Management of Renal Cysts

For asymptomatic simple renal cysts, no intervention or routine follow-up imaging is necessary, regardless of size. 1, 2

Classification and Diagnosis

Renal cysts should be classified using the Bosniak classification system, which predicts malignancy risk: Bosniak I and II (simple cysts) have ~0% risk, Bosniak IIF ~10% risk, Bosniak III ~50% risk, and Bosniak IV ~100% risk 1, 2
Simple renal cysts are characterized by well-defined margins, absence of internal echoes on ultrasound, and no contrast enhancement on CT or MRI 1, 2
Ultrasonography is the preferred initial imaging modality for detecting and monitoring renal cysts due to its non-invasive nature, lack of radiation, and cost-effectiveness 3
MRI is more sensitive than ultrasonography for detecting kidney cysts, particularly in adults and teenage children, but is not the first-line diagnostic method due to cost and potential need for sedation in young children 3

No intervention required for asymptomatic simple renal cysts 1, 2
No routine follow-up imaging necessary for confirmed Bosniak I and II cysts 1, 4
Treatment success is defined by symptom relief rather than volume reduction 2

Active surveillance with repeat imaging in 6-12 months is recommended 1, 5
CT or MRI with and without contrast is preferred for follow-up imaging 1, 6
Radiographic surveillance is an effective management approach, with surgical intervention only if concerning changes develop 5

Intervention is recommended when anticipated oncologic benefits outweigh risks 1
Nephron-sparing approaches should be prioritized, especially in patients with solitary kidney, bilateral tumors, or preexisting chronic kidney disease 1

For symptomatic simple cysts, percutaneous aspiration with ethanol sclerotherapy is an effective first-line treatment 7
Single-session ethanol sclerotherapy has shown complete cyst disappearance in 22% of cases and symptom resolution in 75% of symptomatic patients 7
Laparoscopic cyst decortication may be considered for symptomatic cysts that fail aspiration and sclerotherapy 1

Changes in cyst characteristics during surveillance (development of internal septations, wall thickening, solid components, calcifications, or irregular enhancement) warrant further investigation due to increased risk of malignancy 2, 8
Complicated variations of simple renal cysts should prompt immediate evaluation, as they may indicate malignant transformation 8
For confirmed benign renal masses, patients should undergo occasional clinical evaluation and laboratory testing but do not require routine periodic imaging 1

A solitary cyst in childhood requires follow-up imaging, as it may be a sign of ADPKD in children with a positive family history 3, 2
In children under 15 years with a positive family history of ADPKD, sonographic detection of one or more kidney cysts is highly suggestive of ADPKD 3
Multiple kidney cysts in childhood are highly suggestive of ADPKD or another cystic nephropathy and should be investigated 3

In patients with TSC, kidney cysts are usually asymptomatic 3
For TSC patients, MRI is the preferred modality for detecting and monitoring kidney lesions 3
Imaging follow-up of the kidneys should be performed at intervals of 1-3 years in patients with TSC 3

Core biopsies are not recommended for cystic renal masses due to low diagnostic yield unless areas with a solid pattern are present 1, 2
Never assume a nondiagnostic biopsy indicates benignity 2
Contrast-enhanced ultrasound can be valuable for characterizing cystic renal lesions and guiding interventional procedures 6