Figure 4d. Caliceal diverticulum with calculi in a 64-year-old man. (a, b) Axial unenhanced (a) and nephrographic-phase (b) CT scans demonstrate calculi (arrowhead) layering in a fluid collection (black arrow in b) at the lower pole of the left kidney. An inferior vena cava filter (white arrow) is incidentally noted. (c, d) Axial excretory-phase CT scans demonstrate contrast material excretion into a portion of the fluid collection (arrow), a finding that represents a caliceal diverticulum. An unenhanced fluid-attenuation mass representing a cyst is seen adjacent to the diverticulum (arrowhead in d). (e) Excretory-phase MIP image demonstrates the caliceal diverticulum (arrow).