In other species: domestic cat , white rhinoceros , mountain zebra , dog

Mendelian trait/disorder: unknown

Considered a defect: yes

Cross-species summary: The urachus is a canal present in the foetus, connecting the bladder with the allantois via the navel. It normally disappears after birth. A patent urachus is one which persists after birth, allowing urine to drip out of the bladder through the umbilicus.