Kidney stones, or nephrolithiasis, is a common condition in which hard collections, or calculi, form in the renal system, usually in the tube between the kidney and the bladder. These collections are the result of urine becoming saturated with minerals such as calcium oxalate, calcium phosphate, struvite, uric acid or cystine.^[1]

Common types of stone are:^[2]^[3]

Calcium oxalate stones
Calcium phosphate stones
Uric acid stones
Struvite stones
Cystine stones

Around 80 percent of all kidney stones, also called calculi, are calcium stones.^[4]

These stones can vary in size from a few millimeters to a large staghorn shape a few centimeters in length.[1] Kidney calculi are more common in men than in women and tend to occur in adults between the ages of 20 and 50. People between the ages of 35 and 45 are the most likely to be affected, but the disease can affect people of any age. It is rare to develop a stone for the first time over the age of 50.^[5] Over half a million people in the US are affected by kidney stones every year.^[5] Kidney stones are more common in whites and Asians than in people with African, Native American or African-American heritage.^[3]

Symptoms occur when a stone leaves the kidney and enters the tighter ureter, the tube between the kidney and bladder, on its way to the bladder. A stone that is moving is much more painful than a stone that has not moved from its original place.^[4]

Typical symptoms are severe pain in the back and belly, difficulty urinating and red or brown urine. Common treatment methods include good hydration, pain relief and anti-emetics. About 20% of patients require procedures such as lithotripsy, breaking up the calculus with shock waves, to remove the stones when kidney stones have caused pain, infection or obstruction. Most people recover fully, without any complications.

Signs and symptoms of kidney stones

Typical symptoms are severe pain at the back and flank, difficulty urinating and passing only small amounts of urine at a time. The pain is often cramping or like a spasm and tends to come in waves. Some people might also have nausea, vomiting and may pass red or brown urine. Symptoms occur when a stone leaves the kidney and enters the tighter ureter, the tube between the kidney and bladder.

Other symptoms of kidney stones include:^[1]^[6]

Nausea and vomiting, which diminish as pain is relieved
Fever and chills
Blood in the urine, known as hematuria
Cloudy or bad-smelling urine
Tender abdomen
Lack of urine
Urinary retention
Gravel or stones in the urine

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Symptoms of kidney stones in men and women

Men and women experience the symptoms of kidney stones in much the same way. However, men may experience the pain from a kidney stone slightly differently. In men, the pain from a kidney stone may radiate into the groin or the testicles. However, this does not mean that the stone is present in the testicles or in the groin.

The general symptoms of pain, nausea, fever, cloudy or bad-smelling urine, bloody urine, lack of urine or urinary retention, and stones or gravel in the urine will be experienced in the same way in men and women.

What does the pain from kidney stones feel like?

Pain is one of the most obvious symptoms of kidney stone obstructions. Where the pain is felt, and where it radiates to in the body, can indicate where the calculus is within the renal system. The pain that accompanies a kidney stone is felt acutely in the flank (the side) and radiates down the groin on the same side. Not all stones cause pain that spreads. Some stones may cause no pain at all.

Pain is caused not directly by the kidney stone itself, but instead, it results from the effect that the stone has on the body by leading to muscle spasms, inflammation, and irritation at and around the site of the obstruction.^[5] Factors that influence how painful the kidney stone is, include:^[4]

Whether the stone is moving
Whether it is twisted or tilted in the ureter or urethra
Whether the obstruction is complete or partial
Where exactly it is in the renal system
How big the stone is

Good to know: Pain from kidney stones is often described as excruciating and intermittent, and often occurs in cycles that last between 20 minutes and an hour. People with painful kidney stones often cannot keep still because of the pain. They are often ashen, pale and sweaty, with a tender abdomen.^[6]

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Risk factors and causes of kidney stones

Kidney stones are more common in men, and in adults between 20 and 50 years of age, but very rare in children. It is most common in adults who have a low fluid intake and consequently produce little urine, which can contain high amounts of stone-forming substances.^[7]

Kidney stones are also more common in people who have gout (in the case of uric acid stones), or who have a family member who also suffers from kidney stones. The genes that can increase a person’s chance of developing nephrolithiasis have been identified.^[7]

Infections of the urinary tract may lead to kidney stones. Other general risk factors are dehydration and being overweight or obese.

