A 49-year-old female visited our hospital with a complaint of pelvic pain. She was under treatment for diabetes mellitus and dilated cardiomyopathy. Radiography revealed a radiolucent area in the bladder. We suspected vesicorectal fistula. Computed tomography showed gas within the bladder wall and the lumen. Cystoscopy revealed diffuse emphysema in the bladder wall without fistula. These findings were consistent with a diagnosis of emphysematous cystitis. The urine culture yielded Escherichia coli. After urinary drainage and antibiotic therapy, she was cured of emphysematous cystitis.