Last partial update: July 2016 - Please read disclaimer before proceeding

 

An overview of kidney disease in Australia

About 11 per cent of Australian adults (1.8 million people) have moderate to severe kidney failure and may be at risk of developing end-stage renal failure. Early kidney disease has few symptoms and therefore often goes undiagnosed. In fact, symptoms often do not occur until end-stage disease (stage 5: see below) is reached. (About 500,000 Australians have undiagnosed and therefore untreated early kidney failure and many more have less serious chronic kidney disease that may proceed to kidney failure and increase patient risk of cardiovascular disease and death.)

Complications of significant renal failure include anaemia, high blood pressure, bone disease and malnutrition, and it can lead to end stage renal failure that requires dialysis or kidney transplant, significantly reducing quality of life. About 2,400 patients each year either commence renal dialysis or have a kidney transplant. (End stage renal failure affects about 13,000 Australians, causing about eight per cent of all deaths.)

Even more importantly, people with kidney failure have a much increased risk of both cardiovascular disease (heart attacks) and premature death from cardiovascular disease. People with chronic renal failure are 20 times more likely to suffer premature death (mainly from cardiovascular disease) than people of the same age and sex without chronic kidney disease. Many will not live long enough to develop end stage renal failure!!

Treatment of people with early kidney failure has been shown to reduce the rate of disease progression by between 20 and 50 per cent. A screening program for at risk people (see adjacent list) would allow early detection and early treatment of the majority of kidney disease and could potentially prevent about 33%per cent of all cases of end-stage kidney failure requiring dialysis treatment.

 

What do the kidneys do?

 

The kidneys are two bean-shaped organs about the size of a fist whose main function is to filter the blood. (Each kidney has a million or so tiny filter units called nephrons.) In doing this, the kidneys act to:

  • remove body waste products circulating in the blood
  • regulate body chemicals such as sodium and potassium
  • regulate body fluid balance

 The kidneys also produce several hormones including:

  • Renin, which helps control blood pressure
  • Erythropoietin, which stimulates red blood cell production in the bone marrow
  • The active form of Vitamin D, which helps maintain healthy bones.

 

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What is chronic kidney disease?

Chronic kidney disease is defined as being EITHER of the following.

Older people and the diagnois of chronic kidney disease:

In about two thirds of people, GFR does reduce with age after the age of 30 years and about 25% of people over 70 will have a GFR < 60. The other one third do not experience such a decline. In those people whose GFR does decline without other evidence of kidney disease, there is considerable debate about whether this decline should be considered normal ageing or due to underlying disease such as high blood pressure or vascular disease.) Many people over the age of 70 with a borderline low GFR may not be at high risk from kidney disease complications.

In general, people over the age of 70 who have no evidence of kidney disease and have a GFR that is both between 45 and 59 and stable (i.e. not decreasing over time) may be regarded as having a GFR that is age appropriate and are less likely to suffer the complications associated with chronic kidney disease. They do need to be carefully watched and have regular GFRs done to make sure their GFR is not decreasing.) People under the age of 70 with a GFR between 45 and 59 do have chronic kidney disease and are at increased risk of its complications.

What causes chronic kidney failure in Australia?

There are several main causes of kidney failure in Australia as follows.

Damage caused to the kidneys by chronic kidney disease is measured by determining how much blood the kidneys can filter over a given period. This measurement is called the glomerular filtration rate (GFR). (It is expressed in mLs per minute per 1.73m2.) There are several ‘stages’ of chronic kidney disease (or kidney failure) as indicated in the table below.

 

Stages of chronic kidney disease and Prevalence in Australians*

Stage

Description

GFR

(mLs/minute/1.73m2)

Estimated prevalence in Australian adults

% of adults (number)

1

Kidney damage with no reduction in GFR

90 or above

3.1%

(400,000)

2

Kidney damage with a mildly reduced GFR

60 to 89

4.0%

(500,000)

3

Moderate reduction in GFR

30 to 59

10.9%

(1,400,000)

4

Moderate reduction in GFR

15 to 29

0.3%

(40,000)

5

Kidney failure / End stage renal disease

Less than 15 or on dialysis

0.02%

(13,200)

*About 50 per cent of Australians with chronic kidney disease are unaware they have the condition.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Who is at most risk from kidney disease?

