Chapter One · The label most people are given
One of the things people type into Google most is what is a normal eGFR for my age
.
The honest answer is: normal compared to whom? Your own number from last year tells you more than any table. This chapter is about reading the trend, not the threshold.
A stage number, a follow-up in six months, and no name for the cause.
Start with a phone call. Your doctor’s office has a triage line and a nurse will talk it through with you. They are good at this, they do it all day, and it costs nothing. You ring the main number and ask for the triage nurse. There is no charge and you do not need an appointment.
If it feels more serious than that, go to urgent care. You will usually be seen faster than at a hospital.
If it feels life-threatening — chest pain, trouble breathing, confusion, no urine at all for a day — call 911 or go to the emergency room. Do not wait until you are sure. Take the more cautious road.
Rather listen?
Takes about 8 minutes, read aloud. It is the same words as the page below, so nothing is missing if you would rather read. Download it to keep on your phone — it will play with no signal, in a waiting room or a car.
Chronic kidney disease is a description, not a cause. It says the kidneys are
filtering less well than they should and have been for a while. It says nothing about
why.
→ where this is explained: What those three words actually say
A stage is a measurement, not an explanation. Stage 3 means a filtering
estimate in a certain range on two occasions. Two people at the same stage can have
nothing else in common.
→ where this is explained: A stage is a ruler, not a reason
In a large share of cases nobody ever looks for the cause — not from
carelessness, but because a plausible reason is already on the chart.
→ where this is explained: Why the cause often goes unlooked-for
Tick the ones that apply. The bar below shows how much they add up to.
What we would do, as a friend rather than as your doctor. This is our opinion and we stand behind it. It is not medical advice and we are not examining you.
It is not a one-time reading. If you start feeling worse while you are deciding, move up a level. Nobody has ever been criticised for turning up and being sent home. A false alarm is the best possible outcome here.
If none of these apply, the rest of this chapter is worth your time. Take it slowly; there is no clock on it.
Chronic means it has been present for at least three months. Kidney disease means the kidneys are not filtering as well as expected for your age, or that something is leaking through them that should not be — usually protein.
That is the whole content of the phrase. It is a finding, in the way that “a fever” is a finding. Nobody stops at fever.
The stage comes from an estimate of how fast the kidneys are filtering, calculated from a blood test. It is a useful ruler. It measures how much, never why.
Grade B The estimate itself has a known weakness worth understanding: it is calculated from creatinine, a waste product of muscle. Someone who has lost muscle produces less of it, so the estimate can read better than the kidneys actually are. A second test, cystatin C, does not depend on muscle. Where the two disagree, the difference is information.
Not carelessness. Usually the opposite — a reason is already on the chart.
If you also have diabetes or high blood pressure, either is a common and sufficient explanation for failing kidneys, and the reasoning stops there. Most of the time that reasoning is right. When it is wrong, it is wrong quietly and for years, because nothing prompts anyone to reopen it.
There is one pattern that should reopen it: heavy protein in the urine. Damage from long-standing high blood pressure does not usually cause heavy protein loss, and diabetic kidney damage that heavy is normally accompanied by diabetic changes in the eyes. Heavy protein without those is a mismatch, and a mismatch is a reason to look further.
Two causes sit inside the circle, and they are connected.
MGRS — a small number of cells in the bone marrow make one abnormal protein. Too few to be called a cancer. The protein itself damages the kidney.
C3 glomerulopathy — part of the immune system that is meant to idle instead runs continuously, and deposits in the kidney’s filters.
They are connected because in adults, particularly after fifty, the first can be the cause of the second. A finding of C3G in an older adult is a reason to look for a monoclonal protein, and that look is often not made.
“What do you think is causing this, and how sure are we?”
“How much protein am I spilling, and is that amount consistent with the cause we are assuming?”
“Has a cystatin C been done alongside the creatinine? Do the two agree?”
“If the cause is not certain, what would it take to find out — and is a kidney biopsy on the table?”
A free app called Insight Kidney walks through the kidney from the whole organ down to a single filter, and shows what changes at each stage, from one to five. It is the clearest picture of this we have found, and some people take in a shape far faster than a paragraph.
It is made by Anima Res, a German medical animation studio, and it was paid for by Novartis, who sell drugs for some of these conditions. We have no connection to either one. We link it because the anatomy is good, and we name who paid so you can weigh that yourself.
It is a phone app, and it opens outside this book. App Store · Google Play · what it is
Next chapter: My blood has an odd protein and my kidneys are getting worse
Written from the general clinical literature. Nothing on this page comes from any individual’s medical record. Where a statement rests on evidence that is established rather than universal, it carries a grade.