What Is Kidney Stone?
A kidney stone is a stone made up of various possible materials that forms in the kidneys. Factors that increase the risk of forming kidney stones include high levels of calcium, uric acid, and oxalate in the urine, low levels of citrate in the urine, abnormal urine pH, low urine volume, certain urinary tract infections, and certain genetic conditions.
Pain is usually experienced in the abdomen or flank, depending on the location of the stone. A diagnosis is made by imaging and urine studies.
Treatment options include hydration and medications to facilitate spontaneous stone passage and various procedures to remove the stone.
Kidney stones can be painful, so go to the nearest urgent care center or emergency room. The course of treatment depends on the size of the stone. Small stones can pass out of the body without any treatment, which can take two days to four weeks. You can help this process by drinking plenty of water to increase the flow of urine. Strong painkillers can also help with the pain. If a stone is stuck in a tube (ureter), your doctor might recommend a medication called an alpha-blocker, which can help make the tube bigger and thus help the stone to pass.Larger stones might not pass on their own, and thus surgery or shock wave therapy might be used. Shock wave therapy uses shock waves to break up stones into small pieces that can pass out of the body.
Kidney Stone Symptoms
The most common symptom of kidney stones is abdominal or flank pain.
- Flank pain: Stones located higher up in the urinary system usually cause flank pain.
- Abdominal or groin pain: Stones located lower down in the urinary system can cause abdominal or groin pain.
- Varying: The pain usually comes in waves and can be mild or severe.
Other likely symptoms
Some people with kidney stones may also experience:
- Blood in the urine (hematuria): However, sometimes the blood cannot be seen with the naked eye and can only be noticed under the microscope (microscopic hematuria).
- Nausea and vomiting
- Pain with urination or increased urge to urinate
Kidney Stone Causes
There are a number of different types of kidney stones, including calcium stones, uric acid stones, struvite stones, and cystine stones. Different factors can increase the risk of developing different types of stones. These factors include:
High levels of calcium in the urine
Thirty to 60 percent of adults with kidney stones have high levels of calcium in the urine . Calcium levels in the urine may be high due to a number of reasons, including increased calcium absorption through the gut, increased calcium leaking through the kidneys, or hormonal imbalances such as caused by hyperparathyroidism.
Abnormal levels of other substances in the urine
These include high levels of uric acid (which contributes to the formation of calcium stones and uric acid stones), high levels of oxalate (which can combine with calcium to form kidney stones), and low levels of citrate (which normally prevents kidney stones from forming).
Abnormal urine pH
An abnormal acidity of urine can occur with certain disorders of the kidney and with certain medications.
Low urine volume
Low urine volume can increase the risk of forming kidney stones by concentrating substances within the urine that form stones. This can occur if you are dehydrated.
Urinary tract infection by certain organisms
Urinary tract infection (UTI) by certain organisms that produce a substance called urease can lead to the formation of a type of kidney stone called struvite stones.
Cystinuria is a genetic condition that can lead to the formation of kidney stones in uncommon cases. In cystinuria, the kidneys are impaired in their ability to absorb a substance called cystine, which becomes concentrated in the urine and forms cystine stones.
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Treatment Options and Prevention for Kidney Stone
Kidney stones can be treated either conservatively with hydration and medications to encourage spontaneous passage of the stone, or with one of three main procedures. Kidney stones can be prevented or not reoccur with certain lifestyle and dietary adjustments.
Hydration and medications
Most people with kidney stones can be treated with hydration and medications to encourage spontaneous passage of the stone.
- Spontaneous passage: Stones are more likely to pass spontaneously if they are <4 mm in size and lower down in the ureter (the "tube" that connects the kidney to the bladder).
- Pain medication: Pain medications such as ketorolac (Toradol) are needed to relieve the pain associated with passage of the stone.
- Other medication: Other medications have also been shown to increase the chance of successfully passing the stone. These include calcium channel blockers such as nifedipine or alpha blockers such as tamsulosin (Flomax) .
If kidney stones do not pass spontaneously, one of three main procedures will be completed. Percutaneous nephrolithotomy is usually performed on large kidney stones.
- Shockwave lithotripsy: In this procedure, sound waves are used to break up the stone and make it easier to pass. This procedure is usually done under deep sedation or general anesthesia. This procedure is most commonly used for smaller stones (usually <2 mm) located higher up in the ureter.
- Ureteroscopy: In this procedure, an endoscope is passed through the urethra (the opening where urine passes out) to access the stone and retrieve it. In some cases, the stone can be broken up to facilitate retrieval. Ureteroscopy has been shown to be more effective than shockwave lithotripsy, but can be associated with higher complication rates and longer hospital stays .
- Percutaneous nephrolithotomy: In this procedure, an endoscope is passed through the skin in the lower back directly into the kidney to access and remove the stone. This procedure is done under general anesthesia. This procedure has a high success rate (80 to 90 percent) and is usually used for stones larger than 2 cm or complex-shaped stones .
Prevention is important to avoid recurrent stone formation. Methods of preventing recurrent stone formation include those below.
- Increased fluid intake and dietary changes: Increased fluid intake and dietary changes have been shown to reduce the risk of getting recurrent kidney stones. Specifically, you should drink at least 2.5 liters of fluids per day, limit the amount of salt you consume, limit dietary protein, and limit oxalate intake (found in certain fruits and vegetables, such as raspberries and spinach) .
- Medications: Certain medications can decrease the risk of getting recurrent kidney stones. The medication recommended will usually vary depending on the specific type of kidney stone. Thiazide diuretics such as hydrochlorothiazide can decrease the risk of getting calcium stones. Potassium citrate (Urocit-K) and allopurinol can decrease the risk of getting calcium or uric acid stones.
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When to Seek Further Consultation for Kidney Stone
If you develop symptoms of a kidney stone you should see your physician. Your physician can order imaging and urine studies to determine if you have a kidney stone and the type of kidney stone, then offer the appropriate treatment.
Questions Your Doctor May Ask to Determine Kidney Stone
To diagnose this condition, your doctor would likely ask about the following symptoms and risk factors.
- Any fever today or during the last week?
- Is your abdominal pain getting better or worse?
- How would you describe the nature of your abdominal pain?
- Is your abdominal pain constant or come-and-go?
- How long has your abdominal pain been going on?
If you've answered yes to one or more of these questions
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- Khan SR, Pearle MS, Robertson WG, et al. Kidney stones. Nat Rev Dis Primers. 2016;2:16008. NCBI Link
- Aggarwal R, Srivastava A, Jain SK, Sud R, Singh R. Renal stones: A clinical review. European Medical Journal. Published May 9, 2017. EMJ Link
- Harris J. How to eat a low oxalate diet. University of Chicago Kidney Stone Evaluation and Treatment Program. UChicago Link
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