Pyometra is a relatively uncommon cause of non-gastrointestinal colic signs in the horse. Pyometra occurs in mares with cervical adhesions that prevent uterine drainage. Cervical adhesions are the result of cervical lacerations, which are most often seen following a dystocia. This mare presented with a 24 hour history of mild to moderate intermittent colic signs, fever, severe leukopenia and an approximately 17x10cm fluid filled viscus within her caudal abdomen. She had previously been used as a broodmare and retired following a dystocia. Her cervix was not identifiable by vaginal speculum exam, transrectal ultrasound, or vaginal or transrectal palpation. A diagnosis of closed pyometra was made, which could not be converted to an open pyometra, and an ovariohysterectomy was performed. Post-operatively, a stump pyometra remained and was managed medically.