At the International Kidney Stone Institute, our goal is nothing less than the cure.
The steps in the prevention process explore each patient's unique characteristics that promote stone growth. The following should be considered:
Kidney stone disease tends to run in families. Some stone types, such as cystine, are entirely inherited from parents or grandparents. The tendency to form other types, such as calcium oxalate, stone, may be partially inherited, but can be reduced with medication and diet changes. While family history is an interesting part of the stone formation story, it is inalterable, and as such, is not a factor in prevention efforts. However, there may be a role here for genetic counseling in the future.
Some patients form stones because their urine is unable to empty properly from the kidney. This can be caused by a calyceal diverticulum (a pocket in the kidney where urine collects and the fluid is absorbed, but the minerals stay behind) or a ureteropelvic junction obstruction (the tube draining the kidney is kinked and urine stagnates in the urine collection area, giving more time for the minerals to link and form stone crystals).
Both of these conditions can be treated surgically to allow the urine to flow more freely to the bladder. While this may stop stone formation, the patient should still be evaluated for abnormal urine and blood studies to rule out other reasons stones might form.
Specialized laboratories perform chemical analysis of stones passes naturally or removed surgically. Reports from these labs identify the type of crystals contained in a sample and what percentage of each crystal is present. While some stones are pure, such as a 100% uric acid stone, many stones are of mixed type and contain a combination of crystals. Also, a patient may form different types of stones at different times of life. Knowing the type of crystals formed by an individual patient allows a physician to direct prevention efforts by targeting the urine factors that promote that specific stone type. The most common types of stones are calcium oxalate and uric acid. Other relatively common types are calcium phosphate, cystine and struvite stones, the latter being caused by infection. Finally, some stones are caused by the metabolism of certain medications, such as one for AIDS and one for seizures; the solution to ending stone formation is to discontinue that medication.
Urine and blood tests can identify abnormalities that cause stones to form. Patients collect urine for 24-hour periods to evaluate risks of stone formation. This long test displays urine volume and the body's excretion of elements over an entire day and night. Information gleaned from these studies is extraordinarily significant and includes many factors, such as the overall volume of urine, the presence and concentration of stone crystals, levels of calcium, sodium, oxalate, uric acid and citrate. In addition, the urinary pH (acid/base balance) is an important factor tested, as certain crystals are more likely to form in acid or basic urine. One major advantage of these urine tests is the ability to track changes over time. As an example, imagine a patient who forms calcium-oxalate stones. The first urine test on this patient showed excess of calcium and oxalate in the urine. If the provider prescribes a medication to reduce calcium excretion and a dietary restriction of foods containing oxalates, a repeat test in two months will show whether the calcium and oxalate have indeed been reduced by these recommendations. If they have, the therapy should be continued. If not, then the provider may need to explore other therapies. (High calcium in the blood can be caused by certain medications or by conditions such as an over-production of hormone from the parathyroid gland. Like the anatomic factors listed above, an over-active parathyroid would need to be corrected surgically before proceeding with other prevention efforts.)
For many patients, diet is a primary factor in the formation of stones. Patients can often significantly reduce their stone formation by changing what they eat and how much they drink. Dietary information is obtained from both diet recall and from the results of urine testing.
The urine test shows the volume of urine excreted in a day and also the related concentrations of stone molecules in the sample. While this does not show the actual intake of fluid (some fluid is lost through perspiration, breathing and in the bowel), the concentration does show whether the volume is sufficient. Also, the 24-hour urine tests quantify sodium excretion and oxalate excretion, which are directly related to their intake.