A renal cyst with calcific mural nodule

Findings on sonography:

Multiple cysts (2 in number) of the left kidney are present. 

There's also a simple hepatic cyst of the left lobe. 

Left lower pole renal cyst of 3 cms with calcific mural nodule seen on ultrasound imaging.

Calcification of the mural nodule can be a sign of a potentially malignant cyst. 

Color Doppler ultrasound shows no vascularity within the cyst.

A left lobe of liver simple cyst also seen, which is typically benign and may not require treatment.

Analysis of the cyst:

Left renal complex cyst:

Presence of a calcific nodule within the cyst is concerning, as it can be a sign of a potentially malignant lesion.

The size of the cyst is also an important factor to consider, as larger cysts are more likely to harbor malignancy. In this case, the cyst measures 3 cm, which is a moderate size that warrants further evaluation.

The shape and borders of the cyst are also important to evaluate. A cyst with irregular borders or a complex internal structure may be more concerning for malignancy. Additionally, the presence of any solid components within the cyst, such as the calcific nodule in this case, can increase the risk of malignancy.

Further imaging studies such as CT or MRI may be recommended to better characterize the cyst and determine the optimal management strategy.

How to classify this renal cyst:

The Bosniak classification system is the most commonly used ultrasound classification system for renal cysts. It was developed by Dr. Morton Bosniak in 1986 and later revised in 2019. It divides renal cysts into different grades based on their complexity, risk of malignancy, and the need for follow-up.

The Bosniak classification system includes the following grades:

Bosniak I cysts: Simple cysts with a thin, smooth wall and no septations, calcifications, or solid components. They have a negligible risk of malignancy and do not require follow-up.

Bosniak II cysts: Cysts with a few thin septations, calcifications, or a slightly thicker wall. They have a low risk of malignancy and may require follow-up imaging.

Bosniak IIF cysts: Cysts with thicker septations, multiple septa, and/or calcifications. They have an intermediate risk of malignancy and usually require follow-up imaging.

Bosniak III cysts: Cysts with thick, irregular septations, nodularity, or a solid component. They have a high risk of malignancy and should be surgically removed or biopsied.

Bosniak IV cysts: Cysts with a clearly defined solid component or masses with enhancing solid components. These cysts have a high risk of malignancy and should be surgically removed or biopsied.

What is the Bosniak grade for this complex cyst?

The renal cyst in this case could be classified as Bosniak II cyst. This is because it has a small mural calcific nodule, which is considered a feature that slightly increases the complexity of the cyst, but not enough to classify it as a Bosniak III cyst. A Bosniak II cyst has a low risk of malignancy, but may require follow-up imaging.

The 2nd simple left renal cyst is a Bosniak grade I.

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Sonography of renal complex cysts