Table 1.

An overview of the pathological entities addressed in the paper with corresponding imaging details on baseline US and CEUS, as well as the references.

Pathological entities	Baseline US findings	CEUS findings	References
Differential diagnosis between solid renal masses and pseudotumours	Normal variants cannot always be differentiated from tumours	Tumour vascularity is different from normal parenchyma, at least in one vascular phase Any area enhancing differently is suspicious (Figure 1)	[15]
		Pseudotumours enhance parallel to the kidney parenchyma in all phases (Figure 2)	[14, 16]
	Solid tumours cannot be characterised as benign or malignant	Solid tumours do not show specific perfusion patterns to differentiate between benign and malignant lesions	[15]
	Colour Doppler has limitations in imaging neoplastic invasion of the renal vein and collecting system	Malignant renal vein thrombus enhances, while bland thrombus does not show contrast uptake. Enhancing material in the collecting system is characterised as neoplastic tissue contrary to nonenhancing infectious material (Figure 3)	[15, 19]
Differentiation between cystic and solid lesions	Colour Doppler has limitations in imaging perfusion in echogenic content of cysts	Solid hypovascular tumours enhance, even minimally, while debris does not (Figure 4)	[15, 17, 20]
		CEUS is superior to CT and MR for diagnosing cystic renal cell carcinoma	[8, 21, 22]
Characterisation of complex cystic renal masses	Colour Doppler has limitations in imaging perfusion in septa and nodules of cysts	CEUS shows enhancement in solid septa and nodules, with equal or superior diagnostic accuracy compared to CT for cyst classification using the Bosniak system (Figures 5–8)	[23, 36–38]
		CEUS is an alternative to CT for complex cysts followup	[20, 38, 42]
Renal ischaemia	Colour Doppler has limitations in imaging perfusion in small blood vessels with slow flow	CEUS is comparable to CECT for detecting parenchymal ischaemia. Infarcts appear as triangular or wedge-shaped areas with no contrast uptake (Figure 9)	[15, 16, 46]
		CEUS differentiates infarcts from parenchymal areas with diminished perfusion	[15]
Renal infections	B-mode US is needed to rule out the presence of calculi and urinary tract obstruction	Focal pyelonephritis shows areas of reduced enhancement. An abscess appears as a non-enhancing area with peripheral uptake (Figure 10)	[15]
		Puss in the collecting system or bladder shows no uptake (Figure 11)	[14]
Renal trauma	Baseline US is adequate for fluid detection but has low sensitivity for imaging traumatic lesions, which may be isoechoic and can be missed	CEUS reveals injuries not visible on baseline US as nonenhancing areas (Figure 12)	[51, 52, 57–59]
		Patients initially imaged with CT can be followed with CEUS	[59]
Renal artery stenosis	Doppler examination of renal arteries is the first imaging examination to be performed for assessing stenosis	Routine use of CEUS offers no significant advantage for renal artery stenosis evaluation	[15, 61]
Percutaneous ablation therapy assessment	Baseline US does not offer significant information	CEUS confirms treatment results, imaging remaining tumour vascularity. Areas still enhancing afterablation are considered as residual tumour	[62–64]