You are here: Urology Textbook > Signs and symptoms > Proteinuria
Proteinuria: Causes and Differential Diagnosis
Definitions of Proteinuria
Proteinuria is the presence of excess serum proteins in the urine.
Normal Protein Excretion:
Protein in the urine should be in the range of 50–150 mg in a 24-hour urine collection.
Proteinuria, up to 500 mg/24 h, without the presence of kidney disease is called functional proteinuria. Causes are fever, exercise, orthostasis, exposure to heat and cold, heart insufficiency, or drugs.
Microalbuminuria is the presence of more than 30 mg and up to 300 mg albumin in a 24-h urine collection.
Selective Glomerular Proteinuria:
Selective glomerular proteinuria is the increased excretion of more than 300 mg medium-sized negatively charged proteins such as albumin in a 24-h urine collection.
Non-Selective Glomerular Proteinuria:
Non-selective glomerular proteinuria is the increased excretion of more than 3000 mg proteins of any size in a 24-h urine collection.
Tubular proteinuria is the presence of more than 150 mg of small proteins (such as alpha 2-microglobulin) in a 24-h urine collection, while the serum proteins have normal concentrations.
The increased concentration of small filtered proteins from the plasma leads to overtaxed tubular reabsorption (overflow proteinuria).
Proteinuria from the upper urinary tract, bladder, prostate, or urethra.
Differential Diagnosis of Proteinuria
- Physical activity
- Heat or cold
- Heart failure
Microalbuminuria indicates an abnormal leakage of albumin in the renal glomerulus and is a sign of kidney damage:
- Diabetic nephropathy (stage III)
- Hypertensive Nephropathy
- Also possible in fever, after physical activity or due to infections.
Selective glomerular proteinuria:
Selective glomerular proteinuria indicates moderate glomerular damage:
- Glomerulonephritis (e.g., minimal-change GN)
- Lupus nephritis with low activity
Non-selective glomerular proteinuria:
Non-selective glomerular proteinuria indicates severe glomerular damage:
- Lupus nephritis
Small proteins are in part filtrated in the renal glomerulum and reabsorbed by tubular cells. Tubular proteinuria indicates tubular cell damage:
- Interstitial nephritis
- Analgesics nephropathy
- Chronic pyelonephritis in vesicoureteral reflux
- Acute renal failure
- Tubular toxins like aminoglycosides, contrast media or ciclosporin.
- Bence Jonce proteinuria in multiple myeloma or Non-Hodgkin lymphoma
Tumor, urogenital trauma, urinary tract infections, hematuria, semen, vaginal contamination.
Diagnostic Workup of Proteinuria
- Urine sediment and urine culture
- Protein concentration in 24-hour urine collection
- Protein electrophoresis of urine and serum
- Sonography of the urinary organs: renal ultrasound and bladder ultrasound imaging.
- Intravenous urography or computed tomography of urinary organs if postrenal proteinuria is suspected.
- Immun-electrophoresis, if Bence Jones proteinuria is suspected
- Renal biopsy if severe proteinuria or signs of renal dysfunction are present.
Index: 1–9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Deutsche Version: Differentialdiagnose der Proteinurie