Is a renal cyst dangerous in an adult with no prior history of kidney disease?

Is a Renal Cyst Dangerous?

A simple renal cyst in an adult with no prior kidney disease is not dangerous and requires no treatment or routine follow-up. 1, 2

Simple Cysts Are Benign and Extremely Common

• Simple renal cysts (Bosniak class I and II) affect approximately 50% of individuals older than 50 years and are acquired, sporadic lesions—not hereditary. 1, 2
• These cysts are not associated with end-stage renal disease and have no clinical significance when asymptomatic. 2, 3
• The American College of Radiology explicitly states that asymptomatic simple cysts require no further evaluation or follow-up. 1

When to Be Concerned: Red Flags Requiring Further Evaluation

While simple cysts are benign, certain features warrant additional investigation:

Complex Cyst Features (Potential Malignancy Risk)

• Septations, calcifications, internal echoes, or irregular walls require further characterization with CT or MRI, as these may indicate malignancy risk and potentially require excision. 1, 4
• Ultrasound is first-line for characterization, but CT or MRI is needed when complexity is detected to distinguish hemorrhagic cysts from malignant tumors. 1

Multiple Cysts or Family History (Hereditary Disease)

• Multiple kidney cysts are highly suggestive of autosomal dominant polycystic kidney disease (ADPKD) or another cystic nephropathy and require clinical work-up. 5, 1
• In hereditary polycystic kidney disease, cysts do not resolve and progressively increase in number and size, eventually leading to chronic kidney disease. 4
• A positive family history of ADPKD should prompt evaluation, as penetrance approaches 100% if patients live long enough. 5

Pediatric Population (Different Rules Apply)

• Simple cysts are rare in children, so any solitary cyst requires follow-up imaging to exclude ADPKD. 5, 1
• Multiple cysts in childhood are highly suggestive of ADPKD or another cystic nephropathy and mandate clinical work-up. 5, 1

Symptomatic Cysts: When Intervention May Be Needed

• While most cysts remain asymptomatic, some may cause pain, collecting system compression, hematuria, hypertension, or secondary infection—in these cases, treatment may be indicated. 6
• The mere presence of a cyst is not an indication for intervention; symptoms or secondary obstruction drive treatment decisions. 6

Special Populations: When Surveillance May Be Appropriate

• In patients with prior history of kidney stones, obstruction, frequent urinary tract infections, or family history of ADPKD, ultrasound surveillance may be indicated. 1, 4
• However, in patients with kidney disease, hypertension, or diabetes, routine ultrasound surveillance of simple cysts has minimal impact on diagnosis and management. 1, 4

Common Pitfalls to Avoid

• Do not confuse simple cysts with acquired cystic disease (ACD), which occurs exclusively in end-stage renal disease and dialysis patients and carries increased malignancy risk. 2, 4, 3
• Do not assume all cysts are simple—complex features on imaging require further evaluation to exclude malignancy. 1, 4
• Do not over-surveil simple cysts—repeated imaging in asymptomatic patients with confirmed simple cysts provides no clinical benefit. 1