To describe a new hypothesis for the initial events leading to urinary stones. A biomechanical perspective on Randall's plaque formation through form and function relationships is applied to functional units within the kidney we have termed the "medullo-papillary complex" - a dynamic relationship between intratubular and interstitial mineral aggregates.
A complete MEDLINE search was performed to examine the existing literature regarding the anatomical and physiological relationships in the renal medulla and papilla. Sectioned human renal medulla with papilla from radical nephrectomy specimens were imaged using a high resolution micro X-ray computed tomography. The location, distribution, and density of mineral aggregates within the medullo-papillary complex were identified.
Mineral aggregates were observed proximally in all specimens within the outer medulla of medullary complex and were intratubular. Distal interstitial mineralization at the papillary tip corresponding to Randall's plaque was not observed until a threshold of proximal mineralization was observed. Mineral density measurements suggest varied chemical compositions between the proximal intratubular (330 mg/cc) and distal interstitial (270 mg/cc) deposits. A review of the literature revealed distinct anatomical compartments and gradients across the medullo-papillary complex that supports the empirical observations that mineralization proximally triggers distal Randall's plaque formation.
The initial stone event is initiated by intratubular mineralization of the renal medullary tissue leading to the interstitial mineralization that is observed as Randall's plaque. We base this novel hypothesis on a multiscale biomechanics perspective involving form and function relationships, and empirical observations. Additional studies are needed to validate this hypothesis. This article is protected by copyright. All rights reserved.
BJU international. 2016 Jun 16 [Epub ahead of print]
Ryan S Hsi, Krishna Ramaswamy, Sunita P Ho, Marshall L Stoller
Department of Urology, University of California San Francisco, Can Francisco, CA., Department of Urology, University of California San Francisco, Can Francisco, CA., Division of Biomaterials and Bioengineering, Department of Preventive and Restorative Dental Sciences, School of Dentistry, University of California San Francisco, San Francisco, CA., Department of Urology, University of California San Francisco, San Francisco, CA.