clinical T stage disease, and to evaluate patterns of discrepancy between radiological and pathological staging of RCC.

MATERIALS AND METHODS

Preoperative CT studies of 92 patients with 94 pathologically proven RCCs were retrospectively reviewed. CT stage was compared with pathological stage using the American Joint Committee on Cancer (AJCC), 7(th) edition (2010). The presence or absence of tumour necrosis, perinephric fat standing, thickening of Gerota's fascia, collateral vessels were noted, and correlated with pT stage. The sensitivity, specificity, and positive (PPV) and negative predictive values (NPV) for predicting pT stage ≥pT3a were derived separately for different predictors using cross-tabulations.

RESULTS

Twenty-four lesions were pathological stage T1a, 21 were T1b, seven were T2a, 25 were T3a, 11 were T3b, four were T3c, and two were T4. There were no stage T2b. Sixty-three (67%) patients had necrosis, 27 (29%) thickening of Gerota's fascia (1 T1a), 25 had collateral vessels (0 T1a), 28 (30%) had fat stranding of <2 mm, 20 (21%) of 2-5mm and one (1%) of >5 mm. For pT stage ≥pT3a, the presence of perinephric fat stranding had a sensitivity, specificity, PPV and NPV of 74%, 65%, 63%, and 76%, respectively. Presence of tumour necrosis had a sensitivity, specificity, PPV, and NPV of 81%, 44%, 54%, and 72%, respectively. Thickening of Gerota's fascia had a sensitivity, specificity, PPV, and NPV of 52%, 90%, 81% and 70%, respectively; and enlarged collateral vessels had a sensitivity, specificity, PPV, and NPV value of 52%, 94%, 88%, and 71% respectively.

CONCLUSION

The presence of perinephric stranding and tumour necrosis were not reliable signs for pT stage >T3a. Thickening of Gerota's fascia and the presence of collateral vessels in the peri- or paranephric fat had 90% and 94% specificity, with 82% and 88% PPV, respectively, for the presence of tumour stage for pT stage >T3a. These are considered reliable signs of locally advanced renal cancer.

Increased renal cyst density on abdominal CT at 100-kVp compared with 120-kVp: a preliminary evaluation

OBJECTIVE

To compare the radiographic density of renal cysts on contrast-enhanced computed tomography (CT) scans performed at tube voltages of 100 versus 120 kVp.

METHODS

Thirty-six renal cysts from contrast-enhanced CT performed on 21 subjects at both 120 kVp and 100 kVp were compared by Kolmogorov-Smirnov statistical testing.

RESULTS

The radiographic density (mean+/-standard deviation in Hounsfield units) of cysts was greater on 100-kVp than on 120-kVp CT scans for both 5-mm and 2-mm reconstructed slice thicknesses: 16.6+/-5.6 versus 10.9+/-4.9 and 14.1+/-5.6 versus 8.5+/-3.9, respectively.

CONCLUSIONS

Decrease in tube voltage significantly increases measured radiographic density of renal cysts on CT. Further studies are indicated to assess the clinical impact of lower-tube-voltage CT.

Bosniak classification for complex renal cysts: history and critical analysis

The Bosniak classification for renal cysts was developed in the late 1980s in an attempt to standardize the description and management of complex cystic renal lesions. Alterations were made to such a classification in the 1990s and, the last one, in 2005. Currently, five categories of cystic renal lesions are defined - namely, I, II, II-F, III and IV –, according to their degree of complexity and likelihood of malignancy. Despite being initially described for computed tomography, this classification has been also utilized with some advantages also for magnetic resonance imaging. The present article reviews the different phases of this classification, its diagnostic efficacy and the most controversial features of its use.

Bosniak classification system: inter-observer and intra-observer agreement among experienced uroradiologists

BACKGROUND

The Bosniak classification is a diagnostic tool for the differentiation of cystic changes in the kidney. The process of categorizing renal cysts may be challenging, involving a series of decisions that may affect the final diagnosis and clinical outcome such as surgical management.

PURPOSE

To investigate the inter- and intra-observer agreement among experienced uroradiologists when categorizing complex renal cysts according to the Bosniak classification.

MATERIAL AND METHODS

The original categories of 100 cystic renal masses were chosen as "Gold Standard" (GS), established in consensus by two experienced uroradiologists. Three experienced uroradiological readers were blinded from the previous CT reports. Weighted κ was calculated to assess agreement, defined as: fair, 0.21-0.40; moderate, 0.41-0.60; good, 0.61-0.80; and very good, 0.81-1.00.

RESULTS

For readers the distribution of correctly classified lesions were as follows: BI, 95-100%; BII, 59-93%; BIIF, 54-92%; BIII, 58-95%; and B IV, 77-100% for the first review. Weighted κ for inter-observer/intra-observer variation was for Reader A: 0.85/0.99, Reader B: 0.97/0.99, and Reader C: 0.98/0.99, (P ≤ 0.001).