There are seven groups of people at significantly increased risk of kidney disease and these individuals need to be screened annually. These groups are as follows.

(It is worthwhile remembering that many Australians with diabetes or high blood pressure are unaware they have the disease.)

 

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Preventing kidney disease

Much kidney disease can be prevented by:

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Common medications that can worsen existing kidney disease

The important medications that can worsen kidney function are:

  • Arthritis drugs (non-steriodal anti-inflamatories and COX-2 inhibitors) (The use of these types of medication with a diuretic can be particularly damaging.)
  • Some contrast agents used when taking some Xrays.
  • Aminoglycosides (A group of antibiotics, usually used only in patients admitted to hospital.)
  • Lithium

    (The use of any of the above medications should be avoided wherever possible in people with chronic kidney disease.)

    While avoiding these medications in people with known chronic kidney disease is relatively easy, the fact that 50 per cent of people with this condition do not know they have it creates an obvious problem. This is another important reason for finding out if chronic kidney disease exists.

  • Angiotensin converting enzyme (ACE) inhibitors and angiotensin 2 receptor antagonists. (Occasionally a problem.) 
These medications are used for reducing blood pressure and are very commonly used for this purpose in people with chronic kidney failure. A problem arises, however, if significant blockages are present in the arteries that supply blood to both kidneys and in this situation, using these medications can make kidney failure significantly worse. Such blockages are not that common and it is thus not usual to do investigations for look them prior to commencing treatment with these medications. Thus, when being started on these medications, a close eye needs to be kept on kidney function to see that it does not suddenly worsen. This is done by regularly checking the blood creatinine level. (The use of either of these medications with an arthritis drug and a diuretic can be particularly damaging.)

Some effects of some medications are increased in people with chronic kidney disease, mainly because their excretion from the body via the kidney in reduced. The dosage used needs to be deceased in these people. Some important examples include acetazolamide (used for chronic glaucoma, an eye problem), aciclovir (an antiviral medication), colchicine (used for gout), digoxin and sotalol (used for heart problems), gabapentin (used for epilepsy), lithium (used to treat mania in people with bipolar disease), and suphonylureas and metformin (used for diabetes). The dosage of all medications considered for use in people with chronic kidney disease needs careful consideration prior to prescription.

Special care needs to be used in prescribing metformin to patients with moderate kidney failure (GFR < 50) as there is a significantly increased risk of the serious side effect called lactic acidosis.)

Finally, some Chinese herbal remedies can worsen kidney failure, as can viral illnesses such as Hepatitis B, Hepatitis C and HIV that can be contracted through intravenous drug use.

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How do I find out if I have kidney disease? - Screening for kidney disease

 

Screening for chronic kidney disease should be done by assessing kidney function (usually by doing an eGFR) and by looking for protein in the urine. Importantly, these screening tests do not determine the cause of any abnormality found and further investigation to determine the cause, usually by a kidney specialist, is required so that appropriate treatment can be commenced.

 

It is important to note that testing urine protein alone in people with diabetes is not adequate to exclude chronic kidney disease. Up to 33% of people with diabetes who progess to kidney failure do so without ever having protein (albumin) in their urine. Thus, blood tests to check renal function also need to be done regularly.

 

Reasons for testing urine

 

Testing for abnormalities in the urine is done for three reasons;

  • It helps detect diseases originating in the urinary tract (i.e.  kidneys, bladder, prostate etc.)
  • It helps detect diseases originating outside the urinary tract that affect the kidneys, such as diabetes and high blood pressure.
  • It detects excess excretion of substances in the urine that indicate an abnormality in the body. For example, patients who are jaundiced due to liver disease excrete abnormal amounts of bilirubin in the urine.

