Kidney stones are clumps of mineral that accumulate from dissolved materials on the inner lining of the kidneys.
The kidneys are important to regulate the body’s fluid levels, filter wastes and toxins from the blood, regulate blood pressure, activate vitamin D to maintain healthy bones, direct production of red blood cells and keep blood minerals (sodium, potassium and phosphorous) in balance (1).
Every 30 minutes the kidneys filter all the blood in the body, removing excess waste and excess fluid. When a kidney stone develops, it not only blocks the urinary tract, but also can lead to an infection in the bladder and lead up the kidneys themselves, putting the person at high risk for severe health issues and in need of medical attention.
The medical term for kidney stones is Nephrolithiasis or Renal Lithiasis. A kidney stone is a solid mass that can be as small as a grain of salt or as large as a golf ball that can be caused from a variety of things, but is made from chemicals within urine.
Since urine contains many waste products within it, when there is not enough liquid to support the amount of waste, crystals begin to form.
When this occurs over and over again, the crystals begin to build up and form a bigger and harder substance that begins to block the urinary tract. The only way to get this mass out is through urination or surgical removal. The best way to prevent stones from occurring or get present stones ones out, is by drinking plenty of fluids to eliminate any possible crystals. Passing a kidney stone is very painful though since it blocks the urinary tract and can take up to a few days to pass it (2).
One in ten Americans will develop a kidney stone at some point in their lifetime. It is estimated that the prevalence of kidney stones have increased from 3.8% in the 1970’s to 8.8% in the 2000’s of all races. Men are more likely to develop kidney stones though than women.
The lifetime risk of a man developing a kidney stone is 19% while it is only 9% for women. Kidney stones can develop at any time, although they are most common among adults over the age of 30. Kidney stones are also more likely to occur in Caucasians versus any other race (3).
It is important to know which type of kidney stone a person has because it is what can help determine what may be forming the stones and what step may be taken to prevent them from occurring again. The most common types of kidney stones are; calcium oxalate, uric acid, struvite and cystine.
Calcium oxalate is the most common stone of these four that can develop and is from calcium combining with oxalate in the urine.
Improper fluid or calcium intake are the most common reasons for this occurring. A uric acid stone is most often caused from foods with high amounts of purines within them. Some foods with purines in them are organ meats and shellfish. Under the right conditions, monosodium urate can develop causing a stone to form. Struvite stones are less common compared to the other stones formed but can result from upper urinary tract infections. One genetic stone that can form as well is the cystine stone. Most often these stones occur due to them running in families. The type of stone that may be present in a patient can be determined through a lab analysis if the person can catch it once it passes or if it is causing symptoms in a patient it can be retrieved surgically or with a scope inserted through the urethra into the bladder to then be sent for lab analysis (4).
Some symptoms of a kidney stone are more prominent then others depending on the size of the stone present and stone type. Some of the most common symptoms are blood in the urine, urine that is cloudy or smells bad, nausea, vomiting, chills, fever, stomach pain or lower back pain.
When a stone is present and blocking the urinary tract, it can cause any of the above symptoms as well as a lot of pain. Most stones can pass themselves without a problem, but in some cases, immediate medical assistance is needed (5).
Based on these symptoms a person may have, further action will be needed to diagnosis a person with a kidney stone or another medical problem. If a physician suspects a kidney stone is present, blood testing can be conducted to reveal too much calcium or uric acid in the blood. Urine testing can be done through a 24-hour urine collection test which may show if a person is excreting too many stone-forming minerals or too few stone-preventing substances.
Imaging is another way to show if kidney stones are present in the urinary tract and options range from simple abdominal x-rays to high speed dual energy computerized tomography also known as a CT scan to see the tiny stones. A final diagnostic method would be an analysis of the stones already passed by a person to reveal the makeup of the stone and how to prevent possible future stones (6).
