How would polycystic kidney disease typically appear on a radiograph after the injection of an iodinated contrast agent?

Polycystic kidney disease (PKD) is characterized by the presence of numerous fluid-filled cysts that replace normal kidney tissue. When iodinated contrast is administered and a radiograph is taken, the cysts within the kidneys typically appear as multiple radiolucencies, or dark areas, on the image.

These radiolucencies indicate regions where the contrast agent cannot penetrate due to the cysts being filled with fluid, which does not absorb the x-rays in the same way as the surrounding renal tissue. This gives the radiograph a distinctive appearance where the healthy renal cortex is interspersed with these lighter areas, resulting from the fluid-filled cysts.

In contrast, solid masses in the renal pelvis, homogeneous density across the kidneys, or a single enlarged renal mass would not adequately represent the cystic nature of PKD and would suggest other conditions that do not correlate with the typical findings associated with polycystic kidney disease. The correct identification of these features is essential in differentiating PKD from other renal pathologies during imaging studies.