How does one urinalysis determine kidney damage/disease?

Kidney disease: If one's urinalysis (U) shows protein (P), blood (B) or red blood cell casts (R), one may have kidney disease. If P is found, a 24 hour urine collection for creatinine clearance and protein needs to be done, along with blood work. If one has R, work up for a glomerulonephritis needs to be be done. If one has B, one needs to have a UTI ruled out and it is, a urologist needs to be consulted.