From the Research
A 1.8x1.7x2 cm kidney cyst should be followed up with a repeat ultrasound in 6-12 months, as recommended by the most recent and highest quality study 1. This recommendation applies to simple renal cysts that show typical benign characteristics on imaging (well-defined, thin-walled, fluid-filled without internal echoes). Some key points to consider when evaluating kidney cysts include:
- The Bosniak classification system, which provides a useful way to classify cystic masses 1
- The use of multimodal imaging, including ultrasound, CT, and MRI, to characterize renal cysts 2, 1
- The importance of follow-up imaging to monitor for changes in cyst size or appearance, which may indicate the development of cystic renal cell carcinomas If the cyst remains stable in size and appearance after the initial follow-up, subsequent imaging can be extended to every 2-3 years. However, if the cyst shows any concerning features such as irregular walls, solid components, or calcifications, or if it grows significantly (more than 0.5 cm per year), earlier follow-up with contrast-enhanced imaging like CT or MRI may be warranted within 3-6 months. The follow-up schedule is based on the low but present risk that some cysts may represent or develop into cystic renal cell carcinomas, as discussed in the literature 3, 1. Most simple renal cysts under 3 cm are benign and remain stable or grow very slowly, which is why conservative monitoring is appropriate in most cases rather than immediate intervention.