CONCLUSION

According to the calculated weighted κ all readers performed "very good" for both inter-observer and intra-observer variation. Most variation was seen in cysts catagorized as Bosniak II, IIF, and III. These results show that radiologists who evaluate complex renal cysts routinely may apply the Bosniak classification reproducibly.

Microsimulation model of CT versus MRI surveillance of Bosniak IIF renal cystic lesions: should effects of radiation exposure affect selection of imaging strategy?

OBJECTIVE

The objective of this study was to quantify the effects of radiation-induced cancer risks in patients with Bosniak category IIF lesions undergoing CT versus MRI surveillance.

MATERIALS AND METHODS

We developed a Markov-Monte Carlo model to determine life expectancy losses attributable to radiation-induced cancers in hypothetical patients undergoing CT versus MRI surveillance of Bosniak IIF lesions. Our model tracked hypothetical patients as they underwent imaging surveillance for up to 5 years, accounting for potential lesion progression and treatment. Estimates of radiation-induced cancer mortality were generated using a published organ-specific radiation-risk model based on Biological Effects of Ionizing Radiation VII methods. The model also incorporated surgical mortality and renal cancer-specific mortality. Our primary outcome was life expectancy loss attributable to radiation-induced cancers. A sensitivity analysis was performed to assess the stability of the results with variability in key parameters.

RESULTS

The mean number of examinations per patient was 6.3. In the base case, assuming 13 mSv per multiphase CT examination, 64-year-old men experienced an average life expectancy decrease of 5.5 days attributable to radiation-induced cancers from CT; 64-year-old women experienced a corresponding life expectancy loss of 6.9 days. The results were most sensitive to patient age: Life expectancy loss attributable to radiation-induced cancers increased to 21.6 days in 20-year-old women and 20.0 days in 20-year-old men. Varied assumptions of each modality's (CT vs MRI) depiction of lesion complexity also impacted life expectancy losses.

CONCLUSION

Microsimulation modeling shows that radiation-induced cancer risks from CT surveillance for Bosniak IIF lesions minimally affect life expectancy. However, as progressively younger patients are considered, increasing radiation risks merit stronger consideration of MRI surveillance.

EAU guidelines on renal cell carcinoma: 2014 update

CONTEXT

The European Association of Urology Guideline Panel for Renal Cell Carcinoma (RCC) has prepared evidence-based guidelines and recommendations for RCC management.

OBJECTIVES

To provide an update of the 2010 RCC guideline based on a standardised methodology that is robust, transparent, reproducible, and reliable.

EVIDENCE ACQUISITION

For the 2014 update, the panel prioritised the following topics: percutaneous biopsy of renal masses, treatment of localised RCC (including surgical and nonsurgical management), lymph node dissection, management of venous thrombus, systemic therapy, and local treatment of metastases, for which evidence synthesis was undertaken based on systematic reviews adhering to Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. Relevant databases (Medline, Cochrane Library, trial registries, conference proceedings) were searched (January 2000 to November 2013) including randomised controlled trials (RCTs) and retrospective or controlled studies with a comparator arm. Risk of bias (RoB) assessment and qualitative and quantitative synthesis of the evidence were performed. The remaining sections of the document were updated following a structured literature assessment.

EVIDENCE SYNTHESIS

All chapters of the RCC guideline were updated. For the various systematic reviews, the search identified a total of 10,862 articles. A total of 151 studies reporting on 78,792 patients were eligible for inclusion; where applicable, data from RCTs were included and meta-analyses were performed. For RCTs, there was low RoB across studies; however, clinical and methodological heterogeneity prevented data pooling for most studies. The majority of studies included were retrospective with matched or unmatched cohorts based on single or multi-institutional data or national registries. The exception was for systemic treatment of metastatic RCC, in which several RCTs have been performed, resulting in recommendations based on higher levels of evidence.

CONCLUSIONS

The 2014 guideline has been updated by a multidisciplinary panel using the highest methodological standards, and provides the best and most reliable contemporary evidence base for RCC management.

PATIENT SUMMARY

The European Association of Urology Guideline Panel for Renal Cell Carcinoma has thoroughly evaluated available research data on kidney cancer to establish international standards for the care of kidney cancer patients.

Patient and tumor characteristics can predict nondiagnostic renal mass biopsy findings

PURPOSE

Identification of patient and tumor characteristics associated with nondiagnostic biopsies is necessary to improve prebiopsy counseling and patient selection.

