ALOT. A urine analysis (ua) can show: state of hydration (spec grav), kidney disease (protein), diabetes (sugar/ketones) , stone/tumor (blood), liver disease (bilirubin), infection (white cells/nitrite). Also seen under the microscope are casts, crystals, bacteria, yeast. Separate tests check pregnancy (HCG) and drug screen. Remember to do ua as a 'clean catch' wipe area, urinate, catch urine, finish.
A lot. Urinalysis reveals clues about not only kidney disease, but systemic diseases also. A few of the diseases that may be diagnosed by examining urine are: urinary infection, tumors of urinary tract, diabetes, nephrotic syndrome, pregnancy, drug abuse, poisonings, hormonal disorders, and metabolic disorders etc.
Lots. Urinalysis can show sugar in the urine, a sign of diabetes. Protein can also be detected, with indicates kidney damage. Nitrites and white blood cells indicate infection; ketones are present whenever the body is predominatly burning fat for energy, such as when people are starving, don't have insulin, or are on really low carb diets. How concentrated the urine is indicates hydration.