label: Allantoic cyst
label_lc: allantoic cyst
description: "A swelling formed at the base of umbilicus associated with a patent urachus which results from an allantoic remnant. The urachus is a fibrous remnant of the allantois which communicates from the apex of the urinary bladder to the umbilicus. Failed obliteration of the urachus can lead to various abnormalities: urachal cyst, urachal diverticulum, sinus or patent urachus - the most common type. Allantoic cysts in infants with patent urachus can be formed due to the drainage of urine into the umbilical cord, or in uncommon situations, after leakage of hypo-osmotic urine into the Wharton's jelly."