Editing Upper Urinary Tract Urothelial Cancer (section)

=== Normal upper tract urothelium ===
* '''Bladder is derived from the endoderm; ureter and renal pelvis are derived from the mesoderm'''
* The urothelial lining of the upper urinary tract closely approximates that of the bladder except for the markedly reduced thickness of the muscle layer and the abutting of the urothelium to the renal parenchyma proximally.
* The epithelial layer is continuous from the level of the calyces to the distal ureter.
** It has been suggested that the urothelial layer may even “extend” into the collecting ducts, raising the possibility that collecting duct renal cancers may be closely related to urothelial cancers and perhaps better treated by agents used for urothelial cancers
* '''Renal pelvis and calyces'''
** '''The walls of the calyces and the pelvis''' '''contain''' fibrous connective tissue and 2 layers of '''smooth muscle''' and are lined on their inner surfaces with urothelium
* Ureter
** The 3 muscular layers of the ureter merge with the 3 muscular layers of the bladder