Crystalline phase differentiation in urinary calcium phosphate and magnesium phosphate calculi.
Phosphates are encountered as the main components in about 15% of urinary calculi. Except for struvite, no specific correlations have been found between the crystalline phase of the phosphates and the cause of nephrolithiasis.


OBJECTIVE
The relationship between aetiological factors and crystalline phases or carbonate rate in calcium phosphate stones were assessed.


METHODS
From a series of 1148 phosphate calculi, we investigated the relationship between composition and aetiological factors.


RESULTS
Carbapatite was the most frequent crystalline phase (74.0%). It was associated with many possible causes, including hypercalciuria, hypocitraturia, primary hyperparathyroidism, tubular acidosis, medullary sponge kidney and chronic urinary tract infection. The carbonate rate of carbapatite may be of clinical interest because carbonate rates above 15% are frequently related to urinary tract infection with urea-splitting bacteria. Conversely, the carbonate rate was commonly less than 10% in cases of carbapatite induced by metabolic disorders. Among other phosphates, brushite was found in hypercalciuric states and primary hyperparathyroidism and whitlockite in cases of urinary tract infection by non-urease-producing bacteria.


CONCLUSIONS
Identification of crystalline phases and measurement of carbonate rate in calcium phosphate calculi is of clinical interest for identifying stone aetiology.
Maurice-Estepa
L
L
Laboratoire de Biochimie A and INSERM U90, Département de Néphrologie, Hôpital Necker-Enfants malades, Paris, France.
Levillain
P
P
Lacour
B
B
Daudon
M
M
D000138:Acidosis / Q000150:complications; D002130:Calcium Phosphates / Q000032:analysis*; D003460:Crystallization; D005260:Female; D006801:Humans; D006961:Hyperparathyroidism / Q000150:complications; D007669:Kidney Calculi / Q000737:chemistry* / Q000209:etiology; D017616:Magnesium Compounds / Q000032:analysis*; D008297:Male; D013057:Spectrum Analysis; D014551:Urinary Tract / Q000002:abnormalities; D014552:Urinary Tract Infections / Q000150:complications
D002130:Calcium Phosphates; D017616:Magnesium Compounds