Figure 1

In a 63-year-old male, a hypoechoic nodule measuring 1.8 × 1.8 cm was observed in the lower pole of the right kidney, with an unclear boundary and regular shape that extended outside the kidney (A). An intravenous injection of the ultrasound contrast agent SonoVue resulted in heterogeneous hyperenhancement in the cortical phase (B), isoenhancement in the medullary phase (C), and heterogeneous hypoenhancement in the delayed phase (D) within the nodule. The pathology report confirmed an oncocytoma."

Figure 2

In a 54-year-old male, a 3.0 × 2.4 cm slightly echogenic nodule was seen in the left kidney, with a clear boundary, irregular shape, and extension beyond the renal capsule. After intravenous injection of the ultrasound contrast agent SonoVue, the nodule showed hyperenhancement in cortical phase (A), isoenhancement in medullary phase (B), and slight hypoenhancement in the delayed phase (C). There were small non-enhanced areas seen in all phases. The pathology report confirmed a renal clear cell carcinoma."

Figure 3

In a 40-year-old female, an echogenic nodule measuring 1.7 × 1.4 cm was detected in the left kidney, with a clear boundary and regular shape. After intravenous injection of the ultrasound contrast agent SonoVue, the nodule demonstrated slightly hyperenhancement in the cortical phase (A) and medullary phase (B). The delayed phase (C) showed isoenhancement. The pathology report confirmed a chromophobe renal carcinoma."

Figure 4

Example of CEUS in the diagnosis of an indeterminate renal mass. (A) Prior to contrast arrival a 7 cm mass (white arrows) is apparent in the right kidney with echoic components on B-mode suggesting solid components and possible malignancy. (B) Following arrival of the contrast agent (2 ml of Lumason, Bracco), no enhancement is observed within the suspected mass (white arrows), indicating it is a hemorrhagic cyst and ruling out RCC."

Figure 5

Example CEUS and time-intensity curve analysis of a renal mass later confirmed as papillary RCC on tissue sampling. Top images: Regions of interest are placed around the indeterminate mass (yellow) and adjacent renal cortex (blue). Bottom image: Contrast signal intensity is then plotted as a function of time for each region of interest. Notice the RCC demonstrates faster contrast signal washout relative to the renal parenchyma, a hallmark of RCC."

Figure 6

In a 54-year-old female, a hyperechoic mass of 4.9 × 4.3 cm was seen in the lower pole of the right kidney, with clear boundary and regular shape, and part of it protrudes out of the renal capsule (A). After intravenous injection of ultrasound contrast agent SonoVue, homogenous iso- and hypo-enhancement seen in the cortical (B) and the medullary (C) phases, and very low enhancement seen at the delayed phase (D)."

Figure 7

Example of 2D and 3D CEUS of a Multilocular renal cyst. (A) Grey-scale ultrasound shows an anechoic multicystic mass with thin echogenic wall and septa (white arrows); (B) 2D dual imaging shows enhancement of wall and septation during the arterial phase (25 sec post-UCA injection); (C) Continuous CEUS 3D imaging was subsequently performed following a second bolus injection. The multilocular cyst is well visualized in three orthogonal planes (white arrows) and in the volumetric reconstruction (bottom right panel)."

Figure 8

Example of 2D and 3D CEUS of a Clear cell RCC with cystic features. (A) Grey-scale image demonstrating a hypoechogenic 3 × 2.9 cm renal mass; (B) 2D dual imaging shows a diffuse, heterogeneous enhanced tumor with both solid and cystic components during the arterial phase (37 seconds post-UCA injection); (C) Continuous CEUS 3D imaging was subsequently performed following a second bolus injection. The tumor is well visualized in three orthogonal planes (white arrows) and in the volumetric reconstruction (bottom right panel)."

Table 1

Bosniak classification system"

Table 2

Modified bosniak classification system using CEUS"

Figure 9

Example of 2D and 3D CEUS of a 2.5 cm ablation cavity (white arrows) 18 months post cryoablation. (A) 2D dual imaging shows no enhancement within the ablation cavity during the arterial phase (39 seconds post injection of 1ml Optison, GE Healthcare); (B) Similar lack of enhancement on 2D CEUS is observed in the later phases (1:07 post injection); (C) Continuous 3D imaging was subsequently performed following a second 1 ml bolus injection. The ablation cavity is well visualized in three orthogonal planes (white arrows) and in the volumetric reconstruction (bottom right panel); (D) Post-processing was then performed to evaluate the volume on a slice by slice basis with slice distances of 1.3 mm in order to confirm lack of enhancement throughout the cavity."

Figure 10

A 29-year-old man with 19-year diabetes and renal failure underwent combined pancreas-kidney transplantation. (A) At 19 days after transplantation with a creatinine of 556umol/L, Doppler ultrasound showed a high-resistance reverse flow of renal artery during diastole; (B-D) Contrast-enhanced ultrasound displayed apparent filling of the renal artery and its branches with no evident signs of venous return, consistent with renal vein occlusion."

Figure 11

Kidney injury in a 23-year-old female patient involved in a traffic accident. (A) CT scan showed a low-density mass without a clear boundary in the lower pole of the right kidney (arrow); (B) Gray-scale ultrasound image at the same region in figure A showed a complex mass (white arrows); (C) CEUS imaging showed the lesion without enhancement (perfusion defect denoted by marks, 2.5 × 1.8 × 2.5 cm). No active bleeding was identified during the CEUS exam; (D) An unenhanced fluid collection (white arrows) was seen under the left lobe of the liver."

Figure 12

A 33-year-old male patient who had elevated creatinine for 4 years was diagnosed with chronic renal failure-uremic stage and underwent kidney transplantation. Ultrasound was performed 10 days after kidney transplantation with a creatinine of 130umol/L. (A) Gray-scale ultrasound showed that the size and shape of the transplanted kidney were average, and the demarcation between the cortex and medulla was clear; (B-C) Contrast-enhanced ultrasound showed a narrowed segment of the renal artery branch at the lower pole, with a diameter of about 0.3 cm, suggesting the presence of renal artery stenosis in the transplanted kidney."

Figure 13

A 62-year-old man underwent kidney transplantation for chronic renal failure. Presented with oliguria for over 2 months and creatinine of 638umol/L. Real-time CEUS was used to see renal perfusion status. (A) Before contrast injection; (B) 12 sec after contrast injection, the capsule of the transplanted kidney was enhanced (white arrows); (C-D) 14 sec after injection, the main renal artery and the intrarenal segment arteries were enhanced gradually and visualized sequentially; (E-F) The upper pole of renal parenchyma identified a non-perfusion area (white arrows) measuring 4.9 × 4.3 × 4.0 cm and irregular enhancement within the kidney, consisting of a localized renal infarction and inhomogeneous hypoperfusion status."