A case of priapism following intrathecal morphine injection in a dog

BACKGROUND: Priapism refers to prolonged erection unrelated to sexual stimulation, with severe sequelae unless treated. In humans, it is a rare complication associated with epidural or spinal opioid administration. Its pathophysiology is unclear. This is the first report of priapism following neuraxial anesthesia in dog. CASE DESCRIPTION: An intrathecal morphine injection (30 mcg/kg) at L5–L6 for postoperative analgesia was given at the end of surgery for removal of cutaneous mastocytomas of the abdomen and left axillary lymphadenectomy. Painless penile erection occurred 2 hours later and lasted 6 hours, before spontaneously resolving 7–8 hours after the injection. No pain or other adverse events (e.g., nausea, urinary retention, and itching) were recorded. Recovery was complete without treatment. CONCLUSION: Painless, self-resolving priapism is a rare complication associated with intrathecal morphine injection in dogs.