Diabetic kidney disease – a worldwide catastrophe
As a result of changing lifestyle characterized by increased intake of high calorie food and reduced physical exercise, the incidence of type 2 diabetes (the type of diabetes which usually affects middle aged and elderly) has increased in the recent years. One of the major complications of long standing diabetes is kidney failure. In several countries, diabetes has become the leading cause of kidney failure.
Magnitude of the problem
Figures from US and Europe suggest that diabetes (type 2) has become the most important cause of kidney failure. This trend is slowly spreading towards Asian countries also. Indian data from major centers in our country has also shown that in approximately i40% of patients with kidney failure diabetes is the cause.
There are several reasons for the increased Incidence of diabetes as well as kidney disease due to diabetes. First of all, incidence of diabetes has increased in the recent years as a result of reduced physical exercise and consumption of rich food (so called western lifestyle). Kidney disease in diabetes is generally related to the duration of diabetes. Longer the duration of diabetes higher are the chances of developing kidney disease. In the earlier years, heart disease was a major cause of death in patients with diabetes. Nowadays, mortality due to heart disease has come down, as majority of people have access to treatment for heart disease. As a result of this, many patients with diabetes who would have died earlier due to heart disease, now live long enough to develop kidney disease. Thirdly, treatment of kidney disease is neglected during the early stages as all the efforts are focused on heart disease. As a result of this, kidney failure that would have been preventable or treatable in the early phase attracts attention only when it is far too late.
The first detectable abnormality in the kidney due to diabetes is mild leakage of albumin in the urine. This condition is called microalbuminuria and it is characterized by urinary albumin excretion,20 to 200 µg per minute in an overnight urine sample. Microalbuminuriaaffects 20 to 40 percent of patients 10 to 15 years after theonset of diabetes. Untreated microalbuminuria subsequently progresses to severe protein leaking (macroproteinuria) and this is characterized by swelling of legs. This occurs in 20 to 40 percent of patients over a period of 15 to20 years after the onset of diabetes. This is followed by decline of kidney functions. Once decline in kidney function starts severe kidney failure will set in over a period of several months, the exact rate of which will vary from patient to patient.
Kidney disease could also occur within 10 years after the diagnosis of diabetes and occasionally kidney disease may already be present at the time of diagnosis of diabetes. This may be explained by the delay in the diagnosis of type 2 diabetes, as several people with diabetes do not have any symptoms early in the course of the disease.
Blood sugar levels frequently drop and the dosage requirement of insulin comes down usually once the patient develops kidney failure. This may give a false assurance to patients that diabetes has been cured. In fact, far from gone the disease is very much present and all the complications due to diabetes continue unabated.
Nearly one third of patients with diabetes have hypertensionat the time of the diagnosis of diabetes. When nephropathy develops,almost 70 percent of patients would have developed high blood pressure. High blood pressure accelerates the course of protein leaking and decline in renal functions. Botheffects are prevented or limited by adequate control of blood pressure.
Once significant kidney failure develops oral medications for treating diabetes should be stopped and blood sugars should be controlled with insulin. Duration of action of orally acting medicines increases with the development of kidney failure and this may precipitate life- threatening hypoglycemia (low blood sugar level). Due to reasons mentioned earlier, in some patients diet control alone will be sufficient. Urine sugar should not be used for deciding the dose of insulin, as this is unreliable in patients with kidney disease.
Once kidneys start failing, further progression to end stage kidney failure is inevitable. The latter is a condition in which kidney functions deteriorate to such low levels that life cannot be sustained without artificial replacement of kidney functions. Modalities for providing kidney functions artificially are dialysis and kidney transplantation. There are two types of dialysis; haemodialysis (blood from the body is purified in a machine and returned back to the patient) and peritoneal dialysis (fluid is put into the abdominal cavity and removed at regular intervals). However, the best treatment for diabetic patients with kidney failure is kidney transplantation. All these treatments need to be continued lifelong and they are considerably expensive which makes it difficult for a common man to afford them. Shortage of organs still plagues the transplantation programme and cadaver (using kidneys of people who die in accidents) transplantation is still not taken off in our country. Furthermore, survival of diabetic patients though has improved in the recent years is still far from satisfactory.
Several studies have shown that good control of blood sugars can reduce the risk of diabetic nephropathy. The disease is also amenable to treatment during the phase of microalbuminuria. Every patient with diabetes irrespective of the duration of diabetes should have urine tested for microalbuminuria on a regular basis. Good blood sugar control is effective in prevention of kidney disease and reducing further progression during the phase of microalbuminuria.
Once protein leaking becomes significant, control of blood pressure assumes great importance. Target blood pressure should be lower in diabetic patients with kidney disease as compared to those who have do not have diabetes or kidney disease. Studies have shown that even the so called normal blood pressure (less than 140/ 90 mm Hg) is too high for a patient with diabetes and kidney disease. The current recommendation is to keep blood pressure, in this group of patients as low as possible. Systolicpressure of less than 130 mm Hg and a diastolic pressure ofless than 80 mm Hg are desirable targets.
Drugs like angiotensin converting enzyme inhibitors (ramipril, enalapril) and angiotensin receptor antagonists (losartan, irbasrtan) are effective in the treatment of kidney disease. Studies have shown that, before the phase of microalbuminuria, they are helpful in preventing the development of kidney disease. These drugs are also effective during the early phases of the disease such as microalbuminuria, significant proteinuria and mild kidney failure. However, caution has to be exercised while using these drugs as they can occasionally precipitate a sudden decline in kidney function. Blood pressure medications such as amlodipine or nifidipine (so called dihydropyridine calcium channel blockers) should not be used alone in patients with diabetes, as these drugs are associated with worsening of kidney functions in the long term.
Treatment of high lipid levels in the blood, weight reduction and cessation of smoking are also important in preventing further progression of the disease.
Finally, education of the public is the only effective method, which can contain this silent epidemic. Most people still think that diabetes is a harmless condition at least with respect to its effect on kidney. Many do not think that it can reduce life span. More importantly, several young and middle-aged people who have the disease are not aware that they have the disease and are of the opinion that diabetes is a disease, which affect only the elderly. This state of affairs is reminiscent of the ignorance regarding cholesterol in the past. Now most people are aware of the complications due to high cholesterol levels in the blood. A similar awareness regarding diabetes will go a long way in reducing the risk of diabetic complications.