Protein in Urine but not a Kidney Infection?

What causes protein in urine?

Protein in urine is a result of kidney disease that damages the renal glomeruli (filtration system, tiny cluster of capillaries, responsible for filtering) and the renal tubules (re-absorption system, reabsorbing urine into the blood, also collecting and conducting the remaining urine into renal calyx and pelvis, and then into the ureter, bladder).

These kidney diseases can be divided into three types: glomerular disease, tubular disease, renal vascular disease. Among them, glomerulonephritis is the leading cause of protein in urine. There are also many other diseases that can cause cloudy urine. For example, kidney infection (pyelonephritis), diabetes, high blood pressure, allergic purpura, systemic lupus erythematosus, HBV, myeloma and lymphoma, all of them can cause kidney disease when in advanced stage. Thus, proteins are filtered out from blood, then present in urine. Sometimes, a slightly elevated protein in urine can be harmless; The trigger factors include:

• Great physical exertion, sport activities;
• Intake of protein-rich food;
• Exposure to excessively low temperature or too high temperature;
• Having a fever;
• Emotional stress;
• During pregnancy.