LabCorp and its Specialty Testing Group, a fully integrated portfolio of specialty and esoteric testing laboratories.
To evaluate the composition of a kidney stone in order to determine the cause of its formation and to guide treatment
When a stone has passed through or has been removed from your urinary tract
A stone or stones filtered from your urine or surgically removed from your urinary tract by a healthcare practitioner
Kidney stones are small, hard masses that form within the kidneys. Kidney stone testing uses one or more test methods to examine and determine the composition of the stone. This is done in order to help identify the cause of the stone and, where possible, to prevent the formation of more stones.
The kidneys are part of the urinary tract, which also consists of two ureters, the bladder, and the urethra. The kidneys filter waste out of the blood and produce urine, which is transported from the kidneys to the bladder through the tube-like ureters. Urine is eliminated from the bladder through the urethra. This is a continual process of waste filtration, urine production, and elimination.
Commonly called kidney stones, calculi can form in the kidneys and cause problems either because they grow large enough to obstruct urine flow or because they become dislodged or break off and begin to travel from a kidney through the ureter. They can cause temporary obstruction but also stretch, irritate, and/or damage the walls of the ureters. This movement can cause abrupt, extremely severe pain that may be intermittent or continuous.
Many stones will eventually pass out of the body in the urine, but some are too large or have too irregular a shape for the body to expel. With very large stones, which typically cannot pass from the kidney into the ureters, and for smaller stones that get into but do not pass through the ureters, some form of treatment will be required. The stone may need to be surgically removed, often using devices that pass through the urethra and bladder to the site of the stone. With some stones, it is possible to pulverize the stone in place using targeted shock waves. This process is called extracorporeal shock wave lithotripsy. The smaller particles and fragments that remain can then pass through the urinary tract.
Stones can develop for several reasons, but the most common is because there is a high concentration of a particular chemical in the urine that is no longer soluble and precipitates to form crystals. It can also occur when a person chronically fails to take in adequate amounts of fluids, resulting in highly concentrated urine. Depending on how much and what type of material crystallizes and where it forms, a kidney stone may be round, sharp and pointy or irregular with branches (called a staghorn). It can range in size from a grain of sand to bigger than a golf ball. The composition of the stone depends upon what excessive amounts of chemicals are present. It may be all one chemical compound or have different chemicals in different layers.
According to the National Institute of Diabetes and Digestive and Kidney Diseases, around 11% of men and 6% of women in the U.S. will have kidney stones at least once in their life. In the U.S., more than half a million people go to the emergency room each year with kidney stones and about a million visit their healthcare provider.
How is the sample collected for testing?
The healthcare practitioner or laboratory typically provides you with a clean container and a straining device that has a fine mesh. You should filter all of your urine through the fine mesh. This is necessary because there is no way to determine exactly when a stone will pass from the urinary tract. You then examine the mesh for any particulates, keeping in mind that stones may be easily visible or as small as grains of sand. If a stone is found, it is placed into the clean container, allowed to dry, and returned to the laboratory or healthcare provider as instructed. It is important not to add anything to the stone, such as tissue or tape, as this can make testing more difficult.
If you are in a hospital, then medical personnel will filter the urine. With a kidney stone that is too large to pass, a healthcare practitioner may perform a surgical procedure to remove it.
Is any test preparation needed to ensure the quality of the sample?
No personal test preparation is needed. Collection filter must be available.
A kidney stone analysis is performed to determine the chemical composition of a stone when it is filtered out of the urine or removed from the urinary tract. A laboratory will typically document the physical characteristics of a stone – its size, shape, weight, color, and texture. Often, a picture of the stone will be taken to document its size and appearance. The stone may also be fractured so that its layers can be observed. One or more tests will then be performed to determine the stone's composition.
Kidney stone analysis is ordered when you have passed a kidney stone and it has been filtered out of the urine or when a stone has been removed from your urinary tract.
Sometimes, your healthcare practitioner may suspect that you have a kidney stone and will search for a stone either in voided urine or within your body using imaging tests when you have signs and symptoms such as:
When you have recurrent stones, the first stone found would be tested. Subsequent stones would be analyzed as your healthcare practitioner deems necessary.
