The evaluation of renal masses, encompassing both cystic and solid lesions, is a critical aspect of urological imaging. Traditional modalities such as computed tomography (CT) and magnetic resonance imaging (MRI) have long been the mainstay in this domain. However, the advent of contrast-enhanced ultrasound (CEUS) has introduced a valuable alternative, particularly advantageous in specific clinical scenarios [1-5].

CEUS employs microbubble contrast agents that remain strictly intravascular, providing real-time assessment of tissue perfusion without the nephrotoxic risks associated with iodinated or gadolinium-based contrast agents used in CT and MRI. This characteristic renders CEUS especially beneficial for patients with renal insufficiency or allergies to conventional contrast media. Moreover, CEUS offers superior spatial and temporal resolution in evaluating microvascular blood flow, enhancing the detection and characterization of renal lesions [1, 3, 5].

In the context of cystic renal lesions, the Bosniak classification system has been pivotal in stratifying malignancy risk and guiding management decisions. Originally developed for CT imaging, this classification has undergone revisions to incorporate advancements in imaging techniques. The 2019 update aimed to refine criteria and improve diagnostic accuracy. Building upon this, the European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB) proposed a CEUS-adapted Bosniak classification in 2020, acknowledging the unique capabilities of CEUS in depicting enhancement patterns within cystic lesions [2, 3].

For solid renal masses, accurate characterization is crucial for determining appropriate management strategies. CEUS has demonstrated efficacy in differentiating benign from malignant lesions by assessing enhancement patterns, vascularity, and wash-in/wash-out kinetics. Studies have indicated that CEUS can distinguish between various subtypes of renal cell carcinoma and benign entities such as oncocytomas and angiomyolipomas, thereby potentially reducing unnecessary interventions [1, 5].

Despite its advantages, CEUS is not without limitations. The technique is operator-dependent and requires a learning curve for accurate interpretation. Factors such as patient body habitus and the presence of bowel gas can impede image acquisition. Additionally, while CEUS provides excellent resolution for superficial lesions, its efficacy may diminish with increasing lesion depth [1, 4, 5]. Therefore, a comprehensive understanding of both the capabilities and constraints of CEUS is essential for its optimal application in clinical practice.

This work encompasses a comprehensive review of the current literature, including scientific publications, guidelines, and expert recommendations pertinent to the application of CEUS in the characterisation of both cystic and solid kidney lesions. Additionally, we conducted a retrospective analysis of cases from our institution, examining imaging studies and patients' medical histories to assess the practical utility and outcomes associated with CEUS application.