Solution: Pyelitis cystica (ureteritis cystica) is a condition related to chronic irritation of the urinary collecting system, most frequently stone or infection. The filling defects identified on the retrograde pyelogram represent multiple small epithelial-lined cysts that are cystic degeneration of epithelial cell nests within lamina propria. Usually seen in older women and often persists even after the clearance of the underlying irritant, but is not generally symptomatic in and of itself.