From the Guidelines
Hemorrhagic or proteinaceous renal cysts can be present and are characterized by homogeneous high T1 signal intensity lesions with smooth borders and a lesion to renal parenchyma signal intensity ratio of >1.6 on MRI.
Characteristics of Hemorrhagic or Proteinaceous Cysts
- Homogeneous high T1 signal intensity lesions
- Smooth borders
- Lesion to renal parenchyma signal intensity ratio of >1.6 These characteristics can help differentiate them from renal cell carcinoma (RCC) 1.
Diagnostic Approaches
- MRI without and with IV contrast is optimal for renal lesion characterization
- MRI without IV contrast can also provide diagnostic information, such as characterizing simple cystic lesions or those with thin septations on noncontrast T2-weighted imaging
- Diffusion-weighted imaging and specialized MRI sequences, like arterial spin labeling, may also be used to characterize renal lesions 1.
Classification and Management
- The Bosniak classification system is used to distinguish five categories of renal cystic masses based on CT or MRI diagnostic criteria, predicting the risk of malignancy and guiding management 1.
- Bosniak III cysts have a 10% risk of malignancy, and cautious surveillance is a reasonable alternative to primary surgery, as many of these lesions have low malignant potential 1.
From the Research
Presence of Hemorrhagic or Proteinaceous Renal Cysts
- Hemorrhagic renal cysts are present, as evidenced by a case report of a 73-year-old male with a right renal cyst containing echogenic debris consistent with a hemorrhagic cyst 2.
- Proteinaceous renal cysts are also present, with a study reporting that most hyperattenuating renal masses are benign hemorrhagic or proteinaceous cysts 3.
- A case report of a 21-year-old patient with a spontaneous rupture of a simple renal cyst complicated by hemorrhagic shock also supports the presence of hemorrhagic renal cysts 4.
- The high protein concentration in a renal cyst can cause high attenuation values on computed tomography, making it a cause of CT hyperdense benign renal cysts 5.
- A retrospective analysis of 204 patients found that T1-weighted lesion-to-muscle signal-intensity ratio can be used to distinguish between hemorrhagic cysts and renal cell carcinomas, with a optimal cutoff value of 1.39 6.
Characteristics of Hemorrhagic and Proteinaceous Renal Cysts
- Hemorrhagic renal cysts often have irregular borders and echogenic material within their walls and within the cyst 2.
- Proteinaceous renal cysts can have high attenuation values on computed tomography due to the high protein concentration 5.
- Hemorrhagic cysts can be distinguished from malignant tumors using computed tomography or magnetic resonance imaging 2, 6.
- The presence of internal echoes, septations, or calcifications can indicate a complex renal cyst, which may be hemorrhagic or infected 2.