Introduction: Who Should Undergo Diagnostics

If you have been living with chronic kidney disease for some time, your doctor will monitor your kidney function regularly to watch for signs that the disease is progressing. End-stage renal disease, also known as kidney failure, happens when your kidneys can no longer filter waste and excess fluids from your blood well enough to keep you alive without medical help.^[1] This stage is defined by a glomerular filtration rate, or GFR, of less than 15 milliliters per minute—meaning your kidneys are working at less than 15 percent of their normal capacity.^[2]

Anyone with chronic kidney disease should undergo regular diagnostic testing, especially if they have conditions like diabetes, high blood pressure, heart disease, or a family history of kidney problems. These underlying conditions increase the risk that kidney disease will worsen over time.^[1] Testing becomes especially important when you begin noticing symptoms such as severe fatigue, nausea, vomiting, loss of appetite, changes in urination patterns, swelling in your feet or ankles, shortness of breath, or chest pain from fluid buildup.^[1] However, early kidney disease often causes no symptoms at all, which is why regular screening is vital—testing may be the only way to know your kidneys are failing before serious complications arise.^[7]

People who already know they have earlier stages of chronic kidney disease need ongoing monitoring to track how the disease is progressing. Your healthcare provider will recommend how often you should be tested based on your current kidney function, your overall health, and whether you have other medical conditions that affect the kidneys.^[7] If you develop new or worsening symptoms, or if blood work shows your kidney function is declining rapidly, more frequent testing will be necessary.

Diagnostic Methods

Doctors use several types of tests to diagnose end-stage renal disease and to understand what might have caused your kidneys to fail. The process usually starts with a detailed medical history and physical examination. Your doctor will ask about your family’s health history, any medications or supplements you take, and whether you have conditions like diabetes or high blood pressure that are known to harm the kidneys over time.^[7] A physical exam may reveal signs of kidney disease such as swelling, high blood pressure, or changes in your heart and lung sounds caused by fluid buildup.

Blood Tests

Blood tests are the cornerstone of kidney disease diagnosis. One of the most important tests measures the level of waste products in your blood, particularly creatinine and urea, also called blood urea nitrogen or BUN. When your kidneys are healthy, they remove these waste products efficiently. When they fail, creatinine and urea build up in the bloodstream, causing dangerous levels of toxins.^[7] Measuring creatinine is especially helpful because it allows doctors to calculate your glomerular filtration rate, the number that tells how much blood your kidneys are filtering each minute.

The GFR is the most important measure of kidney function. A GFR below 15 milliliters per minute per 1.73 square meters of body surface typically means you have reached end-stage renal disease.^[2] Your doctor will also look at how GFR changes over time—if it drops quickly, that signals rapid progression of kidney damage. Blood tests also check for imbalances in electrolytes like potassium and sodium, as well as acid levels in your blood, all of which can become dangerous when kidneys fail.^[7]

Urine Tests

Urine tests help doctors see what your kidneys are letting slip through into the urine. Healthy kidneys keep proteins, especially a protein called albumin, in the bloodstream. When kidneys are damaged, albumin leaks into the urine, a condition called proteinuria or albuminuria.^[7] Testing for albumin in the urine is a key part of diagnosing and staging chronic kidney disease. High levels of protein in the urine indicate significant kidney damage and help predict how quickly the disease might progress.

Your urine may also be tested for blood, infection, or other abnormalities that could point to kidney problems or complications. A simple urine sample collected at the doctor’s office is usually all that’s needed for these tests.^[7]

Imaging Tests

Imaging studies help doctors see the size, shape, and structure of your kidneys and look for blockages, cysts, tumors, or other unusual areas. Common imaging tests include ultrasound, which uses sound waves to create pictures of your kidneys; CT scans, which take detailed cross-sectional images using X-rays and a computer; and MRI scans, which use magnets and radio waves to produce detailed images of soft tissues.^[7] These tests are painless and non-invasive, though CT and MRI may require you to lie still inside a machine for a period of time.

Ultrasound is often the first imaging test used because it is safe, widely available, and does not expose you to radiation. It can show whether your kidneys are smaller than normal, which often happens in chronic kidney disease, or if there are structural problems like cysts or stones.

Kidney Biopsy

In some cases, your doctor may recommend a kidney biopsy to learn more about the type and extent of kidney damage. During a biopsy, a thin needle is inserted through your skin and into the kidney to remove a tiny sample of tissue.^[7] The procedure is usually guided by ultrasound imaging to make sure the needle reaches the right spot. The tissue sample is then examined under a microscope by a specialist who looks for specific patterns of damage, inflammation, or scarring. A biopsy can help identify the underlying cause of kidney disease and guide treatment decisions, though it is not always necessary for diagnosing end-stage renal disease if the diagnosis is already clear from blood and urine tests.

Tracking Disease Progression

Certain tests are repeated regularly to track how your kidney disease is progressing. Monitoring your GFR, creatinine, urea, and albumin levels over time helps your doctor see whether your kidneys are declining slowly or rapidly. This information is critical for planning when to start dialysis or pursue a kidney transplant.^[7] The Kidney Disease: Improving Global Outcomes, or KDIGO, guidelines recommend staging chronic kidney disease based on GFR and the amount of albumin in the urine. End-stage renal disease is the final stage, sometimes called stage 5, and means your kidneys are functioning at less than 15 percent of normal capacity.^[2]

Diagnostics for Clinical Trial Qualification

If you are considering participating in a clinical trial for end-stage renal disease, you will need to undergo additional testing to determine whether you are eligible. Clinical trials are research studies that test new treatments, medications, or procedures to see if they are safe and effective. They follow strict rules about who can participate, and these rules are based on specific diagnostic criteria.^[2]

Most clinical trials for end-stage renal disease require that your GFR be below a certain threshold, usually less than 15 milliliters per minute, to confirm that you truly have kidney failure.^[2] Trials may also require proof that you are already receiving dialysis or are about to start, or that you are on a waiting list for a kidney transplant. Blood tests will be repeated to confirm creatinine and urea levels, and urine tests will measure albumin to assess the severity of kidney damage. These baseline measurements help researchers understand your starting point and track how the experimental treatment affects your kidney function over time.

In addition to confirming your diagnosis, trials often look at other health factors. You may need tests to evaluate your heart health, check for infections, measure blood pressure, or assess your nutritional status. Researchers want to make sure that any changes they observe during the trial are due to the treatment being tested, not to other health problems.^[2] For example, a trial testing a new medication might exclude people with severe heart disease or uncontrolled diabetes because those conditions could interfere with the results.

Some trials focus on complications of end-stage renal disease, such as anemia, bone disease, or problems with fluid and electrolyte balance. If you are joining one of these studies, you will undergo specialized tests related to the specific complication being studied. For instance, a trial about anemia in kidney failure would require blood tests to measure your red blood cell count and hemoglobin levels.^[2]

Eligibility for clinical trials also depends on your willingness and ability to follow the study protocol, which may involve frequent visits, repeated testing, and adherence to treatment schedules. Your healthcare team will explain what tests are needed and why, and will make sure you understand the commitment involved before you enroll.