Why the Kidneys Are Called the “Silent Organs” — and How to Protect Them

Last updated 14 July 2026

A man goes for a company medical check-up. He feels fine. He has felt fine for years: no pain, no swelling, nothing that would make him take a day off work. A week later the clinic calls him back, because a routine blood test has shown he has already lost more than half of his kidney function. Nothing hurt, because a kidney does not hurt when it is dying. It simply gets quieter.

That is the whole problem with kidney disease, and it is why doctors call the kidneys the silent organs. Almost every other organ complains: a blocked heart artery causes chest pain, an inflamed stomach burns. Failing kidneys do none of this. They keep working quietly until they can no longer cover for the damage, and by then much of it cannot be taken back.

A million filters, and a very generous safety margin

Each kidney is made up of roughly one million tiny filtering units called nephrons, a figure published by the National Institute of Diabetes and Digestive and Kidney Diseases in the United States. That is about two million filters working in parallel. Between them, according to the National Kidney Foundation of Malaysia, they take in about a fifth of all the blood your heart pumps and filter some 180 litres of fluid a day, returning nearly all of it and passing about two litres as urine.

Two million filters is far more than you need. The surplus is reserve, and it is the reason kidney disease can quietly destroy years of function without producing a single symptom you would notice.

Hyperfiltration: how the survivors cover for the dead

When nephrons are damaged and die, whether from years of high blood sugar or high blood pressure, they are not replaced. You cannot grow new ones. Instead, the surviving nephrons take on more work. Each one increases the rate at which it filters blood, so the kidney’s total output stays roughly the same even though fewer units are doing the job. Nephrologists call this glomerular hyperfiltration, and it is the real biological answer to the question in the title.

Think of a factory that loses a third of its workers. If those who remain each speed up, total output looks unchanged, and anyone reading the production figures would conclude nothing is wrong. That is exactly what a blood test shows in early kidney disease: normal numbers, from a kidney quietly running short of staff.

The compensation is very effective, which is precisely the trouble. Creatinine, the waste product used to estimate kidney function, does not climb meaningfully in the blood until a substantial share of filtering capacity is already gone. Your result stays normal. You feel normal. The nephrons keep dying. Nor is the compensation free: driving the survivors harder puts them under pressure that damages them in turn, so the rescue mechanism becomes part of the disease.

The one-kidney confusion, and why it misleads people

There is a common belief that our kidneys are so efficient that if one is damaged, the other simply carries on. People point to living donors as proof: someone gives away a kidney, walks out of hospital, and lives a completely normal life.

That part is true. People with a single healthy kidney generally have no symptoms and lead full lives, and serious complications are uncommon. Losing one kidney is genuinely survivable. But it is the wrong mental model for chronic kidney disease, and holding it is dangerous.

A donor loses one whole kidney and keeps one entirely healthy one. Chronic kidney disease does not work like that. Diabetes and high blood pressure travel in the blood, and blood goes to both kidneys. The damage is not sitting in one organ while the other stands by as a spare. Both kidneys are injured at the same time, at the same rate, by the same disease. There is no healthy backup in reserve.

So the image of the spare kidney is exactly backwards. You do not have a second kidney to fall back on. You have a reserve of nephrons spread across both kidneys, and chronic kidney disease eats through it on both sides at once. The silence is not a sign of safety. It is a sign that the reserve has not run out yet.

The staging ladder, and where symptoms actually appear

Doctors track kidney function with the eGFR, or estimated glomerular filtration rate. Roughly speaking, it is a percentage of normal filtering capacity. Malaysia does not run its own staging system for this. The Ministry of Health’s clinical practice guideline on chronic kidney disease instructs doctors here to classify the disease using the international KDIGO staging, which sorts kidney function into five G stages.

Stage	eGFR	Loss of function	Typical symptoms
G1	90 or higher, with kidney damage	Normal filtering, but already leaking protein	None
G2	60 to 89, with kidney damage	Mild	None
G3a	45 to 59	Mild to moderate	Usually none
G3b	30 to 44	Moderate to severe	Vague, if any
G4	15 to 29	Severe	Often present, but easily misread
G5	Below 15	Kidney failure	Dialysis or transplant needed

Look at where the symptom column stays empty. A person can walk through stages 1, 2 and 3 feeling perfectly well, and stage 3 already means roughly half their filtering capacity is gone. By the time the disease reaches G5, the stage the guideline calls renal failure, filtering is below 15, which is under a sixth of what a healthy adult starts with. And symptoms stay unreliable right up to that point. In the nationwide Malaysian study of kidney disease published in BMC Nephrology in 2020, only 5 percent of the people found to have chronic kidney disease knew they had it. Nineteen out of twenty were walking around unaware.

When the symptoms do come, they lie

Eventually the reserve runs out and symptoms appear. The cruelty is that not one of them says “kidney”. Every one has an innocent explanation ready.

• Tiredness that does not lift. Failing kidneys stop making enough of the hormone that drives red blood cell production, so anaemia sets in. Blamed on work or age.
• Itchy skin. Wastes and minerals build up in the blood. Blamed on dry skin.
• Swelling in the ankles, feet or around the eyes. Fluid is no longer cleared properly. Blamed on standing too long.
• Foamy or bubbly urine. Protein leaking through damaged filters, one of the more specific signs. Usually ignored.
• Waking at night to pass urine. Blamed on drinking late, or the prostate.
• Poor appetite, nausea, a metallic taste. Blamed on gastric problems.

