Urachal cyst is a congenital urachal anomaly characterized by a failure of complete closure of the urachus, in which both ends are closed but the central lumen remains patent. It is typically asymptomatic but may become clinically significant when infected, presenting as a mass in the umbilical region accompanied by abdominal pain and fever. The disease is urachal cyst (MONDO_0018844, a Monarch Disease Ontology identifier). Also known as: urachal cyst (disease).