title: Situs anomalies on prenatal MRI.
abstract: OBJECTIVE
  Situs anomalies refer to an abnormal organ arrangement, which may be associated with severe errors of development. Due regard being given to prenatal magnetic resonance imaging (MRI) as an adjunct to ultrasonography (US), this study sought to demonstrate the in utero visualization of situs anomalies on MRI, compared to US.
  
  
  METHODS
  This retrospective study included 12 fetuses with situs anomalies depicted on fetal MRI using prenatal US as a comparison modality. With an MRI standard protocol, the whole fetus was assessed for anomalies, with regard to the position and morphology of the following structures: heart; venous drainage and aorta; stomach and intestines; liver and gallbladder; and the presence and number of spleens.
  
  
  RESULTS
  Situs inversus totalis was found in 3/12 fetuses; situs inversus with levocardia in 1/12 fetuses; situs inversus abdominis in 2/12 fetuses; situs ambiguous with polysplenia in 3/12 fetuses, and with asplenia in 2/12 fetuses; and isolated dextrocardia in 1/12 fetuses. Congenital heart defects (CHDs), vascular anomalies, and intestinal malrotations were the most frequent associated malformations. In 5/12 cases, the US and MRI diagnoses were concordant. Compared to US, in 7/12 cases, additional MRI findings specified the situs anomaly, but CHDs were only partially visualized in six cases.
  
  
  CONCLUSIONS
  Our initial MRI results demonstrate the visualization of situs anomalies and associated malformations in utero, which may provide important information for perinatal management. Using a standard protocol, MRI may identify additional findings, compared to US, which confirm and specify the situs anomaly, but, with limited MRI visualization of fetal CHDs.
authors.affiliation: Department of Radiology, Division of Neuroradiology and Musculoskeletal Radiology, Medical University Vienna, Waehringer Guertel 18-20, A-1090 Vienna, Austria.
authors.forename: Stefan F
authors.initials: SF
authors.lastname: Nemec
authors.forename: Peter C
authors.initials: PC
authors.lastname: Brugger
authors.forename: Ursula
authors.initials: U
authors.lastname: Nemec
authors.forename: Dieter
authors.initials: D
authors.lastname: Bettelheim
authors.forename: Gregor
authors.initials: G
authors.lastname: Kasprian
authors.forename: Gabriele
authors.initials: G
authors.lastname: Amann
authors.forename: David L
authors.initials: DL
authors.lastname: Rimoin
authors.forename: John M
authors.initials: JM
authors.lastname: Graham
authors.forename: Daniela
authors.initials: D
authors.lastname: Prayer
mesh_terms: D005260:Female; D059446:Heterotaxy Syndrome / Q000000981:diagnostic imaging* / Q000473:pathology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D011296:Prenatal Diagnosis / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014463:Ultrasonography / Q000379:methods