WHAT IS PROTEINURIA?
Proteinuria is the condition where the urine contains an abnormal amount of protein.
HOW PROTEIN LEAKS IN THE URINE?
Protein is found in the blood and usually is not present in the urine. Proteins are molecules that help in normal body processes such as enzymes, fighting infection (as antibodies), carriers of other substances and blood clotting.
There are millions of tiny filters called glomeruli in the kidneys. As blood passes through healthy kidneys, the glomeruli filter the waste products. Proteins are large molecules and are unable to pass through the glomeruli into the urine. However, when the glomeruli are damaged by a disease process, proteins are then able to pass through them and escape into the urine.
WHY IS PROTEINURIA DANGEROUS?
Proteinuria is not a disease. However, it is an indicator that the kidneys have been damaged in some way. Protein should not appear in the urine in large quantities. Doctors usually say there is proteinuria if more than 150 mg per day is detected in the urine.
WHAT CAUSES PROTEINURIA?
Some of the causes of proteinuria are:
a) Primary kidney disease called nephritis
b) Secondary kidney diseases due to:
 Diabetes
Hypertension or high blood pressure
Cancers
Pregnancy
Medications
c) Others
Excessive weight gain
Heart failure
Slightly higher excretion of protein may occur normally in certain circumstances such as pregnancy, during fever and after strenuous exercise. These are not clinically significant if the amount is only minimally raised and returns to normal levels soon after.
ARE THERE DIFFERENT TYPES OF PROTEINURIA?
There are essentially two types of protein: albumin which is a smaller molecule and globulin which is larger. When the disease is minor or early, albumin leaks out first. The quantity is then small and not detected by conventional methods used for detecting protein. This is called microalbuminuria implying that the amount leaked out is in small amounts. When the disease is more advanced, larger molecules other than albumin leaks out and we term this state collectively as "proteinuria".
WHO ARE AT RISK OF PROTEINURIA?
People with diabetes, hypertension, or certain family backgrounds are at risk of proteinuria. In both type 1 and type 2 diabetes, the first sign of kidney damage is the presence of small amounts of albumin in the urine ( microalbuminuria ) . As kidney function declines, the amount of albumin in the urine increases, and microalbuminuria becomes full-fledged proteinuria.
WHAT ARE THE SIGNS AND SYMPTOMS OF PROTEINURIA?
By itself, proteinuria causes foamy or frothy urine. Patients may also say they see bubbles in the urine. If loss of protein is in very large quantities (more than 3 grams per day), a patient may have the nephrotic syndrome where he complains of swelling of legs, abdominal distention and breathlessness especially on lying down.
If a patient also has kidney failure, the complaints will be that experienced by other renal failure patients.
HOW CAN I TEST FOR PROTEINURIA?
 Urine dipstick: This is a simple method using a test strip immersed into a urine sample to detect presence of protein in the urine. However, it only measures the concentration in that specific specimen. The concentration of urine passed throughout the day actually varies so this is not very accurate.
24-hour urine collection for protein or microalbumin is used to assess how much protein or microalbumin is passed into the urine over 24 hours.
We can grade proteinuria as follows:
| 1. |
Microalbuminuria |
30-150mg/day |
| 2. |
Mild proteinuria |
150-500mg/day |
| 3. |
Moderate proteinuria |
500-1000mg/day |
| 4. |
Heavy proteinuria |
>1000mg/day |
Because the methods used for albumin and protein are different, there will be some difference in the amounts when albumin and protein are tested on the same sample.
The amount of proteinuria may also be reported as a ratio of protein to creatinine in the urine - urine protein/creatinine ratio. If both are measured in grams, it will parallel the 24 hour results. The urine microalbumin/creatinine ratio (both measured in mg) will also closely relate to the 24 hour urine microalbumin result.
HOW IS THE SEVERITY DETERMINED?
There are many reasons for having protein in the urine and the seriousness will depend on the cause and amount of protein leak. The doctor will perform a series of investigations which often include:
- Blood test to check on the kidney function
- Urine test to determine amount of protein present in the urine
- Ultrasound of the kidney and bladder to determine cause of proteinuria
- Kidney biopsy may be indicated in some cases for more specific diagnosis and prognosis
NATURAL COURSE AND PROGNOSIS OF PROTEINURIA
If left untreated, proteinuria on occasion could disappear or could remain stable for many months and years. It could also get worse and cause kidney failure especially:
- If it is associated with high blood pressure
- If the proteinuria is heavy (more than 1 gm/day). The higher the proteinuria is the greater the risk of kidney failure
- If medications that are not 'kidney friendly' are used indiscriminately
TREATING PROTEINURIA
Other than treatment for specific kidney diseases, the following need to be observed to prevent deterioration to / of kidney failure
- Good blood pressure control with any class of antihypertensives suited to the patient. In cases of heavy proteinuria, the target blood pressure is 125/75.
- Use of medications to specifically reduce proteinuria and stabilise the kidney function such as the Angiotensin Converting Enzyme (ACE) inhibitors or Angiotensin Receptor Blockers (ARBs).
- Diet modifications for a low salt diet as recommended by the dietitian and if appropriate, a low protein diet for renal failure.
SOME USEFUL HINTS :
Proteinuria may be a sign that your kidneys are damaged and that you are at risk of kidney failure.
It is recommended that people in the high risk group be regularly checked for proteinuria so that kidney disease can be detected and prevented from progressing.
Those at risk of proteinuria and kidney failure include people who have diabetes or hypertension and who have a family history of kidney disease.
If you have diabetes or high blood pressure or both, the first goal of treatment will be to control your blood glucose and blood pressure.
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