Microvascular Complications of diabetes

Uncontrolled diabetes and Microvascular Complications

In our day-to-day living, we commonly see many diabetics land up in chronic complications. We may not always know how high blood sugar affects our health. The longer you have diabetes — and the less controlled your blood sugar — the higher the risk of complications.

Long-term complications of diabetes develop gradually. Eventually, they may be disabling or even life-threatening. Overall, diabetes complications can be studied into 2 majors i.e. Microvascular and Macrovascular. This write-up highlighting the microvascular complications of diabetes.

Microvascular Complications

Damage to small blood vessels is called microangiopathy or microvascular disease. In microvascular disease, persistent hyperglycemia contributes to a thickening of the basement membrane in small blood vessels, which is thought to limit the passage of nutrients and oxygen to the tissues that these blood vessels supply. 

This starves the tissues and can result in damage. Other molecular mechanisms in the pathogenesis of microvascular disease are under investigation. 

Diabetic Neuropathy

Neuropathy, or nerve damage, occurs in about 60% to 70% of patients with diabetes. It is thought that hyperglycemia damages the blood vessels that supply the nerves, decreasing the number of nutrients and oxygen that nerves receive. 

Hyperglycemia is also thought to directly damage the nerves themselves. The damage to the nervous system occurs primarily in the nerves that supply the extremities and those that supply abdominal organs.

This damage of nerves can produce a variety of symptoms, including pain, strange/unpleasant sensation, decreased sensation, and more rarely muscle weakness. The legs are usually affected before the hands; distal points (e.g. feet, legs, and hands) are usually affected first and then the abnormal sensation can progress proximally.

Due to the decreased sensation in the feet, patients may not notice a cut or sore, and a serious infection can become established before medical attention is sought. If a patient also has impaired blood flow due to peripheral vascular disease, healing will be further retarded. Such foot injuries and infections may progress to gangrene and amputation of the affected body part may be required. 

Neuropathy can also affect nerves that supply the organs of the body. The symptoms depend on the organ system that is involved. For example, if the nerves supplying the gastrointestinal system are involved, patients can have symptoms of diarrhea or constipation. If the nerves supplying the heart are involved, patients may have abnormalities in heart rate or rhythm or may not experience the warning signs (such as pain) of a heart attack. 

Bladder dysfunction can occur if the urinary system is involved. In addition, a study that surveyed the presence of erectile dysfunction among patients with diabetes showed that 71% of men with diabetes had erectile dysfunction.

Neuropathy is generally diagnosed on the basis of history and clinical exams. In some cases, physicians may also perform nerve conduction tests. The results of several major clinical trials showed that improved glucose control can help delay the onset and slow the progression of neuropathy and its associated outcomes.

Diabetic Nephropathy

Hyperglycemia and hypertension can contribute to the development of kidney disease. The kidneys filter waste products from the blood and retain necessary compounds used by the body, including many proteins.

When the kidneys are damaged, toxic waste products can accumulate in the blood, while other key compounds are lost in the urine. Diabetes is the most common cause of kidney failure. It occurs in 20% to 40% of patients with diabetes.

Diabetic nephropathy can be diagnosed based on the measurement of the amount of albumin in the urine, using either several random urine samples or all the urine that has been collected over a specific time (such as 24 hours). The ratio of albumin to creatinine in the urine is usually analyzed.

Kidney damage proceeds through several stages;

  • One of the earliest signs of kidney damage is the leakage of small amounts of protein into the urine, termed as microalbuminuria (30-299 mcg/mg creatinine); albumin is the most common protein in the blood.
  • As damage to the kidneys becomes greater, the amount of protein that leaks into the urine also becomes greater, until it is termed as macroalbuminuria (>300 mcg/mg creatinine), or commonly called proteinuria. Hypertension also usually develops in concert with kidney damage and hypertension also contributes to the further decline of kidney function.
  • The rate at which the kidneys are able to filter the blood then brings to decrease.
  • Finally, the kidneys are unable to filter and purify the blood, which is called end-stage renal disease (ESRD); diabetes is the leading cause of ESRD.

The stages of kidney disease are defined using the Glomerular Filtration Rate (GFR). It is considered as the best measure of overall kidney function.

StageDescriptionGFR (mL/min/1.73m2)
1Kidney damage with normal or increase in GFRMore than or equal to 90
2Kidney damage with mild decrease in GFR60 to 90
3Moderate decrease in GFR30 to 59
4Severe decrease in GFR15 to 29
5Kidney FailureLess than 15 or dialysis

Diabetic Retinopathy

Long term hyperglycemia associated with Type 2 Diabetes can damage the tiny blood vessels in the retina of the eye. This condition is called retinopathy and is the leading cause of blindness among adults aged 20 to 74 years. 

Since many patients are not diagnosed with Type 2 diabetes many years after diabetes begins, about 25% of patients have retinopathy when they are first diagnosed. Over 60% of patients who have had type 2 diabetes for 20 years develop retinopathy. Retinopathy is diagnosed through a comprehensive eye examination that includes dilation of the pupils to allow the physician to see to the retina at the back of the eye. 

Several clinical trials have shown that effectively controlling blood glucose levels can help delay the onset of retinopathy or reduce its progression. Data also show that controlling blood pressure can also reduce the risk of retinopathy. A procedure called laser therapy can also help slow the progression of retinopathy and visual loss.

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