What can the microstructure of stones tell us?

Abstract

How stones are retained within the kidney while small in size is still not fully understood. In this paper we 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 an apatite region 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. We propose that knowing the mechanisms of stone retention during early stone formation could allow for better treatment of stone diseases.

Raman chemical imaging, a new tool in kidney stone structure analysis: Case-study and comparison to Fourier Transform Infrared spectroscopy

“…For more details about stone morphology classification, please refer to Daudon et al [ 54 ]. Very small spots of apatite smaller than 0.5mm on the surface of some COM stones attached to renal papilla are known as Randall’s plaque [ 28 ]. These patients may have altered gene expression associated to renal inflammation and oxidative stress [ 55 ].…”

“…Yet, chemical composition is not the only characteristic to take in consideration when analyzing kidney stones. Structure of stones as well as the presence of some particular elements, like Randall’s Plaque, are also providing information about stone formation and associated diseases [ 26 – 28 ]. Most of the time, calculi are made up of more than a single element, and the localization of the different chemical elements also gives clues on the stone “history” [ 29 , 30 ].…”

Papillary Ductal Plugging is a Mechanism for Early Stone Retention in Brushite Stone Disease

“…5 The early calculus is retained in the renal calyx by the anchoring of the small stone to the collagenous connective tissue of the renal papilla via the Randall’s plaque. 6 Stones growing in this manner can eventually be freed from the papillary anchor 7,8 but they retain the mineral signature that shows the early origin on papillary plaque. 9 …”

Endoscopic observations as a tool to define underlying pathology in kidney stone formers

“…Three pathways of human kidney stone formation have recently been proposed [5, 6]. The first pathway is overgrowth on interstitial apatite plaque (Randall’s plaque), which has been suggested to be the main pathway in idiopathic CaO x nephrolithiasis; in the second pathway crystals deposit in the renal tubules as the starting point for renal stone formation; and the third pathway implies free solution crystallization as seen in patients with urinary stasis [6]. Our data clearly show that digital endoscopy of the renal collecting system has the potential to differentiate among these underlying pathways.…”

“…Eight decades ago, Alexander Randall proposed sub-epithelial calcium phosphate deposits at the tip of the renal papillae as the origin of renal calculi [4]. His findings were not adequately recognized as an important step forward in our understanding of the pathogenesis of renal stone formation, until recent research using modern investigational tools brought the unique findings into further perspective [5, 6]. It is now widely accepted that some kidney stones develop attached to sub-epithelial plaques of calcium phosphate crystals (Randall’s plaques) [7].…”