Diabetes Mellitus and the Kidneys

Article excerpt

Diabetes mellitus causes significant blood vessel and nerve damage, leading to progressive involvement of many body parts, including the kidneys.

It is the leading cause of kidney failure in the United States. People who have diabetes and develop kidney disease have a dramatically increased mortality rate in comparison to those who do not. There are a number of treatment options available and hope for more elective treatments in the future.

Diabetes mellitus is an endocrine (hormonal) disease that results from an abnormality in either the production of insulin or how insulin is used by the body. Insulin stabilizes the level of glucose (sugar) in the blood. After meals, insulin helps the cells of the body consume sugar (glucose) as energy, or store it for use between meals. Diabetes is characterized by abnormalities in blood levels of sugar and fats, such as cholesterol and triglycerides.

There are two types of diabetes mellitus:

Type I diabetes generally begins in childhood and is caused by a deficiency in the amount of insulin secreted by the pancreas. People who have Type I diabetes require injections of insulin to regulate their blood sugar levels.

Type II diabetes generally begins in adulthood. In this type of diabetes, the pancreas secretes insulin, but the cells of the body have become resistant to its effects. The declining ability of the pancreas to secrete insulin also plays a role.

About 35 percent of people who have Type I diabetes and 15 to 60 percent of individuals with Type II diabetes will develop end stage renal disease requiring either dialysis or transplantation. Both types of diabetes have similar effects on the kidneys. The information in this article applies to both types, unless otherwise stated.

Our kidneys in health and diabetes

Our kidneys eliminate toxic wastes and regulate the balance of water and dissolved salts (e.g., sodium and potassium) in our bodies. They also assist in: adjusting the acid content of the body; making hormones that help regulate blood pressure (renin) and prevent anemia (erythropoietin); regulating calcium and phosphorus; and vitamin D metabolism. To accomplish these functions, the kidneys receive about a quarter of the body's blood supply.

The kidneys filter the blood in the glomerulus (a network of small blood vessels), and the filtered fluid is passed into the tubule, where it is either reabsorbed into the bloodstream or excreted as urine. (For more information about the filtering action of the kidneys, see "Blood Pressure Control in Individuals with Pre-kidney Disease," Exceptional Parent, March 1999, pp. 36-39.)

Diabetes alters the pressure and flow in the glomerulus and causes a number of complex biochemical changes in their operation. These alterations ultimately lead to severe scarring and "leaks" in the filtering mechanism, manifested by excessive loss of blood proteins, such as albumin, into the urine. This leakage itself may also be toxic, causing further damage. Ultimately, there is also a decline in the filtration function, resulting in kidney failure with accumulation of these toxic wastes.

Stages of the kidney involvement

Microalbuminuria: Microalbuminuria is predictive of progressive diabetic renal damage over the next 10 to 15 years, especially in individuals with Type I diabetes. At this stage, progressive damage to the kidneys can be prevented or significantly retarded, so testing is very important. Routine urinalysis cannot reliably detect microalbuminuria, so a 24-hour urine collection or a morning urine sample must be ordered. Annual urine screening should begin five years after the onset of Type I diabetes and immediately on the diagnosis of Type II diabetes. If positive, the test should be repeated twice within the next 3-6 months. Microalbuminuria is present if at least two of the samples are positive.

Macroproteinuria: If kidney damage is undetected or untreated, protein leakage gets worse over time. …