Treatment for kidney stones varies depending on the patient and the type of stone that is present, but oral hydration and pain management are part of the acute treatment for all types of kidney stones. For kidney stones that are 10mm or less in size, calcium channel blockers and alpha blockers can be used to relax the smooth muscle of the ureters to pass the stones through within a week’s time. Oral corticosteroids have been used in the past but now have been proven to show little to no improvement in treating kidney stones. Patients who are unable to intake fluids or medications orally, have low blood pressure or show other signs of early hemodynamic instability should be treated intravenously.
If an infection is suspected, empiric antibiotics should be administered to work against both gram-negative bacilli and gram-positive cocci present in the urinary tract. Urine calcium excretion is an important risk factor for kidney stone formation and is increased with diet acid loads, increased salt intake and both inadequate and excessive vitamin D levels (7).
Many herbal supplements on the market today are being promoted in preventing or curing kidney stones, but most research behind them is still inconclusive.
Supplements such as black tea, chanca piedra, cranberry, IP-6, magnesium, phosphate salts, sweet orange and vitamin B6 are those which seem to be the most common remedies to treat or reduce symptoms of kidney stones. Based on current research now, it is concluded that black tea is possibly effective, chanca piedra is likely ineffective, cranberry has insufficient evidence, IP-6 is possibly effective, lemon has insufficient evidence, magnesium has insufficient evidence, phosphate salts are possibly effective, vitamin B6 is possibly effective and sweet orange still has insufficient evidence.
For other approved medications, most are prescribed by a doctor but some are available without a prescription such as NSAIDS to relieve pain while a stone is passed or alpha-beta blockers.
Medicines that are available to prevent stones are dependent on the type of stone that may present in a person. For calcium stones, orthophosphate, thiazides, or potassium citrate may be used. For uric acid stones, allopurinol, potassium citrate or sodium bicarbonate may be used to prevent these types of stones. For cystine stones, penicillamine, tiopronin, or potassium citrate may be used.
Struvite stones on the other hand, form because of frequent kidney infections and antibiotics most often must be used to help cure the infection present and prevent new stones from forming (8).
The medical management of kidney stones involves metabolic evaluation, including a 24-hour urine collection and serum assessment of creatine, electrolytes, parathyroid hormone, vitamin D, and or uric acid levels. Once the source of the kidney stone present has been determined, dietary modifications can be made, however there is not always a nutritional cause to the stone present such as high levels of calcium (hypercalciuria), oxalate (hyperoxaluria), uric acid (hyperuriosuria) or low amounts of citrate in the urine (hypocitraturia).
Nutrition therapy should be individualized though to the patient based on their current health status and known risk factors. Knowing the patients diet history is also a key factor in determining if there is an excess or deficiency in any of the nutritional factors that can influence the urinary profile. One example of this would be hypercalciuria which can result from animal foods or diets low in fiber.
Diets high in oxalates, or low in calcium, magnesium, fiber and fruits/vegetables can cause hyperoxaluria. For hypocitraturia, a high salt intake, diet with high acid load potential or one with low levels of potassium, magnesium, or fruits/vegetables has been shown to be of concern. In past research, a low calcium and low oxalate diet was suggested for treating those with calcium oxalate stones, which is still the case for some patients, but more recent studies have concluded that only a small amount of oxalate is actually derived from the diet because of its irregular absorption rate, bioavailability, and inverse relationship with calcium. People with diets deficient in calcium have been shown to have higher incidences of kidney stones which is why reaching the recommended dietary allowance (RDA) for calcium is essential. Due to calcium’s ability to bind with oxalate in the gastrointestinal tract, consuming calcium from dairy sources or supplements with a meal can be helpful. Balancing renal acid load can easily be done by including more fruits, vegetables and fiber since they are rich in magnesium and potassium which are associated with lower incidences of kidney stones. Limiting sodium intake is another important factor to take into consideration into ones diet. Since it competes with calcium for absorption, it can affect daily calcium intake and a person’s risk to kidney stones. Limiting high purine foods can help with this as well in treating uric acid stones. Regardless of the stone type though, there is usually a need to increase fluids in patients with kidney stones in order to get a urinary output of at least two liters per day for adolescents or adults. As far as which fluids should be encouraged, that is still not definite. Some beverages act as mild diuretics, such as coffee and tea to increase urinary output but other sources that include citrate can increase urinary pH and help prevent stone formation from the start. Assessing all these nutritional risk factors are what will help in the medical nutrition therapy for the treatment of kidney stones and to help minimize their recurrence (9).
