The blood and urine tests listed below may provide the first indication of a kidney problem or may be requested if CKD is suspected due to a person's signs and symptoms. These tests reflect how well the kidneys are removing excess fluids and waste products.
A blood pressure measurement is also important since high blood pressure (hypertension) can lead to CKD. When a structural problem is suspected, a variety of imaging tests can be used to evaluate the kidneys. A sample of kidney tissue, a biopsy, is sometimes helpful in diagnosing the specific cause of a problem.
Tests commonly used for screening and diagnosis
The National Institute for Health and Care Excellence (NICE) recommend that people who are at high risk be screened for kidney disease to detect it in its earliest stages. Risk factors include diabetes, high blood pressure, heart disease, or a family history of these or kidney disease. NICE recommend two laboratory tests to screen for kidney disease:
- Urine protein—a few different tests may be used to screen for protein in the urine:
- Urine albumin—this test may be done on a 24-hour urine sample, or both urine albumin and creatinine can be measured in a random urine sample and the albumin to creatinine ratio (ACR) can be calculated. The ACR as the preferred test for screening for albumin in the urine.
- Urinalysis—this is a routine test that can detect protein in the urine as well as red blood cells and white blood cells. These are not normally found in the urine and, if present, may indicate kidney disease.
- Urine total protein or urine protein to creatinine ratio (UPCR)—detects not just albumin, but all types of proteins that may be present in the urine.
Urinalysis and urine total protein are not as sensitive as urine albumin for detecting kidney damage.
- The glomerular filtration rate (GFR) refers to the amount of blood that is filtered by the glomeruli per minute. As a person's kidney function declines due to damage or disease, the filtration rate decreases and waste products begin to accumulate in the blood. To estimate the GFR a blood creatinine test, or possibly a cystatin C test, is performed.
Tests to monitor kidney function
If a person has been diagnosed with a kidney disease, several laboratory tests may be requested to help monitor kidney function. Some of these include:
- Blood levels of creatinine are measured from time to time to see if the kidney disease is getting worse.
- The amount of calcium and phosphorus in the blood and the balance of serum electrolytes can also be measured as these are often affected by kidney disease.
- Haemoglobin in the blood, measured as part of a full blood count (FBC), may also be evaluated as the kidneys make a hormone, erythropoietin, that controls red blood cell production and this may be affected by kidney damage.
- Parathyroid hormone (PTH), which controls calcium levels, is often increased in kidney disease and may be checked to help determine if enough calcium and vitamin D are being taken to prevent bone damage.
Tests to help determine the cause and/or guide treatment
Other tests may be requested to help determine the cause and/or guide treatment, depending on several factors including a person's signs and symptoms, physical examination, and medical history. Some examples of these tests include:
- Urinalysis with a urine culture may be done when someone has symptoms suggesting infection to confirm the presence of a bacterial infection.
- Hepatitis B or C testing—to detect a hepatitis viral infection associated with some types of kidney disease
- Antinuclear antibody (ANA)—to help identify an autoimmune condition such as lupus that may be affecting the kidneys.
- Kidney stone risk panel—this test evaluates a person's risk of developing a kidney stone, to help guide and monitor treatment and prevention
- Kidney stone analysis—this test determines the composition of a kidney stone passed or removed from the urinary tract and may be done to help determine the cause of its formation, to guide treatment, and prevent recurrence
- Complement tests, most commonly C3 and C4—may be tested and monitored with glomerulonephritis
- Urine protein electrophoresis—may be done to determine the source of a high level of protein in the urine
If a structural problem or blockage is suspected, imaging of the kidneys can be helpful. Imaging techniques such as an ultrasound, CT scan (computed tomography), isotope scan, or intravenous pyelogram (IVP) may be used.
A biopsy is sometimes used to help determine the nature and extent of structural damage to a kidney. Analysing a small piece of kidney tissue, obtained using a biopsy needle and diagnostic imaging equipment, can sometimes be useful when disease of the glomeruli (or sometimes the tubules) is suspected.