Bosniak developed a classification of complicated (complex) cystic lesions of the kidney. This can help determine the appropriate management strategy for the patient. The author is from the New York University Medical Center in New York City.
A complicated (complex) renal cyst is one that is not simple, i.e. one or more of the following is present:
(1) calcifications
(2) septations
(3) thick, proteinaceous fluid (higher attenuation than clear fluid)
(4) thick-walled
(5) irregularly shaped
(6) hyperdense
Findings on Imaging Studies
Category
simple cyst with a thin, smooth wall; no enhancement
I
one or more septations that are very thin; fine calcifications; may be hyperdense; minimal internal echoes
II
multiple septations that are thin; extensive thin calcifications; thicker wall than II; no enhancement
III
solid elements that enhance with contrast media; thick walled; numerous thick calcifications
IV
Category I lesions are simple renal cysts.
Category IV lesions are considered clearly malignant and are handled accordingly.
Category III lesions are indeterminate with features of both benign and malignant lesions.
Category
Management
I
none
II
follow with ultrasound or CT
III
explore
IV
explore or perform radical nephrectomy
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