As the symptoms of glomerulonephritis are not always obvious, it is often only diagnosed after a routine medical check-up or tests for another condition.
In most cases, blood and urine tests offer a good indication of kidney problems.
A blood test can measure your creatinine level. Creatinine is a substance produced by your muscles and is present in your bloodstream. The kidneys usually remove creatinine from the blood.
If your kidneys are not working normally, the creatinine level in your blood will rise, which can be detected during a blood test.
The creatinine result is converted into a value called the 'estimated glomerular filtration rate' (eGFR) to determine kidney function.
Your urine can be tested in two ways:
- Your GP or another healthcare professional can dip special strips into a sample of your urine. This is called the dipstick technique, and the strip changes colour if there is any blood or protein in your urine.
- A sample of your urine is sent to a laboratory to more accurately measure how much protein it contains or to look for blood cells.
The results of blood and urine tests may be combined to decide whether you need to see a specialist for further investigations.
Specialist blood tests
Several specialist blood tests may be carried out to look for causes of glomerulonephritis. These include:
- tests to look for systemic lupus erythematosus, such as an anti-nuclear antibody test – see diagnosing lupus for more information
- the anti-neutrophil cytoplasmic antibody (ANCA) blood test, used to diagnose vasculitis (inflammation of the blood vessels)
- tests to look for specific infections such as hepatitis B or hepatitis C
- the anti-glomerular basement membrane blood test, used to diagnose Goodpasture’s disease (when antibodies attack the membranes of the glomeruli)
If your kidney problem needs to be investigated further, you may need to have an ultrasound scan of your kidney.
An ultrasound scan uses high-frequency sound waves to create an image of your kidneys which will be looked at by a specialist. The specialist will be able to check the size of your kidneys, make sure there are no blockages and look for anything else that might explain why they are not working as they should.
If you need a kidney biopsy (see below), you will need a kidney ultrasound scan first.
If glomerulonephritis is suspected, a procedure to remove a small sample of kidney tissue may be recommended. This is called a biopsy.
A kidney biopsy is usually carried out using local anaesthetic to numb the area. An ultrasound machine will be used to locate your kidneys and a small needle will be used to take a sample. The test carries a small risk of bleeding so you will need to remain in hospital for a while on the day of the procedure, or sometimes overnight.
The tissue sample will then be examined under a microscope in a laboratory to confirm a diagnosis of glomerulonephritis, find out how serious the condition is, and determine the most appropriate course of treatment. Read more about treating glomerulonephritis.