welcome to another MedCram lecture we're going to talk about
nephrotic versus nephritic syndrome now these are both syndrome types that occur
in the kidney the question is what's the difference between them and why do they
happen in the first place and to understand that we really need to get
into the pathophysiology of how these syndromes are different so what we have
here is picture of a cross-section of the capillaries in a kidney and what we
have here is the endothelium
it's the endothelial cell and it completely surrounds the lumen of the
vasculature and you notice that there's little slits here that allow things to
get through but not the red blood cells typically then this blue line represents
the basement membrane which is permeable to a number of things and then finally
on the outside is this epithelial cell now the epithelial cell has little foot
processes that you see here that look like little triangles around the edge
and basically these form a very tight sieve which allows only very small
things to get through typically not even proteins are allowed to get through here
proteins are too large and these what we call podocytes
are helpful for that so if you want to imagine that we've got fluid okay
leaving and when that fluid leaves the vasculature lumen and goes through the
slits in the endothelium and the basement membrane and comes out even
through the podocytes of the epithelial cells in the kidney what we're left with
here is basically Bowman's space
this is in Bowman's capsule of course and all of this fluid eventually unless
it gets reabsorbed is going to go down into the toilet okay flushes down so
basically anything that gets outside this area is going to eventually end up
in the urine I think that's a very important thing to remember if you can
remember the schematic of what a glomerulus looks like you remember that
you've got a vascular Chur that comes in and then leaves and you've got a
Bowman's capsule here that picks that up that's what we're looking at here in
this picture and that gets picked up goes into the proximal convoluted tubule
down the descending loop of Henle up the a sending loop into the distal
convoluted tubule and then into the collecting ducts and then out again to
the toilet so once again this is a epithelial cell and this is a
endothelial cell
so what I'd like to do is I'd like to divide this picture if you will into two
and on this side we're going to talk about nephrotic syndrome and on this
side we'll talk about nephritic syndrome
so nephrotic syndrome is fairly straightforward it's a process where for
some reason these podocytes which are all connected to the epithelial cell
aren't working or they get lost or they recede or they involute something makes
them disappear and as a result of that they're not able to keep the protein in
and so as a result of that there is loss of protein and it's quite substantial in
fact on the order of 3 and 1/2 grams of protein per day can be lost
now this tremendous loss of protein has its consequences one of the first
symptoms that you'll see is that the urine is very frothy plus frothy urine
is caused by protein in the urine now don't get alarmed if your urine is
frothy because there's a certain amount of protein that's in there naturally I
guess there is some surfactant and the other type of chemicals that will make
naturally your urine frothy but if it's especially frothy think about protein in
the urine now as a result of this you're also losing protein so if there's not
enough protein in your intravascular space you're not going to be able to
keep that fluid in the intravascular space and you're going to have more
leakage of fluid and so this is what we see in patients with loss of protein is
they become a de mattes and they'll have edema just about all over their bodies
periorbital e-even in their legs and sometimes even in their lungs probably
the main loss of protein is albumin albumin is
the major protein that keeps fluid in the blood vessels now when albumin goes
down because of its loss the liver has to compensate and when the liver
compensates we get increased lipids in the blood this is another sign of
nephrotic syndrome there's also another protein that's lost
called anti thrombin 3 now antithrombin 3 is a very important anticoagulant in
fact it's the same protein that heparin utilizes to exert its effect so the
point is is that if antithrombin 3 is also going down in the situation the
patient is going to have a hypercoagulable state and since this
protein is lost here in nephrotic syndrome because these podocytes are not
working very well the renal vein this is the blood going back after it's lost is
going to be especially poor in antithrombin 3 and that's where we tend
to see thrombosis and if there's thrombosis in the renal vein this could
embolize and you could get blood clots to the lung so you should think of DVT s
and pulmonary embolisms or Pease in patients with nephrotic syndrome so to
review nephrotic syndrome it's basically a problem with the
podocytes or even the basement membrane anything that allows protein to sieve
through here causing frothy urine decreased albumin increased lipids both
in the serum and also in the urine okay you'll see antithrombin 3 being reduced
that leading to a hypercoagulable state typically there's about three and a half
grams of protein lost per day now there are diseases that are not of the kidney
which can cause nephrotic syndrome these are called secondary causes of nephrotic
syndrome and there are diseases which specifically affect the kidney which can
cause nephrotic syndrome these are called primary nephrotic diseases we'll
talk about those in another lecture now on
the nephritic side completely different mechanism of action for causing
nephritic syndrome whereas before there was a problem with the loss of podocytes
in nephritic syndrome what we have is immune complexes so an antibody meeting
up with another antigen and complexing
this type of an immune complex will lodge itself in the capillary as seen
here and it will elicit an immune response against these capillaries and
against these antigens now as a result of this a number of white cells are
recruited as drawn here there will be many more white cells as a result of
this inflammatory response to these immune cells these areas will become
inflamed breakdown and it will allow red blood cells to pour through these
openings not only that but also white blood cells to come through and of
course since these openings are big enough for whole cells to get through
there's also very easily allowed for protein to come through as well and so
very often even though the patient may have nephritic syndrome they may also
have what we call nephrotic range protein area so the protein may also be
high in the frit --ax ind room and leading to all the things that we saw
over here in nephrotic syndrome but in addition to that there's something
that's very very different remember we said all of this stuff on the outside
eventually goes into the urine and so what do you think we would expect to see
in the urine in addition to protein as just mentioned we would also expect to
see blood in the urine sediment in the urine because of this breakdown products
and also what we all pyuria or white cells in the urine
as well and so as a result of this there are a few symptoms that we see in this
nephritic syndrome the first thing we see is hematuria that's blood in the
urine the next thing that we'll see is oliguria or low urine output and that's
because the glomerulus is being damaged and so it can't filter as much because
this immune deposition here is not going to allow the free filtration of filtrate
it's going to become inflamed and the glomerulus is going to start to shut
down that causes a low GFR the other thing that you'll see is high blood
pressure because of that lack of filtration so hypertension the last
thing you'll see is granular casts so this is the main difference between
nephritic and the product usually there's more inflammation on the
nephritic side there's less on the nephrotic side typically if you just see
an increase in protein in the urine at very high levels like 3 and a half grams
a day and nothing else there's no active sediment is what they would say then
think of nephrotic syndrome if on the other hand you see a lot of cells debris
sediments and inflammatory cells think of nephritic syndrome
now just in nephrotic syndrome where there are primary and secondary diseases
which can cause nephrotic syndrome there are also primary and secondary
diseases that can cause nephritic syndrome and we'll discuss that in
upcoming lectures
you