If you’re experiencing symptoms of kidney stones, most notably pain in the abdomen or on one side of your lower back, you’ll likely want to see your doctor as soon as you can. Stones can be diagnosed by a primary care physician, urologist, or nephrologist, but in many cases the pain is so sudden and intense that people head straight to the emergency room (ER), with one report finding more than one million visits to the ER because of kidney stones in a single year.
Regardless of where you receive care, you can expect to undergo some combination of imaging tests, urine tests, and blood tests to confirm your diagnosis of kidney stones. Some of these tests can help determine the cause of your stones, too.
Imaging Tests That Help Doctors Diagnose Kidney Stones
Doctors typically diagnose kidney stones based on a physical exam, signs and symptoms you’re experiencing (such as blood in the urine and difficulty urinating, among others), and imaging tests. Imaging tests that examine the kidneys, the bladder, and the ureters (the tubes that carry urine from the kidneys to the bladder) help doctors identify stones, says Sean Hashmi, MD, a nephrologist at Kaiser Permanente in Southern California.
The most common imaging tests used for diagnosing kidney stones are:
Computerized Tomography (CT) ScanThis imaging test creates three-dimensional images of the abdomen and pelvis, does not require a contrast dye, and can be performed with a low dose of radiation, says Dr. Hashmi. ER doctors often order a CT scan for a suspected kidney stone because the test helps them make a quick and accurate diagnosis.
Ultrasound An ultrasound uses sound waves to create real-time images of the body. Doctors may use this test to diagnose kidney stones in pregnant women and other people who want to avoid radiation. One drawback of using ultrasound in the ER is that it may only be moderately accurate for diagnosing kidney stones. Ultrasound can miss small stones in the kidney or stones in the ureter.
When Urinalysis and Other Urine Tests Help in Kidney Stone Diagnosis
In addition to imaging tests, doctors usually order urine tests to help determine what type of stone you may have and why you are developing stones. This information can help your doctor better advise you about how to prevent future kidney stones, says Naim Maalouf, MD, a professor of internal medicine at UT Southwestern Medical Center in Dallas. At least 31 percent of people diagnosed with kidney stones develop another one within 10 years.
Kidney stones are made of minerals and other substances that can be found in the urine that can be identified with testing. Types of kidney stones include calcium stones (both calcium-oxalate and calcium phosphate stones), uric acid stones, struvite stones, and cystine stones.
Notably, a urinalysis test and urine culture can also tell doctors whether you also have an infection, which is a potentially life-threatening complication in combination with a kidney stone, says Seth K. Bechis, MD, an associate professor of urology at UC San Diego Health in California. If urine is trapped behind an obstructing stone in the ureter, urine can become infected. This scenario can cause an infection of the kidney tissue or spread to the bloodstream.
Doctors may perform the following urine tests in kidney stone diagnosis:
Urine pH Test A dipstick urinalysis can determine the pH of the urine, meaning how acidic or alkaline it is. The results can help doctors figure out what type of stone you have, says Hashmi. For instance, higher pH levels may mean you have a struvite stone, which forms from the waste products of bacteria, while lower levels can mean you have a uric acid stone.
Urinalysis With Microscopy For this test, urine is analyzed under a microscope to look for crystals made of minerals that are associated with specific types of kidney stones, says Hashmi. For example, uric acid crystals may be found in the urine of someone with uric acid stones. Calcium oxalate crystals in the urine may indicate a calcium oxalate stone.
A urinalysis with microscopy can also help doctors find evidence of bleeding or infection, says Dr. Maalouf.
24-Hour Urine Collection Doctors often perform a 24-hour urine collection, says Maalouf. This means patients need to collect all of their urine in a container over a 24-hour period. Some doctors recommend two of these tests over two consecutive days.
From this urine sample, doctors can tell whether people are predisposed to stone formation. “We call it a stone risk profile,” says Maalouf.
The test measures levels of calcium, oxalate, and uric acid, which are found in certain types of kidney stones, says Anil Agarwal, MD, a clinical professor of nephrology at the University of California San Francisco School of Medicine.
Levels of citrate (a form of citric acid) and the mineral magnesium, both of which help to prevent stones, are also measured. The test can also analyze sodium levels in urine, as high levels can increase urine calcium levels, which raises risk of developing a stone.
A stone analysis test analyzes a stone that is passed out the urethra to determine what the stone is made of, such as calcium oxalate or uric acid.
When Blood Tests Are Used to Diagnose Kidney Stones
In addition to imaging tests and urine tests, a doctor may order blood tests, which can reveal important information about what may have caused a kidney stone, or about your future risk of developing more stones. Blood tests may help:
Detect Underlying Conditions For example, doctors can measure the levels of uric acid or calcium in the blood. High levels of uric acid may mean you have gout, a form of arthritis that may cause uric acid stones to form. High levels of calcium in the blood may mean your parathyroid gland is overactive, says Hashmi. This condition, called hyperparathyroidism, may cause calcium stones to form in your kidney.
