Dr. med. Dirk Manski



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Proteinuria: Causes of Protein in Urine

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.

Functional Proteinuria:

Proteinuria up to 500 mg/24 h without the presence of a kidney disease is called functional proteinuria. Causes are fever, exercise, orthostasis, exposure to heat and cold, heart insufficiency or drugs.

Microalbuminuria:

Microalbuminuria is the presence of more than 30 mg and up 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:

Tubular proteinuria is the presence of more than 150 mg small proteins (such as alpha 2-microglobulin) in a 24-h urine collection, while the serum proteins have normal concentrations.

Prerenal Proteinuria:

The increased concentration of small filtered proteins from the plasma leads to an overtaxed tubular reabsorption (overflow proteinuria).

Postrenal Proteinuria:

Proteinuria from the upper urinary tract, bladder, prostate or urethra.

Differential Diagnosis of Proteinuria

Functional Proteinuria:

Microalbuminuria:

Microalbuminuria indicates an abnormal leakage of albumin in the renal glomerulus and is a sign of kidney damage:

Selective glomerular proteinuria:

Selective glomerular proteinuria indicates moderate glomerular damage:

Non-selective glomerular proteinuria:

Non-selective glomerular proteinuria indicates severe glomerular damage:

Tubular proteinuria:

Small proteins are in part filtrated in the renal glomerulum and reabsorbed by tubular cells. Tubular proteinuria indicates tubular cell damage:

Prerenal Proteinuria:

Postrenal Proteinuria:

Tumor, trauma, infection, bleeding, semen, vaginal contamination.

Diagnostic Work-Up of Proteinuria







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References



  Deutsche Version: Proteinurie