Bladder outlet obstruction at the level of the urethra. It occurs in approximately 1 in every 5000 to 8000 live births and only occurs in males. Since PUV always affects both sides of the urinary tract, patients with posterior urethral valves are at the greatest risk for developing chronic kidney disease and end-stage renal disease due to obstructive uropathy. A ureterocele is a cystic dilation of the end of the ureter that can occur in the bladder and/or in the urethra. It occurs in approximately 1 in every 5000 live births, is most commonly seen in females and involves both ides of the
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.