| Specimen requirement | Urinary calculus obtained from spontaneous passage or surgical intervention. |
| Plain bottle for stones | |
| Authorisation code required | No |
| 24 Hr available service | No |
| Method | Attenuated Total Reflection Fourier Transform Infra-red analysis (ATR-FTIR) |
| Reference interval | Not applicable |
| Clinical indication | Aid in establishing the etiology, identification of risk factors for stone recurrence and in planning rational therapy |
| Result interpretation |
Infrared spectrum is collected from pulverised calculus. The mineral composition is then determined semi-quantitatively by comparing the spectrum against the spectra in a library. Kidney stones are commonly composed of one or more of the following substances: calcium oxalate, calcium phosphate, uric acid, magnesium ammonium phosphate, and rarely cystine. Stones containing calcium may indicate hypercalciuria. Calcium oxalate monohydrate stones may indicate hyperoxaluria, while calcium oxalate dihydrate stones are associated with hypercalciuria.
Uric acid stones, or stones with a uric acid nidus, may indicate strongly acidic overnight urine or hyperuricosuria.
Magnesium ammonium phosphate (triple phosphate) stones indicate bacterial infection.
Cystine stones indicate cystinuria. |
| Measurement of uncertainty | N.A. |
| Frequency of measurement | Biweekly |