Kidney Stone Risk Panel

A kidney stone risk panel is used to identify biochemical risk factors for the development of more stones in someone who has already had at least one stone in their urinary tract. Testing is particularly important for people already at high risk for forming more stones or for people who are likely to develop kidney damage with further stones.

This testing can be used to help guide and monitor treatment to prevent the formation of further kidney stones.

Several other laboratory tests may also be used to help evaluate a person who has had a kidney stone, including:

Several other laboratory tests may also be used to help evaluate a person who has had a kidney stone, including:

• Individual 24-hour urine tests that may not be part of the kidney stone risk panel, such as cystine, sodium, potassium, chloride, or magnesium
• A urinalysis to evaluate urine constituents (protein, red and white blood cells, pH, and presence of crystals or bacteria)
• Blood tests such as a urea and creatinine to evaluate kidney function, electrolytes (sodium, potassium, chloride, bicarbonate) and calcium, to evaluate the body’s handling of these substances, especially when compared to urine results
• A urine culture if a person shows signs of a urinary tract infection
• If a kidney stone is collected during surgery or if it passes on its own, kidney stone analysis is often performed to evaluate the specific substances present in it.

A kidney stone risk panel is usually performed several weeks after treatment for a kidney stone has finished and is frequently run on two separate 24-hour urine sample collections to determine whether elevated concentrations of a substance are temporary or persistent. In most cases, testing will be requested when a person has had at least two episodes of kidney stones, but it may be requested after a first stone when a person is considered to be at high risk of further stone formation or kidney damage. This may include people who:

• Formed stones as a child or young adult
• Have a family history of kidney stones
• Had multiple or bilateral kidney stones when they were first diagnosed
• Have a single functional kidney, including those who have had a kidney transplant

Sometimes testing is performed to monitor treatment, including when a person has made changes to their lifestyle (such as recommended dietary changes or drinking more water) or been given medication.

The results of the kidney stone risk panel are evaluated along with other risk factors to determine a person’s risk of developing another stone. In general, if a substance, such as calcium or uric acid, is present in excess in either the blood or the urine, it represents an increased risk for kidney stone formation and a condition that may need further investigation to determine the cause.

Test results, however, cannot predict who will actually develop another kidney stone or when. Some people with mild elevations (or even results within normal ranges) will form stones, while other people with significantly increased results will not.

In a person who has changed their lifestyle or medication, decreasing concentrations of stone promoting substances and increasing levels of stone inhibiting substances represent a decreased risk of stone formation.

If a person is dehydrated, the amount of urine produced in 24-hours (urine volume) will be low and the urine will be concentrated. This can result in an excess of a substance per volume (dissolved in less liquid) and increase the likelihood of stone formation. Kidney stone formation is also affected by urine pH (acidic/​alkaline). Uric acid and cystine crystals form more easily in acidic urine, while calcium phosphate and struvite stones form in alkaline urine. Struvite stones consist of magnesium ammonium phosphate (often mixed with calcium) and are associated with bacterial urinary tract infections.

The table below summarises what some test results may indicate:

Other less common tests are summarized below:

Kidney stones may be as small as a grain of sand, as large as a golf ball, or even larger, with some filling up the entire collecting system of the kidney. These are sometimes called ​“staghorn” calculi because the shape of the urinary collecting system resembles the antlers of a deer. Stones can cause problems either because they grow large enough to obstruct urine flow in a kidney or because they become dislodged or break off and begin to travel from a kidney through the ureter. They can stretch, irritate and damage the walls of the ureter and can cause temporary obstruction. Movement of a stone often causes abrupt, extremely severe pain that may be intermittent or continuous. It is referred to as ​‘renal colic’.

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 stuck in the ureters, some form of treatment is needed.

Not everyone who drinks too little water or who has an excess amount of substances in their urine will form kidney stones. Conversely, some people will have normal results for the stone risk panel tests and yet form stones for other reasons. Those who have had one kidney stone are at increased risk of forming another.

Abnormalities in the structure of the kidneys and/​or urinary tract may cause the flow of urine to be impeded and crystals to be deposited, leading to formation of stones.

No, the test is not a general screening test and is not intended for people who have never had a kidney stone.

One of the easiest things to do is to make sure that you stay hydrated by consistently drinking plenty of water. Guidelines state that adults are advised to drink 2.5 to 3 litres of water per day and children and young people (depending on their age) 1 to 2 litres. Fresh lemon juice may be added to drinking water but carbonated drinks should be avoided. If you are at an increased risk of stones, your health care provider may recommend additional measures. 

You should work with your healthcare professional unless you have an unusual diet, avoiding calcium-containing foods does not help to prevent further stones and can actually increase stone formation and also cause bone problems. Advice is to maintain a normal calcium intake of 700 to 1200 mg for adults and 350 to 1000mg per day for children and young people (depending on their age). 

Some people absorb too much calcium from their food, but excess calcium in the urine is more often related to an excess of sodium, so people who have had calcium-containing stones are usually advised to decrease salt intake rather than reduce calcium intake. Adults are advised to have a daily salt intake of no more than 6g and children and young people (depending on their age) 2 to 6g. 

Yes, your health care provider needs to know how much urine you are producing over a 24-hour period (volume) and how much of each of the substances is present. Since the substances may be eliminated in the urine at varying rates during the day and night, the 24-hour urine is a better representation than a single or random urine sample. 

That will depend on the information that your healthcare professional wants to evaluate. It is common to compare some substances in both the blood and the urine to see how they are handled by the kidneys.

Yes. For example, stones can form in the bladder and are typically caused by an inability to completely empty the bladder during urination. This is often due to an underlying urinary tract problem such as lack of bladder control, enlarged prostate, or urinary tract infection. Bladder stones are less often caused by excess amounts of particular substances in the urine compared with kidney stones.