In 1986, based on CT findings, Bosniak divided the renal cystic mass into four levels:
Grade I - simple cyst, benign.
CT findings: 1 type of round, no wall; 2 uniform water sample density (CT value 0 ~ 20HU); 3 clear boundary, smooth and sharp edges; 4 enhanced scanning without enhancement.
Grade II - minor complex cysts, benign (including compartmentalized cysts, tiny calcified cysts, infectious cysts, high density cysts).
CT performance: 1 The wall of the capsule is thin and uniform with less separation (<2) and fine (<1 mm) and regular. 2 The wall or partition may have fine calcification. 3 The wall or partition may be slightly strengthened.
Grade III - more complex cysts, uncertainty, including benign and malignant (eg, multi-sac cystic nephroma, complex compartmental cysts, chronic infectious cysts, calcified cysts; cystic kidney cancer).
CT performance: 1 wall or separation thickness (> 1mm) and irregular. 2 separate increases (≥ 3). 3 The wall or partition may have calcification, more calcification, and the capsule wall may have smaller solid components. 4 separation or wall reinforcement is obvious. 5 part is benign lesion
Grade IV - a clear malignant cystic mass, mainly cystic kidney cancer.
CT findings: 1 has the characteristics of a grade III cyst. 2 adjacent to the wall or separated by separate soft tissue components.
Grades I and II are benign, no surgery and follow-up are required, and grade III and IV require surgical resection.
Grade I and IV CT are relatively specific and easy to diagnose, but some lesions cannot be accurately classified as grade II or grade III. To this end, in 1993, Bosniak proposed a diagnostic criteria for CT in grade IIF (F-fallow up follow-up) for moderately complex cysts: 1 uniform wall thickness and uniform thickening. 2 increased calcification. 3 The wall and partition can be slightly strengthened. 4 High-density cysts ≥ 3 cm in diameter and completely within the renal parenchyma. That is, the lesion has some features of grade II and grade III, but does not meet the diagnostic criteria of grade II and grade III, and needs to be followed up to clarify its biological behavior.
so, u need regularly follow-up.