Management of Simple Renal Cysts

Diagnosis and Classification

Simple renal cysts are characterized by specific imaging criteria, including well-defined margins, absence of internal echoes on ultrasound, and no contrast enhancement on CT or MRI, as recommended by the European Urology guidelines 1, 2, 3, 4
The Bosniak classification system is used to categorize renal cystic masses based on CT or MRI findings, distinguishing five categories that predict malignancy risk, with Bosniak I and II having ~0% malignancy risk, Bosniak IIF having ~10% malignancy risk, Bosniak III having ~50% malignancy risk, and Bosniak IV having ~100% malignancy risk, according to the European Urology guidelines 3, 4

No follow-up is recommended for asymptomatic simple renal cysts regardless of size, as stated by the Journal of Hepatology guidelines 1
Treatment success is defined by symptom relief rather than volume reduction, as defined by the Journal of Hepatology guidelines 1

Changes in the characteristics of a simple renal cyst during surveillance, such as development of internal septations, wall thickening, solid components, calcifications, or irregular enhancement, warrant further investigation with CT or MRI due to risk of malignancy, as recommended by the Journal of the American College of Radiology and European Urology guidelines 1, 3, 5
Simple renal cysts may be associated with hypertension, particularly when multiple cysts are present, as noted by the Nature Reviews Nephrology guidelines 2

A solitary cyst in childhood requires follow-up imaging as it may be a sign of ADPKD in children with a positive family history, as recommended by the Nature Reviews Nephrology guidelines 2
Core biopsies are not recommended for cystic renal masses due to their low diagnostic yield unless areas with a solid pattern are present, as stated by the European Urology guidelines 3
Never assume a nondiagnostic biopsy indicates benignity, as warned by the Journal of the American College of Radiology guidelines 5