People can help prevent kidney stones by making small changes in fluid intake and, depending on the type of kidney stone, changes in sodium, animal protein, calcium and oxalate intake. Making sure that a person is drinking enough fluids is essential, since it is the best way to prevent kidney stones from occurring of any kind.
It is recommended that a person should drink two to three liters per day which would be between eight to 16 cups of fluids per day. Those with cystine kidney stones though are advised to drink even more. Although water is the best fluid to have, other fluids will work as well in helping to prevent kidney stones such as citrus drinks. For calcium oxalate stones, it is advised to reduce sodium intake, animal proteins such as eggs, meat and fish, avoid foods with high levels of oxalate such as spinach, rhubarb, nuts and wheat bran, and also to be sure that calcium intake is adequate. For calcium phosphate stone, it is important to reduce sodium intake, reduce the amount of animal protein, and make sure that calcium intake is adequate as well. For uric acid stones, the only recommended advisory in preventing them is to limit animal protein intake. A 24-hour urine collection may be used to determine the volume of urine produced during a day and if the volume of the urine is too low, a person can be advised to increase fluid intake. Some research also suggests that citrus drinks like lemonade and orange juice protect against kidney stones since the citrate within them prevent crystals from forming into stones (11).
In conclusion, kidney stones are one of the most prevalent conditions that should be researched further to learn more about their specific causes, relation to special populations, relationships among other health conditions, treatment and prevention. They can occur at any age to any person and are one of the most painful conditions a person can have, affecting their quality of life when they do occur. Although there is no cure for kidney stones, preventive methods are available as well as treatment methods for when a stone is present through dietary changes and medications.
1) National Kidney Foundation. Fast Facts. Available at: https://www.kidney.org/news/newsroom/factsheets/FastFacts.
2) Mayo Clinic. Diseases and Conditions, Kidney Stones. Available at: http://www.mayoclinic.org/diseases-conditions/kidney-stones/basics/definition/con-20024829.
3) CDC. FastStats. Available at: http://www.cdc.gov/nchs/fastats/kidney-disease.htm.
4) National Kidney Foundation. Kidney Stones. Available at: https://www.kidney.org/atoz/content/kidneystones.
5) Mayo Clinic. Diseases and Conditions, Kidney Stones. Available at: http://www.mayoclinic.org/diseases-conditions/kidney-stones/basics/tests-diagnosis/con-20024829.
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7) WebMD. Vitamins and Supplements Search. Avaiable at: http://www.webmd.com/vitamins-supplements/condition-1338-Kidney+stones+nephrolithiasis.aspx?diseaseid=1338&diseasename=Kidney+stones+(nephrolithiasis)&source=0.
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9) American Dietetic Association. Nutrition Therapy for Kidney Stones. Available at: http://mydoctor.kaiserpermanente.org/ncal/Images/Nutrition%20Therapy%20for%20Kidney%20Stones%20%28requested%20permission%20ADA%29_tcm75-240176.pdf.
10) National Kidney and Urologic Diseases Information Clearinghouse, NKUDIC. Diet for Kidney Stone Prevention. Available at: http://kidney.niddk.nih.gov/KUDiseases/pubs/kidneystonediet/#diet.
11) Lieske J, Mehta R. Supplement. The Journal of Urology. 2014; 191: e838.
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