What distinguishes a simple renal cyst from a polycystic kidney disease cyst on imaging?

• A. Simple cysts solitary or few, thin-walled, anechoic; PKD features multiple bilateral parenchymal cysts with family history
• B. PKD features single cyst with family history
• C. Simple cysts are multiple bilateral cysts
• D. Simple cysts occur in medulla

Answer: (A)

The main idea is that imaging distinguishes simple renal cysts from polycystic kidney disease by number and distribution of cysts and by location in the kidney.

Simple renal cysts are typically solitary or few in number, arise in the cortex, and appear as thin-walled, anechoic spaces with posterior acoustic enhancement and no internal septations or solid components. They’re usually incidental findings and don’t distort the overall renal shape.

Polycystic kidney disease cysts, in contrast, are numerous and involve both kidneys (multifocal and bilateral), filling the renal parenchyma and often enlarging the kidneys with loss of normal corticomedullary differentiation. The pattern is diffuse rather than solitary, and a positive family history supports the diagnosis.

So the option that matches: solitary or few simple cysts that are thin-walled and anechoic, versus PKD with multiple bilateral parenchymal cysts and family history. The other statements shift the number, bilaterality, or location away from the characteristic patterns.