None of these is a reliable early warning. Waiting for symptoms is, in practice, a decision to find out late.

How to catch a disease that never announces itself

You cannot feel chronic kidney disease, but you can measure it. Two tests, both cheap, both available at any government klinik kesihatan.

1. A blood test for creatinine, which gives you your eGFR

Creatinine is a waste product of muscle breakdown, cleared by healthy kidneys. The lab measures it in your blood and uses it to calculate your eGFR. Chronic kidney disease is defined, in the Ministry of Health’s guideline on managing the disease in adults, as an eGFR below 60 that has been present for more than three months, or evidence of kidney damage present for more than three months whatever the eGFR. If you have ever had a “renal profile” done, your creatinine was measured. Ask your clinic for the number.

2. A urine test for albumin: the uACR

This is the one most people have never had, and for early detection it is the more important of the two.

Albumin is a protein that belongs in your blood. Healthy filters hold it back; damaged filters let it slip into the urine. The uACR measures how much is escaping.

Here is why it matters so much. Because of hyperfiltration, your eGFR can look completely normal while your filters are already leaking. That second half of the definition above, evidence of kidney damage with a normal eGFR, is precisely this situation. The guideline asks for an early morning urine sample, and tells doctors to confirm a positive result with a repeat test within three months, because a single raised reading can be caused by fever, exercise, a urinary infection or menstruation. It also tells them to do the albumin test on people with diabetes even when the ordinary urine dipstick shows nothing, because the dipstick misses the early leak. The urine test sees the damage while the blood test is still reassuring you.

uACR result	Category	What it means
Below 30 mg/g	A1	Normal to mildly increased
30 to 300 mg/g	A2	Moderately increased; needs repeat testing and follow-up
Above 300 mg/g	A3	Severely increased; needs prompt medical attention

If you take one thing from this article, take this: ask for a urine albumin test, not just a blood test. Blood alone is not enough.

Who should be tested, and how often

The National Renal Registry’s 32nd Report of the Malaysian Dialysis and Transplant Registry recorded 55,237 people on dialysis in this country at the end of 2024. Among those who started dialysis that year, diabetes was the cause in 54.6 percent of cases and high blood pressure in a further 31.1 percent: more than eight in ten between them.

Now set that against how common those conditions are. The National Health and Morbidity Survey 2023, run by Malaysia’s Institute for Public Health, found that 15.6 percent of Malaysian adults have diabetes and 29.2 percent have hypertension. The same survey found 85.2 percent of Malaysians rate their own health as excellent or good. Feeling well is not evidence of being well.

The Ministry of Health’s guideline sets out who should be screened, and it is worth knowing whether you are on the list. Anyone with diabetes or high blood pressure should be screened at least once a year, without exception. Screening should also be considered if you have any of the following:

• Age over 65.
• Obesity.
• Heart disease, or metabolic syndrome.
• A family history of kidney disease or hereditary kidney disease.
• Gout.
• Regular use of drugs that can harm the kidney, including long-term painkillers and long-term proton pump inhibitors.
• Kidney stones, structural problems of the urinary tract, or an enlarged prostate.
• Protein or blood found in the urine by chance during some other check.

If you have diabetes, it is worth understanding how diabetes raises your heart risk too, because the same blood vessel damage that harms your kidneys harms your heart.

What protecting your kidneys actually means

Once you know your numbers, protection becomes specific.

Control the two diseases behind most of the damage. Blood sugar and blood pressure are not side issues. They are the main event, and keeping them in range is the most powerful thing you can do for your kidneys. Cutting back on salt helps directly, and our guide to how much salt, sugar and fat is too much is a practical place to start.

Ask about kidney-protective medicines. The Malaysian guideline names ACE inhibitors and angiotensin receptor blockers as proven treatments for delaying kidney disease, not merely for lowering blood pressure. Worth raising if your uACR is high.

Be careful with painkillers and unregulated remedies. The guideline tells doctors to avoid anti-inflammatory painkillers in people with kidney disease and names them individually, from mefenamic acid to diclofenac. It also warns that certain herbal products, including those containing aristolochic acid, are associated with chronic kidney disease. Our companion article on everyday kidney care covers this in detail.

And on water, a correction. Your kidneys are not a filter that gets rinsed clean by drinking more. They filter your blood continuously, every minute, whether you drink a lot or a little. Extra water does not scrub anything out of them, and no daily quota protects them. Drink enough to keep your urine pale, and more in hot weather or during exercise. That is all.

More importantly, this advice reverses in advanced kidney disease. People with advanced kidney disease or heart failure are often put on a strict fluid restriction, because their kidneys can no longer clear the extra water and it backs up into their legs and lungs. For them, drinking more is not healthy. It is harmful. If your doctor has given you a fluid limit, follow it.

The kidneys will not tell you when something is wrong. That is not a flaw you can outsmart by paying closer attention to how you feel. It is built into how they work. The only way to hear a silent organ is to test it. Read more in our kidney health section.