Kidney Stones
Mineral deposits forming in the urinary tract when the concentration of lithogenic substances in urine exceeds its solubility threshold — a classic RCT by Borghi showed that simply increasing fluid intake by nearly half cuts recurrence risk.
Number of studies
2
Safety
Requires caution
Time to effects
Increased fluid intake lowers the concentration of lithogenic substances in urine almost immediately, but a measurable reduction in recurrence risk in the Borghi et al. study was observed over a 5-year follow-up period.
Who it's for
Table of contents
TL;DR
Mineral deposits forming in the urinary tract when the concentration of lithogenic substances in urine exceeds its solubility threshold — a classic RCT by Borghi showed that simply increasing fluid intake by nearly half cuts recurrence risk.
- →Increasing fluid intake to at least 2 liters a day cuts the risk of stone recurrence by more than half in a randomized controlled trial
- →Early diagnosis with ultrasound allows detecting and monitoring stones without exposure to ionizing radiation, especially for recurrent cases
- →Identifying the stone type (calcium, uric acid) enables targeted, more effective dietary and pharmacological prevention
| Condition type | Mineral deposits in the urinary tract — most often calcium oxalate or calcium phosphate (about 80% of cases) |
|---|---|
| Level of evidence | Strong — randomized controlled trials on prevention plus large epidemiological studies |
| Target group | People with low fluid intake, obesity, gout, or a prior kidney stone episode |
| Key risk factors | Chronic mild dehydration, a diet high in sodium and animal protein, obesity, genetic predisposition |
| Diagnostics | Ultrasound as the first-line test; non-contrast CT as the gold standard for unclear cases |
| Status | A common recurrent problem — prevention (hydration, diet) significantly reduces the risk of further episodes |
Understand
Overview
Kidney stones (nephrolithiasis, urolithiasis) form when hard mineral deposits develop in the urinary tract — the kidneys, ureters, or bladder — as the concentration of substances capable of crystallizing exceeds their solubility threshold in urine. The most common type, accounting for roughly 80% of all cases, is calcium oxalate or calcium phosphate stones; less common are uric acid stones (linked to hyperuricemia and gout), struvite stones (forming due to chronic urinary tract infections), and cystine stones (linked to a rare genetic amino acid transport defect).
The classic symptom is renal colic — sudden, very severe, wave-like pain in the flank radiating downward toward the groin and genitals, often accompanied by nausea, vomiting, blood in the urine, and urinary urgency. The pain results from stretching of the ureter and renal pelvis wall by the lodged stone and a sharp rise in pressure in the urinary tract above the obstruction. Smaller stones, generally under 5 millimeters, have a good chance of passing on their own, while larger ones often require a procedure.
Kidney stones are a common condition, and according to data from recent decades, their prevalence has been steadily rising, partly linked to the growing prevalence of obesity and metabolic syndrome as well as changes in dietary habits. Key risk factors include low fluid intake and chronic mild dehydration, a diet high in sodium and animal protein, obesity, gout, certain metabolic conditions (e.g., hyperparathyroidism), a family history, and living in a hot climate that promotes excessive fluid loss. Kidney stones affect men more often than women, though this gap has been narrowing in recent decades.
Diagnosis usually begins with abdominal ultrasound, which can detect stones in the kidneys and dilation of the collecting system without exposing the patient to ionizing radiation — particularly important for people with recurrent stones who need repeated follow-up imaging, and for pregnant women. Non-contrast CT remains the diagnostic gold standard with the highest sensitivity, especially when the clinical picture is unclear or complications are suspected, but it involves radiation exposure, so in clinical practice ultrasound often serves as the first-line test, with CT reserved for cases that require it.
An important part of caring for a patient with kidney stones is determining which type of stone is responsible, since secondary prevention differs depending on its chemical composition — calcium oxalate stones require a different dietary approach than uric acid stones, for which treating the underlying hyperuricemia may be key. Chemical analysis of a passed or removed stone, when possible, provides the most direct and reliable information here.
