Although identification of the key artery that perfuses the spinal cord is essential to avoid occurrence of paraplegia after surgery on the thoracoabdominal aorta, reliable and noncomplicated measures are not yet available. A new method of determining it by using echocardiography with a saline injection into the lumbar artery was evaluated for feasibility and adequacy in a canine model. In two mongrel dogs, the abdominal aorta was opened and saline was directly injected into the lumbar arteries while the spinal cord was visualized by echocardiography through the intervertebral disc. When the echogenic or Doppler signal was detected in the spinal cord, the particular lumbar artery was determined as "positive", or as "negative" when the signal was not detected. After the dog was sacrificed, red resin was injected into the "positive" arteries and blue resin into the "negative" arteries. In the extracted spinal cord, the anterior and posterior spinal arteries were filled with red resin, rather than with blue resin, to indicate that the key arteries were correctly identified. There were multiple "positive" arteries, which were mainly located on the left side and accounted for approximately one-third of the entire lumbar arteries. The "negative" arteries mainly perfused the muscles around the vertebra. Injected resin came out of the adjacent lumbar arteries of the same category, suggesting that communication is present among the positive arteries, but independently of that among the negative arteries. Echo-guided identification of key arteries is technically feasible and correctly determines the key arteries in this preliminary canine model.