Other risk factors include:^[1]^[5]^[8]^[9]

Anatomical abnormalities such as horseshoe kidney or ureteral stricture
Hyperparathyroidism, i.e. an overactive parathyroid gland
Metabolic disorders, such as hypercalciuria, hyperuricosuria or chronic metabolic acidosis
Intestinal problems such as Crohn’s Disease
Bariatric (weight-loss) surgery), such as a sleeve gastrectomy or a gastric bypass
Living in a hot climate and its risk of dehydration
Too much exercise and its risk of dehydration
Too little exercise and its risk of obesity
A diet high in protein, salt or sugar, especially fructose and sucrose

Some medications can increase the risk of forming kidney stones. These include among others:^[4]

Indinavir, an antiretroviral medication
Atazanavir, an antiretroviral medication
Guaifenesin, an expectorant medication
Triamterene, a medication used for the treatment of hypertension and edema
Silicate, which is used in antacids
Sulfasalazine, a medication used for the treatment of rheumatoid arthritis, colitis and Crohn’s disease
Sulfadiazine, a drug used for the treatment of otitis media ear infections
Ceftriaxone, a drug used for the treatment of bacterial infections

Stones caused by struvite, as opposed to calcium, are caused by urea-splitting bacteria such as Klebsiella, Pseudomonas, and Proteus species, and indicate an underlying urinary tract infection. Struvite stones are more common in women than in men,^[3] and are responsible for between 1 and 5 percent of kidney stones.^[1] They will reoccur if the underlying UTI is not treated.^[6]

Kidney stones caused by uric acid are associated with acidic urine, usually with a pH of below 5.5.^[4] These account for only around 10% percent of stones and are often associated with gout. Chemotherapy for conditions such as leukemia and lymphoma, as well as these conditions themselves, which increase tissue breakdown, may also lead to the urine becoming more acidic.

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Diet and kidney stones

It is generally thought that certain foods can increase the risk of developing some kinds of kidney stones. These include animal protein from meats or fish, in the case of uric acid stones, and some vegetables, drinks, and nuts in the case of calcium oxalate stones.^[5]^[4] Excessive salt and excessive sucrose and fructose intake have in some studies also been shown to overall increase the risk of stones forming, and should therefore be avoided in excess and only consumed in moderation.

Calcium oxalate stones and diet

People who have had calcium oxalate stones in the past or who have a high rate of oxalate excretion should reduce consumption of certain foods and food types, including:^[10]

Rhubarb
Spinach
Cocoa
Tea
Nuts
Vitamin C

Uric acid stones and diet

A high intake of purine in the diet causes the body to produce large amounts of monosodium urate. The risk of developing uric acid stones has a hereditary component in some people, meaning it tends to run in the family.^[5]

People with uric acid stone disease or hyperuricosuria calcium oxalate stones should reduce consumption of:^[10]

Calf thymus
Liver
Kidneys
Poultry skin
Herrings with skin
Anchovies
Sprats

Hereditary and genetic risks of kidney stones

There is some evidence that a predisposition to developing certain types of kidney stones may, at least partly, be hereditary.^[11] Risk factors, such as high levels of uric acid in the blood and high levels of calcium in the urine, for example, maybe influenced by genetic factors.^[12]

Cystine stones are rare and may be caused by genetic factors^[5] that cause the body to reabsorb cystine, ornithine, lysine, and arginine from the kidneys. In cases where cystine stones develop, the urine is saturated to above a certain level with cystine, causing crystals to be deposited and stones to form.^[4]

Diagnosing kidney stones

Diagnosis of kidney stones is often based on the typical symptoms and physical examination. A urine dipstick test may show blood and pus in the urine, and help confirm the presence of a kidney stone.

A person being examined for kidney stones will be asked about their medical history and will be physically examined. They will also be given a computerized tomography (CT) scan. X-rays and ultrasound tests can determine the presence of stones, but CT scans are preferred during the diagnostic process because they can determine the size and location of the stone. MRI scans are not generally helpful.^[6] In pregnant women; a kidney ultrasound is usually ordered. An ultrasound of the kidneys and ureters is also often used to diagnose kidney stones in children, although in some cases a CT scan may also be needed.^[13]

The overall health of the kidneys may be tested using:^[2]^[4]

24-hour urine collection test, once the patient is free of stones, to measure changes in the values for urinary electrolytes, reduced urine volume and to determine the underlying metabolic cause for nephrolithiasis
Blood tests, if the person is feverish and may have an infection

The calculus/kidney stone will be analyzed after it has been passed in the urine or extracted during surgery.^[6]

People with the following conditions may need further tests, as determined by their physicians:^[6]

Sarcoidosis
Myeloma
Bone metastases
Solitary kidney
Urinary tract anomalies

Treatment of kidney stones

The treatment of kidney stones varies depending on the size of the kidney stone and the severity of the symptoms. Small stones usually pass with no need for medical assistance. Drinking plenty of water may help to flush the stone from the urinary system.