Who might genuinely benefit from this knowledge? Above all, people who have already had one kidney stone episode and want to reduce their recurrence risk — recurrence is common in this group without preventive measures. It's also useful for people with risk factors (low fluid intake, gout, obesity) who can start prevention before a first episode occurs, and for anyone who has experienced sudden, severe flank pain and is wondering whether it warrants urgent medical attention.
Kidney stones remain one of the few chronic conditions in which a single, simple behavioral intervention — increasing fluid intake — has documented effectiveness in a randomized controlled trial for preventing recurrence that rivals many pharmacological interventions, though some patients with recurrent or metabolically complex stone disease need further workup and targeted treatment under the supervision of a urologist or nephrologist.
Mechanism of action
Kidney stone formation is a physicochemical process based on urinary supersaturation — when the concentration of substances capable of crystallizing (calcium, oxalate, phosphate, uric acid ions) exceeds their solubility threshold for a given urine volume and pH, nucleation occurs, forming the first microscopic crystals. The risk of supersaturation rises as urine output falls — the less fluid we drink, the more concentrated the urine becomes, and the more easily lithogenic substances reach the crystallization threshold.
The resulting crystals can then aggregate and grow into progressively larger stones — a process governed by the balance between factors that promote crystallization (high calcium, oxalate, or uric acid concentrations, low urine pH for uric acid stones) and natural crystallization inhibitors present in urine, such as citrate and magnesium, which bind calcium ions and limit stone formation. A urinary citrate deficiency (hypocitraturia) is one of the more commonly identified, modifiable factors contributing to calcium stone recurrence.
Urine pH plays a particularly important role for uric acid stones — uric acid crystallizes mainly in an acidic environment, so chronically low urine pH, common in people with metabolic syndrome or insulin resistance, promotes this type of stone regardless of blood uric acid concentration itself. This is why alkalinizing the urine (e.g., with potassium citrate) is one of the pillars of uric acid stone prevention, alongside lowering uric acid levels.
When a formed stone moves from the kidney into the ureter and becomes lodged in it, pressure rises sharply in the urinary tract above the obstruction, along with a reflexive spasm of the ureter's smooth muscle trying to push the stone further along — it's this combination of urinary tract wall stretching and smooth muscle spasm that accounts for the characteristic, wave-like, very severe pain of renal colic, one of the most intense pains described in medicine.
Urinary supersaturation with lithogenic substances
When calcium, oxalate, phosphate, or uric acid concentrations exceed urine's solubility threshold, crystallization begins.
Nucleation and crystal growth
The first microcrystals form and grow when factors promoting crystallization outweigh natural inhibitors such as citrate and magnesium.
Aggregation into a stone
Crystals combine into progressively larger deposits, whose further growth depends on urine volume, pH, and inhibitor concentration.
Stone migration and renal colic
A moving stone that lodges in the ureter causes a rise in urinary tract pressure and smooth muscle spasm, producing the severe pain of renal colic.
Evidence: strong — based on 2 studies in this database.
Benefits
Common myths
MythSince calcium stones are most common, dietary calcium should be avoided.
FactAdequate, not reduced, dietary calcium binds oxalate in the gut and limits its absorption — it's too little, not normal, dietary calcium intake that increases the risk of calcium oxalate stones.
MythEvery kidney stone requires a procedure.
FactMost stones under 5 millimeters have a good chance of passing on their own with adequate hydration and pain control, without needing a procedure.
MythKidney stones are purely a result of a poor diet.
FactGenetics, metabolic conditions, climate, and hydration play at least as significant a role as diet alone, and for some patients a key factor is, for example, coexisting gout.
MythOnce a stone has passed, the problem is solved for good.
FactWithout preventive measures, above all adequate hydration, kidney stone recurrence is common — which is why identifying and modifying risk factors matters.
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Practice
Frequently asked questions
The pain results from stretching of the ureter and renal pelvis wall by a lodged stone and a sharp rise in pressure in the urinary tract above the obstruction, combined with a reflexive spasm of the ureter's smooth muscle.
No — stones under about 5 millimeters have a good chance of passing on their own with adequate hydration and pain control. Larger stones or those causing significant obstruction may need a procedure, such as lithotripsy or ureteroscopy.