A kidney stone analysis identifies the chemical composition of the stone. Common types of kidney stones include:
These four types make up about 95% to 99% of kidney stones, with calcium oxalate stones being the most common.
Less common stones include:
However, stone analysis does not give the reason that the stone formed.
You may have an underlying disease or condition that may produce and/or release an excess of a specific chemical into the urine. Not drinking enough fluids and/or having urine with a high or low pH can contribute to your risk of forming stones. Preventing kidney stones from developing again depends upon identifying and addressing the cause of stone formation.
In general, if you have a:
A variety of other types of stones may be formed when an excess chemical is present and/or when the urine is very concentrated, which can occur with dehydration.
Not everyone who drinks too little liquid or who has an excess amount of a chemical in their urine will form kidney stones. Some stones will form in people for other reasons. Those who have had one kidney stone are at an increased risk for developing additional stones.
Other factors that can contribute to the formation or increased risk of kidney stones include:
Blood, urine, and 24-hour urine tests are often ordered to determine whether you produce excess chemicals that may contribute to the formation of kidney stones and to evaluate your overall health. The test results can help distinguish between a probable stone and other conditions that may have similar symptoms but require different treatment. Testing may include:
Yes, as long as you have a suspected stone and are instructed to do so by your healthcare provider. Since it is impossible to determine when the stone will pass, it is important to screen all of the urine in order to find and send it for analysis.
Blood and urine can provide important information about your condition, but they will not indicate exactly which chemical compounds constitute the stone. The more information your healthcare practitioner has, the better the chance that he or she can help you prevent stone recurrence.
It depends upon the stone and will vary from person to person, but it is often severe and sometimes must be treated with strong prescription pain medications. For most people, the pain is most intense when the stone is moving through the urinary tract.
You should work with your healthcare provider to determine the best treatment for you. If you had a stone with calcium in it, your healthcare practitioner may have you decrease your intake a modest amount, but the clinical picture is often less black and white than taking more or less. Some people absorb extra calcium from their food, but some excess calcium in the urine is related to an excess of sodium, so people who have had calcium-containing stones are often told to decrease salt intake rather than reducing calcium intake. Taking large doses of supplemental calcium may play a role in kidney stone formation. Sometimes drastic reductions in calcium can worsen stone formation as well as affect bone health.
The healthcare practitioner can use imaging tests to locate and evaluate a kidney stone. These tests can help determine whether a stone is likely to pass out of the body without medical intervention.
This testing requires specialized equipment and expertise. It is not offered by every laboratory. In most cases, your stone will be sent to a reference laboratory.
Approximately 80% of patients who develop a kidney stone will have another one. Not every stone can be prevented, but the most helpful action is to drink a sufficient amount of water to remain well hydrated. Other actions will depend upon your specific circumstances.
Common methods of kidney stone analysis include infrared spectroscopy and X-ray diffractometry. You can read more about these and other methods at the web site for the Louis C. Herring and Company Kidney Stone Analysis Laboratory.
Sources Used in Current Review
Kidney Stone Analysis. MedlinePlus. Available online at http://medlineplus.gov/lab-tests/kidney-stone-analysis/. Accessed 5/15/2019.
Kidney Stones. National Institute of Diabetes and Digestive and Kidney Diseases. Available online at https://www.niddk.nih.gov/health-information/urologic-diseases/kidney-stones. Accessed 5/15/2019.
Kidney Stone Analysis. Mayo Clinic Laboratories. Available online at https://www.mayocliniclabs.com/test-catalog/Clinical+and+Interpretive/8596. Accessed 5/15/2019.
Calcium Oxalate Stones. National Kidney Foundation. Available online at https://www.kidney.org/atoz/content/calcium-oxalate-stone. Accessed 5/15/2019.
Types of Kidney Stones. NYU Langone Health. Available online at https://nyulangone.org/conditions/kidney-stones-in-adults/types. Accessed on 5/15/2019.
Kidney Stones. National Kidney Foundation. Available online at https://www.kidney.org/atoz/content/kidneystones. Accessed 5/15/2019.
