The trunk kidney is one of two paired kidneys located on both sides of the sacrum (sometimes), developing in the process of evolution; it corresponds to a paired bone canal called the mesonephric canal. The kidney connects the body wall of animals with the reproductive tubule (through the fusion of serous membranes). The bodies of the segmental ganglia lie above the spinal cord and run along with the veins. The tributaries of the right kidneys flow into the lumbar vein, the tributaries of the left kidneys into the internal iliac veins. As these nodes enlarge, they are connected by commissures, forming a venous sinus in the spleen.
Blood from the renal vessels enters both the lower parts of the aortic arch and through the proper renal artery.