 

1.   Testing urine for the presence of protein (and blood).

Protein: Testing urine for protein is the preferred way to screen for chronic kidney disease. Protein in the urine is a very important marker for kidney damage, either from diseases that primarily affect the kidneys such as glomerulonephritis or from other diseases such as diabetes, high blood pressure and heart failure. As well as illness from kidney damage, people with albumin (a type of protein) in their urine have a higher incidence of heart attacks and a higher death rate generally. Treating the cause can often prevent much of this illness, especially if it is commenced early.

 

The presence of protein in the urine is often a transient phenomenon. Thus, a single positive test (unless very high) should be repeated to ensure that the problem is a persistent one. Generally an elevated test is repeated twice in the next two months and if either of these follow up tests is abnormal, then chronic kidney disease is present. (The likely significance of an initial positive test will obiously depend on how much protein is present and on whether the person has a likely cause that increases the significance of the abnormality found; such as a history of poorly controlled diabetes.)

 

Protein in the urine can be tested in the surgery by using two types of dip-sticks; special ‘microalbuminia sticks’, which are used when greater testing sensitivity is needed, such as in people with diabetes and a general multipurpose dipstick, which is mainly used for the initial screening of other at risk individuals and general testing in the surgery. If there is an abnormality on the less sensitive protein stick, then a more sensitive test is done.

 

Testing timed urine collections for protein or calculating the albumin / creatinine ratio from an early morning specimen are more relaiable tests as they give an indication of the rate of albumin excretion over a period of time. (The timed assessment is the best and is usually done on either an overnight collection or a 24 hour collection.) This test is used in the initial screening of people with diabetes for chronic kidney disease and If there is an abnormality on the less sensitive protein stick test used for screening other at risk people. An elevated test is repeated twice in the next two months and if either test is abnormal then chronic kidney disease is present.

 

Why is finding microalbinuria in people with diabetes important? The amount of albumin in the urine in people with diabetes is a good indicatior of how quickly kidney failure is likely to occur and finding the problem early (i.e. diagnosing microalbuminuria) alllows early treatment (e.g. by lowering blood pressure), which has been shown to significantly reduce the likelihood of kidney failure occurring. Halving the amount of albumin in the urine doubles the time it takes renal failure to occur. Treatment also significantly reduces the risk of heart attacks and death occurring.

 

Tests available for estimating albumin excretion by the kidneys

(Albumin is the main protein excreted by ‘damaged’ kidneys. Any positive test needs to be repeated, as the presence of small amounts of albumin in the urine is often a transient abnormality and might not signify a problem exists.)*

 

Test

(In order of decreasing sensitivity)

 

Normal level of albumin in urine**

Micro-albuminuria

(Small amount of albumin present in urine)

Macro-albuminuria***

(Larger amount of albumin present in urine)

Urine albumin measurement from a timed urine collection 

(Enables accurate estimation as it reflects the amount of albumin excreted per unit time; usually per day or per minute)

The collection is usually done overnight but can be done over 24hours. (See below.)

10 to 30 mg/day

(Usually about 10)

 

(or 7 to 20 micrograms/min

(Usually about 7)

30 to 300 mg/day

 

 

(or 20 to 200

micrograms/min)

Over 300

mg/day

 

 

(or over 200

micrograms/min)

Urine albumin creatinine ratio****

Measurement of the ratio of albumin (in mg) to creatinine (in mmol) in the urine sample.

(An early morning sample is required.)

Male

Less than 2.6

mg/mmol

(usually about 0.8)

2.6 to 25 mg/mmol

Over 25mg/mmol

Female

Less than 3.6

mg/mmol

(usually about 1.2)

3.6 to 35 mg/mmol

Over 35

mg/mmol

Microalbinuria estimation  using albumin sensitive sticks*****

(‘Micral’ test strips)

Measures albumin content (in mg) per litre of urine up to 100mg/L.

(20mg/L is equivalent to 30mg/day or 20micrograms/min in the timed collection measurement. See above.) (Any urine sample can be used.)

0 to 20

mg/L

 

Over 20

mg/L

 

Normal dipstick testing of urine

(The lease accurate test. It cannot identify the presence of a small amount of albumin in the urine. The minumum level detected is about 500g/L of total protein.)