Find Signs of Anemia Doctors may also order a complete blood count. This test can show whether you have anemia, meaning a low red blood cell mass, which indicates you have a low hemoglobin level from bleeding associated with the kidney stone, says Hashmi.
Diagnose Infection A complete blood count can also tell doctors whether you have elevated white blood cell levels, a sign of infection, adds Hashmi.
Assess Kidney Function Because stones can potentially damage the kidney, doctors may conduct blood work to evaluate your kidney function, says Maalouf. These tests can include measurements of creatinine and blood urea nitrogen, which are waste products that the kidneys filter from the blood.
Measure Electrolytes Another valuable blood test is a complete electrolyte panel, says Hashmi. It shows levels of electrolytes, or important salts and minerals in the body such as sodium and potassium, which may be altered because of a kidney stone.
Tips for Seeing Your Doctor About a Kidney Stone
If you suspect you have a kidney stone, here are some ways to prepare for your doctor’s appointment:
Write down your symptoms and questions you want to ask your doctor.
Be prepared to talk about any underlying medical conditions you have, as well as your medical history and medication you’re taking, says Shidham.
Keep track of how much you drink throughout the day, says Daniel Marchalik, MD, a urologist and director of the kidney stone program at MedStar Washington Hospital Center in Washington, DC.
Share information about your dietary habits, which can raise or lower your risk of kidney stones, adds Dr. Marchalik.
Send or bring prior medical reports, including results of imaging tests and laboratory work, says Prakash N. Maniam, MD, a urologist affiliated with HCA Florida Oviedo Urology in Oviedo, Florida.
Drink some water so you’re ready to give a urine sample for your doctor to examine, says Dr. Maniam.
If you pass a kidney stone, keep it and bring it to the appointment so doctors can analyze it and identify what kind it is, says Marchalik.
Common Questions & Answers
How do doctors diagnose kidney stones?
Doctors diagnose kidney stones based on a physical exam, symptoms you’re experiencing (such as blood in the urine and difficulty urinating), and imaging tests of the kidneys, bladder, and ureters (the tubes that carry urine from the kidneys to the bladder).
What are the common imaging tests used to diagnose kidney stones?
The most common imaging tests used to diagnose kidney stones are computerized tomography (CT) scans — which can help ER doctors spot kidney stones quickly — and ultrasounds, which are done without radiation (good for pregnant women).
How do urine tests help in the diagnosis of kidney stones?
Urine tests reveal the type of kidney stone and whether there is an infection present, which is a potentially life-threatening complication in combination with a kidney stone. They can also help doctors advise patients on how to prevent future kidney stones.
What information can blood tests provide in the diagnosis of kidney stones?
Blood tests can detect underlying conditions that may have caused the kidney stone, assess kidney function, measure electrolyte levels, and diagnose infection or anemia.
What should patients do to prepare for a doctor's appointment concerning kidney stones?
Patients should write down their symptoms and questions, provide information about their medical history and medications, keep track of their fluid intake, bring prior medical reports, and be prepared to provide a urine sample or bring any passed kidney stones for analysis.
Igor Kagan, MD, is an an assistant clinical professor at UCLA. He spends the majority of his time seeing patients in various settings, such as outpatient clinics, inpatient rounds, and dialysis units. He is also the associate program director for the General Nephrology Fellowship and teaches medical students, residents, and fellows. His clinical interests include general nephrology, chronic kidney disease, dialysis (home and in-center), hypertension, and glomerulonephritis, among others. He is also interested in electronic medical record optimization and services as a physician informaticist.
A native of Los Angeles, he graduated cum laude from the University of California in Los Angeles (UCLA) with a bachelor's in business and economics, and was inducted into the Phi Beta Kappa honor society. He then went to the Keck School of Medicine at the University of Southern California (USC) for his medical school education. He stayed at USC for his training and completed his internship and internal medicine residency at the historic Los Angeles County and USC General Hospital. Following his internal medicine residency, Kagan went across town to UCLA's David Geffen School of Medicine for his fellowship in nephrology and training at the UCLA Ronald Reagan Medical Center. After his fellowship he stayed on as faculty at UCLA Health.
Heather Lindsey is a freelance health and medical writer who covers topics such as cancer, digestive disorders, heart disease, diabetes, obesity, arthritis, allergies, nutrition, fitness, pregnancy, pediatrics, aging, and complementary medicine. In addition to contributing to Everyday Health, she writes and edits patient and academic web content for NYU Langone Health, covers research news for Weill Cornell Medicine, and reports on healthcare trends for Business Insider. She has also blogged for UCLA Health Connect and Johns Hopkins Healthy Aging and Healthy Mind. Heather lives in the New York metropolitan area.
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
Resources
When and Why to Refer Kidney Stone Patients to a Specialist. Cleveland Clinic. August 12, 2015.
Mills L et al. Ultrasound for the Diagnosis and Management of Suspected Urolithiasis in the Emergency Department. The Journal of Emergency Medicine. February 2018.
