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Kidney Stones

What is my kidney stone made of, and does it matter?

Korean laboratories analysed 33,078 stones in five and a half years. The composition changes what prevention is even possible.

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Answer

It matters, because prevention differs by composition. In 33,078 Korean stone analyses collected between 2014 and 2019, calcium oxalate was the largest group at 46.41 percent, followed by struvite at 29.66 percent, uric acid at 19.61 percent and calcium phosphate at 4.32 percent.

Key takeaways

  • In 33,078 urinary stone analyses from Korea between January 2014 and June 2019, calcium oxalate accounted for 46.41 percent, struvite 29.66 percent, uric acid 19.61 percent and calcium phosphate 4.32 percent.
  • Composition shifts with age: calcium oxalate falls as patients get older while uric acid rises.
  • Uric acid stones were more common in men than women, 24.5 percent against 11.0 percent, while struvite and calcium phosphate were more common in women.
  • Calcium oxalate stones were most frequent in summer and least frequent in spring.
  • The 2024 European Association of Urology guideline states that an attempt should be made to analyse the stone in every patient, and classes uric acid, infection and cystine stone formers as at high risk of relapse.
  • The Korean male-to-female ratio of stone analyses fell from 1.95 to 1 in 2014 to 1.67 to 1 in 2018.

Patients are usually told they have had a kidney stone. They are much less often told which kind, and the two are not the same piece of information. Prevention that ignores composition is aimed at a mechanism the patient may not have.

What Korean stones are made of

The Korean Society of Endourology and Robotics research series analysed 33,078 stone compositions collected between January 2014 and June 2019 — one of the largest such datasets published from any single country.

Composition of 33,078 Korean urinary stones, 2014 to 2019
TypeShare
Calcium oxalate46.41%
Struvite29.66%
Uric acid19.61%
Calcium phosphate4.32%

The same diagnosis is often a different stone

Composition varied by sex, age, region and season. Two of those patterns run in opposite directions and matter most.

  • Calcium oxalate fell as patients got older, while uric acid rose. A stone in a man in his thirties and a stone in a man in his seventies are frequently not the same chemical problem.
  • Uric acid stones were commoner in men than women — 24.5 percent against 11.0 percent — while struvite and calcium phosphate were commoner in women.
  • Calcium oxalate peaked in summer and was lowest in spring.
  • Uric acid stones were least common in the capital region.

Why composition changes the plan

The 2024 European Association of Urology guideline sets out different diagnostic and therapeutic algorithms by stone type, and it puts three groups at high risk of relapse from the outset rather than after a second stone: uric acid, infection-related and cystine stone formers.

Struvite — nearly a third of Korean analyses — is an infection stone. It forms in urine made alkaline by urea-splitting bacteria, so preventing it is a question about infection rather than about diet. Uric acid stones form in acidic urine and respond to measures aimed at urine pH and urate. Calcium oxalate is the group at which most general dietary advice is actually directed.

Sources

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    Jung HD, Seo IY, Lee JY

    Large database study of urinary stone composition in South Korea: Korean Society of Endourology and Robotics (KSER) research series

    Investigative and Clinical Urology 2021;62(4):462-469

    doi:10.4111/icu.20210039 · PMID:34190438

    https://doi.org/10.4111/icu.20210039
  2. 2

    Skolarikos A, Somani B, Neisius A, Jung H, Petřík A, Tailly T, Davis N, Tzelves L, et al.

    Metabolic evaluation and recurrence prevention for urinary stone patients: an EAU guidelines update

    European Urology 2024;86(4):343-363

    doi:10.1016/j.eururo.2024.05.029 · PMID:39069389

    https://doi.org/10.1016/j.eururo.2024.05.029
  3. 3

    Jung HD, Lee JY, Kang DH, Ko K, Koh DH, Kwon O, Koo KC, Kim KT, et al.

    Korean Society of Endourology and Robotics (KSER) recommendation on the diagnosis, treatment, and prevention of urolithiasis

    Investigative and Clinical Urology 2023;64(4):325-337

    doi:10.4111/icu.20230102 · PMID:37417557

    https://doi.org/10.4111/icu.20230102