So this marks our next section in the
last section of intrinsic renal disease
which is our glomerular diseases,
probably my favorite thing to talk about.
And we'll be talking about it fully in our
nephrotic and nephritic syndrome lectures.
However there's a few
points that I'd like to talk about.
Number one is that when we
think about the nephritic syndromes,
the things that actually result in acute
kidney injury are often what we call
rapidly progressive glomerular
nephritides or RPGNs
and these are marked
by three different types:
Type I is known as antiglomerular
basement membrane or anti-GBM disease.
Type II are immune-complex diseases
that manifest with rapid renal deterioration
and necrosis and crescents on biopsy.
And this includes:
And finally type III, which as a personal favorite
of mine, are the ANCA-associated vasculitides
also called Pauci-immune
And again, and all three of these actually
are part of a nephritic syndrome however,
when they present as a rapidly progressive GN, that
means that we are losing renal function quickly.
There is significant deterioration in renal function
and when we biopsy our patients morphologically,
what we actually see are necrosis in crescents.
So again, I'm underscoring that
many diseases involve the glomeruli
but it's really the RPGNs that present as an
emergent acute kidney injury better outlined here.
So, there are a couple things that are really important
when it comes to diagnosing our patient who have RPGNs.
Laboratory evaluation is critical.
The urine analysis really is important because it's going
to show us that the patients have microscopic hematuria
and proteinuria typically less than
the nephrotic range and remember,
that hematuria often manifests as
dysmorphic red cells and red blood cell casts.
so again, If I'm looking at that urine
sediment underneath the microscope
then I'm going to see those
funny red blood cell shapes.
Again, they're called
dysmorphic red blood cells .
and they typically look like a red blood cell
with a bleb t hat's located on that outer membrane.
Red blood cell cast and what
you can seeion the image over here
is that this is a trichrome stain of
our patient who actually has an RPGN
and you can see all those red blood cells
that are actually collecting in the tubules.
Those are actually on their way
to forming a red blood cell cast.
Those red blood cells will bind
with that Tamm-Horsfall protein
and then once they're passed into the urine, you
see these beautiful exquisite red blood cell cast
And sometimes, in some of
the very exudative types of RPGN
that would be something
like post-infectious GN,
you might be lucky enough to
see a white blood cell cast as well.
Our patient's urine sodium is
oftentimes less than 20 meq/L,
that's not because the
pre-renal but actually because
of something that happens at the principal
cell that causes reabsorption of sodium.
Again, I just want to make a point here.
That we talked about FENa
at the beginning of the lecture,
and this is why FENa can only
distinguish between pre-renal and ATN.
If you can see here that our urine
sodium is less than 20 (meq/L),
that would probably give
us a FENa of less than 1%.
So again we can't use something
like FENa in a case like this.
And then finally if I really want to
clinch my diagnosis for an RPGN,
I have to do a renal biopsy.
That's really gonna give me the
definitive etiology behind what's going on.
So in terms of treatment for our
glomerular diseases that manifest as RPGN,
it's going to depend
on the underlying cause.
So this typically involves high dose parenteral steroids
which can be quite difficult for patients to take.
Cyclophosphamide, which is an alkylating agent or
Rituximab which is a monoclonal antibody to CD20.
And then tapering those steroids over a
6-month period of time to a lower dose.
Again, we'll talk about this much more in depth
when we get to our nephritic syndrome lectures.
And patients will often have an
extended maintenance therapy as well,
either with Rituximab or something like
Azathioprine which is an anti-metabolite
in order to maintain the remission.
Okay, so that concludes
our glomerular diseases.