Bladder outlet obstruction but still have normal renal architecture. This leads to a decrease in the number of nephrons, or functional units of the kidney. Malformation of kidney or bladder architecture. A dysplastic kidney is typically small for age and may contain cysts. A multicystic dysplastic kidney is an extreme example of renal dysplasia. Dilation of the renal pelvis, ureters, or both. Also called hydronephrosis. Kidneys and ureters located in incorrect position, including horseshoe kidney and ectopic ureters. Bladder outlet obstruction is classified based on where along the urinary tract the obstruction occurs, including upper urinary tract obstruction and lower urinary tract obstruction.
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.