welcome to another MedCram lecture we're gonna talk about you 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 it's gonna go down into the toilet okay it flushes down so basically
anything that gets outside this area is gonna eventually end up in the urine I
think that's a very important thing to remember if you can remember this
I'm addict of what a glomerulus looks like you remember that you've got a
vasculature 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
especial the 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 gonna 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 ewwww 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 this situation the patient is going to have a
hypercoagulable state and since this protein is lost here in nephrotic
syndrome because these Poteau sites 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 a
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 break down 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 nephritic syndrome 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 isn't 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 call
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 nephrotic 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 1/2 grams a day and nothing
else there's no active sediment as 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 a 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