Acute Nephritic Syndrome: Fundamentals

00:01 Hello, and welcome back to the nephrology curriculum.

00:03 Today, we're gonna be talking about nephritic syndromes.

00:07 Nephritic syndromes are part of the glomerular diseases and I can say as a nephrologist, they're probably one of the most exciting aspects of my job.

00:14 So, when we think about acute nephritic syndrome, it's characterized by 5 different components from the clinical standpoint.

00:22 This includes hematuria of glomerular origin.

00:26 That means that when I look at the urine underneath the microscope, I can see what we call dysmorphic red blood cells.

00:33 That means that the red blood cell has a funny shape to it.

00:36 So, if you look at the normal red blood cell, you can see that it's beautifully shaped, circular in appearance.

00:41 But when you see a dysmorphic red blood cell, there are these little blebs all over the membrane and sometimes, they even take on a Mickey Mouse appearance.

00:50 It's not uncommon for us to call them Mickey Mouse cells.

00:52 We can also see red blood cell cast and that means that these red blood cells collect in the tubule, they bind with that Tamm-Horsfall protein, and they form this beautiful cylindrical cast full of red blood cells with just a slight reddish hue.

01:07 We also see proteinuria in our nephritic patients and that proteinuria is usually between 150 mg to 3.5 g per day.

01:17 So, what we would term sub-nephrotic.

01:20 Again, we can have some patients who have greater than 3.5 g of proteinuria even though they have nephritic syndrome and these are typically patients who have overlap syndromes.

01:31 That includes membranoproliferative glomerulonephritis and lupus nephritis which we're gonna be talking about today.

01:37 Azotemia also characterizes nephritic syndrome.

01:41 That means we have an elevated blood urea nitrogen, typically that BUN-to-creatinine ratio is greater than 15.

01:48 And oliguria, our patients are classically oliguric, meaning that they make less than 500 mL of urine per day.

01:57 And finally, hypertension.

01:59 Patients who have acute nephritic syndrome will manifest with higher blood pressures.

02:03 This is typically because they are volume overloaded.

02:06 These patients are retaining sodium and it's interesting because they actually have suppression of the renin-angio-aldo system and essentially, they have an increase in the sodium-potassium ATPase at that principal cell that's responsible for that sodium uptake leading to volume overload.

02:24 So, when we think about the different types of disorders that manifest as acute nephritic syndrome, they include membranoproliferative glomerulonephritis.

02:33 It's a little bit difficult to say so we like to abbreviate that as MPGN.

02:38 There's IgA nephropathy, post-infectious glomerulonephritis and some people refer to that as infection-associated glomerulonephritis.

02:48 Lupus nephritis and then there are the rapidly progressive glomerulonephritis.

02:54 And what that means is that patients, clinically, have a rapid deterioration in their renal function and morphologically, when we biopsy these patients, on pathology, we see something called necrosis and crescents.

03:09 These include anti-GBM disease, Goodpasture syndrome if it includes both lung and kidney.

03:15 The immune-complex diseases that I just spoke about.

03:19 That includes lupus, IgA, post-infectious, and MPGN.

03:24 If they manifest with a rapid deterioration in renal function and morphologically, they have crescents and necrosis on pathology, those patients would be considered in RPGN.

03:36 And finally, the Pauci-immune glomerulonephritis and that includes our ANCA-associated vasculitis.