Differential Diagnosis

The provided imaging findings suggest a range of possible diagnoses for the renal lesions and other observed conditions. Here's a categorized differential diagnosis based on the information given:

• Single Most Likely Diagnosis
  • Renal cysts for the bilateral renal cortical hypodensities (too small to characterize) and the left upper pole hyperdense renal cortical lesion. This is because simple cysts are very common in the kidneys, especially as people age, and can vary in density due to the presence of proteinaceous material.
  • Degenerative changes in the spine and hip joints are likely due to osteoarthritis, given the age-related nature of these findings.
• Other Likely Diagnoses
  • For the 13 mm peripherally calcified lesion in the lower pole of the right kidney, a possible diagnosis could be a calcified renal cyst or a benign renal tumor like an oncocytoma. The peripheral calcification pattern can be seen in various benign conditions.
  • The hyperdense focal lesion in the upper pole of the left kidney could also represent a hemorrhagic cyst or a renal abscess, although the latter would typically present with more clinical symptoms and signs of infection.
• Do Not Miss Diagnoses
  • Renal Cell Carcinoma (RCC): Although less likely given the small size and characteristics of the lesions, RCC is a critical diagnosis not to miss. The presence of a solid component, especially in the context of the hyperdense lesion, warrants consideration of RCC.
  • Infectious or Inflammatory Conditions: While the imaging does not strongly suggest an infectious process, conditions like pyelonephritis or renal abscess could present with similar findings, especially if the patient has symptoms like fever or flank pain.
• Rare Diagnoses
  • Angiomyolipoma (AML): This benign renal tumor could present as a hyperdense lesion due to its fatty content. However, AMLs are less common and typically have a more characteristic appearance on imaging with a significant fat component.
  • Metastatic Disease: Although rare without a known primary malignancy, metastases to the kidney can occur and might present as multiple small lesions. This would be less likely without other clinical evidence of cancer.

Next Steps

Given the differential diagnoses, the next steps could include:

• Correlating the findings with any prior imaging to assess for stability or change in the lesions.
• Consideration of ultrasound or MRI for further characterization of the renal lesions, especially if there's a high suspicion of malignancy or if the lesions are changing in size.
• Clinical evaluation for symptoms that might suggest malignancy, infection, or other conditions that could guide further diagnostic testing or management.
• Discussion of the findings and the differential diagnosis with a radiologist or a specialist (nephrologist or urologist) for guidance on the most appropriate next steps, which might include watchful waiting, biopsy, or surgical intervention, depending on the suspected diagnosis and the patient's overall clinical context.