Complications of Diabetes

- Medical topics - Complications of Diabetes

Over time, high blood sugar levels in diabetes lead to changes in blood vessels and nerves of the eyes, kidneys, heart and other organs, and can be the cause of various diseases.

One of the most common complications of diabetes is diabetic polyneuropathy. It is also reported in prediabetes, and manifested by unpleasant sensations primarily in the legs: pain, cramps, stiffness, numbness and tingling. The basis of neuropathy is damage of small blood vessels, capillaries, feeding the nervous system. Our nervous system is divided into central, the brain and the spinal cord, and peripheral, consisting of nerve fibers originating from the brain or spinal cord. When we talk about polyneuropathy, it implies the damage in the peripheral nervous system. Each nerve fiber is consisted of a nerve surrounded by a sheath. The sheath allows proper transport of information through the nervous system. Everything that happens in the periphery must be transmitted as information, to the brain. The brain processes the information, clarifies it, and prepares the body to respond. Example: Shoes are uncomfortable and pressing the toe. This “pressing” information is being transmitted to the brain, directly to the pain center. Toe pressure, after being processed in the brain, becomes pain. As response to pain, we take certain actions to reduce the pain – take off the shoe and replace it with other shoes. If the “pressing” information does not go to the brain, a blister forms. If the information about the blister formation does not go to the brain, the blister bursts, it becomes infected and everything afterwards is well known. 

Changes in small blood vessels primarily damage the nerve sheath. This results in errors in the information transmission. It is something like “broken phones”. When we’re supposed to feel the pain, it is gone. But when we’re supposed to rest, the pain occurs. If the changes in blood vessels last for a long time, and nothing is done to treat them, the damage affects the nerve itself. When a nerve is damaged, then everything is dead. Person no longer feels his arms or legs as his own. Also there is a danger of developing a diabetic foot.

Polyneuropathy is not easy to detect. It is important to observe the patient’s mood, ask how he/she sleeps and pay attention to the way he/she walks. It is also important to examine patient’s feet. Legs in patients with polyneuropathy sometimes look completely normal. By a neurological examination it is checked whether the feet feel sensations like touch, pressure, change in temperature and vibrations. Reflexes are also examined. A sense of touch is examined with a thin thread of cotton wool. A sense of pressure is examined with a thin plastic thread called a microfilament. Healthy feet feel touch and pressure equally well at all examined points.

Diabetic foot occurs when there are two or more risk factors. Diabetic polyneuropathy is the first condition. More than 50% of people with type 2 diabetes have diabetic polyneuropathy. There is an altered sensitivity of the feet, blisters and other injuries remain unrecognized for a long time. These changes do not cause pain but may become infected. Ulceration is difficult to heal. Pressure on the affected area and movement make the condition even worse.

Usually, patients with diabetes also have a circulatory disorder. This typically develops in smokers. It is easily detected by examination. If a doctor cannot feel the pulses of the feet arteries, the patient is sent for an examination called Doppler of the arteries. Doppler examination can determine poor circulation, to what extend it is developed and whether it can be treated with medication or the surgery. If a Doppler examination reveals a circulation disorder, the patient is said to have ischemic leg disease. Healing a change in the area of poor blood circulation is almost impossible. If there is an infection, the ulceration spreads deeper and can affect the bone. Then the prognosis is very serious.

Retinopathia Diabetica is a disease caused by severe damage to the capillaries in the retina. The retina is the inner part of the eye enabling a person to see. The earliest changes are in the form of non-proliferative retinopathy. It is characterized by changes in retinal blood vessels, varicose veins, which later turn into irregular narrowings so that the veins get the “sausage” appearance. There are small bleedings and appearance of white threads. Furthermore, the lesions may progress to proliferative retinopathy. This is characterized by newly formed blood vessels (neovascularization) and connective tissue growth in the eye. New blood vessels have thin walls and often burst and bleed. Frequent vitreous hemorrhages occur. Reabsorption is very slow and lasts for months, and after repeated bleeding a  blurred vision usually remains. All this causes scarring and retinal ablation. The process can involve the macula. Cataracts and glaucoma are common in people with diabetes. The best protection for preserving the vision is to maintain blood sugar levels as close as possible to normal values (from 4 to 7 mmol / l).

