Kidney disease affects nearly one third of people with diabetes and can have varying underwriting implications depending on the stage it is in, writes Sandra Woods
If one kidney was to stop working, a person could probably still lead a normal life. However, if both of that individual's kidneys were to fail, they would be faced with a crisis.
Before kidney disease can be understood, it is useful to understand where the kidneys are and what they do.
The kidneys are bean-shaped organs about the size of a fist. They lie on either side of the spine, just below the rib cage. Many people are born with only one kidney, double kidneys or horseshoe kidneys and do not even know about it because they continue to function normally.
The kidneys have three major functions:
1. The excretion of urea
Excess proteins cannot be stored in the body and so are broken down into fats and glucose. A by-product of this is urea, which is poisonous, and has to be filtered out of the blood via the kidneys.
2. To control the balance of salt in our body
Too much salt in food can cause blood pressure problems. This is because too much salt in the blood means the blood retains more water, increasing the volume of blood in the system and, therefore, increasing the pressure on blood vessels. The kidneys filter excess salt from the blood to maintain the correct balance.
3. The control of water
The kidneys regulate whether people need to excrete or conserve water, while aiming to keep the composition of blood and body fluids constant.
As the blood flows through the kidneys, the filtering takes place in tiny units called nephrons. There are about a million of these in each kidney and they are made up of a tiny blood vessel called a glomerulus, where the main filtering takes place, and collecting tubes that carry the waste products to the ureter for excretion as urine.
As well as filtering the blood, the kidney also produces some hormones responsible for controlling blood pressure, producing red blood cells by stimulating bone marrow, and activating vitamin D to maintain calcium in the bones.
Causes
Although many people develop kidney disease for no known reason, there are certain conditions which increase the likelihood of kidney problems. It is particularly important that people with these conditions are aware of the symptoms of kidney disease, as this will help ensure early diagnosis and treatment. The most common causes of kidney failure are:
n Diabetes (30% of patients with diabetes develop kidney failure)
n Inflammation of the kidney (for example glomerulonephritis)
n High blood pressure
n Long-term infection
n Blockage - possibly due to kidney stones
n Polycystic kidney disease
n Certain medicines
Diabetic nephropathy is where sugar (glucose) levels in the blood of diabetics cause damage to the nephrons. This can be delayed or prevented by good diabetic control.
Inflammation (glomerulonephritis) and long-term infection is when the tiny blood vessels (glomeruli) become inflamed. This affects the kidney's ability to work correctly and efficiently. Glomerular disease or renal failure can be acute or chronic. Acute glomerulonephritis can occur with an infection such as a throat infection or a virus. In these cases, antibodies that were produced to fight the infection attack the glomeruli and cause inflammation with symptoms developing quickly. Chronic glomerulonephritis is more usually associated with auto-immune diseases and symptoms progress slowly. As the kidneys can manage with reduced functionality it can be some time before the effects of renal failure are noticed and symptoms may be quite vague at first. Protein, blood or both in the urine are usually the first signs of glomerular disease, which slowly destroys kidney function. These signs are commonly accompanied by high blood pressure. Because the symptoms develop gradually, quite often they are only discovered when there is an abnormal urinalysis during an examination for an unrelated disorder or at a routine physical - one of the reasons why routine medicals are so valuable. Glomerulonephritis is among the leading causes of chronic kidney failure and end stage renal disease.
High blood pressure can damage the tiny blood vessels in the kidney. This results in the damaged vessels not being able to filter the blood as efficiently as they should.
Kidney stones are formed from the waste substances in the urine. High concentrations can cause crystallisation. This can happen when the urine is concentrated due to dehydration. A small crystal can act as a seed for further crystallisation eventually forming a stone. Small stones can move through the urinary system but larger ones can get stuck and block part of the kidney causing possible permanent damage.
Polycystic kidney disease is a genetic disorder in which many cysts grow in the kidneys slowly replacing the mass of the kidneys. This reduces kidney function and eventually leads to kidney failure.
Some over the counter medicines can be poisonous to the kidneys if taken regularly over a long period of time.
Sandra Wood is life and disability underwriter at Aegon Scottish Equitable
