Comparison of 16-MDCT and MRI for Characterization of Kidney Lesions

A rare case of renal squamous cell carcinoma presenting with psoas sign

INTRODUCTION

Renal cancer is a relatively common form of cancer; however, squamous cell carcinoma of the kidney is extremely rare and it carries poor prognosis.

CLINICAL PRESENTATION

We present a rare case of renal squamous cell carcinoma that was manifested with the psoas sign in a patient with a history of chronic staghorn calculus.

DISCUSSION

Squamous cell carcinoma of kidney is rare and more invasive. Even though many risk factors have been identified, staghorn renal calculi with chronic infection have a higher incidence of renal squamous cell carcinoma (SCC). Squamous cell carcinoma (SCC) has a wider range of atypical presentations; the psoas sign is not commonly reported in other literature. Due to the lack of reporting and sufficient knowledge, there are currently no established management guidelines. Despite advancements in contemporary medicine, the survival rate of renal SCC remains remarkably low, necessitating further research to develop a standardized treatment protocol.

CONCLUSION

Primary renal SCCs are rare tumors and exhibit a strong association with renal stones, requiring prompt assessment and treatment of renal stones in affected patients. Despite their aggressiveness and poor prognosis, timely intervention is crucial.

Importance of tumor subtypes in cancer imaging

Cancer therapy has evolved from being broadly directed towards tumor types, to highly specific treatment protocols that target individual molecular subtypes of tumors. With the ever-increasing data on imaging characteristics of tumor subtypes and advancements in imaging techniques, it is now often possible for radiologists to differentiate tumor subtypes on imaging. Armed with this knowledge, radiologists may be able to provide specific information that can obviate the need for invasive methods to identify tumor subtypes. Different tumor subtypes also differ in their patterns of metastatic spread. Awareness of these differences can direct radiologists to relevant anatomical sites to screen for early metastases that may otherwise be difficult to detect during cursory inspection. Likewise, this knowledge will help radiologists to interpret indeterminate findings in a more specific manner.

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Tumor subtypes can be identified based on their different imaging characteristics.

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Awareness of tumor subtype can help radiologists chose the appropriate modality for additional imaging workup.

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Awareness of differences in metastatic pattern between tumor subtypes can be helpful to identify early metastases.

Prospective Comparison of Contrast-Enhanced Ultrasound and Magnetic Resonance Imaging to Computer Tomography for the Evaluation of Complex Cystic Renal Lesions

OBJECTIVE

To prospectively evaluate the diagnostic accuracy of contrast enhanced ultrasound (CEUS) and MRI compared to computed tomography (CT) as the current gold standard for the characterization of cystic renal lesions using the Bosniak classification.

METHODS

Between July 2014 and October 2017 we prospectively enrolled patients with cystic renal lesions. Based on the Bosniak classification of complex renal lesions (≥BII-F) we evaluated the accuracy of observed agreement by Cohen's Kappa coefficient and calculated sensitivity, specificity, positive and negative predictive values (PPV/NPV) between the three imaging modalities CT, MRI and CEUS.

RESULTS

We evaluated 65 cystic renal lesions in 48 patients (median age 63 years, range 36-91 years; 18 females, 30 males). According to CT 29 (47%) of the cystic renal lesions were classified as complex. The agreement between CEUS and CT in the classification of complex cystic lesions was fair (agreement 50.8%, Kappa 0.31), and was excellent between MRI and CT (agreement 93.9%, Kappa 0.88). Compared to CT, CEUS and MRI had a sensitivity of 100% and 96.6%, a specificity of 33.3% and 91.7%, a PPV of 54.7% and 90.3%, and a NPV of 100% and 97.1% with an accuracy of 63.1% and 93.8% respectively.

CONCLUSION

CEUS has an excellent sensitivity and NPV and represents a promising non-invasive screening tool for renal cystic lesions. The classification of complex renal cysts based on MRI and CT scans correlated closely.

Renal Cell Carcinoma Ablation: Preprocedural, Intraprocedural, and Postprocedural Imaging

The rising incidence of renal cell carcinoma (RCC) in recent decades necessitates careful consideration of additional treatment options, especially for patients who may be poor surgical candidates. An emerging body of evidence suggests that ablation may be performed effectively and safely even in patients with multiple comorbidities. Accordingly, clinical guidelines now include thermal ablation as an alternative for such patients with localized tumors that are 4.0 cm or smaller. Recent experience with these minimally invasive techniques has led to a greater understanding of the imaging findings that merit close attention when ablation is anticipated, or after it is performed. These imaging findings may guide the interventionalist's perception of the risks, technical challenges, and likelihood of treatment success associated with RCC ablation. The present review provides an overview of clinically relevant radiologic findings during the preprocedural, intraprocedural, and postprocedural period in the context of image-guided renal ablation. Keywords: Interventional-Body, Kidney, Percutaneous, Urinary © RSNA, 2019.

