title: Testicular ectopia: Why does it happen and what do we do?
abstract: OBJECTIVE
  Testicular ectopia is rare, but the large range of anatomical locations described in the literature has spawned an abundance of possible theories to explain etiology. However, as the anatomical characteristics of normal testicular descent have only been elucidated recently, many of the theories of testicular ectopia do not incorporate this new perspective. In this study we aimed to determine what was in the literature about ectopic testis since 1980, and then try to explain the different anatomical variants in the light of current knowledge about testicular descent.
  
  
  METHODS
  A literature search was performed and all articles in English published since 1980 about testicular ectopia using several key words were identified.
  
  
  RESULTS
  A total of 271 articles in English were found, of which 31 addressed the pathophysiology and are the primary focus of this study. Case reports and reviews described perineal ectopia (×4), transverse testicular ectopia (×11), and abdominal ectopia (×2), along with 3 reviews/case reports addressing diagnosis and management. A range of proposed causes were found, including obstructed 'third inguinal ring' at neck of scrotum, abnormal CGRP function, aberrant distal gubernacular attachment, mechanical hindrance from retained Müllerian ducts, defective gubernacular formation or disruption of the gubernacular attachment to the testis.
  
  
  CONCLUSIONS
  After reviewing the proposed theories, we propose a unifying theory, based on current knowledge of testicular descent, where testicular ectopia can be explained by a) anomalous attachment of the gubernaculum to the anterior abdominal wall during transabdominal descent, or b) aberrant migration of the gubernaculum during the inguinoscrotal phase of testicular descent.
authors.affiliation: Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Parkville, Victoria, Australia.
authors.forename: Vishal V
authors.initials: VV
authors.lastname: Punwani
authors.affiliation: Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Parkville, Victoria, Australia.
authors.forename: Jeremy S Y
authors.initials: JSY
authors.lastname: Wong
authors.affiliation: Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Parkville, Victoria, Australia.
authors.forename: Christopher Y H
authors.initials: CYH
authors.lastname: Lai
authors.affiliation: Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Parkville, Victoria, Australia.
authors.forename: Jessalynn C Y
authors.initials: JCY
authors.lastname: Chia
authors.affiliation: Department of Paediatrics, University of Melbourne, Parkville, Victoria, Australia; Department of Urology, The Royal Children's Hospital, Parkville, Victoria, Australia; Douglas Stephens Surgical Research Group, Murdoch Childrens Research Institute, Parkville, Victoria, Australia. Electronic address: john.hutson@rch.org.au.
authors.forename: John M
authors.initials: JM
authors.lastname: Hutson
mesh_terms: D003456:Cryptorchidism / Q000209:etiology* / Q000503:physiopathology*; D006801:Humans; D007264:Inguinal Canal / Q000503:physiopathology; D008297:Male; D009095:Mullerian Ducts / Q000503:physiopathology*; D013737:Testis / Q000503:physiopathology*
keywords: Cryptorchidism; Ectopic testis; Gubernaculum; Perineal testis; Testicular descent