Diabetic nephropathy

What is diabetic nephropathy?

Diabetic nephropathy is a condition in which damage occurs to the kidneys due to the long-term effects of diabetes. It is primarily caused by persistently raised blood sugar levels. The primary function of the kidneys is to filter the blood for any wastes and extra water, which is then excreted through as urine. Damage to the kidneys hinders the body’s ability to filter the blood, leading to the build-up of the waste products in the body and inability to regular the volume of water in the body. 

How does diabetic nephropathy occur?

High level of blood sugar leads to the sugars to stick to the cells in the blood. These cells in turn stick to the side of the blood vessels and build up, causing narrowing of the blood vessels, very much like limescale building up in pipes and causing blockages and reducing the flexibility of the blood vessels, causing the blood pressure to go up. Also, the lack or resistance to insulin can change the way the body processes cholesterol, a fatty substance that is found in the blood. In diabetic patients, the amount of cholesterol in the blood also increases and this too can build up in the blood vessels, forming a plaque and contribute towards the narrowing of the arteries.

The kidneys are responsible for filtering the blood for waste products and excess water and excreting them through the urine. The blood also contains various proteins that are also filtered by the kidneys. The kidney filters the blood through an extensive network of small blood vessels that are arranged in coils in filtration units called nephrons. The contents that are filtered out of the blood by the kidneys is primarily determined by the blood pressure as the blood enters the kidneys. In diabetes, the build-up of plaques narrows the arteries as well as reduces the flexibility of the blood vessels to expand, thus increasing the blood pressure. Over time, the blood pressure of the blood entering the kidneys keeps increasing and eventually the blood pressure is too high and starts damaging the small blood vessels in the nephrons, causing them to be leakier and causing products that are normally filtered back into the blood to leak into the urine. This can cause inflammation that further damages the kidneys. It must be noted that the kidneys also play a crucial part in controlling the blood pressure, therefore damage to the kidneys starts a negative loop of inability to control blood pressure leading to kidney damage leading to further inability to control the blood pressure.

The risk factors for diabetic nephropathy are poorly controlled blood sugar levels as well as poorly controlled blood pressure. Other risk factors include:

Smoking

High cholesterol

Obesity

Family history of any kidney disease    

How is diabetic nephropathy diagnosed?

Since the relationship between diabetes and kidney damage has been well established, checking the extent of kidney damage is part of any regular diabetes check-ups that one undergoes. The 2 main ways of assessing the health of the kidneys is through a blood test and a urine test.

The Urine test assesses the Albumin: Creatine Ratio (ACR) in the urine. Albumin is a protein that is normally found in the blood, meaning if there is an increase of ACR, it indicates there is an increase in the amount of Albumin present in the urine, which is not normally the case, thus indicating the presence of damage to the kidneys.

The blood test assesses the estimated Glomerular Filtration Rate (eGFR) by using the creatinine in the blood. Creatine is a waste product that is normally filtered out of the blood into the urine. The eGFR is an assessment of how efficiently the kidneys are filtering the blood. A drop in the eGFR means that there is a decrease in the amount of creatinine that is being cleared by the kidneys, therefore indicating the damage to the nephrons.

Using these 2 main investigations, we can assess the extent of the damage to the kidneys and manage the disease accordingly.

How common is diabetic nephropathy?

Diabetic nephropathy occurs in about 20-40% of patients with type 1 or type 2 diabetes. Patients might already have a degree of diabetic nephropathy when they get initially diagnosed with type 2 diabetes. The occurrence of diabetic nephropathy has been studied more in type 1 diabetes, since the age at which one develops type 1 diabetes can usually be identified. Studies have shown that in patients who have been type 1 diabetic for 50 years, almost 9 in 10 had a noticeable amount of protein in their urine, a symptom of kidney damage. The number of patients developing diabetic nephropathy worldwide is increasing every year.