Differential diagnostic ability of 18F-FDG PET/CT radiomics features between renal cell carcinoma and renal lymphoma

BACKGROUND

The aim of this study is to determine the differential diagnostic value of texture parameters of PET/CT on renal cell carcinoma and renal lymphoma.

METHODS

Twenty renal lymphoma and 18 renal cell carcinoma (RCC) patients were analyzed in this study. The pathological information and basic characteristics were extracted from the electronic medical record system of our hospital. We used LIFEx package to extract data from the radiomics images. Receiver operating characteristic analysis and binary logistic regression analysis was applied in determining the diagnostic accuracy of texture parameters as well as the synthetic parameter, of which the sensitivity and specificity was improved.

RESULTS

There were 14 (two in Histogram, two in Grey Level Co-occurrence Matrix, five in Grey-Level Run Length Matrix, five in Grey-Level Zone Length Matrix) out of the texture parameters showing an area under the curve (AUC) >0.7 and P<0.05. Synthesized parameters of each section showed even higher differentiation ability, with AUC varying from 0.725 to 1.000.

CONCLUSIONS

Texture analysis of ¹⁸F-FDG PET/CT could effectively differentiate between RCCs and renal lymphomas.

Diagnostic Imaging for Solid Renal Tumors: A Pictorial Review

The prognosis of renal tumors depends on histologic subtype. The increased use of abdominal imaging has resulted in an increase in the number of small renal incidentaloma in recent decades. Of these incidentally discovered tumors, 20% are benign lesions warranting conservative management, but most are renal cell carcinomas that warrant a more aggressive therapeutic approach due to their malignant potential. Dedicated diagnostic renal imaging is important for characterization of renal tumors to facilitate treatment planning. This review discusses the ability to detect and differentiate renal cell carcinoma subtypes, angiomyolipoma and oncocytoma based on ultrasound imaging, computed tomography, multiparametric magnetic resonance, and nuclear imaging.

Comparison of MDCT, MRI and MRI with diffusion-weighted imaging in evaluation of focal renal lesions: The defender, challenger, and winner!

Purpose:

To compare the diagnostic performance of multidetector computed tomography (MDCT), magnetic resonance imaging (MRI), and MRI with diffusion-weighted imaging (DWI) in the characterization of focal renal lesions. We also compared MDCT and MRI in the staging of renal cell carcinoma (RCC).

Materials and Methods:

One hundred and twenty adult patients underwent MDCT (40-row and 128-row scanners), MRI (at 1.5 T), and DWI (at b-values of 0 and 500 s/mm²) for characterization of 225 renal lesions. There were 65 malignant neoplasms (44 RCCs), 25 benign neoplasms, 25 abscesses, 45 pseudotumors, 15 hemorrhagic cysts, and 50 benign cysts. A composite gold standard including histology, typical imaging criteria, and follow-up imaging was employed. To determine the diagnostic performance of imaging modalities, area-under-curve (AUC) was calculated by receiver-operating-characteristic analysis and compared. Fisher's exact test was used to compare the diagnostic accuracies and confidence levels with MDCT, MRI, and MRI + DWI. Cross-tabulation was used to assess the precision of MDCT and MRI in RCC staging.

Results:

AUC for MDCT (0.834) and MRI (0.841) in the classification of benign and malignant lesions were within corresponding 95% confidence interval (CI) (P = 0.88) whereas MRI + DWI had significantly better performance (AUC 0.968, P = 0.0002 and 0.0004, respectively). Both CT and MRI had low specificity (66.9% and 68.8%, respectively), which increased substantially with DWI (93.8%) owing to correct diagnosis of pseudotumors. MRI was superior to CT in diagnosing necrotic RCC and hemorrhagic cysts. MRI + DWI had the highest accuracy (94.2%) in assigning the definitive diagnosis and 97.6% lesions were diagnosed with very high confidence, significantly better than CT and MRI. Both CT and MRI had the same accuracy (86.1%) in RCC staging and evaluation of intravascular thrombi.

Conclusions:

Characterization of renal lesions was most accurate with MRI + DWI. The latter is also the most suitable modality in diagnosing pseudotumors and evaluating patients with renal dysfunction. CT and MRI were equivalent in RCC staging.

