How does diabetes affect the kidneys?

We know that after a few years when the blood glucose remains uncontrolled, the cells lining the small arteries and capillaries - the endothelial cells, can be damaged. We have seen the important role played by the endothelial cells in glomerulii where they allow wastes to be filtered out but keep back the useful substances in the blood.

Even the basement membrane gets damaged and cannot function effectively as a selective barrier.

When this happens, the kidneys cannot function properly as the "fabulous filters" they are supposed to be and start "leaking"! Increased amounts of protein leak out in the urine and this is often the earliest way in which diabetic kidney damage is diagnosed. In the early stages, the amount of protein (albumin) which leaks out in the urine is very small in quantity and is called 'microalbuminuria". The presence of microalbuminuria is one of the earliest signs of diabetic kidney damage (when all other causes for the presence of albumin in the urine have been ruled out) and your doctor will often ask you to do a "microalbumin" test to see if the diabetes has affected your kidneys. (In the later stages, when a lot of protein is lost in the urine, this is then called "macroalbuminuria".)

The normal removal of excess salt and water from the body is reduced and toxic substances build up in the blood.

This failure in kidney function resulting from diabetes is called "diabetic nephropathy".

You should realize that all the "filters" do not fail at the same time. But as an increasing number of the filters start failing, increased stress is put on the remaining filters, specially if the blood glucose remains uncontrolled and the blood pressure is high. Soon these too will start failing and this is why there is a gradual decline in kidney function until a stage is reached where the remaining filters are just unable to cope and we reach a stage called end stage renal disease(ESRD), when the kidneys are just not able to carry out any of its functions! ESRD is very serious. A person with ESRD needs either to have a kidney transplant or to have the blood filtered by machine (dialysis).

We have seen that diabetes can also affect the nerves. If the nerves in the body are damaged by diabetes (this is called neuropathy) this can affect control of the bladder, resulting in difficulty in emptying the bladder. Urine can remain in the bladder and the pressure that builds up can back-up and damage the kidneys.

In addition, if the urine stays in the bladder for a long period of time infection may develop because of the rapid growth of bacteria in urine with a high sugar content. People with diabetes must take special care to avoid infections and have them treated immediately.

Who Gets Kidney Disease?

Not everyone with diabetes develops kidney disease. Factors that can influence development include genetics, blood glucose control, and blood pressure.

The better a person keeps diabetes under control, the lower the chance of getting kidney disease. High blood pressure should also be kept under control. The healthier the blood pressure, the healthier the kidneys will be.

More than 40 percent of people with type1 diabetes will one day have kidney disease, compared with perhaps 10 percent of people with type 2 diabetes. People with type 1 diabetes have 15 times the risk of ESRD as those with type 2 diabetes. The longer a person has diabetes, the higher the risk of kidney disease--up to a point. After 40 years with diabetes, if a person does not yet have kidney disease, he or she probably never will.

Men are 50 percent more likely to get kidney disease than women. Most people who get diabetic kidney disease also have diabetic eye problems

How would one know if one has diabetic kidney disease?

The kidneys work so hard to make up for the failing capillaries that kidney disease produces no symptoms until almost all function is gone. Also, the symptoms are not specific. Some of the signs and symptoms which you must look out for are:

1. Frothy urine (signifying protein in urine)
2. Protein in urine (as determined by urine dipstick or other urine tests)
3. Leg swelling (worse after walking/standing)
4. High blood pressure
5. Itching
6. Nausea and/or vomiting
7. Losing weight
8. Lethargy
9. Increased need to urinate at night
10. Requiring less pills or insulin to control diabetes

But more importantly, you may have no signs or symptoms even though your kidneys are affected. Which is why it is very important to see your doctor regularly and your doctor can check your urine for proteins especially microalbuminuria, see about your blood glucose control, check whether blood pressure is high, and detect diabetic eye problems.

Please do NOT wait for the signs and symptoms to develop. They usually are seen when the disease is somewhat advanced.

It is important to diagnose diabetic kidney disease at the earliest stage so that your doctor can advise you about how best to protect your "fabulous filters" from further damage and thereby slow the progression of the disease!

Treatment: Preventing and Slowing Kidney Disease

Treatment for diabetic nephropathy attempts to manage and slow the progression of the disease.

Strict blood sugar control is important in the protection of kidney function. Intensive blood sugar regulation requires frequent monitoring and commitment.

Antihypertensive drugs and low-protein diets can slow kidney disease when significant nephropathy is present, as in stages III and IV. A third treatment, known as intensive management of blood glucose or glycemic control, has shown great promise for people with type 1 and type 2 diabetes, especially for those in early stages of nephropathy.

Studies have shown that a food control of the blood glucose levels can lead to almost a 50% reduction in the development and rate of progression of diabetic nephropathy especially in the early stages (I and II). Other studies have shown that after 5 years of tight control patients showed much less lesions in the glomerulii.

Aggressive blood pressure control is by far the most important factor in protecting kidney function, regardless of the stage of the disease. People with diabetes should keep their blood pressure at 130/85 or lower and that people with renal insufficiency (proteinuria greater than 1 gm/24 hrs) keep their blood pressure at 125/75 or lower.

The combination of kidney disease and high blood pressure is "double trouble"! High blood pressure can not only increase the kidney damage, but such kidney damage also increases the blood pressure. So one gets into a viscious cycle, with kidney disease increasing the blood pressure, which in turn leads to a greater degree of kidney disease! The only way to break this cycle is to control the blood pressure well with all the available means. Early detection and treatment of even mild hypertension are essential for people with diabetes.

High blood pressure, or hypertension, is a major factor in the development of kidney problems in people with diabetes.

Angiotensin-converting enzyme (ACE) inhibitors protect the kidneys more effectively than other antihypertensive medications. A new class of blood pressure medications known as angiotensin-receptor blockers (ARBs) may offer comparable protection. Patients who cannot tolerate ACE inhibitors may use an ARB. Maximum doses of an ACE along with an ARB may provide additional renal protection in people who can tolerate the medications.

In fact, your doctor may start an ACE inhibitor or an ARB even when you do not have high blood pressure. It has been shown that this leads to a decrease in the microalbumin levels and definitely delays the rate at which the kidney disease progresses.

You must ask your doctor about this.

Dietary protein restriction. A diet containing reduced amounts of protein may benefit people with kidney disease of diabetes. In people with diabetes, excessive consumption of protein may be harmful. This is usually of benefit when kidney disease is at an advanced stage.