MATERIALS AND METHODS

We reviewed the clinical records and prebiopsy imaging of all patients treated with percutaneous biopsy for a renal mass 7 cm or less. Univariate and multivariate logistic regression models were constructed to examine the association between biopsy outcome and clinical/radiographic features.

RESULTS

A total of 565 biopsies of renal tumors 7 cm or less in 525 patients were included in the study. There was no significant difference in age, body mass index, Charlson comorbidity score or gender between the patient cohorts with diagnostic and nondiagnostic biopsy. In 83 of 565 patients (14.7%) overall and in 72 of the 413 (17.4%) with a mass of 4 cm or less the biopsy findings were nondiagnostic. Overall 14.7% of masses were cystic and 85.3% were solid with a median tumor size of 2.75 cm (IQR 2.05-4.25). Independent predictors of nondiagnostic biopsy included cystic features, enhancement less than 20 HU, left tumor, tumor diameter and skin-to-tumor distance. The nondiagnostic rate of repeat biopsies was 20.8%, which did not statistically differ from the nondiagnostic rate at the initial renal mass biopsy attempt. Radiologist or pathologist experience was not associated with the biopsy nondiagnostic rate. In 7 of 565 patients (1.2%) hospital admission was required for adverse events after biopsy.

CONCLUSIONS

Nondiagnostic renal mass biopsies are more common in cystic, nonenhancing, small masses when patients have a skin-to-tumor distance of 13 cm or greater. Excluding patients with these criteria decreased the nondiagnostic rate from 14.7% to 8.7%.

Percutaneous radiofrequency ablation of sporadic Bosniak III or IV lesions: treatment techniques and short-term outcomes

PURPOSE

To evaluate retrospectively the techniques and outcomes of percutaneous radiofrequency (RF) ablation for treatment of Bosniak III or IV lesions.

MATERIALS AND METHODS

Between August 2006 and August 2013, 30 patients (25 men and 5 women; mean age, 57 y; range, 22-77 y) with 35 nonhereditary Bosniak III (n = 15) or IV (n = 20) lesions underwent computed tomography-guided RF ablation. The mean size of the lesions was 2.8 cm ± 0.9 (range, 1.1-4.3 cm). The mean follow-up period was 24 months ± 16 (range, 6-70 mo). Duration of ablation, number of sessions and electrode repositions, primary and secondary effectiveness rates, major complication rate, reduction rate of lesion size, estimated glomerular filtration rate (GFR), and local tumor progression were recorded. Wilcoxon signed rank test was used for statistical analysis.

RESULTS

Mean duration of ablation was 18 minutes ± 14 (range, 2-65 min), and median number of sessions was one. Median number of electrode repositions was 1.0 ± 1.6 (range, 0-6). Primary and secondary effectiveness rates were 97.1% (34 of 35) and 100% (1 of 1), respectively. Mean reduction rate of lesion size was significantly greater from before RF ablation to 1 month after RF ablation (7.1 mm/mo ± 4.5) compared with from 1 month after RF ablation to the last month of follow-up (0.2 mm/mo ± 0.2; P < .0001). Mean GFR after RF ablation (65.4 mL/min/1.73 m(2) ± 26.1) was minimally reduced but significantly different from mean GFR before RF ablation (76.0 mL/min/1.73 m(2) ± 28.4; P < .0001). Major complications occurred in 2 of 35 RF ablation sessions for a rate of 5.7%, resulting from pneumothorax. Of 30 patients, 29 (96.7%) did not have local tumor progression or metastasis for 2 years.

CONCLUSIONS

Percutaneous RF ablation is technically feasible and yields excellent short-term outcomes in treating sporadic Bosniak III or IV lesions.

Contrast-enhanced ultrasound (CEUS) in nephrology: Has the time come for its widespread use?

Grey-scale ultrasound has an important diagnostic role in nephrology. The absence of ionizing radiations and nephrotoxicity, rapidity of execution, excellent repeatability, the possibility to perform the test at the patient's bed and the low cost represent important advantages of this technique. Paired with real-time sonography and colour-power-Doppler contrast-enhanced ultrasound (CEUS) reduces the diagnostic gap with computed tomography (CT) and magnetic resonance (MR) and represents a major step in the evolution of clinical ultrasound. Although there are several situations in which contrast-enhanced CT and MR are indicated (i.e. evaluation of cystic or ischemic lesions, traumatisms and ablative therapies of the native and transplanted kidney), the use of CT contrast media presents a high risk of contrast-induced nephropathy (i.e. in elderly people, subjects with comorbidities and those with renal dysfunction), while gadolinium-based RM contrast agents are contraindicated for the risk of nephrogenic systemic fibrosis (i.e. in patients with severe renal dysfunction). In these situations, CEUS may be a viable alternative, however, as any technique associated with the infusion of pharmacological substances, the potential advantages and risks of CEUS should be critically evaluated. In this regard, the European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB) has published the guidelines for the use of CEUS for the kidney imaging and the International Contrast Ultrasound Society (ICUS) has been recently founded. The aim of this review is to offer an updated overview of the potential applications of CEUS in nephrology, reporting some indications and possible risks associated to its use.