The Borghi et al. study found a significant reduction in recurrence with fluid intake sufficient to produce at least 2 liters of urine a day — the exact target is worth setting individually with a doctor, especially with coexisting kidney or heart disease.
Ultrasound is usually the first-line test, safe and radiation-free, while non-contrast CT has higher sensitivity and is the gold standard for unclear cases or suspected complications.
A family history significantly raises kidney stone risk, though it's rarely the only factor — it usually interacts with hydration habits, diet, and metabolic conditions.
What actually helps
Increased fluid intake
Strong evidenceMaintaining urine output of at least 2-2.5 liters a day — the best-studied and most effective single preventive intervention.
Dietary modification tailored to stone type
Moderate evidenceLimiting sodium and excess animal protein while maintaining adequate, not reduced, dietary calcium intake.
Pharmacological treatment (potassium citrate, thiazides, allopurinol)
Strong evidencePotassium citrate alkalinizes urine and binds calcium, thiazides reduce urinary calcium excretion, and allopurinol lowers uric acid levels for uric acid stones.
Procedural treatment (ESWL, ureteroscopy, PCNL)
Strong evidenceUsed for stones too large to pass on their own or causing significant urinary tract obstruction.
What to combine with
Good combinations
Ultrasound (Sonography) — Ultrasound is the most commonly used first-line test for diagnosing kidney stones, avoiding ionizing radiation for recurrent episodes — details on the test itself are in our separate entry
Uric Acid (Blood Test) — Elevated blood uric acid is a key risk factor for uric acid stones — more on interpreting this test in our separate entry
Calcium Blood Test (Total & Ionized) — Checking blood calcium levels can help diagnose causes of calcium stones, including hyperparathyroidism
Safety
Side effects & contraindications
Possible side effects
Acute renal colic causes very severe pain, often requiring emergency intervention
A stone lodged in the ureter can lead to urine stasis and hydronephrosis, and, untreated, kidney damage
Struvite stones, which form due to chronic infections, promote recurrent urinary tract infections
Repeated episodes or unrecognized, chronic ureteral obstruction can lead to permanent kidney function impairment
Infected, obstructing kidney stones can lead to urosepsis — a rare but life-threatening complication
Contraindications
No significant contraindications at typical doses.
Interactions
Low fluid intake and chronic mild dehydration are the strongest, fully modifiable risk factor
A sodium-rich diet increases urinary calcium excretion, promoting calcium stones
Excessive animal protein intake increases uric acid and calcium excretion and lowers urine pH
Paradoxically, too little dietary calcium increases intestinal oxalate absorption, raising the risk of calcium oxalate stones
Obesity and metabolic syndrome increase risk, especially of uric acid stones, by lowering urine pH
A hot climate and intense physical exertion without adequately replacing fluid losses increase urine concentration
Is it worth taking?
Who it's for
- People with low fluid intake or living in a hot climate or with high sweat losses
- People who have had a prior kidney stone episode and face elevated recurrence risk
- People with obesity, gout, or metabolic syndrome
- People with a family history of kidney stones
Not for
- No significant contraindications at typical doses.
Evidence
Worth knowing
Calcium oxalate or calcium phosphate stones account for about 80% of all kidney stone cases.
In the Borghi et al. study, high fluid intake cut stone recurrence from 27% to 12.1% over 5 years.
Ultrasound is usually the first-line test because it doesn't expose patients to ionizing radiation, unlike CT.
Chemical analysis of a passed stone, when possible, allows precisely tailored further prevention.
Studies
Stones recurred in 12.1% of patients assigned to the high fluid intake group, versus 27% in the control group, over five years of follow-up.
Borghi L et al., Journal of Urology, 1996
Urinary volume, water and recurrences in idiopathic calcium nephrolithiasis: a 5-year randomized prospective study
Strong evidenceBorghi L, Meschi T, Amato F, Briganti A, Novarini A, Giannini A · Journal of Urology · 1996
A five-year randomized trial enrolled 199 patients after a first episode of idiopathic calcium stone disease, assigned to either a high fluid intake recommendation (at least 2 liters a day) or a control group. Stone recurrence occurred in 12.1% of the high fluid intake group versus 27% of the control group, with mean time to recurrence of 38.7 and 25 months, respectively.
