RENAL STONES

SUMMARY

1. Stones - calcium oxalate, calcium phosphate, uric acid, struvite.

2. Investigations:
- Chemical analysis of the stone
- Serum calcium, iPTH (exclude hyperparathyroidism)
- Electrolytes and urine pH (exclude Type 1 distal RTA)
- U/A with C+S (exclude stone-forming urinary pathogens; clue = urine pH> 7.5)

- AXR to detect radio-opaque (calcium, cysteine, struvite) vs. radiolucent (uric) stones
- Renal imaging (helical CT is the gold standard; rarely use IVP; in patients with impaired renal function, begin with ultrasound imaging of the kidney)

3. For recurrent stones, perform 24-hour urine collection for: volume, cystine, calcium, Na, urea, uric acid, citrate, oxalate, and creatinine.

Reference(s)

Wilkinson, I., Furmedge, D. and Sinharay, R. (2017). Oxford handbook of clinical medicine. Oxford: Oxford University Press. Get it on Amazon.
Feather, A., Randall, D. and Waterhouse, M. (2020). Kumar And Clark’s Clinical Medicine. 10th ed. S.L.: Elsevier Health Sciences. Get it on Amazon.
Hannaman, R. A., Bullock, L., Hatchell, C. A., & Yoffe, M. (2016). Internal medicine review core curriculum, 2017-2018. CO Springs, CO: MedStudy.
Therapeutic Guidelines. Melbourne: Therapeutic Guidelines Limited. https://www.tg.org.au [Accessed 2021].