Let's move on to our next clinical case.
A 28-year-old man presents to his primary care provider for new onset cola-colored urine.
In questioning him further, he recalls a terrible sore throat a few weeks ago
that resolved with some antibiotics he was given at the urgent care center.
On physical exam, he's noted to have an elevated blood pressure at 147/90 mmHg which is new for him.
He was lower-extremity edema and periorbital edema.
His serum creatinine is high at 1.9 mg/dL
and his urine analysis shows numerous red blood cells
and he also has white blood cells in there as well.
Nearly all of those red blood cells, when looking underneath the microscope,
showed dysmorphic features and he actually has 2-3 red blood cell cast per high power field.
On a urinary spot albumin-to-creatinine ratio, it estimates about 2 g per gram of albumin.
So, estimating about 2 g of protein excretion with a 24-hour period of time.
He has a low serum complement C3 but he has a normal serum complement C4.
So, what is the etiology of this patient's renal presentation?
Let's see if we can find some clues in our case.
So, one of the things that is important to note, he has cola-colored urine.
When people describe tea or cola-colored urine,
remember, that really is a symptom or sign of gross hematuria.
Hematuria or blood cell seen with a naked eye.
The other thing that's really important is he's describing an infection,
an upper respiratory infection, in particular, a sore throat.
But that happened weeks ago before the onset of the tea-colored urine.
So, that temporal correlation is important.
It's not synpharyngitic like it was with our IgA nephropathy.
He had the sore throat first, treated with antibiotics,
and now, he's manifesting with a tea-colored urine.
That's more indicative of a post-infectious glomerulonephritis.
The other thing which is important,
he's got some signs of nephritic syndrome with his elevated blood pressure.
Again, those dysmorphic RBCs. He is volume overloaded or hypertensive.
Again, he's got that periorbital edema. And his laboratory values.
So, he's got an elevated creatinine, he's got those dysmorphic-looking red blood cells,
and I think the clincher here is we have a low C3 complement and a normal C4.
That is an alert to us telling us that the alternative pathway of complement activation is being turned on
and there's only a couple of things that we need to think about with that.
We're either thinking about complement mediated MPGN
or something like infection-associated GN and in fact, that's what this gentleman has,
post-infectious or infection-associated GN.