Imaging of iatrogenic complications of the urinary tract: kidneys, ureters, and bladder

Iatrogenic complications of various severities may arise from many, if not all, forms of medical and surgical treatment. Most of these occur in spite of proper precautions. Every system in the human body may be affected, and the urinary tract is no exception. Radiologists are often the first to suspect and identify such iatrogenic injuries and, therefore, awareness of the pertinent imaging findings is vital. This review explores and illustrates many of the common and less common iatrogenic complications affecting the kidney, ureters, and bladder.

Efficacy, safety and effectiveness of image-guided percutaneous microwave ablation in cystic renal lesions Bosniak III or IV after 24 months follow up

PURPOSE OF THE STUDY

The aim of the study was to assess the efficacy, safety and effectiveness of percutaneous image-guided microwave ablation (MWA) in Bosniak category III or IV cystic renal lesions after 24 months follow-up duration.

METHODS

Between May 2008 and December 2012, computed tomography (CT)- or ultrasound (US)-guided MWA was performed in 6 patients with 7 cystic renal lesions (range 13.8-27 mm, mean 17.02 mm, SD 8.5 mm) Bosniak category III or IV. The number of treatment sessions, treatment results, lesion size changes and complications were evaluated. Technical success (TS), technical effectiveness (TE), local tumor progression rate (LTPR), cancer-specific survival rate (CSSR) and overall survival rate (OSR) were computed.

MAIN FINDINGS

TS was 100% (7/7) and TE was 100%; LTPR was 0%; CSSR and OSR were 100%. No major complications were observed.

CONCLUSION

Our preliminary experience with MWA shows a potential role for US/CT-guided percutaneous MWA in treating Bosniak category III or IV cystic renal lesions, as a safe approach to treat selected patients not suitable for surgery.

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%).

Accuracy of contrast-enhanced dual-energy MDCT for the assessment of iodine uptake in renal lesions

OBJECTIVE

The objective of our study was to assess the accuracy of iodine-related attenuation and iodine quantification as imaging biomarkers of iodine uptake in renal lesions on a single-phase nephrographic image with dual-energy MDCT.

MATERIALS AND METHODS

Fifty-nine patients (41 men, 18 women; age range, 28-84 years) with 80 renal lesions underwent contrast-enhanced dual-energy CT during the nephrographic phase of enhancement. Renal lesions were characterized as enhancing or nonenhancing on color-coded iodine overlay maps using iodine-related attenuation (in Hounsfield units) and iodine quantification (in milligrams per milliliter). For iodine-related attenuation the iodine uptake thresholds of 15 and 20 HU were tested; a threshold of 0.5 mg/mL was used for iodine quantification. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of iodine-related attenuation and iodine quantification were calculated from chi-square tests of contingency with histopathology or imaging follow-up as the reference standard. The 95% CIs were calculated from binomial expression. Differences in sensitivity and specificity were assessed by means of McNemar analysis.

RESULTS

A significant difference in sensitivity and specificity was found between iodine-related attenuation with the thresholds of 15 HU (sensitivity, 91.4%; specificity, 93.3%; PPV, 91.4%; NPV, 93.3%) and 20 HU (sensitivity, 77.1%; specificity, 100%; PPV, 100%; NPV, 84.9%) (p = 0.008) and between iodine quantification (sensitivity, 100%; specificity, 97.7%; PPV, 97.2%; NPV, 100%) and iodine-related attenuation with a threshold of 20 HU (p = 0.004). No significant difference in sensitivity and specificity was found between iodine quantification and iodine-related attenuation with a threshold of 15 HU.

CONCLUSION

Contrast-enhanced dual-energy MDCT with iodine-related attenuation and iodine quantification allows accurate evaluation of iodine uptake in renal lesions on a single-phase nephrographic image.

Single-photon emission CT using (99m)Tc-dimercaptosuccinic acid (DMSA) for characterization of suspected renal masses

OBJECTIVE

A retrospective analysis of the clinical utility of (99m)Tc-dimercaptosuccinic acid (DMSA) single photon emission CT (SPECT) for characterization of suspected renal masses.

METHODS

15 patients who had undergone (99m)Tc-DMSA SPECT were identified, and 13 patients also had SPECT/CT. (99m)Tc-DMSA uptake in the renal lesion was characterized semiquantitatively. Other imaging tests, histology and clinical data were available for correlation.

