What is the treatment for a simple renal cyst?

Management of Simple Renal Cysts

For simple renal cysts, observation is the recommended management approach as they typically follow an indolent course without requiring intervention unless symptoms develop. 1

Diagnosis and Classification

• Simple renal cysts are characterized by specific imaging criteria including:

  • Well-defined margins
  • Absence of internal echoes on ultrasound
  • No contrast enhancement on CT or MRI 1

• The Bosniak classification system (updated in 2019) is used to categorize renal cystic masses based on CT or MRI findings, distinguishing five categories that predict malignancy risk 1:

  • Bosniak I and II: ~0% malignancy risk
  • Bosniak IIF: ~10% malignancy risk
  • Bosniak III: ~50% malignancy risk
  • Bosniak IV: ~100% malignancy risk 1

Management Approach

Asymptomatic Simple Renal Cysts

• No follow-up is recommended for asymptomatic simple renal cysts regardless of size 1
• Treatment success is defined by symptom relief rather than volume reduction 1

Symptomatic Simple Renal Cysts

• Ultrasound should be the first diagnostic modality used when symptoms occur 1

• Common symptoms that may warrant intervention include:

  • Renal pain
  • Hypertension (particularly with large cysts)
  • Hematuria 2

• Treatment options for symptomatic simple renal cysts include:

  1. Percutaneous aspiration with ethanol sclerotherapy

     • Success rates of complete or partial cyst ablation exceed 90%
     • Low complication rates (minor hematuria, low-grade fever)
     • Resolution of pain in most patients 2

  2. Surgical options (when sclerotherapy fails):

     • Laparoscopic cyst decortication
     • Open surgical removal (rarely needed) 2

Special Considerations

Complicated Variations of Simple Renal Cysts

• Any change in the characteristics of a simple renal cyst during surveillance warrants further investigation with CT or MRI due to risk of malignancy 3
• Changes of concern include:
  • Development of internal septations
  • Wall thickening
  • Solid components
  • Calcifications
  • Irregular enhancement 1, 3

Hypertension and Simple Renal Cysts

• Simple renal cysts may be associated with hypertension, particularly when:
  • Located on both kidneys (bilateral)
  • Multiple cysts are present (two or more)
  • Cysts are larger than 1 cm in diameter 4
  • Large cysts may cause hypertension through compression of renal tissue and activation of the renin-angiotensin system 5

Monitoring

• For simple renal cysts that have been treated, routine follow-up imaging is not recommended as treatment success is defined by symptom relief 1
• If imaging is performed post-treatment, CT or MRI allows for good estimation of remnant cyst volume 1

Cautions and Pitfalls

• A solitary cyst in childhood requires follow-up imaging as it may be a sign of ADPKD in children with a positive family history 1
• Core biopsies are not recommended for cystic renal masses due to their low diagnostic yield unless areas with a solid pattern are present (Bosniak IV cysts) 1
• Never assume a nondiagnostic biopsy indicates benignity 1
• Be vigilant for complicated variations of simple cysts during surveillance, as these have a high probability of malignancy 3