Kidney transplantation is required. Most people need two or three such injections, and many are not completely insulin-free. The transplant surgery takes about three hours. The donor kidney will be placed in the lower abdomen and its blood vessels connected to arteries and veins in the recipient's body. When this is complete, blood will be allowed to flow through the kidney again. The final step is connecting the ureter from the donor kidney to the bladder. In most cases, the kidney will soon start producing urine. Depending on its quality, the new kidney usually begins functioning immediately. Living donor kidneys normally require
Swim bladder similar structure known as the "oval window", the bladder is in contact with blood and the oxygen can diffuse back out again. Together with oxygen, other gases are salted out in the swim bladder which accounts for the high pressures of other gases as well. The combination of gases in the bladder varies. In shallow water fish, the ratios closely approximate that of the atmosphere, while deep sea fish tend to have higher percentages of oxygen. For instance, the eel "Synaphobranchus" has been observed to have 75.1% oxygen, 20.5% nitrogen, 3.1% carbon dioxide, and 0.4% argon in its swim bladder.