Imaging Characterization of Renal Masses

Abstract

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.

Keywords: computed tomography (CT); magnetic resonance imaging (MRI); renal cell carcinoma; renal cyst; renal mass; ultrasound.

Figure 1

Diagnostic algorithm for the characterization of cystic renal masses. US: Ultrasound, CT: Computed Tomography, MRI: Magnetic Resonance Imaging.

Figure 2

Main features of cystic renal masses following the Bosniak classification. Data in the table are adapted from previous and updated version [12].

Figure 3

Bosniak IV cyst in a 77-year-old man. (a) Coronal fast spin-echo T2-weighted MRI shows a heterogeneous well-defined mass at the lower pole of the left kidney. (b) Pre-contrast T1-weighted image shows minimal heterogeneity of the mass. (c) Post-contrast T1-weighted image shows an 8 mm enhancing nodularity (arrow) arising from the posterior wall of a cystic mass corresponding to a Bosniak IV cyst.

Figure 4

Evaluation of complex cysts with Contrast Enhanced Ultrasound (CEUS). (a) CT image shows a cyst with a thin septum (arrow) corresponding to a Bosniak II cyst in a 36-year-old woman; (b) CEUS image of the same cyst also shows the thin septum. Septa are usually better visualized by CEUS due to the possibility of real-time evaluation and its higher sensitivity for detecting microvascularization; (c) US image shows a complex cyst with suspicion of soft-tissue mass (arrow) in a 42-year-old woman; (d) CEUS image shows absence of enhancement of the intracystic lesion (arrow), corresponding to a Bosniak II cyst that does not require further examinations.

Figure 5

Diagnostic algorithm for the characterization of well-defined solid renal masses.

Figure 6

Angiomyolipoma in a 67-year-old woman. (a) Axial T2-weighted image shows a 2.3 cm hyperintense renal mass; (b) axial in-phase (c) and opposed-phase T1-weighted images show India ink artifact on the opposed-phase image; (d) axial fat-suppressed T1-weighted image shows low signal intensity of the mass. Scale size: 5 cm

Figure 6

Angiomyolipoma in a 67-year-old woman. (a) Axial T2-weighted image shows a 2.3 cm hyperintense renal mass; (b) axial in-phase (c) and opposed-phase T1-weighted images show India ink artifact on the opposed-phase image; (d) axial fat-suppressed T1-weighted image shows low signal intensity of the mass. Scale size: 5 cm

Figure 7

Oncocytoma in a 57-year-old man. (a) Axial T2-weighted MRI shows a nodular mass in the left kidney with heterogeneous but mainly hyperintense signal; (b) Axial contrast-enhanced T1-weighted image shows heterogeneous enhancement with intratumor hypoenhancing areas; (c) Axial diffusion-weighted image with high b = 1000 (d) and Apparent Diffusion Coefficient (ADC) map show absence of restriction.

Figure 7

Oncocytoma in a 57-year-old man. (a) Axial T2-weighted MRI shows a nodular mass in the left kidney with heterogeneous but mainly hyperintense signal; (b) Axial contrast-enhanced T1-weighted image shows heterogeneous enhancement with intratumor hypoenhancing areas; (c) Axial diffusion-weighted image with high b = 1000 (d) and Apparent Diffusion Coefficient (ADC) map show absence of restriction.

Figure 8

Papillary renal cancer in a 66-year-old man. (a) Axial T2-weighted MRI shows an almost complete low-signal mass (arrow) in a small kidney with a thin cortex due to chronic renal disease; (b) Axial fast spin-echo T1-weighted MRI shows isointensity of the mass without macroscopic fat (arrow); (c) Axial diffusion-weighted image with high b = 1000 (d) and ADC map show areas of restricted diffusion (arrow). No sequences after the administration of the contrast agent were performed due to the chronic kidney disease. Scale size: 5 cm.

Figure 9

Diagnostic algorithm for the characterization of infiltrative renal masses. TCC: Transitional Cell Carcinoma.

Figure 10

Bilateral metastases in a 65-year-old man. (a) Enhanced coronal CT image in portal phase of the left kidney and (b) right kidney show multiple cortical poorly-defined hypoenhancing lesions; (c) Enhanced axial CT image of the abdomen shows the multiple renal masses and also identifies the presence of stranding and nodularity of the bilateral perirenal fat, thickening of perirenal fascias, multiple retroperitoneal enlarged lymph nodes, and ascites. Diagnosis obtained by biopsy of a renal mass was metastases of high-grade carcinoma of unknown origin. Scale size: 7 cm.

Figure 11

Expansive and infiltrative clear cell renal cell carcinoma in a 70-year-old man. (a) Axial pre-contrast T1-weighted image and (b) axial post-contrast T1-weighted image show a right renal mass with poorly defined margins between the mass and the adjacent renal parenchyma (arrows) with heterogeneous enhancement; (c) Axial postcontrast T1-weighted image also identifies a thrombus within the renal vein (arrow); (d) Coronal T2 weighted-image shows the heterogeneous renal mass involving the renal cortex and sinus, and confirms the thrombosis of the renal vein minimally bulging into the inferior vena cava, but without invading it (arrow). Scale size: 8 cm.