From the Guidelines
For a right renal cyst detected on ultrasound, the most appropriate workup includes a contrast-enhanced CT scan of the abdomen and pelvis to better characterize the cyst, as recommended by the European Association of Urology guidelines on renal cell carcinoma, updated in 2022 1. The workup for a right renal cyst should prioritize the use of imaging modalities that can accurately characterize the cyst and assess its potential for malignancy.
- The Bosniak classification, updated in 2019, is a useful tool for categorizing renal cystic masses based on their diagnostic criteria on CT or MRI, and can predict the risk of malignancy 1.
- A contrast-enhanced CT scan is the preferred initial imaging modality for characterizing renal masses, including cysts, as it provides better resolution than ultrasound and can detect solid components or enhancement that may suggest a more serious condition 1.
- Additional steps in the workup may include urinalysis and urine cytology to rule out associated urinary tract issues, and serum creatinine test to assess kidney function 1.
- If the CT scan confirms a simple cyst (Bosniak category I), no further action is usually needed beyond periodic monitoring, but if the cyst has complex features, additional steps may include MRI of the kidneys for more detailed imaging, and consultation with a urologist for potential biopsy or surgical intervention 1. The use of contrast-enhanced ultrasound (CEUS) may also be considered, particularly in cases where CT or MRI is not feasible, as it has been shown to be more sensitive than contrast-enhanced CT in characterizing cystic renal masses 1. However, the most recent and highest quality study, the European Association of Urology guidelines on renal cell carcinoma, updated in 2022, recommends the use of CT or MRI for characterizing renal masses, including cysts 1. Therefore, a contrast-enhanced CT scan of the abdomen and pelvis is the most appropriate initial imaging modality for characterizing a right renal cyst detected on ultrasound.
From the Research
Diagnostic Approach
The diagnostic approach for a right renal cyst detected on ultrasound (US) involves further imaging modalities to differentiate between benign and malignant entities.
- The majority of incidental renal masses are simple cysts that can be easily diagnosed by conventional ultrasonography 2.
- However, some incidental renal masses are not simple cysts, and differentiation between benign and malignant entities requires further imaging modalities such as contrast-enhanced ultrasonography (CEUS), computed tomography (CT), and magnetic resonance imaging (MRI) 2, 3, 4.
Role of Contrast-Enhanced Ultrasonography
CEUS has been proven to be a useful imaging modality to characterize complex renal cysts using the Bosniak classification in a similar way as CT 3.
- CEUS helps not only in the characterization of complex cysts detected on baseline US but also in the characterization of indeterminate cystic lesions on CT or MRI 3.
- The diagnostic accuracy of CEUS in the characterization of complex renal cysts is comparable to that of CT and MRI, and several studies have demonstrated its reliability also in identifying solid lesions such as pseudotumors, typical angiomyolipomas, and clear cell renal carcinomas 2, 4.
Bosniak Classification
The Bosniak classification is used to classify renal cysts into 5 different categories and is used for decisions of further clinical treatment 5.
- This classification was developed for CT and has been adopted for MRI as well as CEUS 5.
Importance of Further Evaluation
It is essential to recognize that renal cell carcinoma (RCC) may occur in what appears to be a simple renal cyst based on imaging results 6.
- Biochemical analysis of the cystic fluid may help identify the presence of malignancy 6.