# Kidney Stones: Analyze the Stone, Test the Urine, Review Evidence

Stone analysis and an adequate urine collection turn general advice into a targeted prevention plan; monitor actual recurrence as well as chemistry.

![Infographic: Kidney Stones: Analyze the Stone, Test the Urine, Review Evidence](https://urinenephrology.org/visual-reference/images/student-stone-prevention.png?v=20261003c)

## Exclude the emergency first

Fever or sepsis with an obstructing stone needs urgent antibiotics and drainage assessment; anuria or threatened solitary-kidney function also changes urgency. Prevention counseling follows stabilization. Retrieve a passed or removed stone for analysis rather than inferring composition from symptoms.

## Test recurrent or high-risk stone formers

Review serum chemistry, calcium, diet, medicines, imaging burden, and stone composition. One or two 24-hour urine collections can measure volume, calcium, oxalate, citrate, uric acid, sodium, pH, and creatinine. Check collection completeness before prescribing treatment from the result.

## Dilute urine and retain dietary calcium

Aim for at least 2.5 L urine/day when medically appropriate; fluid intake needed varies with losses. For calcium stones with high urine calcium, limit sodium toward ≤2300 mg/day and maintain dietary calcium about 1000–1200 mg/day. Taking calcium-containing foods with meals helps bind intestinal oxalate.

## Match drug to urine and stone

Low citrate with recurrent calcium stones can support potassium citrate, after assessing potassium and kidney function. Uric-acid stones usually need urinary alkalinization rather than allopurinol alone. Excess alkalinization can increase calcium-phosphate risk, so follow urine pH and composition.

## Explain the thiazide uncertainty

NOSTONE found no substantial reduction in its composite recurrence outcome across hydrochlorothiazide doses versus placebo. This challenges routine use for every calcium-stone patient. If selecting therapy for persistent hypercalciuria, discuss uncertain clinical benefit, sodium intake, potassium, gout, glucose, and monitoring.

## Check whether prevention worked

Repeat a 24-hour urine within about 6 months after starting therapy, then follow recurrence, imaging, adherence, and adverse effects. A lower urine calcium is a mechanistic response, not proof that future stones are prevented. Avoid broad food bans that undermine adequate nutrition.

## Supporting evidence

- [Official clinical guidance](https://www.auanet.org/documents/Guidelines/PDF/clinical-guidance/Medical-Management-of-Kidney-Stones.pdf)
- [PubMed 36856614](https://pubmed.ncbi.nlm.nih.gov/36856614/)

## Source lessons

- [nephrolithiasis student handout](https://urinenephrology.org/student-resources/uti/nephrolithiasis-student-handout.html)

Read alongside the full lessons; the findings and decisions shown here require the stated clinical context.