RESULTS

(99m)Tc-DMSA was not taken up in all five renal masses with histological confirmation of malignancy (uptake 7-19% of normal renal tissue); in two further masses, which were clinically likely to be malignant; and in one indeterminate mass (lack of sufficiently long follow-up). No renal malignancy was identified in any of the seven patients whose renal masses had normal (99m)Tc-DMSA uptake (41-130%).

CONCLUSION

Although caution with regard to applying those results in clinical practice must be advised, owing to the retrospective nature of this report and the small number of patients included, it seems that (99m)Tc-DMSA SPECT shows a clinically useful diagnostic accuracy for distinguishing true renal masses (which in many cases require surgery) from pseudomasses.

ADVANCES IN KNOWLEDGE

(99m)Tc-DMSA SPECT is a clinically useful adjunct test for characterization of suspected renal masses.

Impact of dual-energy multi-detector row CT with virtual monochromatic imaging on renal cyst pseudoenhancement: in vitro and in vivo study

PURPOSE

To investigate whether dual-energy multi-detector row computed tomography (CT) with virtual monochromatic imaging can overcome renal cyst pseudoenhancement in a phantom experiment and a clinical study.

MATERIALS AND METHODS

This retrospective single-center HIPAA-compliant study was approved by the institutional review board, with waiver of informed consent. Four renal compartments inserted into torso phantoms were filled with saline to simulate the unenhanced state and with iodinated solutions to simulate the three levels of renal parenchyma enhancement (140, 180, and 240 HU). Saline-filled spheres simulating renal cysts (15 and 18 mm in diameter) were serially suspended in the renal compartments and imaged with dual-energy and single-energy multi-detector row CT at four different energy levels (80, 100, 120, and 140 kVp). In addition, 28 patients (mean age, 66 years ± 10; mean body mass index, 31.3 kg/m(2) ± 6.2) with 34 intrarenal cysts were included. Virtual monochromatic images were reconstructed in 10-keV increments at energy levels ranging from 40 to 140 keV. Phantom and clinical data were analyzed by using multivariate regression analysis.

RESULTS

In the phantom experiment, all polychromatic image data sets showed pseudoenhancement (postcontrast attenuation increase >10 HU) in all investigated conditions, with a significant effect on cyst size (P <.001), location (P <.001), and renal background attenuation level (P <.001). Virtual monochromatic images at energy levels ranging from 80 to 140 keV did not show pseudoenhancement, with the minimum attenuation increase (mean, 6.1 HU ± 1.6; range, 1.6-7.7 HU) on 80-keV images. In patients, pseudoenhancement never occurred on virtual monochromatic images at energy levels ranging from 90 to 140 keV. Patient body size had a significant effect (P = .007) on selection of the optimal monochromatic energy level.

CONCLUSION

Dual-energy multi-detector row CT with reconstruction of virtual monochromatic images at an optimal energy level can overcome renal cyst pseudoenhancement.

Robotic partial nephrectomy for cystic renal masses: a comparative analysis of a matched-paired cohort

OBJECTIVE

To compare the outcomes of robotic partial nephrectomy (RPN) for cystic and solid renal neoplasms.

METHODS

Our RPN database was queried to identify consecutive patients who underwent RPN for cystic and solid renal masses in the period between July 2007 and July 2013. Cystic renal masses were diagnosed on cross-sectional imaging (computed tomography or magnetic resonance imaging). Matching was done between the patients with cystic renal masses and patients with solid renal masses (1:1 matching) by age, gender, tumor size, and nephrometry score.

RESULTS

Of 647 cases, 55 patients with cystic masses (group 1) were matched with 55 patients with solid tumors (group 2). There was no cyst rupture or positive surgical margin observed in group 1. The volume of resected rim of healthy renal parenchyma surrounding the tumor was the same for both groups (P=.9). There was no difference between the groups in terms of percentage of glomerular filtration rate preservation postoperatively (85% vs 86%; P=.94). There was no difference in term of overall complications between the 2 groups. Thirty patients (54.5%) in group 1 and 47 patients (85.5%) in group 2 had renal cell carcinoma (P=.0001).

CONCLUSION

RPN can be safely and effectively performed when treating a suspicious cystic renal neoplasm with outcomes resembling those obtained for solid masses. Thus, when a cystic renal mass in encountered, nephron-sparing surgery can be offered and RPN represents an effective tool for this approach.

In vivo predictors of renal cyst pseudoenhancement at 120 kVp

OBJECTIVE

The purpose of this article is to assess the effects of various CT, patient, and renal cyst characteristics on the occurrence of pseudoenhancement in in vivo renal mass CT examinations using subtraction MRI as the reference standard.

