A case of the patent urachus associated with abdominal abscess was reported. A 44-year-old woman was consulted to our clinic with the complaints of bladder irritability and discharge from the navel on October 27, 1987. A fist-sized tumor around the umbilicus was pointed out and the cystography from the umbilicus demonstrated that the contrast medium reached to the urinary bladder. The cystoscopy showed the protruded lesion on the dome of the bladder. The pre-operative diagnosis was patent urachus. She received resection of the urachus on November 11, 1987. The pathological finding was pyogenic granuloma of the urachus due to chronic inflammation.