Protein in Urine

Should I be Worried?

Protein in urine is an important sign of many kidney diseases and therefore it is always tested for during a urine test. However, protein in urine also occurs because of many non-serious reasons. In fact, most people with an initial positive urine test for protein do not have any serious disease. You may find urine protein finding described as Trace, 1+, 2+,3+ or 4+. These numbers are a rough estimate of the amount of protein present. Here’s what you need to know about it:

 

  • Trace to 2+: Small amount of protein is likely to be a transient or false finding. But you must check this by doing a couple of repeat tests within a month. If two out of three tests come negative, nothing more may be required.
  • 3+ or 4+: Higher amount of protein in urine should be interpreted carefully. It would be wise to see a doctor. A few more tests (for e.g. urine protein to creatinine ratio (UPr/Cr) and creatinine clearance) can tell if it’s anything worrisome.
  • If lots of protein is present and there are other problems as well on your lab tests (for e.g. low creatinine clearance, red blood cells (RBCs) in urine), a thorough evaluation by a kidney specialist (nephrologist) is needed.
  • If you have diabetes or hypertension, protein in urine may indicate early kidney damage. Talk to your doctor. More rigorous blood pressure and blood sugar control may be needed.

What Causes Protein in Urine?

Normally, when blood passes through the kidneys, the kidney’s filtering membrane extracts the waste into urine but leaves back the protein in the bloodstream. A transient leakiness in the kidney’s membrane can occur for several reasons such as fever, infection, etc and cause protein in urine. Transient proteinuria usually requires no special treatment. Long standing conditions such as diabetes, high blood pressure and some other kidney diseases cause irreparable damage to the kidney’s filtering membrane and cause persistent leakage of protein in urine.  In such cases, there is an urgent need to control the underlying disease and prevent further kidney damage.

 

Causes of Transient Protein in Urine:

  • Fever
  • Dehydration
  • Vigorous exercise
  • Emotional stress
  • Exposure to excessive heat or cold

Causes of Significant and Persistent Proteinuria:

  • Kidney Diseases: Persistent proteinuria is a characteristic sign of many kidney diseases. Some diseases involve the main filtering unit called the glomeruli (glomerulopathies). Some involve the tiny tubules and surrounding tissue in kidneys (tubulointerstitial diseases). Glomerular diseases typically cause proteinuria >2g/day or UPr/Cr >2.
  • Glomerular diseases are of two main types:
  • Diseases originating in and limited to the kidneys (Primary glomerulopathies): Several conditions that differ somewhat in pathology, symptoms and clinical course fall in this category. Some are:
  • Focal segmental glomerulonephritis
  • IgA nephropathy (i.e., Berger’s disease)
  • IgM nephropathy
  • Membranoproliferative glomerulonephritis
  • Membranous nephropathy
  • Minimal change disease

Glomerular diseases are best managed by a nephrologist. Long term treatment may be required to keep the disease in check.

  • Glomerular damage in other diseases (secondary glomerulopathies): Many chronic diseases, infections, malignancies and even drugs can damage the glomeruli. Some important ones are:
  • Diabetes mellitus (Most Common)
  • Systemic lupus erthematosus
  • Alport’s syndrome
  • Fabry’s disease
  • Amyloidosis
  • Chronic infections: HIV, Hepatitis B, Hepatitis C,Syphilis
  • Sarcoidosis
  • Sickle cell disease
  • Lymphoma
  • Gastrointestinal cancers
  • Drugs: NSAIDs, ACE inhibitors, penicillamine etc.
  • Overflow proteinuria:  In a small number of cases, the underlying cause of proteinuria is not kidney disease, but rather a disease releasing an excess amount of some abnormal proteins that overwhelm the kidneys filtering capacity and spill into urine (For e.g. multiple myeloma).
  • Postural (orthostatic) proteinuria: Orthostatic proteinuria is an interesting phenomenon in which protein appears in urine when you move about but disappears when you lie down. It is usually seen in adolescents and adults <30 years of age. Its cause is unknown but it is a totally harmless condition. Postural proteinuria can be diagnosed by a special urine collection and testing technique called split 24-hour urine protein test. It requires no treatment and goes away with age.
  • Isolated proteinuria: In some cases no explanation is found for the protein in urine. The quantity of protein is almost always <2g/day (UPr/Cr <2) and all other relevant tests are normal. Doctors generally advise such people to get blood pressure, urinalysis and kidney function tests done every six months. Proteinuria >2g/day with no explanation is rather rare and must be evaluated by a nephrologist.  

When to Seek Medical Attention?

Seek your doctor’s advice if:

 

  • Small amount of protein in urine (Trace to 2+) persists on 2 tests within a month
  • Higher amount of protein is found in urine (3+/4+)
  • Any protein in urine is making you unduly anxious

Who Treats Protein in Urine?

Initial evaluation can be done by a family physician or internist. If kidney disease is suspected, you will be referred to a nephrologist.
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