title: Absence of the spleen(s) in conjoined twins: a diagnostic clue of laterality defects? Radiological study of historical specimens.
abstract: BACKGROUND
  Laterality defects are quite common in thoracoileopagus and parapagus dicephalus but rare in other types of conjoined twins.
  
  
  OBJECTIVE
  To present the presumed laterality defects in cephalothoracoileopagus and prosopothoracoileopagus conjoined twins, based on the unilateral or bilateral absence or duplication of the spleen.
  
  
  METHODS
  Three human anatomical specimens of craniothoracoileopagus (CTIP) twins and one of prosopothoracoileopagus (PTIP) twins were investigated. The specimens were part of the Museum Vrolik collection of the Department of Anatomy and Embryology of the Academic Medical Centre, University of Amsterdam, The Netherlands. The specimens were taken out of their jars and scanned with multidetector CT and volumetric T2-weighted MRI at 1.5 T.
  
  
  RESULTS
  The internal anatomy of the specimens was largely in accordance with previous reports. However, there was no recognisable spleen in the right twin in one CTIP specimen, in the left twin in one other CTIP specimen, and in both twins in the third CTIP specimen and in the PTIP specimen.
  
  
  CONCLUSIONS
  Asplenia and polysplenia are considered reliable indicators of right and left isomerism, respectively. However, three of our four specimens had laterality patterns that did not correspond with those previously reported. Since no other parameters of laterality defects could be verified in these specimens, we concluded that asplenia was unlikely to be caused by laterality defects.
authors.affiliation: Department of Anatomy, Embryology and Physiology, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: R J
authors.initials: RJ
authors.lastname: Oostra
authors.forename: N
authors.initials: N
authors.lastname: Keulen
authors.forename: T
authors.initials: T
authors.lastname: Jansen
authors.forename: R R
authors.initials: RR
authors.lastname: van Rijn
mesh_terms: D000015:Abnormalities, Multiple / Q000175:diagnosis*; D002102:Cadaver; D005260:Female; D006801:Humans; D008297:Male; D011859:Radiography; D013154:Spleen / Q000002:abnormalities* / Q000000981:diagnostic imaging / Q000473:pathology; D014428:Twins, Conjoined