Proteinuria

Proteinuria (from protein and urine) means the presence of an excess of serum proteins in the urine.^[1] The protein in the urine often causes the urine to become foamy, although foamy urine may also be caused by bilirubin in the urine (bilirubinuria),^[2] retrograde ejaculation,^[3] pneumaturia (air bubbles in the urine) due to a fistula,^[4] or drugs such as pyridium.^[5]

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Measurement

Proteinuria is often diagnosed by a simple dipstick test although it is possible for the test to give a false negative even with nephrotic range proteinuria if the urine is dilute. False negatives may also occur if the protein in the urine is composed mainly globulins or Bence-Jones Proteins because the reagent on the test strips, Bromphenol blue, is highly specific for albumin. ^[6][7] Traditionally dipstick protein tests would be quantified by measuring the total quantity of protein in a 24-hour urine collection test, and abnormal globulins by specific requests for Protein electrophoresis.^[8][9]

Alternatively the concentration of protein in the urine may be compared to the creatinine level in a spot urine sample. This is termed Protein/Creatinine Ratio (PCR). The 2005 UK Chronic Kidney Disease guidelines states that PCR is a better test than 24 hour urinary protein measurement. Proteinuria is defined as a Protein:creatinine ratio >45 mg/mmol (which is equivalent to Albumin:creatinine ratio of >30 mg/mmol) with very high levels of nephrotic syndrome being for PCR > 100 mg/mmol.^[10]

Associated conditions

Proteinuria may be a sign of renal (kidney) damage. Since serum proteins are readily reabsorbed from urine, the presence of excess protein indicates either an insufficiency of absorption or impaired filtration. Diabetics may suffer from damaged nephrons and develop proteinuria.

With severe proteinuria, general hypoproteinemia can develop which results in diminished oncotic pressure. Symptoms of diminished oncotic pressure may include ascites, edema, and hydrothorax.

Conditions with proteinuria as a sign

Proteinuria may be a feature of the following conditions:^[7]

• Nephrotic syndromes (i.e. intrinsic renal failure)
• Pre-eclampsia
• Eclampsia
• toxic lesions of kidneys
• Collagen vascular diseases(e.g., systemic lupus erythematosus)
• Dehydration
• Glomerular diseases, such as membranous glomerulonephritis, focal segmental glomerulonephritis, minimal change disease (lipoid nephrosis)
• Strenuous exercise
• Stress
• Benign Orthostatic (postural) proteinuria
• Focal segmental glomerulosclerosis (FSGS)
• IgA nephropathy (i.e., Berger's disease)
• IgM nephropathy
• Membranoproliferative glomerulonephritis
• Membranous nephropathy
• Minimal change disease
• Sarcoidosis
• Alport's syndrome
• Diabetes mellitus
• Drugs (e.g., NSAIDs, nicotine, penicillamine,gold, ACE inhibitors, antibiotics, opiates especially heroin.^[11]
• Fabry's disease
• Infections (e.g., HIV, syphilis, hepatitis,post-streptococcal infection)
• Aminoaciduria
• Fanconi syndrome
• Heavy metal ingestion
• Hypertensive nephrosclerosis
• Interstitial nephritis
• Sickle cell disease
• Hemoglobinuria
• Multiple myeloma
• Myoglobinuria
• Organ rejection- kidney transplant patients may have gamma-globulins in their urine if the kidneys start to reject.^[12]
• Ebola hemorrhagic fever
• Nail Patella Syndrome
• Familial Mediterranean fever

Conditions with proteinuria consisting mainly of Bence-Jones proteins as a sign

• Waldenstrom's macroglobulinemia
• Chronic lymphocytic leukemia
• Amyloidosis
• Malignancies (e.g., lymphoma, other cancers)
• multiple myeloma

See also

• Albuminuria
• Microalbuminuria
• List of terms associated with diabetes