Diagnostic modalities

The incidental detection of small renal masses on imaging undertaken to evaluate unrelated symptoms or conditions is an increasingly common occurrence. Accurate imaging characterisation is fundamental to determining optimum patient management. The goals of imaging small renal masses include determining whether a lesion is solid or cystic, if there are signs of biological aggressiveness and whether the lesion is likely benign or malignant. The current imaging practices and the evidence supporting the use of different imaging modalities for the characterisation of small renal masses are discussed. CT remains the primary imaging modality and is able to classify most masses into surgical or non-surgical lesions. MRI and contrast enhanced ultrasound are most often employed to problem solve in lesions deemed indeterminate on contrast enhanced CT or for patients in which CECT is contraindicated. Percutaneous biopsy should be considered in lesions that remain indeterminate after initial imaging investigations. Given the central role of imaging in the management of small renal masses, all multidisciplinary team members involved in renal cancer care should have an understanding of the performance of the different imaging modalities.

Low-dose gadobenate dimeglumine-enhanced MRI of the kidney for the differential diagnosis of localized renal lesions

Objective

To evaluate low-dose gadobenate dimeglumine-enhanced MRI for the differential diagnosis of malignant renal tumors.

Methods

Sixty-two consecutive patients with unclear diagnosis at MDCT/ultrasound underwent dynamic CE-MRI of the kidneys with 0.05 mmol/kg gadobenate dimeglumine. Retrospective image evaluation was performed by two blinded readers. Lesion diagnosis at CE-MRI was correlated with findings from histology following tumor resection or from imaging follow-up after at least 1 year. Assessments were performed of diagnostic quality and level of diagnostic information.

Results

Thirty-nine (63 %) patients were correctly diagnosed with malignant lesions (36 with RCC, 2 with renal metastases, 1 with lymphoma) while 14 (22.6 %) patients were correctly diagnosed with benign (n = 12) or no (n = 2) lesions. Eight patients were considered false positive (5 with oncocytoma, 3 with atypical AML) and 1 patient false negative (atypical RCC). The sensitivity, specificity, accuracy, PPV, and NPV for the diagnosis of malignant renal lesions were 97.5 % (39/40), 63.6 % (14/22), 85.5 % (53/62), 83.0 % (39/47), and 93.3 % (14/15), respectively. Images were excellent in 60 and good in 2 patients. Minimal artifacts that did not compromise diagnosis were noted in 4/62 patients.

Conclusion

Low-dose gadobenate dimeglumine-enhanced MRI is effective for the differential diagnosis of malignant renal tumors.

Von Hippel-Lindau disease

von Hippel-Lindau (VHL) disease is an inheritable condition with an incidence of 1 in 36000 live births. Individuals with VHL develop benign and malignant tumors including retinal and central nervous system hemangioblastomas, clear cell renal cell carcinomas (RCC), pheochromocytomas, pancreatic neuroendocrine tumors and endolymphatic sac tumors (ELSTs). VHL is caused by germline loss of function of the VHL gene on one allele at chromosome 3p25-26. A somatic "second hit" event leads to the loss of the other allele and tumor formation. Loss of VHL function in cells leads to increased expression and stabilization of hypoxia inducible factor (HIF). VHL protein/HIF pathway has been implicated in tumorigenesis for hemangioblastomas, RCC and other VHL tumors. Clinical examination, imaging, and genetic testing for VHL mutations confirm VHL disease. Management of VHL disease largely consists of surgical resection of symptomatic tumors (hemangioblastomas), tumors prone to metastasize (RCC larger than 3cm), or tumors causing hormonal symptoms (pheochromocytomas). Despite advances in early diagnosis and management of VHL disease, life expectancy for VHL patients remains low at 40-52 years. Secondary effects from VHL manifestations are mitigated by routine surveillance and early detection. In this chapter, we summarize the current state of knowledge in VHL disease.

Imaging techniques for the patient with renal cell carcinoma

The imaging of renal cell carcinoma continues to evolve from radiographic tomography to state-of-the-art three-dimensional imagery using computed tomography (CT) or magnetic resonance imaging (MRI). This article reviews the current techniques of imaging the patient with renal cell carcinoma. Careful and accurate imaging of these patients allows for the appropriate diagnosis, treatment planning, and follow-up care. At each point in the care of these patients, imaging plays an important role. In particular, the diagnosis and staging of renal cell carcinoma can be accomplished with CT and MRI, with each modality having strengths and weaknesses that are contrasted. Intraoperative ultrasound is used during laparoscopic or conventional partial nephrectomies, whereas ultrasound, CT, and MRI can be used for guiding ablative technologies. Imaging also plays an important role in the follow-up care of these patients. The particular follow-up care is dependent on the stage and grade of the lesion and the treatment modality used. In summary, this article reviews the current imaging approaches for the diagnosis, staging, treatment, and follow-up care of patients with renal cell carcinoma.

