The urinary system regulates fluid balance and produces hormones. The kidneys metabolize vitamin D and gluconeogenesis during fasting. Medical abbreviations are used by healthcare professionals to efficiently record patient data. Some common urinary system abbreviations are Cath. for catheterization, Cysto. for cystoscopy, UTI for urinary tract infection, and RP for retrograde pyelogram. Blood urea nitrogen (BUN) is a blood test that measures kidney function.