At-a-Glance Summary
- Kidney stones are diagnosed using a combination of symptoms, medical history, physical examination, imaging tests, urine tests, blood tests, and sometimes stone analysis.
- A non-contrast CT scan is often one of the most accurate imaging tests for suspected kidney stones, especially when symptoms are severe or the diagnosis is uncertain.
- Not every patient with kidney stone symptoms needs a CT scan. Imaging choice depends on pregnancy status, age, prior stone history, radiation exposure, kidney function, clinical stability, and the question your doctor needs to answer.
- Ultrasound may be preferred in certain situations, including pregnancy, children, follow-up imaging, or when radiation exposure should be limited.
- Urine and blood tests help doctors look for infection, kidney function changes, dehydration, mineral imbalance, and metabolic causes of stone formation.
- Stone analysis is important when a stone is passed or removed, because knowing the stone type can guide prevention.
- A kidney stone with infection and obstruction can become a medical emergency and may require urgent drainage of the kidney, not only antibiotics.
Why Kidney Stone Diagnosis Matters
Kidney stone diagnosis is not only about confirming that a stone is present. A careful evaluation helps your care team answer several important questions:
- Is there a kidney stone?
- Where is the stone located?
- How large is it?
- Is it blocking urine flow?
- Is there a sign of infection?
- Is kidney function affected?
- What may have caused the stone to form?
- How can future stones be prevented?
This matters because two people with kidney stones may need very different care. A small stone that is likely to pass may be managed differently from a larger stone, an infected stone, a stone causing obstruction, or a stone in a patient with chronic kidney disease.
A complete diagnosis also helps protect kidney function. When a stone blocks the ureter, urine can back up toward the kidney. This increased pressure can affect the renal pelvis, tubules, and glomeruli, reducing filtration and sometimes causing post-renal acute kidney injury (AKI). This risk is higher when obstruction is severe, prolonged, affects a single functioning kidney, or occurs with infection.
Symptoms That May Suggest a Kidney Stone
Kidney stone symptoms can vary depending on the stone’s size, location, and whether it is blocking urine flow. Some stones cause intense symptoms, while others are found during imaging for another reason.
Common symptoms may include:
- Sharp pain in the side or back, often below the ribs
- Pain that moves toward the lower abdomen, groin, or genital area
- Pain that comes in waves
- Blood in the urine
- Burning or discomfort with urination
- Frequent or urgent urination
- Nausea or vomiting
- Cloudy or foul-smelling urine
- Fever or chills if infection is present
Pain from a kidney stone is not only caused by the stone “scratching” or “moving.” Pain often occurs when an obstructing stone causes urine to back up, increasing pressure within the renal pelvis and stretching sensitive kidney structures. As the stone moves through the ureter, smooth muscle spasms can create waves of severe pain that radiate toward the lower abdomen, groin, or genital region.
This is why kidney stone pain can feel intense, change location, and come in waves.
Blood in the urine is common with kidney stones, but its absence does not always rule out a stone. Imaging and clinical evaluation may still be needed when symptoms strongly suggest stone disease.
Other Conditions That Can Mimic Kidney Stone Pain
Not all flank, abdominal, or pelvic pain is caused by a kidney stone. Similar symptoms may occur with:
- Urinary tract infection
- Kidney infection
- Appendicitis
- Gallbladder disease
- Ovarian or testicular conditions
- Muscle strain
- Gastrointestinal problems
- Vascular conditions
This is one reason a medical evaluation is important, especially when pain is severe, unusual, or accompanied by fever, vomiting, weakness, confusion, or worsening symptoms.
When Kidney Stone Symptoms Need Urgent Care
Some kidney stone situations need prompt medical attention. Seek urgent care if you have:
- Fever or chills
- Severe pain that does not improve
- Persistent nausea or vomiting
- Trouble urinating
- Blood in the urine with worsening symptoms
- Known chronic kidney disease
- A single kidney
- A history of kidney transplant
- Pregnancy
- Symptoms of dehydration, weakness, or confusion
A kidney stone that blocks urine flow while an infection is present can become a medical emergency. In this situation, antibiotics alone may not be enough. The kidney may need urgent drainage through a ureteral stent or percutaneous nephrostomy to relieve pressure, control infection, and protect kidney function.
In urgent situations, especially when a stone is blocking urine flow and infection is suspected, care may involve both nephrology and urology. A urologist may perform drainage with a ureteral stent or percutaneous nephrostomy, while the broader care team monitors infection, kidney function, fluids, electrolytes, and medication safety.
People with a single functioning kidney or a kidney transplant should be evaluated promptly when kidney stone symptoms occur, because obstruction may affect overall kidney function more quickly than in someone with two functioning kidneys.
