Transitional Metaplasia of Renal Collecting Ducts in Vesicoureteral Reflux and Chronic Pyelonephritis: An Immunohistochemical Study of a Case and Review of the Literature

The capability of the urinary tract to undergo metaplastic changes such as squamous, intestinal, glandular, mucinous, or ciliated epithelium in renal pelvis has been previously reported, which hypothetically is due to the mechanical irritation of the transitional epithelium. However, transitional metaplasia is a rare presentation in the collecting ducts. The aim of this paper was to report this type of extremely rare metaplasia and to inform pathologists that they may encounter this kind of metaplasia. A 25-year-old man, a known case of vesicoureteral reflux (VUR), referred to the Imam Reza Hospital; affiliated to the Mashhad University of Medical Sciences, for bilateral nephrectomy. Gross evaluation of bilateral nephrectomy specimens showed atrophic kidneys and dilated pelvicalyceal systems. The light microscopic evaluation showed transitional metaplasia in the background of chronic pyelonephritis, confirmed by GATA3 nuclear immunohistochemical stain.  In this study, we presented a rare case of a renal collecting duct with transitional epithelial lining replacing the normal epithelium as a metaplastic change, with the hypothesis that previous medical history including VUR, or hemodialysis could be the trigger for the metaplastic change, which should be confirmed by further studies.