title: Why do undescended testes and posterior urethral valve occur together?
abstract: OBJECTIVE
  Undescended testis (UDT) occurs in ~2 % of newborn males, and occasionally these infants also have posterior urethral valve (PUV). The cause of this relationship is uncertain. We aimed to review the literature to identify publications documenting co-occurrence of UDT and PUV, and to summarise the theories of co-occurrence.
  
  
  METHODS
  A search of the literature (Embase, Medline, Pubmed; 1947-2015) was undertaken to identify publications describing the link between UDT in PUV patients, as well as PUV in UDT patients. Ten publications in English were found with both UDT and PUV: 9 articles describing the frequency of UDT in patients with PUV, and 1 article examining the frequency of PUV in infants with UDT.
  
  
  RESULTS
  UDT occurred in 12-17 % of PUV compared with 1-2 % in the control population, consistent with a 10-fold increase. PUV occurred in 1.2 % of UDT patients compared with 0.01 % in the control population, consistent with a 100-fold increase.
  
  
  CONCLUSIONS
  PUV leads to a 10-fold increase in occurrence of UDT, while the presence of UDT causes a 100-fold increase in occurrence of PUV. Four main theories of causation have been proposed, each of which have some merit but little supporting evidence, leaving the cause of simultaneous occurrence of PUV and UDT uncertain.
authors.affiliation: Faculty of Medicine, University of Melbourne, Melbourne, Australia.
authors.forename: Jeremy
authors.initials: J
authors.lastname: Wong
authors.affiliation: Faculty of Medicine, University of Melbourne, Melbourne, Australia.
authors.forename: Vishal
authors.initials: V
authors.lastname: Punwani
authors.affiliation: Faculty of Medicine, University of Melbourne, Melbourne, Australia.
authors.forename: Christopher
authors.initials: C
authors.lastname: Lai
authors.affiliation: Faculty of Medicine, University of Melbourne, Melbourne, Australia.
authors.forename: Jessalynn
authors.initials: J
authors.lastname: Chia
authors.affiliation: Department of Paediatrics, University of Melbourne, Melbourne, Australia. john.hutson@rch.org.au.|Urology Department, The Royal Children's Hospital, 50 Flemington Road, Parkville, Melbourne, 3052, VIC, Australia. john.hutson@rch.org.au.|Douglas Stephens Surgical Research Group, Murdoch Childrens Research Institute, Melbourne, Australia. john.hutson@rch.org.au.
authors.forename: John M
authors.initials: JM
authors.lastname: Hutson
mesh_terms: D003456:Cryptorchidism / Q000209:etiology*; D006801:Humans; D007231:Infant, Newborn; D007674:Kidney Diseases / Q000150:complications; D008297:Male; D014521:Urethra / Q000002:abnormalities*; D014522:Urethral Diseases / Q000151:congenital / Q000209:etiology*; D001745:Urinary Bladder Diseases / Q000150:complications; D014564:Urogenital Abnormalities / Q000196:embryology*
keywords: Cryptorchidism; Posterior urethral valve; Undescended testis