Where do WBC urine casts come from?

[pizzadude]

Hi everyone.

Can someone explain to me how WBCs become WBC casts in urine? Where do the WBCs come from? How do they get into the distal tubules and collecting ducts? Do they leak through the glomeruli like RBC casts? Do they somehow diffuse through the tubular nephron walls?

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[zhopv10]

Not sure but I suspect they are recruited in and migrate through the tissues. They are pretty big so I can't imagine they are filtered. Anyway once in they precipitate basically with Tamm-Horsfal (sp) mucoprotein and that forms the casts.


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[dorster]

I think its the same way WBCs get into any other tissue in the body, they come from the blood vessels (here the renal arterioles) they extravasate through the tissue into the tubules and then build up in the tubules forming WBC casts. I don't think they are filtered through the glomerulus unless theres damage to the glomerular basement membrane in which the larger molecules could get through.