Protein in urine, or proteinuria, may occur as a result of conditions such as exposure to cold heat or cold, strenuous physical exercise, and diseases such as heart disease, cardiac failure, renal infection and multiple myeloma, states Mayo Clinic. Goodpasture's syndrome, leukemia, glomerulonephritis, high blood pressure and pericarditis are other diseases that may cause protein in urine. While the first three conditions may not be signs of renal damage, the other causes may indicate kidney damage.
Depending on the cause of the protein in the urine, the condition can last for a long or short time, according to Mayo Clinic. For instance, while strenuous exercise and exposure to heat may result in proteinuria that lasts for a short time, diseases that signify kidney damage, such as glomerulonephritis and Goodpasture's syndrome, may cause long-lasting proteinuria.
Proteinuria is a condition in which the level of protein in the urine is higher than normal as a result of inefficiency in the kidney's filtration system, notes Mayo Clinic. One method of testing the urine for protein is urinalysis. Once the results of urinalysis indicate the presence of protein in the urine, a doctor may order another test that shows the quantity of protein in the urine. While it is normal for the urine to contain low protein levels, it may be dangerous when the protein level is high, especially when the condition persists.