Urethral doubling is a rare congenital malformation of the lower urinary tract. A little more than 200 cases of various forms of this defect have been described in the literature worldwide. We present a rare clinical case of duplication of the urethra in combination with the megaureter of the only functioning kidney. In this patient, we encountered a previously undescribed anomaly within the generally accepted classification of the kidney collecting system in combination with a true diverticulum of the bladder and a descending orthotopic ureterocele.