Protein In Urine – Proteinuria

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What is proteuinuria? – This refers to the presence of protein in urine beyond a level that is considered normal (less than 300mg in 24 hour urine collection). The normal level is usually not detectable by the regular testing strips.

Why does protein appear in urine?

The kidneys filter blood to remove waste products. Among the substances present in the blood are proteins of different weights. Proteins with heavy weight are returned to the blood by the glomerulus (the filtering unit) of the kidney, while proteins with low molecular weight are filtered but almost completely reabsorbed back into the blood through the renal tubules. Only minimal quantity of protein, which is below detectable level, is lost in normal urine.

Protein is detected in urine when there is a problem with filtration, re-absorption or both. This may be due to a temporary or permanent damage to the structures responsible for filtration (glomerulus) and re-absorption (renal tubules), leading to leakage of protein into urine.

When the glomerulus is damaged, large proteins that should not be filtered will get filtered; and because the renal tubules are not designed to absorb them, they are passed in urine. When there is a problem with re-absorption, the proteins that should be reabsorbed by the renal tubules will end up in urine, leaving larger quantity of protein in urine than necessary.

What conditions are associated with proteinuria?

Sometimes, proteinuria may be caused by conditions that are not too dangerous to the body such as:

  1. Dehydration 
  2. Exposure to extreme cold environment
  3. Urinary tract infection
  4. Kidney stone
  5. Strenuous exercise
  6. Fever
  7. Prolonged use of analgesics such as aspirin

In some cases, however, proteinuria may be caused by more serious medical conditions that may result in kidney damage such as:

  1. Diabetes
  2. Hypertension
  3. Inflammation of the kidney (glomerulonephritis)
  4. Auto-immune conditions such as lupus erythematosus 
  5. Chronic kidney disease
  6. Preeclampsia (new onset hypertension and proteinuria in pregnancy)
  7. Heart failure  

What are the symptoms of proteinuria?

Proteinuria, when minimal (proteinuria of greater than 300mg/24 hours but less than 3.5g/24 hours), may give no symptom or sign. However, when it is heavy (up to or greater than 3.5g/24 hours), affected persons may present with: 

  1. Generalised body swelling (oedema)
  2. Facial puffiness which appears in the morning and resolves during the day
  3. Tiredness 
  4. Nausea and vomiting 
  5. Shortness of breath 
  6. More frequent urination
  7. Loss of appetite
  8. Weight loss 

How is proteinuria diagnosed?

Proteinuria is diagnosed by laboratory analysis of urine (urinalysis), which may form part of the steps in making diagnosis for certain disease conditions. The test can be done using urinary dipstick which detects proteinuria by colour change.

The colour change is compared with standards to ascertain the presence of proteinuria and its severity. More detailed analysis is done in the laboratory using appropriate reagents. This urinalysis is repeated to ascertain if the proteinuria is transient or persistent.

Laboratory testing, apart from detecting proteinuria, also examines urine for bacteria, crystals, pus (white blood) cells, red blood cells, casts etc. Each of these may point to specific problem with the kidneys or along the urinary tract.

Once protein in urine is ascertained, the next step is to quantify the amount, which can be done by using single voided urine (spot urine) or 24-hour urine collection. Other tests that may help in diagnosing the disease conditions leading to proteinuria include:

  1. Blood testing for kidney function which involves checking for blood urea and creatinine, as well as electrolytes
  2. Kidney biopsy which involves taking part of the kidney tissue to the laboratory for testing

How is proteinuria treated?

Proteinuria is treated by treating the underlined medical condition. Conditions causing transient proteinuria such as dehydration, extreme cold, strenuous exercise, excessive use of analgesics etc. may not need special treatment. Correction of the underlying problem is all that is necessary to clear the protein in urine. Serious medical conditions causing proteinuria may need treatment. These include:

  1. Urinary tract infection – Treatment involves antibiotics following culture and antibiotic sensitivity testing
  2. Kidney stone – Removal of the stone either medically or surgically 
  3. Hypertension – Consistent use of blood pressure drugs to keep blood pressure (BP) in check is important in those with proteinuria due to hypertension. Termination of pregnancy in those with preeclampsia may lead o resolution of proteinuria. Reduction in salt intake helps in BP control.
  4. Diabetes mellitus – Appropriate management of high blood sugar in those with diabetes mellitus may help slow down kidney damage and reduce proteinuria.
  5. Chronic kidney failure – Those with kidney disease need close consultation with their doctors for dietary modifications in order to slow down kidney damage. There may also be need for dialysis depending on the stage of the disease.

How can proteinuria be prevented?

Proteinuria is a manifestation of some disease conditions. Therefore, its prevention can be achieved by preventing the disease conditions causing it. This includes:

  1. Balanced diet; avoiding excess protein consumption as protein cannot be stored in the body
  2. Adequate intake of water to prevent dehydration
  3. Maintain healthy weight with body mass index (BMI) within normal range (18.5kg/m2 to 25kg/m2)
  4. Avoid strenuous exercise
  5. Avoid prolonged use analgesics
  6. Maintain good perineal hygiene to prevent urinary tract infection
  7. Appropriate treatment of hypertension and diabetes to avoid kidney complication
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