Nephrolithiasis. Medscape. Available online at https://emedicine.medscape.com/article/437096-overview. Accessed 5/15/2019.
Calcium Intake and Urinary Stone Disease. Translational Andrology and Urology. Available online at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4708574/. Accessed 5/15/2019.
Sources Used in Previous Reviews
Pagana, K. D. & Pagana, T. J. (© 2011). Mosby's Diagnostic and Laboratory Test Reference 10th Edition: Mosby, Inc., Saint Louis, MO. Pp 1015-1016.
C. Türk et. al. (© 2011) Guidelines on Urolithiasis. European Association of Urology [On-line information]. PDF available for download at http://www.uroweb.org/gls/pdf/18_Urolithiasis.pdf. Accessed August 2011.
Liou, L. (2009 January 14). Kidney Stones. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000458.htm. Accessed August 2011.
Liou, L. (2009 August 30). Cystinuria. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000346.htm. Accessed August 2011.
Stein, J. (2011 May 27). Guidelines Followed for Assessment of Nephrolithiasis. Medscape News [On-line information]. Available online at http://www.medscape.com/viewarticle/743524. Accessed August 2011.
Wolf, J. S. (Updated 2011 June 16). Nephrolithiasis. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/437096-overview. Accessed August 2011.
(Updated 2010 September 2). Kidney Stones in Adults. National Kidney & Urologic Diseases Information Clearinghouse (NKUDIC) [On-line information]. Available online at http://kidney.niddk.nih.gov/kudiseases/pubs/stonesadults/. Accessed August 2011.
(Updated 2010 September 2). Diet for Kidney Stone Prevention. National Kidney & Urologic Diseases Information Clearinghouse (NKUDIC) [On-line information]. Available online at http://kidney.niddk.nih.gov/KUDiseases/pubs/kidneystonediet/index.aspx. Accessed August 2011.
(© 2011). Kidney Stones & Uretral Stones. AUAFoundation [On-line information]. Available online at http://www.urologyhealth.org/urology/index.cfm?article=147. Accessed August 2011.
(© 2011). Kidney Stones. National Kidney Foundation [On-line information]. Available online at http://www.kidney.org/atoz/content/kidneystones.cfm. Accessed August 2011.
Figge, H. (2011 July 13). Calcium Kidney Stones, Pathogenesis, Evaluation, and Treatment Options. Medscape Today from U.S. Pharmacist [On-line information]. Available online at http://www.medscape.com/viewarticle/745456. Accessed August 2011.
Fathallah-Shaykh, S. and Neiberger, R. (Updated 2011 August 3). Uric Acid Stones. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/983759-overview. Accessed August 2011.
Integrated Approach to Kidney Stone Analysis. Louis C. Herring and Company Kidney Stone Analysis Laboratory [On-line information]. Available online at http://www.herringlab.com/herinte1.html. Accessed August 2011.
(© 1995-2011). Unit Code 8596: Kidney Stone Analysis. Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/8596. Accessed August 2011.
(2013 February). National Kidney and Urologic Diseases Information Clearinghouse. Kidney Stones in Adults. Available online at http://kidney.niddk.nih.gov/kudiseases/pubs/stonesadults/. Accessed 03/21/15.
(2014) Preventing and Treating Kidney Stones. Urology Health. Available online at http://www.urologyhealth.org/_media/_pdf/StonesArticle.pdf. Accessed 03/21/15.
De Biase, I. et. al. (2015 February, Updated). Nephrolithiasis - Kidney Stone. ARUP Consult Available online at http://www.arupconsult.com/Topics/Nephrolithiasis.html?client_ID=LTD. Accessed 03/21/15.
(© 1995–2015). Kidney Stone Analysis. Mayo Clinic Mayo Medical Laboratories. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/8596. Accessed 03/21/15.
Preminger, G. (2014 July, Revised). Urinary Calculi. Merck Manual Professional Edition. Available online through http://www.merckmanuals.com. Accessed 03/21/15.
Pagana, K. D., Pagana, T. J., and Pagana, T. N. (© 2015). Mosby's Diagnostic & Laboratory Test Reference 12th Edition: Mosby, Inc., Saint Louis, MO. Pp 966-967.