India is the capital of kidney diseases in the world. Commonest cause of kidney disease in India is diabetes mellitus (DM).
There are two types of diabetes. Type 1 is Insulin Dependent Diabetes Mellitus (IDDM), which manifests in childhood and depends only on insulin administration for sugar control.
Type 2 where an adult, usually over 30 years of age is found to have diabetes and can be treated with oral medications (Non Insulin Dependent Diabetes Mellitus [NIDDM]).
We will discuss common kidney problems in diabetes and their early detection and treatment.
Anatomy and Physiology
Before we discuss how diabetes affects the kidney, the reader is suggested to review the pertinent anatomy. Click here for a brief overview..
What is Diabetic Kidney Disease ?
When blood sugar levels are abnormally high for a long period of time, they cause changes in the small blood vessels including those that supply the kidneys.
These changes significantly affect the blood vessels of the glomerulus altering its functional abilities.
The affected filter leaks protein in the urine. If untreated, damage to the filter continues, kidneys begin to fail and when the function falls below 10% of normal, artificial means to purify blood (dialysis) are needed.
However, if sugar control is achieved early and consistently, this damage can definitely be delayed by a long period of time.
Can we detect it early?
Even before protein loss is evident in urine, microscopic changes are already present in the kidney, especially in the glomerulus (the ‘filter’).
The protein loss is in very small amounts and is detected by special tests. This stage is called the ‘Microalbuminuria’ stage and precedes the more advanced involvement of kidneys and therefore better amenable to interventions.
If filtration capacity is measured at this early stage, it would be found to be paradoxically higher than normal.
If intervened at this stage, severe damage can be prevented.
How does the disease progress ?
This stage then evolves into varying degrees of protein losses in the urine, over the subsequent 5 to 10 years, before reaching the final stage where all the glomeruli undergo irreversible damage and manifest itself as advanced kidney failure.
If not intervened at this stage, there is usually a steady downhill course hereafter and therein lies the importance of screening patients with diabetes for kidney involvement. In type 1 diabetes, approximately 10 – 20 % patients reach this stage by after 5 to 15 years of diagnosis.
Type 2 diabetes patients are usually found to have complications of diabetes at diagnosis and rarely kidney failure may bring diabetes to notice.
One symptom that is peculiar to kidney involvement is that, when kidneys begin to fail, sugar control improves. This is because insulin, the hormone that reduces blood sugar level & is normally destroyed by the kidney, is no longer destroyed in failing kidneys. Sometimes the sugar levels go abnormally low, occasionally needing hospitalization.
So, when a long standing diabetic patient has an ‘improved’ sugar control or sugar levels fall ‘low’ too frequently, kidney involvement should be suspected.
What is the relation with the eyes?
Just as small blood vessels of kidney are affected by diabetes, so are the small blood vessels of the retina in eyes. This is detected by an ophthalmologist by a simple eye check done in the out patient department (OPD).
Involvement of the eyes and kidney go hand in hand. If eye involvement is noted, evidence for kidney involvement must be actively sought and vice-versa.
Conversely, if a diabetic has significant protein loss in urine, but blood vessels of the retina are normal, the involvement is less likely to be because of diabetes and other causes should be searched for.