Pain medication is often needed while passing a renal calculus. In severe cases, opiates may be prescribed. However, in most cases, acetaminophen/paracetamol is usually sufficient.[1][5] 80 percent of stones pass without serious medical intervention and need no inpatient treatment. About 20 percent lead to situations that require hospitalization.^[4]

People may need to be admitted to the hospital if the following factors are present:^[1]

Anuria, when the kidneys do not produce urine
Fever
Persistent or severe pain
Inadequate fluid intake as a result of nausea or vomiting, resulting in dehydration
Poor social support while they are living alone at home
Inability to access follow-up outpatient care
Pregnancy
Being older than 60 years of age

Good to know: If a fever is present, the infection may also be present. Because infection can be very serious, the affected person should receive medical treatment as soon as possible.^[1]

Treatment at home may be possible for most people because most stones smaller than 5mm pass on their own and do not cause infection or need surgical help to pass. People may be cared for at home if:^[1]

Their pain has been relieved and can be managed with acetaminophen/paracetamol
They can drink fluids
They have good social support
They have no complications, such as fever or urinary blockage

Medication for kidney stones

Painkillers, antiemetics, and antidiuretics are commonly used in both inpatient and outpatient treatment of kidney stones. Painkillers, such as morphine may be used to control severe pain; moderate or mild pain can be controlled with acetaminophen or codeine. Antibiotics are only used in cases where an infection has developed.^[4]

Other medications used to treat uric acid kidney calculi are:^[4]

Uricosuric agents, which increase the amount of uric acid excreted
Alkalinizing agents, such as sodium bicarbonate and potassium citrate

Surgery for kidney stones

Big stones, with a diameter of more than 10mm and which are lodged in the ureter, might need assistance to pass, especially if they are blocking the passage of urine. Stones with a diameter of less than 10mm that are in the distal ureter and do not have complications such as infection, should be removed if they have not passed on their own within four to six weeks.^[14] This can involve lithotripsy (breaking up the stone with shock waves), or the surgical removal of stones, or the removal of the stone with an endoscope, a small tube with a camera, and surgical tools.

Shockwave lithotripsy (ESWL) is a non-invasive procedure where sound waves are used to break the stones into fragments small enough to pass through the ureter and out of the body through the urethra. If lithotripsy is not used, other endoscopic methods are possible, such as stereoscopic lithotripsy (URS) or percutaneous nephrostomy.

In ureteroscopic lithotripsy, an endoscope is introduced to the urethra and moves through the bladder into the ureter to the stone’s location. The stone is then removed. In cases where access to the urethra is complicated because of an enlarged prostate, the endoscope will be introduced via a small incision in the bladder.

In a percutaneous nephrostomy, an endoscope is introduced via a small incision in the skin of the flank, directly into the kidney.

Some very large or complicated stones may need open surgery.

Struvite stones must be removed, as they are infectious or infected foreign bodies. The stones will reoccur if the urinary tract infection that underlies their formation is not resolved.^[6]

Preventing kidney stones

Preventing kidney stones from forming involves changing the diet of the affected person and increasing the amount of fluid, preferably clear fluids such as water, that they consume. In all cases, it is important to remain well hydrated, consuming about 2.5 quarts of water each day.^[8] It is also important to limit sugar and salt in the diet and to eat a diet high in fruit and vegetables.^[5] In cases where the person is overweight, they should lose the excess weight.

Good to know: High-animal protein diets and crash diets should be avoided, as they can unbalance the pH and chemical makeup of urine.^[5] For more information, see the section on the prevention of kidney stones.

In calcium oxalate stones, which are the most common kind, prevention measures include diets that are low in salt, sugars, and animal protein,^[6] and reduced consumption of oxalate-rich foods.^[8]

People who are concerned about the role their diets may play in the formation of kidney stones, should consult their physicians, specialist nephrologists, and/or a dietitian.

Good to know: Low-calcium diets are not indicated for the prevention of calcium oxalate stones, as low calcium diets cause oxalate reabsorption to increase.^[8]

In cases of uric acid stones, allopurinol will be prescribed to prevent high levels of uric acid from building up in the blood. Alkalinizing agents may also be prescribed to make the urine more alkaline.

