RENAL CYSTS AND THE BOSNIAK CLASSIFICATION

RENAL CYSTS AND THE BOSNIAK CLASSIFICATION

Cysts are fluid filed sacs, enclosed by thin layers of tissues.

Certain cysts in human body are harmless and are the result of either ageing of an unknown origin like simple cortical cysts in kidneys and ovaries.

Simple renal cysts are benign in nature, that means these are not harmful or fatal and won’t require any sort of medical intervention.

However, some renal cysts and cystic diseases may require medical intervention due to their serious nature. These may include certain malignant tumors also which may need surgical approach and removal of the kidneys

Some examples of such renal cystic diseases are:

1.       Polycystic kidney disease: Both, Autosomal dominant and auto somal recessive.

2.    Medullary sponge kidney.

3.    Complex cortical cysts.

4.    Glomerulocystic kidney.

5.    Calcified cortical cyst, which may need further evaluation to see whether it is benign or malignant.

 Calcified cortical cysts appear as a result of a calcified area which represents an episode of a violent renal pathology like an impacted renal stone or glomerulonephritis. It may or may not be malignant and requires further diagnosis.

For an accurate diagnosis a classification has been layed down which is known as THE BOSNIAK CLASSIFICATION.  

         THE BOSNIAK CLASSIFICATION

According to this classification, the renal cysts are classified as per their radiological appearance and also the pathology and their nature(BENIGN OR MALIGNANT). This classification was laid down by Dr.Morton Bosniak at the New York Langone Medical centre.

Bosniak Grade 1: Simple cyst

          Appearance/Wall: Thin, Smooth and round or totally imperceptible wall

          Septum : No

          Nature: benign.

          Workup needed: NIL.

          Bosniak Grade 2: A minimal complex cyst

          Appearance/Wall: Non-Enhancing,Well rounded cysts <3 cm in size, with areas of calcifications or small segments of small thick calcification. A dense cyst projection itself out side the margin of kidneys by about 75%.

Septa: Few thin septa may be noted.

Nature: benign.

Workup needed: Nil.

                            

Bosniak 2F:

Appearance/Wall: Appearances of nodular or some irregular areas of calcification noted in the kidneys. The cysts may be located inside the kidneys and are usually larger in size by more than 3 cm.

Septa: Multiple thin septums or popularly called hairline septum(as thin as a hair), may be noted in the lesion.

Nature: Mostly benign, but may also be malignant(5%-10% chances of being malignant)

Workup needed: further workup may be required to find out whether the lesion is benign or malignant. The workup included diagnostic tests like Ultrasound and/or CT scan. However, there may seem to be no strict time bound frame.

Bosniak 3: INDETERMINATE CYSTS.

Appearance/Wall: Thick walls, Large sized cysts, with gross and big confluent patches of calcification.

Septa: Thick, Multiple, irregular and enhancing septa.

          Nature: 50 % chances of lesion being malignant.

          Workup: Partial nephrectomy/ Ablation therapy in case of aged or non compliant patients.

         

     Bosniak 4: Total Malignancy.

          Appearance/Wall: These are enhancing or enlarging or spreading cysts which grow in size containing soft tissue masses. But, there may also be solid components in the cysts.

          Septa: Septa may be independent but are adjacent to the soft tissues, and are multiple thick and largest in size.

          Nature: 100% malignant.

          Treatment: Renal transplant.