II. Epidemiology
- Renal Cysts are present in one third of older adults (Incidence increases with age)
III. Classification: Bosniak Classification
- Category I: Benign Simple Cyst
- No monitoring needed
- Category II: Benign cystic lesion with some complex features
- No monitoring needed
- Category IIF: Nonenhancing complex cysts >3 cm
- Malignancy risk: 5-10%
- Follow with serial imaging
- Category III: Enhancing complex cysts
- Malignancy risk: 50%
- Surgical resection
- Category IV: Malignant cystic mass
- Surgical resection
IV. Evaluation
- Simple Renal Cysts
- Benign in most cases
- Complex cysts
- Complex cysts (especially with enhancement on imaging) have increased malignant potential
- Surgical resection for Category III and Category IV lesions
V. Labs: Biopsy indications
- Suspected abscess
- Suspected Lymphoma
- Suspected metastatic lesions
VI. Management
- Simple cysts (Category I and II) require no additional evaluation
- Fat containing solid lesions consistent with benign angiomyolipoma may be followed or biopsied
- Category IIF lesions should be followed
- Suspicious Renal Masses are resected surgically instead of biopsied (due to biopsy sampling error risk)