Important Safety Note on Pain Medicine
Pain from a kidney stone can be severe, and pain control is an important part of care. However, patients should avoid taking high doses of nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen or naproxen without medical supervision.
This is especially important for people with:
- Chronic kidney disease
- Dehydration from vomiting or poor fluid intake
- A possible urinary obstruction
- A single kidney
- A kidney transplant
- Heart failure or liver disease
- Blood pressure problems
- Medications that affect kidney blood flow or electrolytes
NSAIDs can reduce blood flow inside the kidneys and may worsen acute kidney injury in certain situations. Your care team can help determine which pain-control strategy is safest for your kidney function and overall health.
Step 1: Medical History
The diagnostic process usually begins with questions about your symptoms and health history. Your doctor may ask:
- When did the pain start?
- Where is the pain located?
- Does the pain move?
- Does it come in waves?
- Have you had kidney stones before?
- Do kidney stones run in your family?
- Have you noticed blood in your urine?
- Do you have fever, chills, nausea, or vomiting?
- How much fluid do you usually drink?
- What medications or supplements do you take?
- Do you have chronic kidney disease, gout, bowel disease, recurrent urinary tract infections, or other medical conditions?
- Are you pregnant or could you be pregnant?
This information helps your clinician understand whether symptoms fit with a kidney stone or whether another condition may be causing similar pain.
Step 2: Physical Examination
A physical exam may include checking your abdomen, back, and sides for tenderness. Your doctor may also check:
- Temperature, to look for fever
- Blood pressure and heart rate
- Signs of dehydration
- Abdominal tenderness
- Pain over the flank area
- Overall appearance, especially if pain, vomiting, or infection is suspected
The physical exam alone usually cannot confirm a kidney stone, but it helps guide the next step and can identify warning signs that need faster evaluation.
Step 3: Imaging Tests
Imaging tests help show whether a stone is present, where it is located, how large it is, and whether it is causing blockage. Imaging can also help identify other possible causes of flank, abdominal, or pelvic pain.
Imaging choice is individualized. A CT scan may be the most accurate option in many acute cases, but ultrasound, X-ray, or follow-up imaging may be preferred depending on pregnancy status, age, prior stone history, radiation exposure, kidney function, clinical stability, and the specific question your doctor needs to answer.
| Imaging test | What it can show | When it may be used | Limitations |
|---|---|---|---|
| Non-contrast CT scan | Stone size, location, number of stones, obstruction, complications, and other possible causes of pain. | Often used when symptoms are severe, diagnosis is unclear, or a detailed view is needed. | Very accurate, but it involves radiation. Low-dose protocols may be considered in selected patients. |
| Ultrasound | Kidney swelling, some stones, and signs that urine flow may be blocked. | May be preferred during pregnancy, in children, for follow-up in selected patients, or when radiation should be limited. | Avoids radiation, but may miss small stones or stones located in certain parts of the ureter. |
| X-ray | Some stones, especially certain calcium-containing stones that are visible on X-ray. | May be used in selected cases or follow-up when a stone is known to be radiopaque. | Can miss small stones or stones that are not visible on X-ray. |
Non-Contrast CT Scan
A non-contrast CT scan is commonly used because it can provide a detailed view of the urinary tract without the need for IV contrast. It can help identify:
- The size of the stone
- The location of the stone
- Whether there is more than one stone
- Whether urine flow appears blocked
- Whether kidney swelling is present
- Whether another condition may be causing similar symptoms
CT imaging does not always determine the exact stone composition. However, it provides important information that helps guide treatment decisions.
In selected cases, specialized CT techniques may provide additional information, but most patients do not need advanced imaging beyond the test chosen by their care team.
Ultrasound
Ultrasound uses sound waves rather than radiation. It may be used when avoiding radiation is important, such as during pregnancy or in children. It may also be used for follow-up in selected patients with known stone disease, especially when the clinical question is whether the kidney is swollen or whether obstruction may be present.
Ultrasound can be very useful, but it may not detect every stone, especially small stones or stones located in certain parts of the ureter.
X-Ray
An abdominal X-ray may show some kidney stones, especially stones that contain calcium. However, X-rays are used less often as the main diagnostic test because they can miss small stones or stones that are not easily visible.
X-ray may still be useful in selected patients, especially when a prior stone is known to be radiopaque and follow-up imaging is needed.
Imaging During Pregnancy
During pregnancy, kidney stone symptoms should be evaluated carefully because the safest imaging approach may differ. Ultrasound is commonly considered first because it avoids radiation, but the care team will choose the best approach based on symptoms, gestational age, infection risk, obstruction risk, and maternal safety.
