Characterization of solid renal masses using 64-slice multidetector CT scanner

Role of multidetector ct in quantitative enhancement- washout analysis of solid renal masses

Background

Enhancement washout technique in solid renal masses using multidetector computed tomography (MDCT) can differentiate different type of lesions. 99 Patients who are presenting with suspected renal masses or renal tumour for staging are included in this study. CT examination are carried out at urology and nephrology centre using MDCT. The attenuation values (Hounsfield Unit) will be assesed for each lesion on the pre enhanced, corticomedullary, nephrographic and delayed phases. Washout ratio will be calculated for each phase of enhancement in comparison to the unenhanced attenuation value. The characteristics of enhancement-washout will be correlated with the final histopathological diagnosis.

Results

Early enhancement and washout pattern was noted in 54 renal lesions (54.5%) representing 4 types of renal lesions; Oncocytoma (n = 13), clear cell renal cell carcinoma (n = 16), Chromophobe renal cell carcinoma (n = 15) and unclassified renal cell carcinoma (n = 10).Prolonged enhancement pattern was noted 45 lesions (45.4%); PRCC (n = 14), 10 case of lipid poor AML (n = 10), metanephric adenoma (n = 10) and Xp11 RCC (n = 11). High pre-contrast attenuation was noted in Xp 11RCC showing attenuation value 41.7 ± 6.823HU. The highest CMP values were noted in CCRCC (151.9 ± 20.4) followed by oncocytomas (137.6 ± 19.15HU) and then CHRCC (123.6 ± 16.6 HU)while the lowest values were noted in Metanephric adenoma)57.1 ± 17.4HU)and followed by PRCC (59.9 ± 4.8)and followed by lipid poor AML (79.17 ± 13.666) and RCC unclassified (89.06 ± 18.1).

Conclusions

Four-phase MDCT (the unenhanced, corticomedullary, nephrographic, and excretory phases) evaluate role of MDCT in differentiation of solid renal masses.

Imaging Characterization of Renal Masses

The detection of a renal mass is a relatively frequent occurrence in the daily practice of any Radiology Department. The diagnostic approaches depend on whether the lesion is cystic or solid. Cystic lesions can be managed using the Bosniak classification, while management of solid lesions depends on whether the lesion is well-defined or infiltrative. The approach to well-defined lesions focuses mainly on the differentiation between renal cancer and benign tumors such as angiomyolipoma (AML) and oncocytoma. Differential diagnosis of infiltrative lesions is wider, including primary and secondary malignancies and inflammatory disease, and knowledge of the patient history is essential. Radiologists may establish a possible differential diagnosis based on the imaging features of the renal masses and the clinical history. The aim of this review is to present the contribution of the different imaging techniques and image guided biopsies in the diagnostic management of cystic and solid renal lesions.

Usefulness of MDCT to Differentiate Between Renal Cell Carcinoma and Oncocytoma: Development of a Predictive Model

OBJECTIVE

The objective of our study was to identify the most useful parameters to differentiate between renal cell carcinoma (RCC) and oncocytoma using four-phase CT.

MATERIALS AND METHODS

Ninety-seven patients with solid renal lesions who underwent surgery with four-phase preoperative CT evaluation and with pathologic diagnosis of RCC or oncocytoma were included in the study. Features of tumors and the enhancement pattern in the four CT phases were evaluated and analyzed. Logistic regression models were used to assess independent predictors for malignancy.

RESULTS

Histopathologically, 13 tumors were oncocytomas and 84 were RCCs. RCCs were larger (6.20 cm vs 3.21 cm, p = 0.0004) and more often enhanced heterogeneously (66 vs 6, p = 0.02). Lesions that were larger than 4 cm showed a significantly higher risk of malignancy (p = 0.0046). Significant differences were found in intensity of nodule enhancement between the nephrographic and the excretory phases with respect to the unenhanced phase (p = 0.003 and p = 0.0026). At multivariate analysis, parameters that were independent predictors of malignancy were enhancement pattern, with RCCs more often having heterogeneous enhancement than oncocytomas (odds ratio [OR], 0.18; 95% CI, 0.04-0.90), and nodule enhancement in the excretory phase in relation to the unenhanced phase, with RCCs showing lower enhancement (OR, 0.93; 95% CI, 0.88-0.97), and a size larger than 4 cm (OR, 4.01; 95% CI, 0.70-23.14).

CONCLUSION

The combination of different CT parameters including lesion size larger than 4 cm, lesion enhancement in the excretory phase in relation to the unenhanced phase, and heterogeneous enhancement pattern helps distinguish RCC from oncocytoma.

Triphasic and epithelioid minimal fat renal angiomyolipoma and clear cell renal cell carcinoma: qualitative and quantitative CEUS characteristics and distinguishing features

PURPOSE

To determine the contrast-enhanced ultrasonography (CEUS) characteristics of minimal fat renal angiomyolipoma (AML) (triphasic and epithelioid) and compare them to each other and to clear cell renal cell carcinoma (ccRCC) to explore their differential diagnostic clue.

METHODS

Qualitative and quantitative CEUS analyses were retrospectively conducted for epithelioid renal AMLs (EAMLs) (n = 15), triphasic minimal fat AMLs (TAMLs) (n = 25), and ccRCCs (n = 113). Enhancement patterns and features with CEUS were qualitatively evaluated. As for the quantitative parameters, rise times (RT), time to peak (TTP), and tumor-to-cortex enhancement ratio (TOC ratio) were compared among these renal tumor histotypes.

