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Stone Morphology Suggestive of Randall’s Plaque
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Edité par CCSD ; American Institute of Physics -
International audience. Randall's plaques are found in a number of calcium oxalate stone formers. Stonesdeveloped on a Randall's plaque typically present a small depressed zone ("umbilication")corresponding to the tip of the papilla and containing material detached from the plaque. Byexamining the morphology and infrared composition of 45,774 calculi referred to our laboratoryover the past three decades, we identified 8,916 umbilicated calculi (19.5%). We have selectedthree periods of time corresponding to the first years of each decade. Over these periods, weanalyzed 26,182 consecutive calculi. Among them, we identified 5,401 umbilicated calculi, ofwhich 91.5% had an identifiable plaque. We analyzed the relative prevalence of umbilicatedstones over time and the respective composition of Randall's plaque and stones. The proportionof umbilicated stones rose significantly from 10% in period 1 (1978-1984) to 21% in period 2(1990-1993) and 22.2% in period 3 (2000-2006), with a parallel rise in the prevalence of stoneswith identifiable Randall's plaque. The main component of plaques was carbapatite in 90.8% ofcases, whereas other components such as amorphous carbonated calcium phosphate, sodiumhydrogen urate or uric acid were found in other cases. The morphology of plaques made ofcarbapatite was diverse, as was their carbonate content, thus suggesting variablepathophysiological mechanisms. Stones were made of whewellite as the main component in51.4% of cases, or admixed with weddellite in 26.8%, predominant weddellite in 12.5% andother components (mainly uric acid) in 7.5% of cases. Our findings confirm that Randall'splaques are made of carbapatite in the great majority of cases, but with the stones morefrequently composed of calcium oxalate monohydrate (which is associated with hyperoxaluria)than of calcium oxalate dihydrate (associated with hypercalciuria). In conclusion, in our country,stones developed on a carbapatite Randall's plaque are as frequently made of monohydrate thandihydrate calcium oxalate, thus suggesting a role for a high urine concentration in both oxalateand calcium ions in the lithogenic process.
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