Renal cyst

Renal cysts are composed of enclosed liquid/semisolid fluid and are commonly identified on abdominal imaging.

• M/C lesion of the kidney (present in 40% population)

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Classification

Bosniak renal cyst classification system:

Consists of four categories based on triphasic CT findings, ranging from simple to complex cysts

Sonographic criteria:

• Simple renal cysts (SRC): When all of the criteria are met, the cyst is benign and no follow-up is required.
  1. Absence of internal echoes
  2. Posterior enhancement
  3. Round/oval shape
  4. Sharp, thin posterior walls
• Complex renal cysts: When cysts do not meet the rigid characteristics of the “simple” definition

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Clinical features

Simple renal cysts (SRCs):

2-4% may become symptomatic

• Abdominal pain or hematuria (owing to increasing size or complications like infection, hemorrhage, or rupture)

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Management

• Category I and II renal cysts: No further imaging or follow-up required
• Category IIF (~5% malignant risk): Follow-up by imaging
• Category III (50% malignant risk) and category IV (75-90% malignant risk): Surgical excision recommended
• Large, SRCs:
  • Aspiration & sclerotherapy
  • Laparoscopic surgery

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