FAQs

Other names for nephrolithiasis

Ureterolithiasis
Ureteral stone
Kidney stones

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BMJ Best Practice. “History and exam”. Accessed 8 June 2018. ↩
BMJ Best Practice. “Nephrolithiasis: prevention”. Accessed 8 June 2018. ↩ ↩
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BMJ Best Practice. “Investigations”. Accessed 8 June 2018. ↩
Medscape. “Nephrolithiasis Treatment & Management”. 11 May 2018. Accessed 8 June 2018. ↩
Cleveland Clinic. “Kidney Stones: Oxalate-Controlled Diet”. February 2015. Accessed 28 May 2018. ↩
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Clinical Journal of the American Society of Nephrology. “Soda and Other Beverages and the Risk of Kidney Stones.”. July 2013. Accessed 12 August 2018. ↩ ↩ ↩
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The American Journal of Clinical Nutrition. “Caffeine intake and the risk of kidney stones.”. December 2014. Accessed 12 August 2018. ↩
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**Q: What is Nephrolithiasis (Kidney Stones)?**

**A:** Nephrolithiasis, commonly known⁢ as kidney stones, refers to the formation of solid mineral‍ deposits within the urinary tract, specifically⁣ in the kidneys.‌ These stones can ⁣vary⁤ in size,‍ ranging from small pebble-like crystals to larger⁤ masses⁢ that ⁢obstruct urine flow.

**Q: What Causes Kidney Stones?**

**A:** Kidney stones develop due to a combination of‍ factors, ⁢including:

* **Dehydration:** Inadequate fluid intake concentrates ⁣urine, leading to‍ the crystallization of minerals.

* **Diet:** Consuming certain foods high in oxalates (spinach, rhubarb), calcium (dairy products),⁣ or sodium can contribute to stone‍ formation.

* **Medical conditions:** Conditions like hyperparathyroidism, gout, and diabetes can alter urine chemistry, increasing the risk of stones.

* **Family ‍history:** Genetic factors can influence the‍ predisposition‍ to stone formation.

**Q: What are the⁤ Symptoms of Kidney Stones?**

**A:** Symptoms can vary depending on⁣ the size‌ and location of the stone:

* Severe flank pain radiating to the lower ⁢abdomen or‌ groin

* Painful urination (dysuria)

* Frequent urination (polyuria)

* Nausea‌ and vomiting

* Fever and chills (if an infection develops)

**Q: How are Kidney ⁤Stones Diagnosed?**

**A:** Diagnosis involves a‌ medical⁣ history review, physical examination, and various ⁢tests:

* ⁢**Urinalysis:** ⁢Analyzes the‍ composition of urine for⁢ signs of blood, crystals, or⁢ bacteria.

* **Blood tests:** Measures blood creatinine levels to assess kidney function.

* **Imaging tests:** X-rays, CT scans, or⁤ ultrasounds‌ can visualize⁢ the presence ‌and location of stones.

**Q: How⁤ are Kidney Stones Treated?**

**A:** ‍Treatment depends on the size, location, and composition‌ of‍ the stone:

* **Medical Expulsion ⁢Therapy:** Non-surgical approach using medications ⁤to help the⁤ stone pass spontaneously through the urinary tract.

* **Shock Wave Lithotripsy:** Non-invasive procedure using ultrasound waves to break up stones into smaller fragments, making them easier to pass.

* **Percutaneous Nephrolithotomy (PCNL):** Surgical procedure where⁢ a small⁢ incision ‌is made in the back⁢ to remove larger stones directly ‌from the kidney.

* **Ureteroscopy:**⁢ Minimally ‍invasive procedure using a thin tube and laser to ⁤fragment and remove stones from the ureter.

**Q: How can Kidney⁤ Stones be Prevented?**

**A:** Preventive measures⁢ include:

* **Adequate Hydration:** Stay well-hydrated to dilute‍ urine and prevent⁣ stone formation.

* **Balanced Diet:** Consume⁣ a healthy diet limiting‌ oxalate- and sodium-rich foods.

* **Weight Management:**⁢ Obesity increases the risk of stones.

* **Medical Treatment:** Addressing⁣ underlying medical conditions that increase stone formation.

* **Regular Urinary Tract Monitoring:** For individuals⁤ with a history of kidney stones, regular check-ups and imaging tests can help detect stones early.

What is Nephrolithiasis (Kidney Stones)?

Signs and symptoms of kidney stones

Symptoms of kidney stones in men and women

What does the pain from kidney stones feel like?