Kidney Stones Ammonium Magnesium Phosphate
- Precipitates with increased pH
- Radiopaque on X ray and CT
- Coffin lid crystal (pictured)
- Also known as struvite
- Account for 15% of stones (second most common)
- Caused by infection with urease ⊕ bugs (eg, Proteus mirabilis, Staphylococcus saprophyticus, Klebsiella) that hydrolyze urea to ammonia causing increased urine alkalinization
- Commonly form staghorn calculi (of calyces, pictured); can act as nidus for UTI
- Treatment: eradication of underlying infection, surgical removal of stone