[Calcium-dependent calcium oxalate lithiasis (type IIa). The importance of urinary citrate and the calcium/citrate ratio].
BACKGROUND
Type IIa urinary lithiasis (calcium oxalate dihydrate, weddellite) has a calcium-dependent structure implicating hyper-calciuria for its formation.


METHODS
We observed a case of type IIa lithiasis in a patient without elevated urine calcium. Weddellite crystals with a hexagonal habit were found in the nocturnal urines. The only urinalysis anomaly was a low citrate level giving a calcium/citrate level > 3. Oral potassium citrate normalized urinary citrate and the calcium/citrate ratio. After 3 years follow-up, crystal formation has remained negative.


CONCLUSIONS
As illustrated by this case, the calcium/citrate ratio, rather than total urine calcium, would be a good indicator of urinary calcium output and the potential risk for weddellite crystal formation in the presence of oxalates.
D000328:Adult; D002118:Calcium / Q000652:urine*; D002129:Calcium Oxalate / Q000652:urine*; D019343:Citric Acid / Q000652:urine*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D012307:Risk Factors; D013997:Time Factors; D014545:Urinary Calculi / Q000737:chemistry / Q000652:urine*