MATERIALS AND METHODS

Adult patients imaged with 120-kVp standard kernel biphasic renal mass protocol CT and dynamic contrast-enhanced MRI of the abdomen from January 1, 2005, through May 4, 2012, were identified. Those with nonenhancing Bosniak categories I and II cysts on MRI were selected (n = 33 patients; 110 cysts). By treating measured cyst enhancement (nephrographic CT attenuation minus unenhanced CT attenuation) as either a continuous or categoric outcome variable, a variety of CT, patient-level, and renal cyst characteristics were assessed using mixed effect multivariate models.

RESULTS

On univariate assessment, cysts that exhibited pseudoenhancement (> 10 HU) were significantly more endophytic (p = 0.02), significantly smaller (p = 0.0004), and adjacent to significantly higher attenuation renal parenchyma in the nephrographic phase (p = 0.02). On multivariate assessment, cyst diameter (p < 0.0001) and background nephrographic phase parenchymal attenuation (p = 0.003) were the strongest in vivo predictors of pseudoenhancement. The odds of pseudoenhancement occurring increased by 2.14 (95% CI, 1.41-3.23) for every 5-mm decrease in renal cyst diameter and increased by 2.45 (95% CI, 1.41-4.26) for every 25-HU increase in enhanced renal parenchymal attenuation. Endophytic growth was not significant in the multivariate analyses (p = 0.07).

CONCLUSION

Renal cyst size and enhanced renal parenchymal attenuation are better in vivo predictors of pseudoenhancement than is endophytic growth pattern.

Bosniak classification of renal cystic lesions according to multidetector computed tomography findings

Renal cystic lesions are usually diagnosed in the radiologists' practice and therefore their characterization is crucial to determine the clinical approach to be adopted and prognosis. The Bosniak classification based on computed tomography findings has allowed for standardization and categorization of lesions in increasing order of malignancy (I, II, IIF, III and IV) in a simple and accurate way. The present iconographic essay developed with multidetector computed tomography images of selected cases from the archives of the authors' institution, is aimed at describing imaging findings that can help in the diagnosis of renal cysts.

A Flexible Method for Multi-Material Decomposition of Dual-Energy CT Images

The ability of dual-energy computed-tomographic (CT) systems to determine the concentration of constituent materials in a mixture, known as material decomposition, is the basis for many of dual-energy CT's clinical applications. However, the complex composition of tissues and organs in the human body poses a challenge for many material decomposition methods, which assume the presence of only two, or at most three, materials in the mixture. We developed a flexible, model-based method that extends dual-energy CT's core material decomposition capability to handle more complex situations, in which it is necessary to disambiguate among and quantify the concentration of a larger number of materials. The proposed method, named multi-material decomposition (MMD), was used to develop two image analysis algorithms. The first was virtual unenhancement (VUE), which digitally removes the effect of contrast agents from contrast-enhanced dual-energy CT exams. VUE has the ability to reduce patient dose and improve clinical workflow, and can be used in a number of clinical applications such as CT urography and CT angiography. The second algorithm developed was liver-fat quantification (LFQ), which accurately quantifies the fat concentration in the liver from dual-energy CT exams. LFQ can form the basis of a clinical application targeting the diagnosis and treatment of fatty liver disease. Using image data collected from a cohort consisting of 50 patients and from phantoms, the application of MMD to VUE and LFQ yielded quantitatively accurate results when compared against gold standards. Furthermore, consistent results were obtained across all phases of imaging (contrast-free and contrast-enhanced). This is of particular importance since most clinical protocols for abdominal imaging with CT call for multi-phase imaging. We conclude that MMD can successfully form the basis of a number of dual-energy CT image analysis algorithms, and has the potential to improve the clinical utility of dual-energy CT in disease management.

Renal relevant radiology: radiologic imaging in autosomal dominant polycystic kidney disease

Autosomal-dominant polycystic kidney disease is a systemic disorder and the most common hereditary renal disease, which is characterized by cyst growth, progressive renal enlargement, and development of renal failure. The cystic nature of autosomal dominant polycystic kidney disease and its renal and extrarenal complications (kidney stones, cyst hemorrhage, intracerebral aneurysm, liver cysts, cardiac valve abnormalities, etc.) give radiologic imaging studies a central role in the management of these patients. This article reviews the indications, comparative use, and limitation of various imaging modalities (ultrasonography, magnetic resonance imaging, computerized tomography scan, Positron emission tomography scan, and renal scintigraphy) for the diagnosis and management of complications in autosomal dominant polycystic kidney disease. Finally, this work provides evidence for the value of total kidney volume to predict disease progression in autosomal dominant polycystic kidney disease.

