You already know about your heart. You monitor your hormones. You think about your brain. But the organ most likely to quietly derail your health as you age is one you almost never think about. Meet your kidneys – and the remarkable man who first fought to understand them.
Here is something your GP probably hasn’t mentioned. Right now, as you read this, two organs the size of your fists are doing something extraordinary. They are filtering your entire blood supply – every drop of it – roughly thirty times a day. They are sorting, at a molecular level, between what your body needs and what will poison it if allowed to stay. They are doing this without instruction, without rest, and almost certainly without your notice. They are your kidneys, and they are among the most sophisticated pieces of biological engineering in the human body.
They are also, for most of us, almost entirely invisible – until something goes wrong.
Around 37 million adults in the US have chronic kidney disease. In the UK, the figure runs to around three million. In both countries, nine out of ten people with the condition don’t know they have it. There are no early symptoms. No obvious warning signs. Kidney disease tends to arrive not as a crisis but as a quiet erosion – a gradual loss of function that can go undetected for years while the damage accumulates.
“Nine out of ten people with chronic kidney disease don’t know they have it. It tends to arrive not as a crisis, but as a quiet erosion.”
And it is, statistically, a woman’s problem as much as a man’s. Women are more likely to develop chronic kidney disease than men. They are also less likely to be referred for specialist care once they do. If you are in your forties, fifties or sixties and you are thinking seriously about your health in the decades ahead, your kidneys deserve a place in that conversation – alongside your heart, your bones, your hormones, and your brain.
But to understand why kidney health matters so much, and why medicine was so slow to take it seriously, it helps to know a story. A story that begins in a Dutch hospital in 1938, with a young doctor standing at the bedside of a dying man, and ends with a machine built from sausage casing and a salvaged car part that would go on to save three million lives.
The Man Who Refused to Accept the Answer
Willem Kolff was twenty-eight years old, newly qualified, and in charge of four beds in a Groningen clinic when he met Jan Bruning. Bruning was twenty-two. A farmer’s son. And his kidneys had stopped working.
End-stage renal failure in 1938 was not a diagnosis so much as a sentence. Kolff watched Bruning go blind – the urea accumulating in his blood reaching his optic nerves and taking his sight. Then the vomiting. Then the long, miserable slide into unconsciousness. The body, deprived of the system that keeps it clean, drowning in its own waste products. There was nothing in the medical literature that suggested any other outcome was possible.
When it was over, Kolff went to find Bruning’s mother – a farming woman in the black dress and white cap of her region – and told her that her son was gone. Her son could have been his brother. He was devastated that medicine had no answers to give either of them.
He walked away from that conversation with a question he could not put down: the kidneys excrete roughly twenty grams of urea a day. What if something else could remove that same amount artificially? Not cure the patient. Just – not let them die. It was an engineering approach to a medical problem. Most of his colleagues would likely have thrown their hands up in horror. But he kept his counsel and started to do the maths.
An Occupied Country, and an Unexpected Freedom
Then Germany invaded, and everything changed.
When the Nazis occupied the Netherlands in May 1940, Kolff’s mentor at Groningen – a Jewish professor named Paul Daniels who had sponsored his early research – committed suicide rather than hand himself in to the Nazis. Out of loyalty and patriotism, Kolff chose a form of internal exile. He found a post in Kampen, a small city on the river IJssel, where he became the hospital’s second internist and, in his spare time, the man building a kidney from whatever the occupation had left lying around.
“He built a kidney from sausage casing and a salvaged Citroën drum. By any conventional measure it was not a medical device. It worked anyway.”
Kampen’s chief advantage was its insignificance. The occupation administration had no interest in what a provincial internist was doing between his rounds. He could fail, try again, and fail differently without interference – the most valuable thing available to any serious researcher.
The machine he built there was twenty-one metres of cellophane sausage casing – the kind butchers used – coiled around a wooden drum salvaged from a wrecked Citroën, rotating slowly in a bath of dialysing fluid. Blood moved through the membrane, surrendered its toxins to the fluid on the other side, and came back cleaned. By any conventional measure it was not a medical device. It worked anyway.
His team was assembled on the same principle of necessity over credential. A head nurse with more authority than him. A carpenter-turned-porter who could make anything from anything. A medical student on the run from the Gestapo who needed somewhere to disappear and stayed fifteen months. And his wife, Janke, who funded most of it from her family’s money because no institution would. Her contribution, she said later, was to make an atmosphere in which Pim Kolff could work. There are worse things to leave behind.
Patient Number One
Janny Schrijver was twenty-nine, a housemaid, when she arrived at Kampen in March 1943 on an ambulance bicycle with her father walking alongside. She had collapsed at work months earlier and lost her sight. An ophthalmologist had understood that her eyes were a symptom, not the problem: her kidneys were destroying her. By the time she reached Kolff she was intermittently conscious.
Her father asked the only question that mattered. Kolff told him the truth: she was gravely ill, the chances were poor, he would do what he could. The priest came to give his blessing. Then Janny was taken down the corridor to the room where the drum sat in its bath.
For a fortnight the team worked in relay – blood withdrawn, processed, returned. She held on. But each connection required the sacrifice of a blood vessel, and the body has a finite number of accessible vessels. Running out of time, Kolff made a decision no one had made before: continuous circuit. Her blood in permanent motion through the drum. It had not been attempted anywhere.
On the fourth of April, 1943, Janny Schrijver opened her eyes. She knew where she was. She could speak. The exhausted team standing at her bedside understood they were looking at something that had not, to that point, existed: a person returned from a uraemic coma by a machine.
Two days later she relapsed. They connected the machine and she came back. This happened four times – each time she returned to herself, spoke to her family, was briefly and completely present before the darkness took her again. Her kidneys were chronically destroyed, not acutely failing, and the technology that would eventually make permanent dialysis possible was seventeen years away. The vessels gave out. They disconnected her. She died.
Kolff wrote her up in his records as Patient Number One.
Her father came to find him afterward. He had watched his daughter returned from death four times by a machine built from salvage in a provincial hospital. Every doctor before Kolff had told him she would not survive. She had not. But he had seen her open her eyes, and he knew what that meant. He offered to fund the work. Kolff eventually accepted sixty guilders. The farmer went home, buried his daughter, and became one of Kolff’s most steadfast backers. It was not grief. It was an accurate reading of what he had witnessed.
The Patient Nobody Wanted to Save
The war ended in April 1945. Five months later, a woman named Sophia Schafstadt was connected to the machine as patient number seventeen. She had acute renal failure – the reversible kind, if the body could be held long enough. She also had a problem that had nothing to do with medicine: she was a known collaborator, and the townspeople of Kampen thought she did not deserve to live.
Kolff had taken an oath. He connected her.
Thirteen hours. Eighty grams of urea removed from her blood. In the morning she was alive – the first person in the recorded history of medicine to survive acute renal failure because a machine performed the function her kidneys could not. The experiment that had begun with a dying young man and a mother in a white cap had become, finally, a proof of concept. Kolff’s machine – crude, improvised, built in an occupied country from materials the war had left lying around – had crossed the line from idea to fact.
The Scribner shunt, invented in Seattle in 1960, would eventually solve the vascular access problem and make long-term dialysis possible. Today, three million people worldwide are alive because of the treatment Kolff’s machine made thinkable. The modern dialyser is the size of a thermos flask. It operates on the same principle as twenty-one metres of butcher’s sausage casing rotating in a bath of fluid in a hospital in wartime Holland.
