(a)

(b)

Figure 2: A 34-year-old male presenting with left flank pain. Axial dual energy noncontrast CT. (a) shows a 3 mm calculus in the left renal pelvis on iodine and (b) water-based attenuation. As the calculus is visible on both imaging techniques, this indicates high-molecular-weight elements. This calculus proved to be predominantly calcium based.