Answer: Mosquito larvae
Most of you astutely noted that these are NOT organisms you would expect to find inside the urinary bladder, and most likely result from exogenous environmental contamination after the sample was obtained.
At this magnification, you can appreciate the presence of siphons by which the larvae breath oxygen from the above the surface of the water. That puts them in the Culicine subfamily, which includes the Culex and Aedes genera. Given that these larvae are in urine, they are most likely Culex spp., since this species can tolerate high levels of organic pollution, and may be found in cess pits, open drains, and pit latrines.