Sysmex 2024 Fall Newsletter - Flipbook - Page 7
Spring 2024
What is proteinuria?
The function of your kidneys is to 昀椀lter waste
products from your blood and remove them
from your body through the formation of urine.
The functional unit of the kidney – the nephron
– regulates the removal and reabsorption of
chemicals and water to ensure the proper levels of
salts and minerals for normal body function.
In a healthy kidney, a small amount of protein
passes through the glomerular 昀椀ltration barrier.
Most of the protein is reabsorbed in the proximal
tubules, so normally only small amounts of protein
are present in urine (< 15 mg/dL). Temporarily increased amounts of protein may be due to exercise,
dehydration or in昀氀ammation; however, in certain diseases or defects, the kidneys may allow
excessive protein to pass through the glomeruli or may not be able to reabsorb the protein. This
results in sustained elevated levels of protein in urine, or proteinuria.
Protein is one of the parameters measured on a standard urinalysis (UA) dipstick, and testing can
be performed manually or by automated methods. Proteinuria is often the 昀椀rst indicator of kidney
disease, although, increased protein is not present in all renal disorders nor is renal disease the only
cause of proteinuria. For this reason, prolonged elevated levels of protein in urine require additional
testing to determine the cause, which can generally be classi昀椀ed as prerenal, renal or postrenal.
Prerenal proteinuria is caused by increased plasma proteins that over昀氀ow across the glomerular
barrier. These proteins may be:
•
Acute phase reactants seen in many conditions including septicemia.
•
Hemoglobin or myoglobin.
•
Kappa or lambda monoclonal light chains that are increased in multiple myeloma and
macroglobulinemia (historically termed Bence Jones proteins).
Renal proteinuria can be due to glomerular or tubular defects. There are many conditions that can
be associated with renal proteinuria, including systemic and infectious diseases, drug toxicity and
renal disease. Patients with con昀椀rmed kidney disease may be asked to test their urine protein levels
at home using dipstick kits to monitor ongoing or increased damage to their kidneys. Postrenal
proteinuria is likely due to in昀氀ammation, malignancy or injury in the urinary tract.
Resources:
Fundamentals of Urine and Body Fluid Analysis, Nancy A Brunzel, W. B. Saunders Co., Philadelphia, PA
NEWS |
7
