Stone formation

Abstract

How stones are retained within the kidney while small in size is still not fully understood. In this talk, we will show two examples of how stones are retained during early growth: One is growth on Randall’s (interstitial) plaque, and the other is growth on mineral that has formed as a luminal plug in a terminal collecting duct. These two mechanisms of stone retention during early growth have distinctive morphologic features that can be seen by methods that show the microscopic structure of the stones. Stones growing on Randall’s plaque display a mineralized region (composed of apatite) that is typically not large in size (less than 0.5 mm across) but which usually shows luminal spaces, which are signs of its origin in the connective tissue of the papilla. Stones growing on ductal plugs also show attachment to a piece of apatite, but the apatite regions are typically larger (often >1 mm long and >0.5 mm wide), and they are solid, without spaces running through them. Still other stone formers exhibit neither of these known mechanisms of stone retention, and we propose urinary stasis as a third possible way that stones are retained within the kidney. We propose that knowing the mechanisms of stone retention during early stone formation should allow for better treatment of stone diseases.