How is kidney disease diagnosed?

If chronic kidney disease (CKD) is diagnosed at an early stage, there may be greater opportunities to manage the condition, and potentially slow down progression. Detecting kidney disease earlier can mean your doctor can prescribe treatments which can help maintain your kidney function for as long as possible. Early diagnosis of CKD can also give you the opportunity to make lifestyle changes and manage other health conditions, such as high blood pressure (hypertension) and diabetes, that may contribute to kidney damage.

Awareness and regular health checks are valuable tools in preventing or slowing kidney disease from progressing to more severe stages, including kidney failure, which may require dialysis or transplantation.

Signs and symptoms of kidney disease

There are several stages of chronic kidney disease, ranging from mild loss of kidney function to kidney failure. Early signs and symptoms of kidney disease are often subtle and recognising them can be critical for timely diagnosis and treatment.

Early to moderate chronic kidney disease can often develop without any noticeable symptoms. It is often diagnosed at this stage when a routine test is carried out for another conditions, such as a blood test or urine test.

Common signs of later stages of CKD include tiredness (fatigue), swollen ankles and feet, decreased appetite, changes in urination frequency or appearance and headaches. Some people may experience itchy skin, muscle cramps, and difficulty sleeping..

Seeking medical advice if you notice symptoms could help spot kidney disease, prevent further kidney damage and improve treatment outcomes. Your doctor may run tests to check your kidney function and to help diagnose any problems. It is best to speak to your doctor if you are concerned about any of these issues.

Laboratory tests for kidney function

There are several tests that are used to check the function of your kidneys – they can also be used to monitor kidney function:

Blood tests

A blood test is used to diagnose kidney disease. The test looks at two important values to assess kidney function: the serum creatinine and the estimated glomerular filtration rate (eGFR).

Serum creatinine

A blood test measures the level of creatinine, a waste product in your blood. Healthy kidneys filter creatinine out of the blood so it can be excreted in urine. Elevated levels of creatinine may be a sign of impaired kidney function, suggesting that the kidneys are not filtering waste effectively.

Estimated glomerular filtration rate (eGFR)

The eGFR is based on blood test results, along with other factors such as age and gender, to estimate how well your kidneys are filtering. An eGFR of 90ml/min or higher is in the normal range, while a value less than 60ml/min can indicate kidney disease. An eGFR level of 15 or lower might indicate kidney failure, meaning you would need immediate medical advice.

Abnormal results from these tests imply that the kidneys are not working as well as they should. It's vital to interpret these results within the context of other tests and your overall health status. If kidney function is compromised, it may point towards chronic kidney disease (CKD) or acute kidney injury (AKI). It’s essential for further evaluation and, possibly, treatment to commence promptly.

Urine tests

Urine tests are also important for assessing kidney health. Standard testing involves taking a sample of your urine to check for abnormal levels of protein, sugar, blood cells, bacteria or other changes.

Urine albumin test

The urine albumin test, also known as the urine albumin-to-creatinine ratio (UACR), specifically measures the amount of albumin in the urine compared to the amount of creatinine. This means that the amount of water you drink doesn’t impact the test result. Albumin is a small protein and when the kidneys are working properly, only tiny amounts of albumin pass from the bloodstream into the urine. The presence of albumin in urine can go up when the filtration barrier is damaged and so can be an early indicator of kidney damage.

High levels of protein in the urine (proteinuria) can sometimes be a sign of kidney disease, or other health problems.

These tests can provide early warning signs of kidney problems before other symptoms appear, as well as being used to continually monitor kidney function. This makes urine tests an essential tool in the early detection and management of kidney disease, allowing healthcare professionals to implement preventive measures or treatments that could slow the progression of your condition.

Imaging tests for kidney evaluation

As well as laboratory tests, you might be offered imaging tests to look at your kidneys' structure and function. These include:

Ultrasound

Ultrasound is a non-invasive technique using sound waves to create images of the kidneys, helping detect potential problems such as changes in size, the presence of cysts, tumours, or blockages, and issues with blood flow.

One of the advantages of ultrasound is its ability to reveal structural abnormalities that may not be detected through blood or urine tests. For instance, it can help to identify polycystic kidney disease or obstructions in the tubes of the urinary system.

Kidney biopsy

A kidney biopsy involves taking a small sample of kidney tissue for analysis. The procedure is typically performed under local anaesthesia – using ultrasound imaging guidance to ensure the biopsy needle is placed precisely. A small piece of kidney tissue is then removed and sent to a laboratory where it's examined for signs of damage or disease.

A biopsy might be recommended in various circumstances. For instance, when the cause of certain kidney conditions cannot be diagnosed through history, examination, blood or urine tests alone. Additionally, a kidney biopsy might be undertaken to monitor the health of a transplanted kidney or to determine the effectiveness of ongoing treatment for kidney disease.

Complications are rare after having a kidney biopsy, but they do have potential risks. Risks include pain and bleeding. The benefit of having a biopsy is that it can help diagnose a kidney condition and make sure you get the specific treatment needed – your healthcare team will advise you on this.

Reviewed December 2024