Sidebar: eGFR, EPO, BUN, EIEIO.

Okay… this is my attempt at explaining what all this kidney stuff means. If I could do it in rhyme, Dr. Seuss fashion, I would, because that’s about the level of my understanding.

So the kidneys… they filter pretty much everything. We got that. But they also are very important in the production of red blood cells that carry (among other things) hemoglobin to the rest of the body.

Damaged kidneys = fewer red blood cells = anemia.

EPO: shorthand for erythropoietin, the hormone that prompts the bone marrow to make the red blood cells.

Not enough EPO = fewer red blood cells = anemia.

Creatinine: Not to be confused with creatine, although they are related. Creatinine is a waste product produced by the muscles and filtered out of the system through the kidneys. If the creatinine level is abnormally high, this means the filtering ability of the kidneys is damaged so the creatinine is not being cleared from the blood.

Abnormally high creatinine = likely kidney disease.

BUN: Blood Urea Nitrogen. Similar to creatinine levels, an abnormally high level of BUN indicates kidney disease as the kidneys are not filtering the BUN from the blood effectively. Urea nitrogen is a biproduct of the breakdown of proteins from food. This is done in the liver.

Abnormally high BUN = likely kidney disease.

eGFR: estimated glomerular filtration rate. This is pretty much the gold standard for evaluating kidney function. The glomeruli are the actual filters of the kidneys. If the glomeruli are functioning well, your kidneys are filtering your blood as they should be. The number itself is derived from the creatinine level in your blood, along with your age, weight, and gender. The numbers essentially correspond to the percentage of kidney function. The breakdown is as follows:

Stage 1, eGFR of >90: kidney damage, but normal kidney function.

Stage 2, eGFR of 89 – 60: kidney damage with mild loss of kidney function

Stage 3a, eGFR of 59 – 45: mild to moderate loss of kidney function.

Stage 3b, eGFR of 44 – 30: moderate to severe loss of kidney function.

Stage 4, eGFR of 29 – 15: severe loss of kidney function.

Stage 5, eGFR of <15: kidney failure, also knows as end stage renal disease or ESDR. At stage 5, either dialysis or kidney transplant is required.

Many of the old school tests didn’t provide a specific eGFR number. It would just say >60, and that was good enough. But generally the newer tests will provide a specific eGFR. Check your creatinine level to see if it was in the normal range just for confirmation of your kidney function.

So… my eGFR had dropped from normal to 32 in four months. That’s quite alarming. But as I look back through my painstakingly plotted lab results, it’s easy to see that it had been gradually decreasing since 2016. It’s been hovering in the mid-30s since April of 2019, so at the least, I’m grateful it hasn’t continued to decrease. One can live in stage 3 basically forever, but with the rapid decline I had already experienced, I doubted that I’d be in stage 3 for long.

That’s my incredibly rudimentary explanation of kidney function and how it’s measured.

If I had the time,
I’d make it rhyme.
But I have no skills
Because I’m a dork

Don’t sue me, Dr. Seuss

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