Cystitis cystica et glandularis (CCEG) is widely believed to be innocuous and self-limiting. We report a case of a 32-year-old male patient who was found to have gross bilateral hydroureter and hydronephrosis and an estimated glomerular filtration rate of 3 ml/min/1.73 m2. Cystoscopy revealed extensive cystic and nodular lesions involving most of the bladder urothelium, which proved to be CCEG on histopathological analysis. Retrograde and anterograde stents could not be inserted due to obstruction of the ureters at the level of the vesicoureteric junction. Percutaneous nephrostomies were subsequently inserted. Although there was evidence of improvement of the CCEG on follow-up cystoscopy, no improvement of renal function, despite decompression with percutaneous nephrostomies, was seen. He was subsequently placed on the waiting list for a renal transplant. We believe this to be the only known case reported of florid CCEG obstructing the upper urinary tracts bilaterally, causing irreversible renal injury.