Randall's plaque formation is a very common initial step in the process of kidney stone formation. On morphological stereomicroscopic examination of kidney stones, red/orange deposits at the level of Randall's plaque or at its interface with the kidney stone can be observed in a minority of kidney stones.
We retrospectively reviewed our kidney stone database to determine the prevalence of red/orange deposits observed on morphological examination of kidney stones analysed between 1989 and 2023. When possible, analysis of the deposits was performed by scanning electron microscopy, energy-dispersive X-ray absorptiometry, and Fourier-transform infrared spectroscopy.
Of 44 213 intact kidney stones upon which morpho-constitutional kidney stone analysis was performed between 1989 and 2023, 12 587 stones (28.5%) exhibited a Randall's plaque, of which 142 (1.1%) showed the presence of red/orange deposits at the Randall's plaque or at its interface with the kidney stone. Scanning electron microscopy of the deposits on two kidney stones displayed the deposits as sharp-edged, polygonal prismatic crystals, while Fourier-transform infrared spectroscopy of the deposits on one kidney stone revealed that their composition was calcium bilirubinate. Energy-dispersive X-ray absorptiometry of the deposits on one examined kidney stone demonstrated the absence of iron.
In a minority of Randall's plaques, red/orange deposits consisting of calcium bilirubinate can be detected. Further investigations are required to confirm whether their presence is a feature of an underlying hepatic or biliary disease.
Journal of nephrology. 2026 Apr 07 [Epub ahead of print]
Els Van de Perre, Dominique Bazin, Antoine Boury, Karl Martin Wissing, Ferenc Borondics, Michel Daudon, Emmanuel Letavernier
Department of Nephrology and Arterial Hypertension, Universitair Ziekenhuis Brussel (UZ Brussel), Vrije Universiteit Brussel (VUB), Brussels, Belgium., Institut de Chimie Physique, Unité Mixte de Recherche, Centre National de Recherche Scientifique 8000, Bâtiment 350, Université Paris Saclay, Orsay CEDEX, France., SOLEIL Synchrotron, L'Orme des Merisiers RD128, Saint Aubin 91190, France., Service d'Explorations Fonctionnelles Multidisciplinaires, Hôpital Tenon, Assistance Publique Hôpitaux de Paris, Paris, France.