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Reference Material
Table: Nephrolithiasis
| Content | Frequency | Radiograph Opacity | pH | Microscopic Appearance |
|---|---|---|---|---|
| Calcium oxalate | 70%–80% | ↑↑ | -- |
 Octahedron (square with an "X" in the center) |
| Calcium phosphate | 70%–80% | ↑↑ | >7.0 | • Elongated, wedge-shaped • Forms rosettes |
| Magnesium ammonium phosphate (struvite or triple phosphate) |
15% | ↑ | >7.0 |
 Rectangular prism ("coffin lids") |
| Uric acid | 5% | — | <7.0 |
 Yellow or red-brown, diamond or rhombus |
| Cystine | 1% | ↑ | <7.0 |
 Flat, yellow, hexagonal |
Mnemonics & Tips
- Calcium Oxalate: "Envelope" shape / "X" in box. Most common (70-80%).
- Struvite (MAP): "Coffin lids". Associated with urease + bugs (*Proteus*). Alkaline pH (>7.0).
- Uric Acid: Radiolucent (invisible on X-ray). Acidic pH. Rhomboid/Diamond.
- Cystine: "SIXtine" = Hexagonal (6 sides). Acidic pH. Rare (1%).