A 20 year old Austrian Warmblood mare was presented at the clinic of Vienna Veterinary University for symptoms of polydipsia, polyuria and urinary incontinence and a repeated history of bladder infection. Sampled urine was light yellow, very cloudy, had a low specific weight (1016) and a pH of 9. The dip stick suggested very high hemoglobin concentration. The sediment showed medium numbers of rounded epithelial cells, low numbers of leukocytes. Furthermore, a remarkable quantity of calcium carbonate crystals was present. Urine and plasma chemistry and fractional clearance revealed the following: high blood urea and Ca concentration. The FE of Na and GGT/Creatinine ratio both were increased. These results suggested chronic renal insufficiency and co-existent urinary tract inflammation. Trans-abdominal ultrasound of the kidneys was performed. The left kidney was normal both in size and appearance of medulla, cortex and pyelum. The right kidney appeared morphologically modified such that the border between cortex and medulla could not be identified clearly. At cystoscopy the floor of urinary bladder could not be seen, due to the large quantities of sludge and grainy gravel deposited on it. However, cystic calculi were not identified. The apex vesicae was highly inflamed, with necrotic changes that were coated with gravel and fibrin. Both ureters were highly dilated (thicker than a finger) and appeared to secrete a cloudy fluid. The endoscopic diagnosis was advanced ulcerative sabalous cystitis, and dilated ureters. Because of the poor prognosis of the case the owner decided to have the mare be euthanized. The gross pathology showed a dilated pyelum in both kidneys. The pyelum was filled with gravel. Both ureters were dilated and filled with gravel too. The bladder wall was thickened and just in cranial to its opening, a soft conglomerate of gravel (7x5x0.5cm) was present. The urethra was also filled but not blocked with this gravel. Histopathology showed chronic interstitial nephritis, glomerulonephritis and pyelitis. The muscularis of the bladder was chronically inflamed. The final main diagnosis was chronic sabalous cystitis with subsequent chronic inflammation of the ureters and chronic interstitial nephritis.