Kidney health

Diagnosing problems with kidney health

Blood and urine tests to measure kidney performance

Kidney performance can be calculated from measurements taken on blood and urine samples. A waste product called creatinine is measured in the blood, and urine is checked for the presence of protein. The creatinine level is converted into a measure of how efficiently the kidneys are filtering the blood. For more detail see. ‘How and why is kidney function monitored?’ These measurements can vary over time, so a diagnosis of chronic kidney disease or impairment is made on the basis of repeated blood and urine tests over a three month period showing consistent results rather than a single test.
Following diagnosis, regular blood and urine tests are used to monitor the kidney performance of people who have been diagnosed with mild or moderately impaired performance or early stage chronic kidney disease (see ‘Tests used to monitor kidney health’).

Diagnostic tests for underlying causes of kidney impairment

Impaired kidney performance can be caused by a variety of things, such as having diabetes or high blood pressure, or a structural problem with the kidneys, such as a blockage, and is more common in older people. Some people we spoke to had tests done to try to identify any underlying structural problems with the kidneys. These included an ultrasound scan, biopsy, urine flow test, or intravenous pyelogram (IVP) (see below). Not many people with early stage kidney impairment need these tests, nor are they used for regular monitoring of early stage chronic kidney disease.

An ultrasound scan uses sound waves to create an image of a part of the body, in this case the kidney. As no radiation is used in the procedure it is perfectly safe and is commonly used in pregnancy to see the developing baby. It is necessary to drink a lot of water before the scan to fill the bladder. A lubricating jelly is put on the skin and a handheld probe moved over the part of the body being examined and the pictures can be seen on a screen. The scan is conducted by a specialist technician called a sonographer.

Xanthe had lost one kidney to cancer many years ago, so when she learned recently that there was a new problem with her kidney function she asked for a scan of her remaining kidney to check the cancer had not returned; the scan results looked normal. Jackie has had damaged kidney function since childhood and when she recently moved to a new general practice the doctor arranged an ultrasound scan to provide a new baseline image of her kidneys. During her childhood a different type of scan had been used, called an intravenous pyelogram (IVP), which is a special x-ray examination of the kidneys, bladder, and ureters (the tubes that carry urine from the kidneys to the bladder) using a special dye. This tests how well the kidneys remove the dye and how it collects in the urine. She also recalls having a urine flow test (see below).
Several people mentioned having a urine flow test, known as a urodynamic test. This involves measuring how much urine leaves the bladder over a certain length of time and taking pressure readings from the bladder and abdomen while the bladder is filled and emptied. Some also had a cystoscopy – insertion of a thin tube into the bladder with a camera on the end.
A kidney biopsy involves the removal of a small sample of tissue from the kidney using a hollow needle and sometimes guided by an ultrasound scanner. The area is first numbed with a local anaesthetic so there should be no pain. The tissue sample can then be examined under the microscope or examined in other ways.

Justine’s chronic kidney disease is caused by a condition called IgA nephropathy, which was diagnosed through having a biopsy. She was initially quite worried about having a biopsy and wanted a lot of information about what it would involve before having it. She felt more alarmed by the prospect of having to lie still for six hours afterwards than by the insertion of the needle itself. The first time she went to the hospital the procedure was cancelled because she had taken aspirin the previous evening for a headache - caused by anxiety about having the procedure - and was told the aspirin could cause internal bleeding at the biopsy site. She went back two weeks later and had to wait several hours for a bed to become available so the biopsy could be done. Three samples were taken. It was late at night before she was able to go home; she felt stiff and bruised for a few days afterwards.
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Laura’s doctors suspect that she also has IgA nephropathy but they don’t know for certain because she decided not to have a kidney biopsy. She didn’t want a small piece of tissue removed for examination as she was afraid her kidney might not heal fully afterwards. Healing is not usually a problem after a kidney biopsy but there is a risk of bleeding. A kidney biopsy will only be conducted if the benefits are considered to outweigh the risks.

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