A 48-year-old woman suffering from hematuria was admitted to our hospital due to conscious disturbance. She had lower abdominal phantom tumor, anemia, renal dysfunction, hyperglycemia, metabolic acidosis and electrolyte abnormalities. Because of pelvocaliceal dilatation noted on abdominal ultrasonography, we first diagnosed her as having postrenal failure. With massive blood clots and gas emission from her urethra upon attempting cystoscopy, the remarkable expansion of the urinary bladder and a three-layered structure of gas, urine and complex of blood and debris inside her urinary bladder noted on abdominal CT scan, as well as the increased white blood cell count, we finally concluded our diagnosis as emphysematous cystitis.