The urinary system filters waste from the blood and removes it from the body via the kidneys, ureters, urinary bladder, and urethra. It also regulates water and electrolyte levels and pH. Common abbreviations used when discussing the urinary system include KUB for kidney-ureter-bladder x-ray, RP for retrograde pyelogram procedure, UTI for urinary tract infection, BUN for blood urea nitrogen test, and cysto for cystoscopy. Cystoscopy uses an endoscope inserted into the urethra to examine the bladder.