title: The natural history of the multicystic dysplastic kidney--is limited follow-up warranted?
abstract: OBJECTIVE
  Imaging of patients with multicystic dysplastic kidney (MCDK) has increased over the past three decades. This increased use of imaging has provided additional insights into the natural history of MCDK. The present study looked at this data for predictors of involution and associated anomalies.
  
  
  METHODS
  Institutional review board approval was obtained for this retrospective study. The University of Michigan Departments of Urology and Radiology records were searched to identify unilateral MCDK patients during 1980-2012. Available clinical, radiological and surgical records were reviewed, and pertinent data were recorded. The log-rank test and a Cox proportional regression analysis were performed to identify predictors of MCDK involution. Probability of involution over time was assessed using Kaplan-Meier methodology.
  
  
  RESULTS
  301 unilateral MCDKs were identified; 195 (64.8%) were detected antenatally. Of the MCDKs found, 136 (45.2%) were in girls; 160 (53.2%) were right-sided. Mean size at baseline was 5.0 ± 0.2 cm (Mean ± SE). Associated abnormalities included: contralateral ureteropelvic junction obstruction (n = 10; 3.3%); contralateral ureterovesical junction obstruction/primary megaureter (n = 6; 2.0%); ipsilateral VUR (n = 21; 7.0%); contralateral VUR (n = 63; 20.1%); and renal fusion anomaly (n = 4; 1.3%). The cumulative probability of involution was: 9.8% at one year, 38.5% at five years, and 53.5% at ten years of age. Baseline MCDK size was the only significant predictor of involution at bivariate (p < 0.0001) and multivariate (p < 0.0001; HR 0.58 [95% CI: 0.49, 0.69]) analyses. No MCDK developed malignancy during the follow-up period.
  
  
  CONCLUSIONS
  As many MCDKs eventually involute and the risk of associated malignancy appears to be very low, there is no absolute indication for nephrectomy. Based on the data and other recent studies, it is believed that pediatric MCDK patients with no other urologic abnormalities can safely tolerate more limited urological and radiological follow-up.
authors.affiliation: The University of Michigan, Departments of Urology and Radiology, 1500 E Medical Center Drive, Ann Arbor, MI 48109, USA. Electronic address: eickmeya@med.umich.edu.
authors.forename: A B
authors.initials: AB
authors.lastname: Eickmeyer
authors.affiliation: The University of Michigan, Departments of Urology and Radiology, 1500 E Medical Center Drive, Ann Arbor, MI 48109, USA. Electronic address: ncasanov@med.umich.edu.
authors.forename: N F
authors.initials: NF
authors.lastname: Casanova
authors.affiliation: The University of Michigan, Departments of Urology and Radiology, 1500 E Medical Center Drive, Ann Arbor, MI 48109, USA. Electronic address: change@med.umich.edu.
authors.forename: C
authors.initials: C
authors.lastname: He
authors.affiliation: The University of Michigan, Departments of Urology and Radiology, 1500 E Medical Center Drive, Ann Arbor, MI 48109, USA. Electronic address: ethans@med.umich.edu.
authors.forename: E A
authors.initials: EA
authors.lastname: Smith
authors.affiliation: The University of Michigan, Departments of Urology and Radiology, 1500 E Medical Center Drive, Ann Arbor, MI 48109, USA. Electronic address: juliwan@med.umich.edu.
authors.forename: J
authors.initials: J
authors.lastname: Wan
authors.affiliation: The University of Michigan, Departments of Urology and Radiology, 1500 E Medical Center Drive, Ann Arbor, MI 48109, USA. Electronic address: dabloom@med.umich.edu.
authors.forename: D A
authors.initials: DA
authors.lastname: Bloom
authors.affiliation: The University of Michigan, Departments of Urology and Radiology, 1500 E Medical Center Drive, Ann Arbor, MI 48109, USA. Electronic address: jonadill@med.umich.edu.
authors.forename: J R
authors.initials: JR
authors.lastname: Dillman
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D018450:Disease Progression; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D021782:Multicystic Dysplastic Kidney / Q000175:diagnosis* / Q000209:etiology* / Q000628:therapy; D009392:Nephrectomy; D017063:Outcome Assessment, Health Care; D018579:Patient Selection; D011379:Prognosis; D012075:Remission, Spontaneous; D012189:Retrospective Studies
keywords: Involution; Multicystic dysplastic kidney (MCDK); Wilms' tumor