To differentiate between focal and multifocal renal cystic disease, understanding the physiopathology and imaging features of each entity. To describe ultrasound (US) and computed tomography (CT) findings of cystic renal lesions. To review the Bosniak´s classification in order to categorize renal cystic disease.

Cystic renal lesions are a common finding in abdominal imaging. Is essential for the radiologist to interpret properly their features with different techniques, in order to ensure adequate patient´s management. Different imaging techniques are used to evaluate cystic renal lesions: US, CT and magnetic resonance (MR). US has a high sensibility value in determining whether a detected cyst is simple or complicated, in which case, CT or MR imaging is required for further evaluation. Bosniak´s classification categorizes each cystic renal lesion into five categories (I,...

US findings: Simple cyst: Anechoic, well- marginated lesion, with imperceptible wall, round-ovoid and with posterior acoustic enhancement. Hemorrhagic cyst: Cystic lesion with internal echoes (clot). Thick calcified wall and/or multiloculated appearance due to chronic changes. Infected cyst: Cystic lesion with thick wall and scattered internal echoes. It may contain debris-fluid level. Neoplastic cystic lesion: Cystic lesion with mural nodules and solid components with blood-flow in color Doppler ultrasound. CT findings: In order to classify a renal cystic lesion, applying the Bosniak´s system, we have to...

Understanding the correlation between the pathophysiology and imaging findings of focal and multifocal cystic renal disease, the radiologist can describe and categorize the wide range of entities that can manifest as cystic renal masses. Therefore more precise diagnosis can be made improving patients management.

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