Kidney Stones: Symptoms, CT Diagnosis, and Removal Options

Kidney stones are hard mineral deposits that can cause severe flank pain, urinary symptoms, nausea, or blood in the urine. Diagnosis often involves CT imaging, and treatment ranges from careful observation and pain control to minimally invasive removal procedures.

Overview

Kidney stones, also called renal calculi or urolithiasis, are solid deposits that form from minerals and salts in the urine. They may develop inside the kidney and then move into the ureter, the narrow tube that carries urine from the kidney to the bladder. Some stones are as small as a grain of sand, while others can grow large enough to fill part of the kidney’s collecting system.

Many kidney stones are made of calcium oxalate, but other types include calcium phosphate, uric acid, struvite, and cystine stones. Knowing the type of stone can help guide prevention, especially for people who have repeated episodes. A stone may remain silent for a period of time, but symptoms often begin suddenly when it moves and blocks urine flow.

Modern care for kidney stones is usually highly effective and often minimally invasive. Doctors consider the stone’s size, location, the level of pain, signs of infection, kidney function, and the patient’s preferences before recommending observation, medication, or a procedure. The main goals are to relieve pain, remove or pass the stone safely, protect kidney function, and reduce the chance of future stones.

Kidney Stone Symptoms

The classic symptom of a kidney stone is renal colic: intense pain that often starts in the side or back below the ribs and may move toward the lower abdomen, groin, or testicle in men. The pain can come in waves as the ureter tightens around the stone. Some people cannot find a comfortable position during an episode, while others have milder, intermittent discomfort.

Urinary symptoms are also common. These may include burning with urination, frequent urination, an urgent need to pass urine, cloudy or strong-smelling urine, or visible blood in the urine. Sometimes blood is not visible but is detected on a urine test. Nausea and vomiting can occur because the kidneys, ureters, and digestive tract share nerve pathways.

Symptoms that may suggest infection or a more urgent problem include fever, chills, feeling very unwell, inability to keep fluids down, or difficulty passing urine. A stone with infection or significant obstruction needs prompt assessment because it may require urgent drainage and antibiotics. People with one kidney, known kidney disease, pregnancy, or severe ongoing pain should also seek medical advice without delay.

Causes and Risk Factors

Kidney stones form when the urine contains more crystal-forming substances than it can dilute, or when the natural inhibitors of crystallization are reduced. Low urine volume is one of the most important contributors. This can happen when a person does not drink enough fluids, sweats heavily, lives in a hot climate, or has fluid loss from vomiting or diarrhea.

Diet and medical conditions can also influence stone risk. A high salt intake can increase calcium in the urine, while frequent high intake of animal protein may raise the risk of some stone types. Conditions such as recurrent urinary tract infections, gout, obesity, certain bowel diseases, and some metabolic or genetic disorders may increase risk. A family history of kidney stones also makes stones more likely.

Common risk factors include:

• Previous kidney stone episode
• Low daily fluid intake or concentrated urine
• High sodium diet
• Recurrent urinary tract infections
• Certain supplements or medications, depending on dose and medical context
• Structural abnormalities of the urinary tract

A prevention plan is most accurate when it is based on the person’s stone composition, urine findings, and health history. For patients with recurrent stones, doctors may request a 24-hour urine collection and blood tests to identify correctable risk factors.

CT Diagnosis and Other Tests

Imaging is often needed when kidney stones are suspected, especially if symptoms are severe, diagnosis is uncertain, or complications are possible. A non-contrast CT scan of the abdomen and pelvis is commonly used because it can detect most stones quickly and show their exact size and location. CT can also show whether the stone is causing swelling of the kidney, called hydronephrosis, and can help identify other causes of abdominal or flank pain.

CT diagnosis is particularly useful for planning treatment. A small stone in the lower ureter may be managed differently from a larger stone in the kidney, and a stone’s density and position may affect whether shock wave lithotripsy is likely to work. In some situations, low-dose CT protocols may be considered to reduce radiation exposure while still providing useful diagnostic information.

Ultrasound is another important imaging option. It avoids radiation and is often preferred in pregnancy and in some children, although it may miss small stones or stones in certain parts of the ureter. A plain X-ray can show some calcium-containing stones and may be used for follow-up, but it does not detect all stone types. Urine tests help look for blood, infection, crystals, and pH changes, while blood tests can assess kidney function, calcium, uric acid, and signs of infection.

Treatment Options: Passing a Stone Safely

Not every kidney stone needs removal. Small stones, especially those already in the lower ureter, may pass naturally with supportive care. Treatment may include pain relief, anti-nausea medication, hydration guidance, and follow-up imaging when appropriate. Patients are often asked to strain their urine so the stone can be analyzed in a laboratory if it passes.

Doctors may recommend a period of observation when the stone is small, symptoms are controlled, there is no infection, and kidney function is safe. In selected cases, medication may be used to relax the ureter and help the stone pass, a strategy sometimes called medical expulsive therapy. The decision depends on the stone’s location, the patient’s health, and the likelihood of spontaneous passage.

During conservative management, patients should follow the doctor’s instructions closely and return for follow-up. A stone that does not pass, pain that cannot be controlled, worsening kidney swelling, or signs of infection may change the treatment plan. Drinking fluids is important, but forcing excessive water intake during severe obstruction is not recommended without medical guidance because it can worsen discomfort.