Vascular staging of renal and adrenal malignancies with a noncontrast enhanced steady state free precession technique

PURPOSE

To compare a noncontrast enhanced balanced steady state free precession (bSSFP) MRI technique with a conventional dynamic contrast-enhanced (DCE) three-dimensional (3D) spoiled gradient recalled echo (SPGR) imaging in the vascular staging of renal and adrenal malignancies.

MATERIALS AND METHODS

Sixty-three MRIs with both bSSFP and DCE acquisitions performed for initial staging of renal and adrenal malignancies were retrospectively evaluated for presence and extent of thrombus in the renal veins and inferior vena cava (IVC). Thrombus characterization was also evaluated. DCE imaging was used as the standard-of-reference. Histopathology was available in 46 of 63 cases as an additional external standard.

RESULTS

There is very good agreement between bSSFP and DCE imaging for determining the presence or absence of thrombus in the renal veins (r = 0.95; P < 0.0001) and IVC (r = 0.91; P < 0.0001). BSSFP is less successful at distinguishing bland from tumor thrombus.

CONCLUSION

Noncontrast enhanced bSSFP is an acceptable alternative to DCE imaging for vascular staging of locally advanced renal/adrenal malignancies, with somewhat limited ability to distinguish bland from tumor thrombus.

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.

Follow-up after percutaneous radiofrequency ablation of renal cell carcinoma: contrast-enhanced sonography versus contrast-enhanced CT or MRI

OBJECTIVE

The purpose of this study was to assess, with contrast-enhanced CT or MRI as the reference imaging technique, the diagnostic performance of low-mechanical-index contrast-enhanced sonography in detecting local tumor progression after percutaneous radiofrequency ablation of renal tumors.

MATERIALS AND METHODS

Twenty-nine patients with 30 renal tumors (18 men, 11 women; mean age, 73 years; range, 53-83 years) underwent percutaneous radiofrequency ablation at a single center between March 1998 and January 2007. The imaging follow-up schedule was both contrast-enhanced sonography and CT or MRI 4 months after completion of treatment and every 4 months for the first year. Thereafter, the follow-up schedule was contrast-enhanced sonography every 4 months with CT or MRI every 8 months. The chi-square test with Yates correction was used to evaluate positive and negative predictive values and accuracy.

RESULTS

One patient was scheduled to undergo surgical resection, and another patient was lost to follow-up. Twenty-seven patients with 28 renal tumors participated in follow-up. The concordance between contrast-enhanced sonographic and CT or MRI findings was 100% for 27 of 28 tumors (96.4%) that had a hypervascular pattern before treatment. In the case of the tumor that was hypovascular at imaging performed before percutaneous radiofrequency ablation, local tumor progression was missed at contrast-enhanced sonography. The sensitivity, specificity, positive predictive value, negative predictive value, and overall accuracy of contrast-enhanced sonography were 96.6%, 100%, 100%, 95.8%, and 98.1%.

CONCLUSION

Contrast-enhanced sonography is an effective alternative to CT and MRI in the follow-up of renal tumors managed with percutaneous radiofrequency ablation.

Renal cell carcinoma: diagnosis, staging, and surveillance

OBJECTIVE

This educational review focuses on the staging and radiologic evaluation of renal cell carcinoma. It includes discussion of the epidemiology, pathology, and therapeutic options of renal cell carcinoma and the implications for radiologic follow-up.

CONCLUSION

The incidence of renal cell carcinoma has been increasing. Imaging plays a central role in its detection, staging, and treatment evaluation and follow-up.

Value of contrast-enhanced ultrasonography for detecting renal infarcts proven by contrast enhanced CT. A feasibility study

The effectiveness of contrast-enhanced ultrasonography (CEUS) in the evaluation of patients with acute renal infarcts was investigated, using contrast-enhanced helical computed tomography (CT) as the reference imaging procedure. Twenty-seven consecutive patients with acute renal infarcts detected with contrast-enhanced helical CT underwent CEUS. Digital cine-clips of CEUS were evaluated by two independent readers blinded to CT findings. Image quality was rated subjectively on a four-point scale. Then, readers were asked to assign a confidence level in diagnosis of renal infarct at the upper pole, medium portion, and lower pole of each kidney according to a five-degree scale, ranging from definitely absent to definitely present. ROC curve analysis was employed to assess the overall confidence of diagnosis of infarct, and weighted kappa values were calculated to assess inter-reader agreement. The subjective image quality of CEUS was lower than the image quality of CT at the upper poles. However, the diagnostic performance of CEUS was excellent (area under receiver-operator characteristic curve 0.992 +/- 0.006 for reader 1; 0.991 +/- 0.007 for reader 2), with very good inter-reader agreement (weighted kappa value = 0.83). CEUS is a reproducible tool to detect acute renal infarcts in men, with a diagnostic performance approaching that of CT.