(Any urine sample can be used.)

Negative test

Negative test

Positive test

(One 'plus' or more.

No actual level is determined.)

Notes:

* There are various proteins in the blood and in normal kidneys they are generally too large to allow their passage from the blood into the urine. Albumin is one of the smallest blood proteins and damage to the small blood vessels in the kidneys can allow some of this to enter the urine. Albumin in the urine has been shown to be a good indicator of damage to small blood vessels throughout the body as well as in the kidney and thus to the likelihood of vascular diseases such as heart attacks occurring. Diabetes is a common cause of such small vessel damage and thus albumin in the urine.) The sample needs to go to a pathologist to be tested.

** A very small amount of albumin leaks from the blood filtered by the healthy (normal) kidneys into the urine (i.e. there will always be at least a small amount of albumin in urine.)

*** Once macroalbuminuria occurs, the total protein excretion by the kidneys is considered a better indicator of kidney function and should be estimated by a timed measurement (A urine albumin excretion level of 300mg/day is approximately equivalent to a total protein excretion of 500mg/day.)

***Albumin creatinine ratios. Men have lower ratios. This is because creatinine is produced from the breakdown of the muscle protein creatine. As men generraly have more muscle, they produce more creatinine; all of which is excreted via the kidneys. A higher urine creatinine level results in a lower albumin to creatinine ratio. The sample needs to go to a pathologist to be tested.

**** This test is less accurate as it does not reflect the total amount of albumin excreted by the kidneys each day

Positive tests

The presence of protein in the urine is often a transient phenomenon. Thus, a single positive test (unless very high) should be repeated a few weeks later to ensure that the problem is a persistent one. If an initial positive test is followed by a negative test, then a third test is required.

 

 

If an abnormality is found in any of these tests, a timed (overnight or 24 hour) urine sample is usually taken to accurately measure the amount of protein in the urine.

 

Testing for blood in the urine: Dip-stick tests can easily detect blood in the urine. The cause of any bleeding always needs to be determined so that serious causes such as cancers can be either excluded or found; and hopefully finding a disease earlier than would otherwise have been the case will allow treatment that prevents serious illness.

 

 

Collecting urine samples

 

The collection container

Urine can be collected in a larger container and then transferred to the specimen container provided. The collection container should be cleaned with water; not detergent.

 

First voided specimen

• When you get out of bed in the morning, empty your bladder, collecting the first part of the urine in the urine specimen bottle.

• The first voided urine collection is now complete. Take the specimen and the laboratory form to your doctor’s surgery or to the laboratory.

• If you make a mistake, wash the bottle out with clean water and repeat the collection

correctly the following morning.

Overnight specimen collection

• Just before you go to bed and to sleep, empty your bladder into the toilet and note the time.

• Collect any urine you pass during the night into the laboratory bottle.

• When you get out of bed in the morning, empty your bladder and collect all the urine. Note this time as well.

• The overnight urine collection is now complete. Take the specimen and the laboratory form to your doctor’s surgery or to the laboratory.

• If you make a mistake, wash the bottle out with clean water and repeat the collection correctly the following night.

24 hour urine collection

• When you get out of bed in the morning of the day you are collecting the urine, empty your bladder into the toilet and note the time.

• Collect any urine you pass during that day and night into the laboratory bottle.

• The next morning, get out of bed at the same time as the day before and collect the urine.

• This completes the 24 hour urine collection. Take the specimen and the laboratory form to your doctor’s surgery or the laboratory.

• If you make a mistake, wash the bottle out with clean water and repeat the collection correctly the following day.

 

 

 

2.   Assessing the blood creatinine level and thus determine the GFR (Glomerular filtration rate)

A blood test to check serum creatinine can be used to assess kidney function. (This is used to determine glomerular filtration rate (GFR); see notes below.) When finding an initial abnormal GFR, it should not be assumed that this is an indication of longstanding, slowly progressive disease. Some causes of kidney failure can be rapidly progressive and it is important to repeat the GFR test soon afterwards to identify any significant worsening quickly. It is also important to perform further investigations to diagnose the cause of the kidney failure.