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

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

[Imaging renal cell carcinoma]

Renal cell carcinoma is the eighth most common malignancy in adults and the most common malignancy in the kidney. It is thus a very common disease for radiologists. This review aims to provide a general overview of the imaging techniques used to diagnose, characterize, and help plan the treatment of renal cell carcinoma as well as to review basic aspects related to staging, imaging-guided percutaneous treatment, and follow-up in the most common clinical scenarios.

Sonographically guided transhepatic core biopsies of right renal and adrenal masses: safety and short-term follow-up

OBJECTIVES

The purpose of this study was to retrospectively evaluate the accuracy and safety of sonographically guided transhepatic biopsies of right upper renal and adrenal masses.

METHODS

Ten sonographically guided transhepatic biopsies were performed in 10 patients with 6 right upper renal masses and 4 right adrenal masses that were invisible or inaccessible via an extrahepatic route. The control population comprised 19 sonographically guided extrahepatic biopsies that were performed in 19 patients with 18 right upper renal masses and 1 right adrenal mass. Transhepatic and extrahepatic biopsies were compared with respect to the diagnostic and complication rates. The mass sizes, biopsy distances, numbers and lengths of cores, and biopsy durations were also compared.

RESULTS

The diagnostic rates of transhepatic and extrahepatic biopsies were 90% (9 of 10) and 89% (17 of 19), respectively (P > .999). The complication rates of transhepatic and extrahepatic biopsies were 10% (1 of 10) and 21% (4 of 19; P > .999). None of these biopsies resulted in major complications. The mean mass sizes, biopsy distances, and numbers of cores ± SD for transhepatic and extrahepatic biopsies were 33.0 ± 14.3 and 46.9 ± 18.5 mm, 100.5 ± 17.9 and 76.5 ± 9.9 mm, and 2.7 ± 0.9 and 4.0 ± 0.7, respectively (P = .046, .038, and .001). However, the core lengths and biopsy durations were not significantly different between these biopsies (P = .91 and .077).

CONCLUSIONS

Sonographically guided transhepatic core biopsies appear to be feasible and safe procedures for the histologic diagnosis of right upper renal and adrenal masses that are either invisible or inaccessible via an extrahepatic route.

Impact of size of region-of-interest on differentiation of renal cell carcinoma and renal cysts on multi-phase CT: preliminary findings

INTRODUCTION

To assess impact of size of regions-of-interest (ROI) on differentiation of RCC and renal cysts using multi-phase CT, with focus on differentiating papillary RCC (pRCC) and cysts given known hypovascularity of pRCC.

METHODS

99 renal lesions (23 pRCC, 47 clear-cell RCC, 7 chromophobe RCC, 22 cysts) underwent multi-phase CT. Subjective presence of visual enhancement was recorded for each lesion. Whole-lesion (WL) ROIs, and small (≤ 5 mm(2)), medium (average size of small and large ROIs), and large (half of lesion diameter) peripherally located partial-lesion (PL) ROIs, were placed on non-contrast and nephrographic phases. Impact of ROI size in separating cysts from all RCC and from pRCC based on increased attenuation between phases was assessed using ROC analysis.

RESULTS

Visual enhancement was perceived in 96% of ccRCC, 61% of pRCC, and 9% of cysts. AUCs for separating all RCC and cysts for WL-ROI and small, medium, and large PL-ROIs were 91%, 96%, 91% and 93%, and among lesions without visible enhancement were 60%, 79%, 67% and 67%. AUCs for separating pRCC and cysts for WL-ROI and small, medium, and large PL-ROIs were 78%, 92%, 82% and 84%, and among lesions without visible enhancement were 64%, 88%, 69% and 69%.

CONCLUSION

Small PL-ROIs had higher accuracy than WL-ROI or other PL-ROIs in separating RCC from cysts, with greater impact in differentiating pRCC from cysts and differentiating lesions without visible enhancement. Thus, when evaluating renal lesions using multi-phase CT, we suggest placing small peripheral ROIs for highest accuracy in distinguishing renal malignancy and benign cysts.

Experience of ultrasonography-guided percutaneous core biopsy for renal masses

Purpose

We evaluated the safety and accuracy of ultrasonography-guided percutaneous core biopsy collection in patients with renal masses.

Materials and Methods

From June 2008 to August 2012, 30 percutaneous core biopsies of renal masses were performed. The biopsies obtained were small tumors (<4 cm) with ambiguous radiologic findings or that met classic renal biopsy indications. The biopsy results were compared with the final pathological results after definitive surgical treatment. Ultrasonography was performed on the day after biopsy collection to rule out any complications.