Pregnant patients with severe pain, fever, vomiting, urinary symptoms, or concern for obstruction should seek prompt medical evaluation.
Step 4: Urine Tests
Urine testing can help identify clues that support the diagnosis and reveal factors that may contribute to stone formation.
A urinalysis may check for:
- Blood in the urine
- White blood cells or bacteria, which may suggest infection
- Crystals
- Urine pH, which can be related to certain stone types
- Signs of dehydration
- Other abnormalities that may require follow-up
If infection is suspected, a urine culture may be ordered to identify the bacteria and help guide antibiotic selection. This is especially important when fever, chills, obstruction, recurrent urinary tract infections, or kidney infection symptoms are present.
For people with recurrent stones or higher risk factors, a doctor may also order a 24-hour urine collection. This test measures substances in the urine that can increase or reduce stone risk, such as calcium, oxalate, citrate, uric acid, sodium, and total urine volume.
A 24-hour urine collection is not required for every first-time stone episode, but it may be recommended for recurrent stone formers, high-risk patients, or selected first-time patients when prevention planning needs more detail.
Step 5: Blood Tests
Blood tests help evaluate kidney function and look for medical factors that may contribute to kidney stones.
Blood testing may include:
- Creatinine and estimated glomerular filtration rate (eGFR): These help assess kidney filtration and whether obstruction, dehydration, infection, or another condition may be affecting kidney function.
- Electrolytes: These help evaluate mineral and fluid balance.
- Calcium levels: High calcium may increase the risk of calcium-based stones and may require further evaluation.
- Uric acid levels: High uric acid may be associated with uric acid stones or gout.
- Complete blood count or infection markers: These may be used when infection is suspected.
- Parathyroid hormone (PTH): This may be checked when calcium is high or when primary hyperparathyroidism is suspected as a contributor to recurrent calcium stones.
In acute obstruction, creatinine and eGFR help assess kidney function, but rapid changes may need repeated testing and clinical interpretation. Kidney function can change over time depending on dehydration, infection, severity of obstruction, and whether one or both kidneys are affected.
These results help your care team understand whether the stone is affecting kidney function or whether an underlying condition may be increasing stone risk.
Step 6: Stone Analysis
If you pass a stone, your care team may ask you to collect it. The stone can be sent to a laboratory to identify what it is made of.
Knowing the stone type matters because prevention is not the same for every patient. For example, prevention strategies for uric acid stones may differ from strategies for calcium oxalate stones or cystine stones.
| Stone type | Common urine pattern or cause | Why it matters for prevention |
|---|---|---|
| Calcium oxalate stones | Low urine volume, high oxalate, high urine calcium, or low citrate can increase urinary supersaturation, allowing calcium oxalate crystals to form and grow. | Prevention may focus on fluids, sodium reduction, balanced dietary calcium, oxalate strategy, and citrate levels when appropriate. |
| Calcium phosphate stones | Higher urine pH, high urine calcium, or certain metabolic conditions can promote calcium phosphate crystallization. | Prevention may require careful evaluation of urine pH, calcium balance, medications, and possible metabolic causes. |
| Uric acid stones | Acidic urine pH lowers uric acid solubility, which can trigger uric acid crystal formation. This may be associated with gout, metabolic syndrome, dehydration, or high purine intake in some patients. | Prevention may focus on urine alkalinization, hydration, and addressing uric acid or metabolic risk factors. |
| Struvite stones | Certain urinary tract infections caused by urease-producing bacteria can raise urine pH and promote magnesium ammonium phosphate stone formation. | Prevention requires infection control, close monitoring, and often urologic evaluation because these stones can grow quickly. |
| Cystine stones | An inherited condition called cystinuria can cause excess cystine in the urine, leading to recurrent cystine stone formation. | Prevention often requires specialized long-term monitoring and an individualized treatment plan. |
How Test Results Help Guide Treatment
Diagnosis helps your doctor decide whether a stone may pass on its own or whether treatment may be needed.
| Diagnostic finding | Why it matters |
|---|---|
| Stone size | Smaller stones may be more likely to pass, while larger stones may require a procedure. |
| Stone location | A stone in the kidney may be managed differently from a stone blocking the ureter. |
| Signs of obstruction | Blocked urine flow can increase pressure inside the kidney, reduce filtration at the glomerular level, and sometimes cause post-renal acute kidney injury. |
| Signs of infection | Infection with an obstructing stone can become dangerous and may require emergency drainage plus antibiotics. |
| Kidney function results | Changes in creatinine or eGFR can affect treatment choices, medication safety, imaging decisions, and follow-up timing. |
| Stone composition | The stone type helps guide prevention strategies and future monitoring. |
What Diagnostic Tests May Not Tell Right Away
Even when imaging confirms a kidney stone, some questions may require follow-up.