 

Who needs 'kidney' screening and how often?

People at normal risk (i.e. those not in the ‘at risk’ list mentioned earlier.)

It is not necessary for people at normal risk of kidney disease to have a special ‘kidney disease’ screening visit with their GP. However, all people should have a urine examination with every check up. (These should occur at least every 2 years.) Routine blood tests that are done prior to surgery now measure the person's kidney function by allowing the estimation of the eGFR. (See below.)

 

At risk people (See at risk list above.)

All at risk people, irrespective of age, should have yearly screening for kidney disease which should include all of the following.

  • Urine examination
  • Blood pressure measurement
  • A serum creatinine to help determine their GFR (See later.)

If significant kidney disease is found, an assessment of kidney function will usually need to be done more often than yearly, often at least every three months.

 

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Determining kidney function – The GFR

It is important to understand that while testing the urine is very good at indicating whether there is a problem with the kidneys, it does not give any indication of how much damage has been done to the affected kidney(s) or what is causing the problem. All a urine test can do is indicate that something is wrong.

 

Determining how much damage a particular disease has done to the kidneys requires taking a blood test called a serum creatinine level. When looked at by itself, the serum creatinine is an inaccurate / poor test as it only starts to become abnormal when at least half the overall function of both kidneys is lost; which is too late!

 

However, the blood creatinine level can be used to help assess the ability of the kidneys to filter the blood (their prime purpose) and this is the best way of determining kidney function. The Glomerular Filtration Rate (GFR) is a measurement of this filtering ability, with the GFR decreasing as kidney function worsens. (See below.) Repeated calculation of GFR is the best way of knowing if kidney disease is getting worse.

 

Most people with a significantly abnormal GFR require early referral to a kidney specialist (a renal physician) to help determine the cause of the reduced kidney function and to implement a management plan to minimize further damage.

 

Calculating GFR

 As stated above, all methods of calculating GFR require a blood test to measure the creatinine level in the blood. There are several formulas for calculating the GFR and most of those used in the past have required knowledge of the patient’s height, weight and sex. A simpler and more accurate test has now been developed called the eGFR.

 

The eGFR   -  A common test

A simpler and reasonably accurate method of calculating GFR that only requires the patient’s age and sex has now been introduced. This test has the advantage of not requiring height and weight information and this means that a result for the person’s GFR (called an eGFR) can be calculated from any creatinine blood test. As this test is one of the most common blood tests ordered by doctors (it is part of many routine ‘blood screens’, including pre-operative tests), many more adults will be having their kidney function assessed than has been the case in the past. This will uncover many people with previously unrecognized moderate kidney failure, a problem that is particularly common in elderly females, and will enable the cause of the problem to be investigated and treated earlier, hopefully helping to prevent a further deterioration in kidney function. 

 

At present the plan is to report the eGFR result to the doctor ordering the test if it is below 60, a level that indicates moderate to severe kidney failure; depending on the actual level.

 

It is important to emphasise that a positive test does not indicate the person will inevitably proceed on to severe kidney failure. Indeed, some elderly patients with only moderate kidney failure due to ‘ageing kidneys’ may not require further investigation and may be able to be managed by carefully monitoring their eGFR to make sure their kidney function is not significantly worsening.

 

 

What is a normal / abnormal eGFR?

The eGFR decreases as kidney function worsens.

 

Any abnormal GFR needs regular follow up to ensure that the kidney damage already present is not worsening and most will require further investigation to sort out the cause of the kidney damage. (In some patients the cause may be due to a previously diagnosed condition, such as high blood pressure or diabetes.)

 

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Who needs to see a kidney specialist?

 

A GP will be able to investigate and treat some kidney conditions. However, as most kidney diseases are long-term problems, evaluation by a specialist is often helpful. Unfortunately, about 25% of patients who are referred to specialists are referred later than they should have been and this increases their risk of developing end-stage kidney failure and all its associated illness. The following is a ‘guideline-only’ list of more serious kidney conditions / symptoms where specialist opinion is recommended.