Results

The mean age of the patients was 57.7 years, and the mean tumor size was 3.39 cm. Twelve of the lesions were in the left kidney, and 18 were in the right kidney. All but one core biopsy contained sufficient material for histopathological analysis. The biopsy results showed 17 renal cell carcinomas (56.7%), 3 angiomyolipomas (10.0%), 2 oncocytomas (6.7%), 1 adenocarcinoma (3.3%), and 7 benign lesions (23.3%). A total of 18 cases underwent surgery, and the pathological results confirmed the initial biopsy diagnosis for 17 of 18 cases (94.4%). The one (5.9%) inaccurate biopsy result was found to be a urothelial carcinoma of the kidney. No needle tract seeding was found in the pathological specimens or on follow-up imaging. A small perinephric hematoma (1-2 cm) was seen in 5 cases (16.7%), but all patients remained hemodynamically stable.

Conclusions

Ultrasonography-guided renal biopsy is a safe, effective, and accurate method for evaluating small renal masses. This procedure may help in selecting treatment modalities for small renal masses.

Ten-year treatment outcomes including blood cell count disturbances in patients with simple renal cysts

BACKGROUND

The simple renal cyst is the most common benign kidney disease. It may cause pain and hypertension, especially if significantly enlarged. As in polycystic kidney disease, blood cell count disturbances are frequently observed in simple renal cysts. The aim of our study was to assess such disturbances, changes in blood pressure, and complication rate in our patients undergoing surgery due to simple renal cyst in the last 10 years.

MATERIAL AND METHODS

210 patients with simple renal cysts were underwent surgery between 2002 and 2012. Two different kinds of operation were conducted: aspiration of cyst fluid with injection of sclerosing agent, and laparoscopic/retroperitoneoscopic decortications of the cyst wall. A control group comprised 134 patients with benign prostate hyperplasia. The following data were obtained: cyst burden, hematocrit, hemoglobin, red blood cells, thrombocytes, occurrence of pain, and blood pressure before and after the operation. Complications were collected and presented in Clavien score.

RESULTS

Hematocrit, hemoglobin, and red blood cells were significantly increased in the experimental group. A positive correlation was observed between cyst burden and the parameters mentioned above. Of 91 patients with hypertension, 56 (61.7%) had blood pressure reduction after the operation. Treatment relieved the loin pain in 132 (88%) patients. Complications occurred in 15 (7.4%) patients.

CONCLUSIONS

Patients with simple renal cysts have high values of red blood cells, hematocrit, and hemoglobin. Treatment decreases blood pressure in patients with hypertension. Complications after treatment are rare and mild.

Additional value of dual-energy CT to differentiate between benign and malignant mediastinal tumors: an initial experience

OBJECTIVES

To investigate the feasibility of dual-energy computed tomography (DECT) in differentiating malignant from benign mediastinal tumors.

MATERIALS AND METHODS

We prospectively enrolled 25 patients (14 males; mean age: 56.7 years) who had suspected mediastinal tumors on chest radiography or non-contrast chest computed tomography (CT). All patients underwent a two-phase DECT using gemstone spectral imaging (GSI) mode (GE HD750). For the quantitative analysis, two investigators measured the following parameters of the tumors in the early and the delayed phases: CT attenuation value in Hounsfield units (HU) and iodine concentration (mg/ml). Pathological results were used for a final diagnosis. Statistical analyses were performed using the Fisher's exact test and the Mann-Whitney t-test.

RESULTS

10 patients (40%) had benign pathology, while 15 (60%) had malignant pathology. The iodine concentration measurements were significantly different between benign and malignant tumors both in the early phase (1.38 mg/ml vs. 2.41 mg/ml, p=0.001) and in the delayed phase (1.52 mg/ml vs. 2.84 mg/ml, p=0.001), while mean attenuation values were not significantly different in both phases (57.8 HU vs. 69.1 HU, p=0.067 and 67.4 HU vs. 78.4 HU, p=0.086, respectively).

CONCLUSIONS

Dual-energy CT using a quantitative analytic methodology can be used to differentiate between benign and malignant mediastinal tumors.

Management of a simple renal cyst in a complex patient

Renal cysts are generally classified as simple or complex and are further characterised under the Bosniak classification system. Most simple cysts are benign, asymptomatic and discovered incidentally. However, over time, these simple cysts can enlarge, become symptomatic and develop complications, requiring intervention. We present a case of a 70-year-old man with multiple comorbidities who presented with left lower quadrant abdominal pain and haematuria. An abdominal CT scan revealed a large, 26 cm exophytic cyst with high attenuation areas, septations and haemorrhage. Given the patient's tenuous condition and poor functional status, an interventional radiology-guided renal cyst aspiration was performed, resulting in successful reduction of size and symptom resolution. A follow-up ultrasound at 6 months showed no evidence of recurrence. Primary care providers should be aware of the prevalence of renal cysts and their complications, especially haemorrhage, particularly in high risk and elderly patients on anticoagulation or antiplatelet therapy.

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

PURPOSE

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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