Imaging can estimate stone size and location, but it may not always predict exactly whether a stone will pass on its own, how quickly symptoms will improve, or what the stone is made of. A CT scan may suggest certain features, but stone composition is usually confirmed through laboratory stone analysis when a stone is passed or removed.
This is why the best nephrology programs often combine imaging results with symptoms, urine testing, urine culture when needed, blood work, kidney function, infection risk, medication safety, and follow-up plans.
Who May Need a More Complete Evaluation?
Some patients may need more than a one-time evaluation. A more complete metabolic evaluation may be especially important for people with:
- Recurrent kidney stones
- Kidney stones at a young age
- A family history of kidney stones
- A single kidney
- Chronic kidney disease
- Gout
- Bowel disease or malabsorption
- Uric acid, cystine, calcium phosphate, or struvite stones
- Frequent urinary tract infections
- High-risk occupations where another stone episode could be dangerous
This type of evaluation may include blood tests, stone analysis, and one or more 24-hour urine collections. The goal is to understand why stones are forming and how to reduce the risk of future stones safely.
What to Bring to Your Appointment
You can help your care team by bringing accurate information and useful records to your visit.
Helpful items include:
- A list of medications and supplements
- Prior imaging reports, if available
- Prior stone analysis results, if you have them
- Recent lab work
- A symptom timeline, including when pain started and whether it moved
- Information about fever, chills, vomiting, urinary changes, or blood in the urine
- Pregnancy status, if applicable
- History of chronic kidney disease, single kidney, kidney transplant, gout, bowel disease, or recurrent urinary tract infections
- Any stone you passed, if your care team asked you to save it
Ask your doctor whether you should strain your urine to collect a stone and how to store it safely if one passes.
Do not start major diet changes, supplements, high fluid intake plans, or pain-medication routines without medical guidance, especially if you have kidney disease, heart disease, fluid restrictions, vomiting, dehydration, or take medications that affect electrolytes or kidney blood flow.
Diagnosing Kidney Stones at Florida Kidney Physicians
At Florida Kidney Physicians, kidney stone evaluation is focused on more than confirming a stone. Our nephrology team helps assess kidney function, infection risk, metabolic risk factors, medication safety, and prevention needs so patients can receive a clearer diagnosis and a safer long-term plan.
When needed, care may also involve urology, imaging specialists, primary care clinicians, emergency care teams, or other specialists. This team-based approach is especially important when a stone is obstructing urine flow, infection is suspected, kidney function is changing, or a procedure may be needed.
Frequently asked questions
How are kidney stones diagnosed?
Kidney stones are usually diagnosed with a combination of symptoms, medical history, physical examination, imaging tests, urine tests, blood tests, and sometimes stone analysis.
Do all kidney stone symptoms require a CT scan?
Not always. A CT scan may be recommended when symptoms are severe, the diagnosis is unclear, or detailed information is needed. Ultrasound or other imaging may be preferred in certain patients, such as pregnant individuals, children, or people who need to limit radiation exposure.
What is the best imaging test for kidney stones?
A non-contrast CT scan is often one of the most accurate tests for suspected kidney stones, especially when symptoms are severe or the diagnosis is unclear. Ultrasound may be preferred in certain patients, such as pregnant individuals, children, or people who should avoid radiation when possible.
Can a urine test show kidney stones?
A urine test may not always show the stone itself, but it can reveal blood, crystals, infection signs, urine pH changes, or mineral levels that help support the diagnosis and guide prevention.
Why is a urine culture sometimes needed?
A urine culture may be ordered when infection is suspected. It helps identify bacteria and can guide antibiotic selection, especially when fever, chills, obstruction, recurrent urinary tract infections, or kidney infection symptoms are present.
Why is stone analysis important?
Stone analysis identifies what the stone is made of. This helps your doctor recommend prevention strategies that match your stone type instead of using a one-size-fits-all approach.
Should I save a kidney stone if I pass one?
Yes, if your care team tells you to. A passed stone can often be sent for laboratory analysis, which helps identify the stone type and guide prevention.
Can a blocked kidney stone affect kidney function?
Yes. A blocked stone can cause urine to back up toward the kidney, increasing pressure and reducing filtration. In some cases, this can lead to post-renal acute kidney injury, especially if obstruction is severe, prolonged, affects a single functioning kidney, or occurs with infection.
When should kidney stone symptoms be treated as urgent?
Seek urgent medical care if you have severe pain, fever, chills, persistent vomiting, trouble urinating, known kidney disease, a single kidney, pregnancy, confusion, weakness, or worsening symptoms.