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