"Tram-line" Calcifications in Granulomatosis with Polyangiitis

Nephrocalcinosis consists of deposition of calcium in the renal parenchyma. Renal cortical calcification is a rare entity in comparison to calcium deposits in the medulla and is seen only in a handful of pathologies with corresponding characteristic patterns on imaging. Thin linear calcifications may get deposited in the peripheral renal cortex suggestive of cortical necrosis due to a vascular insult (vasculitis), and rarely due to glomerulonephritis. This pattern of calcification has also been referred to as the "tramline" or "railroad track" sign.