View studyPrevalence of kidney stones in the United States
Strong evidenceScales CD Jr, Smith AC, Hanley JM, Saigal CS (Urologic Diseases in America Project) · European Urology · 2012
Analysis of a nationally representative population survey (NHANES) found that kidney stone prevalence in the United States had risen significantly compared with earlier decades, with clear differences by sex and age group.
View studySources & bibliography
Citations are illustrative for this demo version and require full bibliographic verification by the editorial team before production publication.
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About the authors of this entry
Author
Michał NowakClinical Dietitian
Michał started out as a long-distance runner, before an injury forced him to rethink his career. Looking for a faster way back into shape, he discovered sports nutrition and never left — fascinated by the gap between the research and what "everyone knows" at the gym. He completed a degree in clinical dietetics, earned a sports-nutrition coaching certification, and ran his own practice for several years before joining VitMode. His writing keeps returning to one theme: a supplement won't replace the basics, but the right one, at the right time, makes a real difference — and that's the difference he tries to describe precisely, with citations instead of slogans. He still runs, though these days, as he puts it, purely for the fun of it.
137 publications on this site
Medical review
dr Piotr ZielińskiEndocrinologist
Piotr has practiced endocrinology for more than fifteen years, mostly in male hormonal disorders and metabolic health. He joined VitMode as a scientific consultant because, as he jokes, he got tired of explaining the same testosterone questions at every appointment and decided to write the answers down properly, once. He reviews content on hormone therapy, supplement pharmacology and drug interactions, making sure articles never turn into encouragement to self-supplement in situations that genuinely need diagnostics and medical supervision. His professional motto — "evidence first, enthusiasm second" — has come up more than once with a patient who arrived with a supplement plan they found online.
223 publications on this site
Related entries
4.6Ultrasound (Sonography)
Ultrasound uses high-frequency sound waves, not radiation, to image organs in real time — it's safe, widely available, and inexpensive, though image quality depends heavily on the operator's experience and the patient's anatomy.
4.6Uric Acid (Blood Test)
Uric acid is the end product of purine breakdown — its blood test helps assess the risk of gout and kidney stones, but a single result on its own neither confirms nor rules out disease.
4.6Calcium Blood Test (Total & Ionized)
Blood calcium is one of the body's most tightly regulated parameters — the total and ionized tests measure somewhat different things, and choosing the right one and interpreting it correctly determines whether an abnormality gets caught at all.
4.7Creatinine and eGFR (Estimated Glomerular Filtration Rate)
Creatinine alone tells you surprisingly little about kidney function — only converting it into eGFR using the CKD-EPI equation reveals how much filtration capacity actually remains.
4.6Chronic Kidney Disease (CKD)
A progressive, usually symptomless loss of kidney function affecting up to one in nine adults worldwide — and a condition in which even a small drop in glomerular filtration is linked, in large cohort studies, to a significantly higher risk of cardiovascular death.
4.5Total Protein and Albumin Blood Test
Total protein and albumin are among the oldest, yet also most ambiguous, laboratory panels — the same low result can mean malnutrition, kidney disease, chronic inflammation, or simply blood dilution from IV fluids, and telling these scenarios apart takes more than a single number on a printout.
4.7Hypertension
The 'silent killer' — it runs symptom-free for years, yet it's one of the strongest, and largely modifiable, risk factors for stroke and heart attack in the world.
4.7Type 2 Diabetes
A chronic metabolic disease in which the body loses its ability to properly regulate blood glucose — and one of the few chronic diseases where a large randomized trial showed that lifestyle change alone can outperform a drug.
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Comments (2)
- KW
Kasia W. 2 weeks ago
Very clearly explained, especially the interactions section — I hadn't seen it laid out this well anywhere else.
- MT
Marek T. a month ago
Are you planning to update this with the newest study from this year? I saw an interesting meta-analysis.