In addition, prevention of development of diabetic retinopathy is to perform regular dilated fundus examinations, at least once a year, ideally every 6 months, and more often if necessary. Also, a diet rich in beta-carotene or the use of supplementary medical agents containing lutein is recommended.

How does a person with retinopathy see

Figure 2 – (Left) Normal vision (without rethinopathy) (Right) Same scene seen by someone with diabetic rethinopathy

The examination of the kidney function of each patient with diabetes is done once a year. The goal is to prevent the occurrence of nephropathy (primary prevention) and early detection of patients with kidney dysfunction. In persons with detected kidney disorder, a detailed examination of kidney function is performed in order to prevent further progression of the kidney function (secondary prevention). Kidney function is assessed in people with diabetes over 18 years of age, with no urinary tract infection. Proteins in the morning urine can be detected with a urine test strip. However, presense of albuminuria is usually analysed in the lab. Blood creatinine levels are also analysed and glomerular filtration rate is calculated.

Coronary heart disease, cerebrovascular insult and peripheral vascular disease are the macrovascular complications of diabetes with the highest mortality and morbidity. They make up 75% of the causes of death of people with type 2 diabetes. Prevention of these complications implies timely and adequate treatment of all factors involved in their occurrence, especially dyslipidemia. Diabetic dyslipidemia typically consists of 3 components: moderately elevated triglycerides, low HDL-cholesterol, and the presence of small, dense LDL particles. LDL cholesterol level may not be much higher than in the general population, but it is significantly more susceptible to oxidative modification and non-enzymatic glycosylation. Diabetic dyslipidemia significantly accelerates atherosclerosis.

The atherosclerotic process (clogging of blood vessels) is long-lasting and dynamic. It begins in childhood, and develops further in adults. It goes unnoticed for a long time, until complications occur (pain behind the sternum, heart attack, stroke, blood flow disorders in the legs). It primarily affects the large and medium-sized arteries and causes the formation of a plaque consisting of fat, calcium salts and connective tissue. The wall of the atheromatous artery is no longer smooth, and its inner diameter is reduced. 

Cholesterol, especially in the form of LDL (small dense particles) and triglycerides promote atherosclerosis, while HDL cholesterol (particles with higher density) prevents it. LDL cholesterol is excessively deposited in the inner layer of the blood vessels wall. On the contrary, HDL cholesterol has a protective role. It removes harmful cholesterol from the walls of blood vessels and transfers them to the liver, where it is being broken down.


Recommended values of blood lipids are:

  • total cholesterol up to 5 mmol/l,
  • LDL cholesterol up to 3 mmol/l,
  • HDL cholesterol above 1 mmol/l for men and above 1.2 mmol/l for women
  • triglycerides up to 1.7 mmol/l. 

For patients with diabetes who have suffered a heart attack, the recommended values of blood lipids are even lower: total cholesterol up to 4.5 mmol/l and LDL cholesterol up to 2.0 mmol/l. Up to now there is no routine laboratory analysis for small, dense LDL particles. However, as a rule, the higher the triglycerides (> 2.1 mmol/l), the higher the concentration of small, dense LDL particles; normal LDL particles are found when triglycerides are lower than 1.2 mmol/l. It is important to pay attention to the way the blood is taken. It is correct to determine lipids in the blood after 5 – 10 minutes of sitting or lying down. Triglyceride levels are 9-19% higher when a person is in a standing position.

Diabetes can also lead to non-alcoholic fatty liver degeneration. It is characterized by steatosis (accumulation of fat in the liver), death of liver cells, inflammation and scarring. The process of steatosis is potentially reversible if the cause of its occurrence is removed. However, during its evolution, it can lead to the development of liver cirrhosis and hepatocellular carcinoma. Patients with non-alcoholic fatty liver are generally without problems. They may complain of discomfort below the right costal arch and weakness.  Enlargement of the liver may be found on examination. Non-alcoholic fatty liver should be considered in obese people, with or without diabetes, who have abnormal values of transaminases (AST, ALT< 250 IJ, AST/ALT < 1), with ultrasound findings of enlarged and bright liver. However, biopsy of the liver is the gold standard .

It is difficult to explain the need to prevent vascular complications. Since, most are asymptomatic, the patients do not think of them as possible. Hence, routine check ups are mandatory. Simple explanations also help. 

“Look at the patient through his glasses, in order he/she can better understand and accept you.”


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