Bladder Cancer is one of the common Cancer of the renal pelvis caused by the Urothelial Carcinoma

When the bladder reaches its capacity of urine, the bladder wall contracts, although adults have voluntary control over the timing of this contraction. At the same time, a urinary control muscle( sphincter) in the urethra relaxes. The urine is then expelled from the bladder. The urine flows through a narrow tube called the urethra and leaves the body. This process is called urination or micturition. Cancer occurs when normal cells undergo a transformation whereby they grow and multiply without normal controls forming the tumor.  http://search.ebscohost.com.ezp2.lib.umn.edu/login.aspx?direct=true&db=aph&AN=72474909&site=ehost-live