Differential Diagnosis for Hyperintense Lesions within Bilateral Kidneys on MRI without Contrast

Single Most Likely Diagnosis

• Simple Renal Cysts: The most common benign renal lesion, simple cysts are fluid-filled and would appear hyperintense on T2-weighted MRI images due to their fluid content. They are often bilateral and can be found in a significant portion of the adult population, increasing in frequency with age.

Other Likely Diagnoses

• Polycystic Kidney Disease (PKD): An inherited disorder characterized by the growth of numerous cysts filled with fluid in the kidneys, which can impair their ability to filter waste products from the blood. PKD would show multiple hyperintense lesions on MRI due to the cysts.
• Hydronephrosis: A condition where one or both kidneys become swollen due to the accumulation of urine, often caused by an obstruction in the urinary tract. While not typically described as "lesions," hydronephrosis can cause the renal pelvis to appear hyperintense on T2-weighted images due to the urine accumulation.
• Renal Lymphangiectasia: A rare condition but more likely than some other diagnoses, characterized by the ectatic dilation of renal lymphatic vessels, which can appear as hyperintense lesions on MRI.

Do Not Miss Diagnoses

• Renal Cell Carcinoma with Cystic Components: Although less likely, it's crucial not to miss malignant diagnoses. Some renal cell carcinomas can have cystic components that appear hyperintense on T2-weighted MRI images.
• Infectious or Inflammatory Conditions (e.g., Pyelonephritis, Abscesses): These conditions can cause areas of hyperintensity on MRI due to inflammation or fluid collection and are critical to diagnose promptly due to their potential for serious complications.

Rare Diagnoses

• Renal Angiomyolipoma with Minimal Fat: Typically, angiomyolipomas have a significant fat component, making them identifiable on MRI. However, some may have minimal fat and could potentially appear hyperintense on T2-weighted images, although this is less common.
• Multicystic Dysplastic Kidney (in adults): More commonly diagnosed in children, this condition involves the development of multiple cysts in a non-functioning kidney. While rare in adults, it could be considered in the differential diagnosis for bilateral hyperintense renal lesions.
• Lymphoma or Metastases Involving the Kidneys: Although less common, lymphoma or metastatic disease to the kidneys can cause multiple lesions that might appear hyperintense on T2-weighted MRI images.