Let’s switch gears now to the
second category of proteinuria
which is tubular proteinuria.
These patients usually have a
low fixed level of proteinuria.
Usually, the protein to
creatinine ratio is less than 1.
It’s not in the nephrotic range.
There are many causes
of tubular proteinuria.
We can’t possibly
go through them all
and here’s a list if
but the one I want to focus
on and the most important one
is acute tubular necrosis, which is the
most common cause of this problem.
So acute tubular necrosis results
in a decreased renal perfusion.
It causes a decreased glomerular filtration
rate and this is from an acute injury.
Acute tubular necrosis occurs as a
result of underperfusion of the kidney.
So there are many causes, one of them is
simply hypovolemia or hypovolemic shock.
So patients who are in the ICU with
severe dehydration, for example,
may suffer an acute
It may come from hypoxemia.
The hypoxemia has to be very significant.
It may come as a result of
sepsis or septic shock.
But one area where we see it
that’s interesting is drugs.
and in particular, there are few drugs
that are most likely to cause this.
Those include NSAIDs like ibuprofen
which even when you use that in appropriate
dose can cause an acute tubular necrosis.
Other drugs include aminoglycosides,
amphotericin, lithium, the list goes on.
So, let’s switch now to the
higher loss of protein category
which is true
This is usually a very high rate
of protein loss in the urine.
So these patients have a
high grade fixed proteinuria
and usually that ratio of protein
to creatinine is greater than 1,
greater than 2.
This can happen, additionally, in
patients who have a proteinuria
but have another symptom
from renal dysfunction.
An example would be hypertension,
hematuria and addition to proteinuria,
generalized edema or renal failure.
If a patient has any of these things, it’s
most likely to be a glomerular proteinuria.
So switching to glomerular proteinuria,
there are once again many different
causes of glomerular proteinuria.
These include minimal change disease,
focal segmental glomerulosclerosis,
mesangial proliferative glomerulonephritis,
membranous nephropathy, amyloidosis,
diabetic nephropathy or sickle cell
disease, tubulointerstitial disease,
heavy metal poisoning again which can cause
both tubular or glomerular, et cetera.
I want to focus on some of the more
common ones that might show up on exam.
Let’s start with FSGS or focal
This is a disease that affects
focal areas of the kidney.
So here, you can see a picture or
both normal and abnormal glomeruli.
This one is the abnormal one.
You can see it’s
infiltrated and abnormal.