Urolithiasis

Stones forming in the lumen of the urinary tract, anywhere from renal calyx $\to$ bladder. Types:

• Calcium oxalate 70% - raised calcium
• Urate 5% - raised urate, gout etc
• Cystine 1% - raised cystine eg congenital cystinuria
• Struvite 15% - raised pH of urine so magnesium ammonium phosphate salts precipitate out

Chemotherapy and cell death can increase uric acid levels. In this acute setting the uric acid stones are unlikely to be coated with calcium and will therefore be radiolucent.