Kidney Stone Removal Procedures

When a stone is unlikely to pass, causes repeated symptoms, blocks urine flow, is associated with infection, or threatens kidney function, a procedure may be recommended. Most kidney stone removal is now performed with minimally invasive techniques. The best option depends on stone size, location, hardness, anatomy, infection status, and previous treatments.

Shock wave lithotripsy, often called ESWL or SWL, uses focused sound waves from outside the body to break a stone into smaller fragments that can pass in the urine. It may be suitable for selected kidney or upper ureter stones, especially when they are not too large or too hard. Some patients need more than one session, and fragments may cause temporary discomfort as they pass.

Ureteroscopy involves passing a thin instrument through the urethra and bladder into the ureter or kidney, without external cuts. The surgeon can remove the stone with a tiny basket or break it with a laser. A temporary ureteral stent may be placed to help urine drain and allow swelling to settle. Stents can cause urinary frequency, urgency, or discomfort, but they are usually removed after the planned healing period.

Percutaneous nephrolithotomy, or PCNL, is generally used for large kidney stones, complex stones, or staghorn stones that fill part of the collecting system. It is performed through a small incision in the back, allowing direct access to the kidney to break and remove stone material. Open or laparoscopic surgery is now rarely needed but may be considered in unusual cases with very complex anatomy or other surgical indications.

Prevention and Self-Care

Preventing future kidney stones is an important part of care because people who have had one stone may be at risk for another. The most widely recommended step is to maintain good hydration so the urine stays pale yellow most of the day, unless a doctor has advised fluid restriction for another condition. The exact amount of fluid needed varies by climate, activity level, body size, and health status.

Dietary prevention should be individualized, but several general principles are helpful. Reducing excess salt can lower urinary calcium. Eating normal amounts of dietary calcium from food is usually preferred over unnecessarily restricting calcium, because very low calcium intake may increase oxalate absorption in some people. Patients prone to uric acid stones may be advised to moderate purine-rich animal protein and address urine acidity under medical supervision.

Self-care strategies may include:

• Drinking fluids consistently throughout the day
• Limiting high-sodium processed foods
• Eating a balanced diet rich in vegetables and fruits when appropriate
• Avoiding unnecessary high-dose supplements unless prescribed
• Seeking evaluation for recurrent urinary infections
• Attending follow-up visits after a stone event

For recurrent stones, prevention may include stone analysis, blood tests, and 24-hour urine testing. Based on results, a doctor may prescribe medication to reduce calcium, uric acid, cystine, or infection-related stone risk. Patients should not start or stop medications or supplements for stone prevention without professional advice.

When to See a Doctor

Medical evaluation is recommended for suspected kidney stones, particularly when pain is severe, symptoms are new, or the person has never had a confirmed stone before. Prompt care is especially important if there is fever, chills, persistent vomiting, reduced urine output, pregnancy, a single kidney, known kidney disease, or pain that is not improving with recommended medication. These situations may require urgent imaging, laboratory tests, or drainage of the urinary tract.

Patients should also see a urologist if stones are recurrent, large, associated with infection, or not passing as expected. Follow-up is important even after symptoms improve, because pain relief does not always mean the stone has passed or that obstruction has resolved. Imaging may be needed to confirm that the urinary tract is clear.

International patients may benefit from coordinated evaluation when imaging, urology consultation, laboratory testing, and treatment planning are needed within a limited travel schedule. Acibadem International’s multidisciplinary specialists and JCI-accredited hospitals diagnose and treat kidney stones for international patients, including CT-based assessment and minimally invasive procedures when appropriate. Treatment decisions should always be made after an individual medical assessment.

Frequently asked questions

Can kidney stones pass on their own?

Yes, some kidney stones pass without a procedure, especially when they are small and located closer to the bladder. Passing a stone can still be painful, and medical supervision is important if symptoms are severe or prolonged. Fever, vomiting, or difficulty urinating should be assessed promptly.

Why is CT used for kidney stone diagnosis?

A non-contrast CT scan can detect most kidney stones and show their size, location, and whether they are blocking urine flow. This information helps the doctor choose between observation, medication, or a removal procedure. Ultrasound may be preferred in pregnancy or when avoiding radiation is especially important.

Is blood in the urine always a sign of kidney stones?

Blood in the urine can occur with kidney stones, but it can also have other causes, including infection, inflammation, trauma, or urinary tract conditions. Sometimes blood is visible, and sometimes it is found only on a urine test. A doctor should evaluate unexplained blood in the urine.

What is the least invasive kidney stone removal option?

The least invasive option depends on the stone. Shock wave lithotripsy is performed from outside the body and may be suitable for selected stones, while ureteroscopy uses natural urinary passages without external incisions. The best choice depends on stone size, location, hardness, anatomy, and patient factors.

Will a ureteral stent be needed after stone removal?

A stent is sometimes placed after ureteroscopy or other procedures to help urine drain and allow the ureter to heal. It may cause temporary urinary urgency, frequency, or discomfort. The treating team will explain when and how the stent should be removed.

How can kidney stones be prevented after treatment?

Prevention usually starts with drinking enough fluids and reducing excess salt intake. Depending on the stone type and test results, doctors may recommend specific diet changes or medication. Recurrent stones often require stone analysis and urine testing to create a personalized prevention plan.

References

• European Association of Urology
• American Urological Association
• National Institute of Diabetes and Digestive and Kidney Diseases
• Radiological Society of North America
• Mayo Clinic

This article is for general information only and is not a substitute for professional medical advice. Please consult a qualified doctor about your individual situation.