By Adem Lewis / in , , , , , , , , , , , , , , , , , , , , , , , , /


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


Leave a Reply

Your email address will not be published. Required fields are marked *