Jaslok Hospital and Research Centre,
Diabetic nephropathy is the medical word for kidney problems caused by diabetes. It is estimated that diabetic nephropathy develops in approximately:
Diabetic kidney disease (diabetic nephropathy) is common in long standing diabetics especially in those with poor control of the condition. Diabetes damages blood vessels throughout the body and this includes the kidney. Diabetic nephropathy occurs in both types of diabetes - the insulin requiring (type I) and the non-insulin requiring (type II) diabetics. The occurrence of high blood pressure in diabetics is a strong predictor for diabetic nephropathy. For those with existing diabetic nephropathy, uncontrolled blood pressure will aggravate and hasten the progression of this disease to end-stage kidney failure. It is the commonest cause of end stage kidney disease in many countries.
In order to understand what problems diabetic kidney disease can cause, one must have some basic knowledge about the kidneys and what their function is in the body.
The kidneys are the master chemists of the body. Normally, there are two of them, one on either side of the spine under the lower ribs. They are reddish brown in colour and shaped like kidney beans. Each kidney is about the size of your clenched fist. Many other organs depend on the kidneys in order to work properly.
The main job of the kidneys is to remove wastes from the blood and return the cleaned blood back to the body. Every minute, about one litre of blood (one fifth of all the blood pumped by the heart) enters the kidneys through the renal arteries. After the blood is cleaned, it flows back into the body through the renal veins.
Healthy kidneys do three essential things. Besides removing the wastes from the body via the urine, they regulate the levels of water and different minerals needed by the body for good health. They also produce hormones that control other body functions. In fact, many other organs depend on the kidneys in order to work properly.
Inside each kidney there are more than one million tiny units called nephrons. Each nephron is made up of a very small filter called a glomerulus, which is attached to a tubule.
The filtering is carried out through the capillaries which are present in the Bowman's capsule. Seen to the right of the diagram below.
Water and waste products are separated from the blood by the filters and flow into the tubules. Much of this water is reabsorbed by the tubules and the wastes are concentrated into urine.
The tubules receive a combination of waste materials and chemicals that your body can still use. Your kidneys measure out chemicals like sodium, phosphorus, and potassium and release them back to the blood to return to the body. In this way, your kidneys regulate the body's level of these substances. The right balance is necessary for life, but excess levels can be harmful.
The kidneys remove wastes and extra water from the blood to form urine. Urine flows from the kidneys to the bladder through the ureters.
Now let us take a much closer look at the structure of the capillaries where the filtration takes place.
It is clear that the main barriers to filtration are the gaps between the cells lining the capillary (endothelial cells), the basement membrane and the holes in the cells on the other side of the basement membrane.
Wastes, such as urea and creatinine, must also be removed from the body. Urea and other wastes are made when the body breaks down protein, such as meat. Creatinine is a waste product of the muscles. As blood flows through the blood vessels, small molecules such as waste products squeeze through the holes. These waste products become part of the urine. As kidney function decreases, the levels of urea and creatinine in the blood increase.
Useful substances, such as protein and red blood cells, are too big to pass through the holes in the filter. They stay where they belong--in the blood.
Many of the substances in the blood and body fluid must be kept at the correct level for the body to function properly. For example, sodium and potassium are minerals which come from food. These minerals are needed by the body for good health, but they must be kept at specific levels. When the kidneys are working properly, excess minerals, such as sodium and potassium, are excreted from the body in the urine. The kidneys also help to regulate the levels of other minerals, such as calcium and phosphate, which are important for the formation of bone.
The urine is collected from the tubules in a funnel-like renal pelvis and then flows through a tube called the ureter into the bladder. The bladder stores urine until you urinate. Urine passes out of the body through a tube called the urethra. The kidney normally makes one to two litres of urine every day depending on how much you drink.
The normal kidney has the ability to greatly increase its workload. If one kidney is lost, the other kidney can enlarge and do the work of two.
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.
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.
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
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 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.
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.
Whilst many doctors feel that if we diagnose the presence of diabetic kidney disease early enough and take steps such as using drugs to minimize the microalbumin levels, we may even reverse the disease process. Although some others do not agree with this view, everyone is convinced that early and appropriate treatment can definitely delay the rate at which the disease progresses. The most important thing in the management of diabetic kidney disease (diabetic nephropathy) is the treatment of blood pressure if this should be high. Meticulous diabetic control can slow the progression of diabetic kidney disease.
This once again shows the importance of a regular check up with your doctor!
If the kidneys become so damaged that only about 5% of overall kidney function remains, it is called end-stage kidney failure. The average time between the onset of diabetic kidney damage and end-stage kidney failure is variable and can be delayed by good management. For the diabetic person in a reasonable state of well-being, end-stage kidney failure can be treated by dialysis and/or transplantation.
The treatment of end-stage kidney failure involves what is called "Renal Replacement Therapy" Dialysis/haemodialysis (kidney machine) or peritoneal dialysis and kidney transplantation. The type of treatment chosen is determined by the general health and medical condition of the person, by its impact on the person's lifestyle and by the person's personal preference. Many people may receive each one of these three forms of treatment at various times. What may be the best treatment for one person at one time might not be the best for another or for the same person at a different time. The person's doctor will discuss these different treatments with the person and answer questions.
The two major forms of dialysis are hemodialysis and peritoneal dialysis.
In hemodialysis, your blood is sent through a machine that filters away waste products. The clean blood is returned to your body. Hemodialysis is usually performed at a dialysis center three times per week for 3 or 4 hours.
In peritoneal dialysis, a fluid is put into your abdomen. This fluid, called dialysate, captures the waste products from your blood. After a few hours, the dialysate containing your body's wastes is drained away. Then, a fresh bag of dialysate is dripped into the abdomen. Patients can learn to do this themselves without going to a doctor's office each time. Patients using continuous ambulatory peritoneal dialysis (CAPD), the most common form of peritoneal dialysis, change dialysate four times a day. Another form of peritoneal dialysis, however, can be performed at night with a machine that drains and refills the abdomen automatically.
A donated kidney may come from an anonymous donor who has recently died or from a living person, usually a relative. The kidney that you receive must be a good match for your body. The more the new kidney is like you, the less likely your immune system is to reject it. Your immune system protects you from disease by attacking anything that is not recognized as a normal part of your body. So your immune system will attack a kidney that appears too "foreign." Special drugs can help trick your immune system so it does not reject a transplanted kidney.
Whilst tremendous strides have been made in improving the standards of renal replacement therapy, there is no treatment better than PREVENTION!
Keep your blood sugar as close to normal as you can. Ask your doctor what blood sugar numbers are healthy for you.
Keep your blood pressure below 130/85 to help prevent kidney damage. Below 125/75 if you already have significant kidney disease!
Follow the diet suggested by your doctor. Change your meal plan as your doctor and dietitian suggest. They might suggest you eat less protein, sodium, and potassium.
Have your kidneys checked at least once a year by having your urine tested for small amounts of protein (microalbuminuria).
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.
Don't take your kidneys for granted!
Protecting your fabulous filters is in your hands!