Pyelitis, ureteritis and cystitis cystica is a condition characterized by the presence of numerous small cysts of the mucous membranes of the urinary tract. The lesion may be limited to the bladder, but frequently it is found to be present also in the ureter and renal pelvis. Bullous edema of the bladder may sometimes resemble or be confused with cystitis cystica, but in the latter condition the cysts practically always have a definite epithelial lining (Young). Probably the first description of this condition was made by Morgagni in 1761. Since then, many articles on the subject have appeared. The lesion is usually found to be associated with a chronic inflammatory condition of the urinary tract, and several views have been put forth as to the origin of the cysts. Virchow, in his case report, suggested that the cysts might be caused by blocking of crypts in the mucosa of the