title: Incidentally detected nephrogenic rests in the setting of congenital obstructive uropathy.
abstract: OBJECTIVE
  Nephrogenic rests (NR) are clusters of cells similar to renal blastema. NR are frequently seen in kidneys with Wilms' tumor (WT) and are seen with higher frequency in nephrectomy specimens from obstructed and/or multicystic dysplastic kidneys (MCDK) compared to autopsy series of normal kidneys. The significance of NR and their role in tumorigenesis is largely unknown. We report the findings of two cases with NR associated with ureteral ectopy/obstruction and review the relevant literature.
  
  
  METHODS
  Two cases of upper pole heminephrectomy associated with ectopic upper pole ureter and resultant hydronephrosis were found to have nephrogenic rests present on pathologic examination. A literature search was done to review recent developments in the understanding of NR and their significance, primarily to guide patient recommendations regarding follow-up.
  
  
  RESULTS
  Recent developments in the understanding of NR include the description of intralobar versus perilobar nephrogenic rests and prognostic considerations associated with each. However, the implications of finding nephrogenic rests in upper pole hemi-nephrectomy specimens associated with ureteral ectopy is not well delineated.
  
  
  CONCLUSIONS
  The role of NR in tumorigenesis is still poorly understood. Because of the still undefined relationship with WT we recommend patients with incidentally detected NR be followed with serial abdominal ultrasounds for the first 5 years of life.
authors.affiliation: Department of Urology, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Brian
authors.initials: B
authors.lastname: Blew
authors.forename: Blair
authors.initials: B
authors.lastname: Carpenter
authors.forename: Michael P
authors.initials: MP
authors.lastname: Leonard
mesh_terms: D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007680:Kidney Neoplasms / Q000175:diagnosis / Q000000981:diagnostic imaging; D008297:Male; D021782:Multicystic Dysplastic Kidney / Q000175:diagnosis / Q000000981:diagnostic imaging; D014463:Ultrasonography; D014517:Ureteral Obstruction / Q000151:congenital* / Q000000981:diagnostic imaging; D009396:Wilms Tumor / Q000175:diagnosis / Q000000981:diagnostic imaging