Omphaloarteritis
Omphalophlebitis
Oesophageal obstruction (Choke)
Oesophageal perforation
Oesophageal rupture
Oesophageal stenosis/stricture
Oesophageal ulceration
Oestrus ( " in season " / " on heat " )
Oestrus ovis ( nasal bot fly)
Oesophageal diverticulum