Why does diabetes cause kidney failure?

Doctor's Answer

Hi, I am sorry to hear that your grandmother has diabetes and she is at risk of developing diabetic kidney disease (aka diabetic nephropathy); which means diabetes affecting the kidney, damaging it and potentially leading to kidney failure.

In fact, diabetes is the most common cause of total kidney failure worldwide and in Singapore. Around 40% of patients with diabetes develop kidney problems. Many of them can progress to total kidney failure, needing dialysis or kidney transplant to remain alive.

Besides, patients with diabetic kidney disease and even more with total kidney failure are susceptible to many medical complications, including heart attacks, strokes and disabilities, which can affect dramatically the length and quality of life of the patients who suffer them.

My intention is not to scare you but to create awareness of the potential risks, even if at present the disease seems not to be advanced. But we all know that prevention is better than cure. Thus, I concur with your doctor recommending better blood sugar control to prevent the appearance and/or the progression of diabetic kidney disease into total kidney failure. In addition, good blood sugar control can also help minimising the risk of other complications like blindness and amputations; certainly, it will protect the heart and can reduce blood cholesterol and uric acid and help in losing or maintaining weight.

But how does diabetes cause kidney problems?

Persistent high blood levels of sugar (poor diabetic control) progressively damages many organs of the body which are rich in blood vessels like the heart, eyes, brain and kidneys, and affect the circulation to the limbs. Simplistically, the excess of blood sugar kind of “caramelises” inside the blood vessels and tissues and that causes inflammation, damage and scarring.

Specifically, in the kidney, high blood sugar progressively damages the filters of the kidneys (the ones that clean the blood), and patients start leaking proteins in the urine. If poor sugar control remains, it can lead to progressive scarring of the kidneys, losing their capacity to clean the blood and control body water, with consequent elevation of blood creatinine (a marker of kidney disease) and toxins in the blood.

Never is too late to improve her sugar control. It could prevent the occurrence of diabetic kidney disease, or slow its progression or minimise the impact it has in her health. And the protection of her kidneys will be more impactful if any other little problems that she might have can be controlled and optimised like high blood pressure, overweight, high cholesterol, etc. Doctors also can give some medications to protect, at least partially, the kidneys, the so-called “renin-angiotensin-aldosterone blockade”, and occasionally and if necessary advise on a diet low in protein and salt, and recommend avoidance of bad habits like smoking.

Diet plays a crucial role in the management of diabetic patients to obtain better sugar control, even if taking medications. Medications are necessary for many patients with diabetes, but they are not a substitute for diet control: they are complementary. But many patients think that by taking medications their diet does not need to be controlled. On the contrary, medications will work better if eating a healthier diet; and in fact, many patients can control her diabetes with diet only.

Many patients find difficult to control their diet, as indeed diet and eating are pleasures and social activities, but with good support and advice from doctors and dieticians, it is possible to adopt a healthier diet and improve blood sugar control. And even this can be achieved without excessive restrictions, with a personalised diet; in order to foster the sustainability of the diet regimen and of the blood sugar control.

Dr Francisco, wishing your grandmother the best possible health.

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