  • Anyone with an eGFR less than 30. (Anyone with an eGFR of less than 60 should be considered for referral to a specialist.)
  • Anyone with diabetes and either an abnormal eGFR OR the presence of protein in their urine.
  • Anyone whose kidney function is rapidly worsening. (This is indicated by a decline in eGFR of 15 or more in any 3 month period. Anyone with an eGFR between 30 to 60 needs 3 monthly eGFR checks.)
  • Anyone with blood in their urine.
  • Anyone with an abnormal eGFR and hard to control blood pressure.
  • Anyone with an abnormal eGFR and deteriorating (increasing) serial albumin creatinine ratio tests. (A urine test mentioned above.)
  • Anyone with large amounts of protein in their urine, especially if there is over 1.0 gram present in a 24 hour urine collection.

Some reservations about the eGFR test

  1. The test has not been validated for some ethnic groups, including Australian Aboriginals, Torres Strait Islanders, Asian populations (including Japanese, Chinese and Vietnamese), and Maori and Pacific Islanders. (It probably still better to use an eGFR to screen for kidney disease in these groups than use no test at all.)
  2. It is not suitable for use in children (i.e. under 18 years of age)
  3. Some medications can affect the eGFR, including trimethoprim and cimetidine.
  4. Caution needs to be used when using the test to adjust drug doses as the eGFR is adjusted for body surface area. (A traditional GFR measurement is better here, although an eGFR is still useful where this test is not available. )
  5. It is less accurate or may be unreliable in;
    • people with acute kidney failure
    • people with kidney function that is changing rapidly
    • people on dialysis or with rapidly changing renal function (e.g. people with acute renal failure)
    • people with an eGFR that is normal or close to normal (i.e. greater than 90).
    • people with severe liver disease
    • very thin or obese people
    • people with abnormal muscle mass, including those with muscle diseases, paraplegia, those with high muscle mass and amputees.
    • people who consume unusual diets, including vegetarians diets and high protein diets, and after the recent consumption of cooked meat
    • people taking creatine supplements (usually consumed by people who wish to increase their muscle mass)
    • people with paraplegia / quadriplegia

 In the above cases, the traditional methods of calculating GFR that use weight and height measurements are more accurate.

 

Calculating the eGFR

The calculation for determining eGFR is relatively complex and thus an easy-to-use ‘calculator’ is available on the Kidney Health Australia website at: www.kidney.org.au (Find Kidney Health Quick Links on the home page and click on 'MDRD GFR Calculator'.)


The ‘MDRD formula’ used to calculate the eGFR is as follows.

For males
eGFR = 186 x (Serum creatinine / 88.4) -1.154 x age - 0.203

For females
The same equation is used for calculating female eGFR except that the final result needs to be multiplied by 0.742

For Afro-Americans
The above GFR results need to be multiplied by 1.21

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Treatment of early chronic kidney disease - an outline

  1. Exclude treatable or reversible kidney disease
  2. Optimal treatment of the cause of the kidney disease to reduce disease progression.This is very important in chronic kidney disease due to diabetes or high blood pressure. This will often involve, where appropriate, the use of drugs that reduce protein loss by the kidney;, mainly ACE inhibitor or angiotensin-II-receptor blockers. (As mentioned above, these medications can worsen kidney disease resulting from any blockage in the arteries supplying blood to the kidneys; the renal arteries.)
  3. Reduce risk factors for cardiovascular disease
  4. Use medications appropriately: Avoid the use of medications that can be toxic to the kidneys (See boxed section above) and adjust dosage of medications used to ensure they are appropriate for the decreased level of kidney function. (Many drugs are excreted from the body by the kidneys and this excretion will be slower when kidney function is educed. Thus, the dosage needs to be decreased.)

As stated before, by far the most common cause of death in people with chronic kidney disease is cardiovascular disease. Thus, it is extremely important to minimise risk factors for cardiovascular disease. Important factors that need to be aggressively managed include:

The treatment of end stage kidney failure is beyond the scope of this resource.

 

Further information

Kidney Health Australia
http://www.kidney.org.au/
  

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