Photonephrology: Medullary Sponge Kidney Diagnosed by Unenhanced Magnetic Resonance Imaging

A 24-year-old man presented with fever and arthralgia. Systemic lupus erythematosus was diagnosed, and renal biopsy yielded a diagnosis of diffuse proliferative lupus nephritis. We found renal morphological abnormalities suggesting prominent nephrocalcinosis and multiple cysts by ultrasonography and computed tomography. Unenhanced magnetic resonance imaging combined with magnetic resonance urography revealed that the cystic lesions were concentrated at the corticomedullary junction and that they led to calyces. Since these findings suggested that the multiple cystic lesions were cystic ectasia of collecting ducts, we could diagnose his medullary sponge kidney (MSK). Intravenous pyelography didn’t provide sufficient information because the contrast was poor.