A nephrologist is a kidney specialist. They can perform diagnostic tests and treat conditions related to the kidneys.
Nephrology is a subspecialty of internal medicine. To become a nephrologist, a person should:
- complete an undergraduate and medical degree
- complete a 3 year residency in basic internal medicine training
- complete a 2 or 3 year fellowship focusing on nephrology
- pass a board certification exam (optional)
Nephrologists often work in individual or group practices caring for people referred from family doctors or specialists. Many nephrologists also consult on cases in hospitals and oversee dialysis units, usually in a clinic or a hospital.
Some nephrologists also focus on clinical research, while others work as professors and supervisors.
Nephrologists treat conditions that involve or impact the kidneys, both directly and indirectly.
Some common conditions a nephrologist treats or helps treat include:
- advanced or chronic kidney disease
- glomerular conditions, such as glomerulonephritis and nephrotic syndrome
- tubulointerstitial kidney diseases
- tubular defects
- kidney vascular conditions, such as renal artery stenosis
- kidney infections
- kidney neoplasms, or abnormal growths
- structural or functional abnormalities of the kidney, bladder, or urine collection system, such as nephrolithiasis
- high blood pressure
- autoimmune conditions involving the kidneys
- electrolyte, fluid, and acid-base imbalances or disturbances
- some metabolic disorders, such as diabetes
Their training in internal medicine and nephrology allows nephrologists to perform a very long list of tests, procedures, and treatments.
However, the most common tests they use to diagnose or monitor kidney conditions are blood and urine tests.
The kidneys filter excess fluid and waste from the blood, creating urine. This means that blood and urine tests can often reveal whether or not the kidneys are working properly.
Urine tests can also check for abnormal levels of proteins linked to kidney damage in the urine.
The following sections discuss these types of test in more detail.
Common blood tests include:
The body produces creatinine as a byproduct of day-to-day muscle damage.
However, having high levels of creatinine in the blood, or elevated serum creatinine, is usually a sign of progressive kidney disease.
Serum creatinine levels depend on factors including age, body size, and race. A value of greater than 1.2 for women or greater than 1.4 for men may signal kidney problems.
Glomerular filtration rate
The glomerular filtration rate (GFR) tests how well the kidneys are able to filter out excess fluid and waste from the blood. Nephrologists can determine this value by calculating the serum creatinine level and factoring in age, sex, and race.
Value typically decreases with age, but important GFR values include:
- 90 or above (normal)
- 60 or below (kidney dysfunction)
- 15 or below (high risk of needing dialysis or a transplant for kidney failure)
Blood urea nitrogen
Urea nitrogen is a waste product from the body breaking down protein in foods and drinks. Typically, blood urea nitrogen (BUN) levels increase with decreasing kidney function.
Normally, BUN levels range from 7 to 20.
Common urine tests include:
To perform a urine analysis, or urinalysis, a nephrologist will usually look at a urine sample under a microscope to check for abnormalities.
Urinalysis can also involve a dipstick test, during which a nephrologist will dip a small, chemically treated strip into a urine sample. The strip will change color if it reacts with abnormal protein levels, blood, bacteria, sugar, or pus.
This helps detect many kidney and urinary tract conditions.
24 hour urine test
In a 24 hour urine test, a person will collect their urine for 24 hours to show how much urine the kidneys can produce and how much protein and electrolytes the kidneys leak into urine each day.
A creatine clearance test compares the amount of creatinine in a 24 hour urine sample with that in blood samples to determine how much waste the kidneys are filtering each minute.
A microalbuminuria test is a sensitive type of dipstick test that can pick up small amounts of the protein albumin in urine.
People at risk of kidney conditions, including those with high blood pressure or metabolic conditions such as diabetes, may undergo this test if their standard dipstick test is negative for excess protein levels in the blood (proteinuria).
Nephrologists use several types of procedure to help diagnose, monitor, and treat kidney conditions. These procedures include:
Ultrasound uses sound waves to create a picture of the kidneys. This test can detect changes in the size or position of the kidneys, as well as any obstructions.
A CT scan uses X-rays to create a picture of the kidneys, sometimes with the help of an intravenous contrast dye. This test can detect obstructions or abnormalities in structure.
However, contrast dyes may be problematic for people with kidney conditions.
A biopsy involves inserting a thin needle that has a cutting edge to take tiny slices of kidney tissues so that a healthcare professional can examine them.
A nephrologist may perform a biopsy for a few specific reasons, typically to:
- assess kidney damage
- identify a disease process and learn how it may respond to treatment
- help understand transplant complications
Hemodialysis involves running blood through an artificial kidney machine called a hemodialyzer to remove waste, extra fluid, and extra chemicals before returning it to the body. The blood will return to the body through a port, or catheter, in the arm, leg, or sometimes neck.
Hemodialysis typically treats end stage kidney failure, which occurs when the kidneys have lost around 85–90% of normal function and have a GFR rate of under 15.
People often require 4 hour sessions three times weekly. A nephrologist will usually oversee these sessions.
A transplant involves removing a portion or all of a damaged kidney and replacing it with a matching donor organ.
Surgeons perform transplant procedures, but nephrologists commonly work with a larger care team to help guide people through the process.