Management of Asymptomatic Simple Renal Cysts
No intervention or follow-up imaging is required for asymptomatic simple renal cysts measuring 2 cm, 1.4 cm, and 1.2 cm in an adult without symptoms or complications. 1, 2
Diagnostic Confirmation
Simple renal cysts are extremely common, occurring in nearly one-third of patients over 50 years of age, and the vast majority (two-thirds) measure 2 cm or less in diameter. 3 Your cysts fall squarely within this benign category.
Key imaging characteristics that confirm these are simple cysts:
- Well-defined margins with no internal echoes on ultrasound 1
- Homogeneous attenuation <20 HU on unenhanced CT (if performed) 1
- No contrast enhancement 1
- Bosniak category I classification 3, 4
Management Algorithm
For asymptomatic simple cysts (Bosniak I):
- No treatment required 1, 2, 3
- No surveillance imaging needed 2, 3
- No risk of malignant transformation when truly simple 3
The malignancy risk for Bosniak I simple cysts is essentially 0%. 1
When to Reconsider This Approach
Intervention becomes necessary only if the patient develops:
- Flank pain or abdominal discomfort attributable to the cyst 2, 4
- Hematuria 2
- Hypertension potentially related to segmental renal ischemia from cyst compression 3
- Urinary obstruction from caliceal or pelvic compression 3
- Cyst infection or hemorrhage 4
Follow-up imaging is warranted only if:
- The cyst shape appears irregular or complex on initial imaging, requiring reclassification to exclude Bosniak IIF or higher categories 2, 5
- New symptoms develop 2
Critical Pitfalls to Avoid
Do not confuse simple cysts with complex cysts. If the initial imaging showed any of the following features, the cyst would require further characterization with multiphase contrast-enhanced CT or MRI: 1
- Septations or wall thickening 1
- Calcifications 1
- Any enhancement >10-15 HU on CT or >15% on MRI 1
- Solid components 1
Do not perform routine surveillance imaging on confirmed simple cysts. While one study reported malignant transformation in cysts that developed "complicated variations" during surveillance 5, this applies only to cysts that change character and become complex—not to stable simple cysts. The American College of Radiology guidelines are clear that simple cysts require no follow-up. 1
If initial imaging was ultrasound only and there is any uncertainty about cyst complexity, consider obtaining a single baseline multiphase contrast-enhanced CT or MRI to definitively classify the cysts using Bosniak criteria. 1 Once confirmed as Bosniak I, no further imaging is needed unless symptoms develop.