Table 1.

The Bosniak renal cyst classification [10]

Stage	Cyst wall	Septa	Calcification	Enhancement	Management
I	Hairline thin	No	No	No	No follow-up
II	Minimal regular thickening	Few, hairline thin	Smooth, hairline thin	No	No follow-up
IIFa	Minimal regular thickening	Multiple, minimal smooth thickening	Thick, nodular	No	CT: 3, 6, 12 monthly then annual
IIIb	Irregular thickening	Measurably thick, irregular	Thick, nodular, irregular	Yes	As IIF or surgical
IV	Gross, irregular thickening	Irregular gross thickening	Thick, nodular, irregular	Yes, tissue and cyst	Surgical

^aIIF F denotes follow-up. Cyst size of diameter of 3 cm is also an indication for follow-up.

^bIII: indeterminate Stage III should be managed as IIF, while definitive Stage III should be managed surgically [6].