1. ¹Department of Anatomy and Cell Biology, Indiana University, School of Medicine, Indianapolis, Indiana, USA
2. ²Department of Urology, Methodist Hospital Institute for Kidney Stone Disease, Indianapolis, Indiana, USA
3. ³Department of Medicine, Nephrology Section, University of Chicago, Chicago, Illinois, USA
4. ⁴Department of Urology, Johns Hopkins University, Baltimore, Maryland, USA
5. ⁵Department of Pathology, Indiana University, School of Medicine, Indianapolis, Indiana, USA
6. ⁶Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio, USA

Correspondence: AP Evan, Department of Anatomy and Cell Biology, Indiana University, 635 Barnhill Drive, MS Room 5055S, Indianapolis, Illinois 46223, USA. E-mail: evan@anatomy.iupui.edu

Received 25 September 2006; Revised 29 November 2006; Accepted 5 December 2006; Published online 31 January 2007.

Abstract

To define the renal tissue changes in stone-forming patients with distal renal tubular acidosis (dRTA), we performed intra-operative papillary and cortical biopsies in five patients. The main abnormalities were plugging of inner medullary collecting ducts (IMCD) and Bellini ducts (BD) with deposits of calcium phosphate in the form of apatite; epithelial cell injury and loss was marked. Plugged ducts were surrounded by interstitial fibrosis, but the fibrosis was generalized, as well, and was a main feature of the histopathology even when plugging was not present. In contrast, common idiopathic calcium oxalate stone formers (SF) never manifest intra-tubule crystals or interstitial fibrosis. Patients with brushite (calcium monohydrogen phosphate) stones and those with cystine stones have many fewer IMCD and BD plugged with apatite (or cystine, in cystinuria), and interstitial fibrosis is limited to the regions around plugged ducts. Patients with dRTA often present a radiographic picture of nephrocalcinosis. Our direct surgical observations reveal that these may be surgically removable stones, especially in patients with well preserved renal function. In all, dRTA SF have a more diffuse papillary renal disease than other SF thus studied, and are also unusual for the degree of interstitial fibrosis.