A 20-year-old 582-kg warmblood mare was referred because of a 3-month history of pollakiuria and suspected sabulous cystitis, which is an accumulation of calcium carbonate sludge in the bladder leading to inflammation. Three weeks prior, the referring veterinarian performed a urinary workup, during which transrectal palpation revealed an enlarged bladder. A urinary catheter was passed, the bladder was drained, and a large amount of debris was noticed. Urinalysis and systemic bloodwork revealed no clinically remarkable abnormalities. No change in pollakiuria followed, and 1 week later, a urolith (approx 1 × 1 × 2 cm) covered with a blood clot