Cholesterol is a fatty substance, one of several different types of fat found in the body. It has several very important functions, and is carried around in the blood. If blood vessels are damaged, cholesterol can be deposited, eventually causing narrowings. This is more likely to occur if the blood level of cholesterol is high.
Yes, most definitely. People with kidney disease are more likely to have problems with narrowings in their blood vessels than otherwise healthy people, so that the cholesterol is very important. This applies even with minor abnormalities in the kidneys, when there is chronic kidney disease.
Problems with blood vessels in people with kidney disease may differ slightly from those in people with normal kidneys, because abnormalities with the minerals calcium and phosphate, and in vitamin D, may contribute to blood vessel disease. However, cholesterol remains an important factor.
There is much more to keeping blood vessels healthy than just looking at the cholesterol level. Attention needs to be paid to several areas:-
The cholesterol level depends on several factors. If someone has a high cholesterol level, other family members may also have high cholesterol levels. Some kidney conditions are associated with a high cholesterol, for example nephrotic syndrome (Click here for more information on nephrotic syndrome in adults), and after transplantation, partly due to the drugs used.
Diet also has a large effect on cholesterol levels. A diet high in fat and cholesterol may lead to a high cholesterol level. Someone who is very ill and malnourished may have an unusually low cholesterol level.
Research shows that low cholesterol levels are beneficial, and the medical advice about ideal cholesterol levels is changing in line with ongoing research. The Renal Association has recommended that people with kidney disease who are at risk of disease in their blood vessels should have a total cholesterol level of less than 5.0 mmol/l, and there is a more recent European recommendation of less than 4.5 mmol/l. Research in people without kidney disease has suggested that someone who is known to have disease in their blood vessels should have a total cholesterol of less than 4.0 mmol/l.
Cholesterol is carried around the body in several different forms and, as well as measuring the total cholesterol level, many laboratories routinely measure some of the forms of cholesterol within the total level. One of these is HDL (high density lipoprotein) cholesterol, which includes cholesterol coming out of the tissues and being taken back to the liver for ‘recycling’. A higher level of HDL cholesterol is therefore a good thing.
LDL (low density lipoprotein) cholesterol is the fraction which is most strongly associated with cholesterol being laid down in blood vessels. The level of LDL cholesteterol should be less than 4.0 mmol/l in people with no obvious disease in their blood vessels, and less than 2.0 mmol/l in people with known blood vessel disease.
There are several combinations of these subfractions, and it may be necessary to get advice from the doctors as to the best treatment in individual cases. Some people have a high total cholesterol but a high HDL level, and may not need intensive treatment. The treatment may also be affected by the levels of another type of fat in the blood, called triglyceride.
Changing the diet can have a powerful impact on blood cholesterol levels. The aim with diet is to reduce the intake of harmful fats, and to maintain a balanced diet with the right amounts of protein, carbohydrate, and fresh fruits and vegetables. The best diet varies in detail from person to person, and if a few obvious measures with diet do not reduce a high cholesterol, it is often advisable to speak to a renal dietitian.
Foods that are high in cholesterol include dairy products, eggs, and the fatty parts of red meat. Many processed foods can contain a lot of cholesterol and the data on the labels should be checked. The type of fats that increase blood cholesterol levels are often called ‘saturated fats’, while ‘unsaturated fats’ (which include olive oil) may be less harmful. It is not just foods containing meat that may be high in fat, biscuits for example may be high.
If diet and losing weight do not bring the blood cholesterol down to acceptable levels, drugs may be used.
The type of drug most often used has an effect on the liver, reducing the production of cholesterol. The drugs are called ‘statins’. There are several different drugs in the statin class, all with names ending in -statin. There are slight differences between the different statins, and the prescribing doctor will advise one that should suit someone best.
In many parts of the country there is a preferred statin drug, usually the most cost-effective, but if this does not suit someone an alternative may be used. All the statin drugs have side effects. Some people feel generally unwell with nausea or sickness, and may have to stop the drug if this persists. Statins can cause aches and pains in the muscles, this is a serious side effect and should be reported to a doctor immediately (Click here for more details in the drugs section).
There are several other types of drug that may either be added to a statin, or used if a statin is not tolerated. These affect either the absorption of cholesterol from the food, or the way it is handled in the body.
All drugs used to treat cholesterol require monitoring with blood tests, and the doses may need to be increased over time to maintain a target blood level of cholesterol. The drugs are not a substitute for eating a low fat diet or losing weight or stopping smoking. It is important to keep up measures across all fronts to combat blood vessel disease.
In people without kidney disease, statins are prescribed to those who have a risk of 30% (3 out of 10) or more of a heart attack or stroke over the next 10 years. This includes anyone who has already had a heart attack or stroke; otherwise the risk is estimated from age, sex, cholesterol and blood pressure levels, and whether the person has diabetes. Unfortunately, doctors don’t know for certain when to recommend statins to people with kidney disease. They have been proven to reduce the risk of heart attacks and strokes in people without kidney disease, but those with severe kidney disease (including transplants) were not included in any of the research. If someone has kidney disease, they are often asked to take many different drugs, so adding more should not be done without good reason. Statins can also interact with some of the drugs used to prevent kidney transplant rejection.
Because of this uncertainty, doctors currently make different recommendations according to their point of view. Many doctors believe that statins must give similar protection to everyone and use them just as they would in a people without kidney disease. Others believe that everyone with kidney disease should be given drugs, because their risk of heart attack and stroke is higher than in the general population. Others believe that the decision should be based on the cholesterol level, or the ratio of total cholesterol to HDL cholesterol. The ‘official’ guidance from the Renal Association in the UK is that statins should be offered to people who have a risk of 30% or more of a heart attack or stroke over the next 10 years.
NKF Controlled Document No. 2, Cholesterol and Kidney Disease, written (not available). Last reviewed 15 November 2006.
The National Kidney Federation cannot accept responsibility for information provided. The above is for guidance only. Patients are advised to seek further information from their own doctor.
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Last updated: 30 May 2008
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