RESULTS

No significant differences were detected on conventional ultrasound in the three histotypes of renal tumor. On qualitative CEUS analysis, centripetal enhancement in cortical phase (73.3% in EAMLs, 84.0% in TAMLs vs. 18.6% in ccRCCs, p < 0.001 for both), homogeneous peak enhancement (100.0% in both EAMLs and TAMLs vs. 43.4% in ccRCCs, p < 0.001 for both), and iso-enhancement in parenchyma phase (53.3% in AMLs, 52.0% in TAMLs vs. 26.5% in ccRCCs, p = 0.034 and 0.013, respectively) were valuable traits for differentiating EAMLs and TAMLs from ccRCCs. Furthermore, with quantitative analysis, RT and TTP were much shorter in ccRCCs than those in EAMLs and TAMLs. However, all these qualitative and quantitative characteristics made no significant difference between EAMLs and TAMLs. In the differential diagnosis of EAMLs from TAMLs, pseudocapsule sign was valuable (40.0% in EAMLs vs. 0.0% in TAMLs, p < 0.001), and TOC ratio was much higher in EAMLs (166.01 ± 64.47%) than that in TAMLs (93.74 ± 46.56%)(p < 0.001), though they did make overlaps with ccRCCs. With either heterogeneous peak enhancement or the presence of pseudocapsule or TOC ratio >97.34% as the criteria to differentiate ccRCCs and EAMLs from TAMLs, the sensitivity and specificity were 80.0% and 87.5%, respectively.

CONCLUSIONS

Qualitative and quantitative CEUS analyses are helpful in the differential diagnosis of ccRCCs, EAMLs, and TAMLs.

Virtual Touch quantification using acoustic radiation force impulse (ARFI) technology for the evaluation of focal solid renal lesions: preliminary findings

AIM

To evaluate potential value of Virtual Touch quantification (VTQ) of acoustic radiation force impulse (ARFI) imaging for characterising focal solid renal lesions.

MATERIALS AND METHODS

Two independent operators performed 10 and five measurements of each lesion and adjacent renal cortex, respectively. Mean shear wave velocity (SWV) and shear wave velocity ratio (SWR) of histotypes were compared.

RESULTS

One hundred and ninety-seven renal lesions were evaluated, including 155 renal cell carcinomas (RCCs; 129 clear-cell RCCs [ccRCCs], 14 papillary RCCs [pRCCs], and 12 chromophobe RCCs [cRCCs]) and 42 angiomyolipomas (AMLs). The interoperator reproducibility of SWV of renal tumours and renal cortex were good (ICC=0.852, and 0.903, respectively). SWV of the renal cortex at a depth of <4 cm was significant higher than that at a depth of >4 cm. Regardless of the subtypes of RCC, SWV and SWR of RCCs differed significantly from those of AMLs (2.28±0.85 versus 1.98±0.85; 1.09±0.56 versus 0.78±0.34; p=0.045 and p<0.001, respectively). At cut-off points of SWV >1.87 m/s or SWR >0.84 to differentiate RCCs from AMLs, the sensitivity and specificity were 47.5%, 33.2% or 47.5%, 30.2%, respectively. When the subtypes of RCCs were taken into account, SWV and SWR of ccRCCs were significantly higher than those of pRCCs, cRCCs, and AMLs, while there was no significant difference among the latter. With SWV >1.98 m/s or SWR >0.80 as the cut-off point to differentiate ccRCCs from other renal tumours, the sensitivity and specificity were 69.8%, 65% or 76.8%, 73.4%, respectively.

CONCLUSION

The ARFI technique offers additional information regarding renal tumour elasticity with good reproducibility. SWV and SWR are potential biomarkers in this setting, helping to differentiate ccRCC from other renal tumour histotypes.

Differentiation of oncocytoma and renal cell carcinoma in small renal masses (<4 cm): the role of 4-phase computerized tomography

PURPOSE

We investigate the use of 4-phase computerized tomography with intravenous contrast to help distinguish oncocytoma from renal cell carcinoma (RCC) in tumors <4 cm.

METHODS

We retrospectively identified patients who underwent surgical management for renal tumors <4 cm from 2005 to 2008. Patients who had pre-operative CT evaluation as per our institution's renal mass protocol and had confirmed pathological diagnosis of either oncocytoma or RCC were included in the study. Enhancement readings were obtained for the tumor and the renal cortex using the same slice simultaneously.

RESULTS

Our cohort involved 69 patients (46 men, 23 women; mean age 66) who presented with 79 renal masses. Histopathologically 40 were clear cell, 22 papillary, 5 chromophobe RCC and 12 oncocytoma. On the arterial, venous and delayed phase images, oncocytoma showed the highest mean enhancement change, i.e.,546, 396 and 239% followed by clear cell RCC 261, 261 and 174%, chromophobe RCC 147, 127 and 66% and papillary RCC 137, 184 and 118%, respectively. The enhancement pattern differed significantly on comparing oncocytoma with RCC (P < 0.007). The mean percentage contrast excreted at the end of the delayed phase was 33.3, 13.8, 32 and 53% for clear cell, papillary, chromophobe and oncocytoma, respectively.

CONCLUSION

The enhancement and washout values in Hounsfield units obtained by multiphasic CT scan aid in distinguishing oncocytoma from the commonly seen subtypes of RCC in renal masses <4 cm. This preliminary study demonstrates that arterial phase enhancement greater than 500% and washout values of greater than 50% are exclusively seen in renal oncocytomas.