March 2012: Uncovering the Causes behind Protein in the Urine
29 Feb 2012
Dr. Mohamed M. Salem is a board certified nephrologist associated with Weiss Memorial Hospital. His areas of expertise include diabetes, kidney disease, resistant hypertension and proteinuria.
Mohamed M. Salem, M.D. , F.A.C.P.
Optimum Kidney Care, S.C.
About the kidney
We should think of the kidney as an organ that excretes waste products while, at the same time, keeps and prevents the loss of important substances in the body. Protein is necessary for muscle strength, hormonal balance, and prevention of infection. In fact, antibodies that protect us from infection are made of protein. In view of this, normally very little protein is present in the urine. So, if you calculate the amount of protein that a normal person loses in the urine in a 24-hour collection period, you usually find a minuscule 150 mg of protein.
The kidney achieves this feat through an intact basement membrane, which can be regarded as a filter that selectively prevents protein loss. The integrity of this filter is what prevents protein loss into the urine.
I have protein in the urine. Should I worry?
Protein loss in the urine is called proteinuria. This is detected with a urine analysis. Urine analysis is often done as part of a general screening physical exam. It is an old test that has proven its value over the years.
Urine is made in the kidney and serves as the vehicle to eliminate toxins from the body. While we do not ingest toxins intentionally, some of the breakdown products of everything we eat or drink may need to be excreted and eliminated in the urine.
Whenever there is protein in the urine that means that there is a problem with the filter in the kidney. Your doctor may order some initial tests to see if the condition is temporary and benign or if it requires a referral to a nephrologist (kidney specialist).
What are the common symptoms of proteinuria?
Many times there are no symptoms. In other cases, patients may notice ankle swelling and weight gain due to water and salt retention. Many patients report increased foam in the urine.
What are the causes of protein in the urine or proteinuria?
Many disease states can cause protein loss in the urine. While there are many other causes of proteinuria, the following constitute more than 90 percent of the cases:
- Diabetes Mellitus is by far the most common cause of protein in urine and usually indicates involvement of the kidneys by diabetes.
- Glomerulonephritis is inflammation of the kidneys. There are many types of this condition.
- Hypertension may cause loss of small amounts of protein in the urine.
- Benign conditions such as orthostatic proteinuria where protein appears in the urine with prolonged standing and goes away in the recumbent position.
- Infections, either viral or bacterial.
- Fever may cause transient proteinuria.
What are the common tests ordered?
- Blood tests to detect certain immunological conditions that may cause antibodies to attack the kidney and cause proteinuria, such as lupus erythematosus.
- Blood tests to rule out viral infections such as hepatitis and HIV, which may cause kidney injury and proteinuria.
- Urine collection for 24 hours to determine the amount of protein in the urine.
- A kidney ultrasound to check for a variety of abnormalities including cysts, tumors, obstructions and infections.
- In some cases these tests do not allow an accurate diagnosis and a kidney biopsy is needed.
What treatments are available?
Treatment depends on the cause of the proteinuria and if the proteinuria is associated with decreased kidney function. In some cases, there’s no need to do anything: For instance, orthostatic proteinuria is a benign condition and in general requires no treatment.
Treatment directed at the cause of the protein loss is often successful and can resolve the problem. In some cases, ACEI (Angiotensin Converting Enzyme Inhibitors) are prescribed to help decrease the amount of protein in the urine. These drugs are commonly used to treat patients with heart failure and hypertension and are shown to decrease proteinuria and protect the kidney from the effect of the protein loss.
Patients also may require water pills (diuretics) to decrease water and salt retention.
What about protein intake? Should I eat more or less protein?
Protein intake depends on the cause of the proteinuria. Patients should be aware that eating a high protein diet does not cause proteinuria if they have normal kidneys. It may, however, increase the amount of protein in the urine if the proteinuria already exists.
What if I do nothing?
Proteinuria may be caused by conditions that can progress and cause kidney failure and the need for dialysis. Appropriate diagnosis and treatment may prevent these more serious conditions. Also patients with mild proteinuria have a higher risk of cardiac events. Accurate diagnosis and treatment can help prevent the development of complications.
For more information
If you would like more information about proteinuria or kidney function and disease, please contact Dr. Mohamed M. Salem at (773) 525-4701.