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 for ‘stone screen’ (Edinburgh labs), (plain bottle), to check volume, calcium, oxalate, Na, urate, cystine. Note that creatinine and protein need to be requested separately. |
| 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.