A kidney stone is a solid clump of salts and minerals that can collect in your urine. These substances are normally present and don’t cause problems at lower levels, but they can stick together to form a stone in more concentrated urine. A stone may stay in your kidney or travel down through your urinary tract.
Kidney stones vary in size from the size of a grain of sand to the size of a pearl. A small stone may pass on its own, causing little or no pain. A larger stone may get stuck along your urinary tract. A stone that gets stuck can block the flow of urine and cause severe pain or bleeding.
There are five main substances that can form kidney stones:
- Calcium oxalate
- Calcium phosphate
- Uric acid
- Struvite, also known as infection stones
Kidney stone causes
The following conditions can lead to kidney stones:
- Not drinking enough water – This is the most common reason people develop kidney stones.
- Digestive issues – If you have chronic diarrhea or are dehydrated, your body can’t properly absorb fluids or nutrients, or make enough urine. This causes a higher concentration of minerals and salts in your urine and can lead to kidney stones.
- Unhealthy diet and lifestyle choices – If you eat a diet high in sugar and caffeine, you’re at an increased risk of developing kidney stones. Obesity also increases risk.
- Structural defect in the urinary tract – If your urinary tract is blocked or restricted, it can prevent urine and waste from being eliminated from your body and lead to stone formation.
- Metabolic disorders – If you have a condition or disorder that prevents your body from properly breaking down food, it can lead to high levels of oxalate and cystine in your urine, which leads to stone formation. Examples of metabolic disorders include hypercalciuria, hyperoxaluria, hypocitraturia and gouty diathesis.
- Other medical conditions – Complications from thyroid problems, urinary tract infections and gout can lead to kidney stones.
Kidney stone symptoms
Kidney stones typically don’t cause any symptoms until they start to move through your kidneys and into your urinary tract. If kidney stones become trapped in the urinary tract, you may experience:
- Sudden and severe pain on your side or lower back
- Sharp pain that moves toward your lower abdomen and groin
- Pain that comes and goes and changes from mild to severe
- Pain or a burning sensation while you pee
Other signs of kidney stones may include:
- Urine that appears pink, red, brown or cloudy
- An odd odor to your urine
- Persistent urge to go pee
- Urinating in small amounts or more often than usual
- Nausea and vomiting
- Fever, if infection is present
Kidney stone diagnosis
To diagnose kidney stones, your doctor will do a physical exam and ask about your medical history. Your doctor may ask if you have a family history of kidney stones and about your diet, digestive problems or other health problems. Your doctor may perform the following tests to complete the diagnosis:
- Blood test – Your doctor will take a sample of your blood and have your electrolyte and hormone levels checked to better understand your kidney function.
- Urine test – Your doctor will have you provide a urine specimen, which will be tested for signs of infection and substances that form kidney stones like calcium, oxalate, citrate, uric acid and sodium.
- Imaging tests – Ultrasound or X-ray may be used to find the location of kidney stones in your body. The tests may also be able to show an anatomical defect that caused a kidney stone to form.
Kidney stone treatment
Ohio State provides personalized care to meet your individual needs. If you’re diagnosed with kidney stones, your treatment will depend on the size of the stones, what they are made of and your symptoms.
Small kidney stones usually don’t need treatment, but your doctor may suggest:
- Pain medication – Your doctor can prescribe medicine to help relieve pain experienced when a stone is passing.
- Medical expulsion therapy – Your doctor can prescribe medicine that can relax your ureter and help speed up the rate of stone passage.
- Drinking more fluids – Your doctor will recommend you drink lots of water to help move the stone along. If you’re vomiting often or don’t drink enough, you may need to go to the hospital for fluid replacement.
If you have a large kidney stone (1.5-2 cm) or your urinary tract is blocked, your doctor can remove the stone or break it into small pieces with the following treatments:
- Shock-wave lithotripsy – Your doctor can use a shock wave machine to crush the kidney stone. The shock waves go from the machine through your body and to the stone. The smaller pieces of the stone then pass through your urinary tract.
- Ureteroscopy – Your doctor will use a long, tube-like tool with an eyepiece, called a ureteroscope, to find the stone. The tool is fed into the urethra and through the bladder to the ureter. Once the stone is found, the urologist can remove it or can break it into smaller pieces with laser energy.
- Percutaneous nephrolithotomy (PCNL) – Your surgeon will make a small incision in your groin or abdomen to surgically remove the kidney stone.
Recurrent kidney stones are treated by a team of specialists at Ohio State’s Metabolic Stone Clinic.