Recurrent stone formation is common, but people who have frequent early recurrences should be screened for risk factors.
Check:
| Blood | Renal function Ca and PO4 Uric acid HCO3 |
| Urine | Infection
Request 24h urine collections for ‘stone screen’ to check volume, calcium, oxalate, Na, urate, cystine. Note that creatinine and protein need to be requested separately. This screen requires two separate 24 hour collections: one in a plain container and one in an acidified container. See Edinburgh Lab Medicine pages. |
| Stone | don’t forget to analyze the stone itself |
| Family history | hypercalciuria, medullary sponge kidney, distal RTA, Dent’s disease |
| Drug history | occasionally stones formed from drugs (including ephedrine) |
| Dietary assessment | important. See Diet. |
As for protein, urinary calcium can be measured as a ratio with creatinine, instead of a 24h clearance:
|
Ca/Creat ratio
|
Comment
|
Oxalate/Creatinine |
|
< 0.6
|
Normal
|
< 50 micromol/mmol * |
|
0.6 – 0.8
|
Equivocal
|
|
|
> 0.8
|
High
|
* After the age of 5 years. Ratios are higher in infancy (Matos et al 1999).
Management principles
Important principles are common to most stones:
- Maintain high urine volume, especially at night
- Restrict dietary sodium
- Maintain good dietary calcium intake, but avoid calcium supplements
- Consider thiazide for hypercalciuria (avoid loop diuretics)
- High protein diet is associated with stones – reduce
For management of individual metabolic abnormalities, seek specific information.
Further information
Patient information on renal stones from EdRenINFO
Acknowledgements: Neil Turner was the main author for this page. The last modified date is shown in the footer.