Kidney stones

Types of kidney stones

Type	Clinical features
Calcium phosphate	*Normal urinary values* 24-hour urine calcium < 250 mg (women), < 300 mg (men) 24-hour urine citrate > 325 mg 24-hour urine pH 5.8-6.2 *Risk factors* Hypercalciuria Hypocitraturia Urine pH > 7 Distal RTA Carbonic hydrase inhibitors Medullary sponge kidney High protein intake *Shape of stones* Flat or wedge shaped prisms typically in rosettes
Calcium oxalate	*Normal urinary values* 24-hour urinary calcium as above 24-hour urinary oxalate < 40 mg *Risk factors* Hypercalciuria Hyperparathyroidism Immobilization Vitamin D excess Cushing syndrome Sarcoidosis High sodium intake Idiopathic Hyperoxaluria Increased GI oxalate absorption due to bowel pathology Bariatric surgery Short bowel syndrome Malabsorption syndromes Primary hyperoxaluria Increased vitamin C intake (men) *Shape of stones* Dumbbell or envelope shaped
Struvite	*Risk factors* Increased urinary ammonium and bicarbonate UTI with urease-splitting organism (eg, Proteus, Klebsiella) *Shape of stones* Rectangular, coffin-lid, or sometimes amorphous Stones composed of magnesium-ammonium- phosphate and/or carbonate apatite
Urate	*Normal urinary values* 24-hour urine uric acid < 0.75 mg (women), < 0.8 (men) *Risk factors* Hyperuricosuria Urine pH < 5.5 Type 2 diabetes Metabolic syndrome *Shape of stones* Rhomboid, football shaped, or possibly others Often yellow-brown color
Cystine	*Risk factors* Cystinuria *Shape of stones* Hexagonal shape
Xanthine	*Risk factors* Xanthine oxidase deficiency causing increased urine and blood xanthine Rare cause of stones (< 1% of cases) *Shape of stones* Various shapes

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