often measure protein in the urine (i.e. proteinuria
) because proteinuria is one quantitative measure that can be used to track the risk and progression of kidney disease. The test is done on a sample of urine alone, although doctors will often ask for blood tests as well as they can provide additional information about the functioning of the kidneys.
As the kidneys become affected by certain diseases that affect their ability to filter the blood, protein that is normally kept within the bloodstream will start to leak out into the urine. If the amount of protein in the urine is high enough (reaching "nephrotic-range" levels of 3.5 grams per day), certain complications can develop. With less protein in the blood, fluid will begin to seep into the soft tissue causing edema. Proteins that are important in the regulation of lipids can be lost into the urine, which can cause high levels of cholesterol in the blood. Additionally, proteins that are important in regulating the blood clotting cascade can also be lost in the urine, leading to a higher rate of blood clots.
There are a number of diseases that can cause proteinuria, ranging from common illnesses such as diabetes to rarer autoimmune illnesses that primarily affect the kidneys. Fortunately, there are a number of treatments that can be very effective in reducing the pressure within the kidneys and thereby reducing the amount of proteinuria. If you are concerned about proteinuria or have questions about the tests that your doctor is ordering, then you should contact your primary care physician
to discuss the issue further.