Proteinuria
Urinary protein excretion greater than 150mg/day is considered proteinuria.
Clinical Findings
Proteinuria is the leading symptom of the nephrotic syndrome, which includes peripheral oedema due to low serum protein levels. Hypertension and haematuria my be present but are not the leading symptoms as in nephritic syndrome.
Classification
Molecular weight allows to distinguish glomerular and tubular proteinuria. The latter is also known as low molecular weight proteinuria. The former may be further divided into selective and unselective glomerular proteinuria. Pathological proteins, such as Bence Jones protein, happen in urine in the course diseases with protein overproduction.
Microalbuminuria is a highly slective glomerular proteinuria with virtually only traces of albumine excretion (30-300mg/d).
Staging
Dip sticks allow to measure proteinuria semiquatitatively:
traces 15-30mg/dL,
1+ 30-100mg/dL,
2+ 100-300mg/dL,
3+ 300-1000mg/dL,
4+ >1000mg/dL.
Nephrotic range proteinuria is above 3500mg/day.
