Normally, the allantois undergoes fibrous degeneration between the 4th and 6th weeks to form a fibrous cord called urachus. Rarely, part or all of the allantois may remain patent. If the lumen persists only in a small part of the urachus, secretory activity of the lining epithelium may give rise to a urachal cyst. Such a cyst does not produce any symptoms unless it becomes infected and enlarges in size. Persistence of lumen in the superior part of the urachus to the formation of a urachal sinus that opens at the umbilicus. If the entire allantois remains patent, a urachal fistula is produced, resulting in the leakage of urine from the umbilicus.