title: A simplified method for determining hiatal biometry.
abstract: BACKGROUND
  The levator hiatus is the largest potential hernial portal in the human body. Its dimensions are measured in the axial plane and are strongly associated with female pelvic organ prolapse. We aimed to compare two commonly used methods for measuring hiatal dimensions.
  
  
  METHODS
  We performed offline analysis of 100 consecutive 4D ultrasound volume datasets of women seen in a tertiary urogynecological clinic. Hiatal measurements were obtained in sectional planes (SP, Method A) and rendered volumes of 1-2 cm thickness (RV, Method B).
  
  
  RESULTS
  A test-retest series in 20 women showed similar repeatability for both methods, with an intraclass correlation (ICC) of 0.85 (CI 0.81-0.88) for Method A (SP) and of 0.88 (CI 0.85-0.9) for Method B (RV). Measurements taken from rendered volumes were generally lower than those taken in axial plane slices, reaching significance for area on Valsalva (P=0.005), sagittal diameter and area on pelvic floor contraction (P=0.009 and 0.044). Method B seemed more strongly associated with symptoms of prolapse than Method A (P=0.008 vs P=0.027).
  
  
  CONCLUSIONS
  We recommend that hiatal dimensions be measured in rendered volumes whenever possible because this method seems more valid and at least as repeatable. This is probably due to the fact that the plane of minimal hiatal dimensions is non-Euclidean, i.e., warped, which can be compensated for by measuring in a rendered volume of 1-2 cm thickness.
authors.affiliation: Sydney Medical School Nepean, Nepean Hospital, University of Sydney, Penrith, NSW 2750, Australia. hpdietz@bigpond.com
authors.forename: Hans P
authors.initials: HP
authors.lastname: Dietz
authors.forename: Vivien
authors.initials: V
authors.lastname: Wong
authors.forename: Ka Lai
authors.initials: KL
authors.lastname: Shek
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001699:Biometry / Q000379:methods; D005260:Female; D006801:Humans; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging* / Q000473:pathology*; D017773:Pelvic Floor / Q000000981:diagnostic imaging* / Q000473:pathology*; D056887:Pelvic Organ Prolapse / Q000000981:diagnostic imaging*; D011446:Prospective Studies; D015203:Reproducibility of Results; D014463:Ultrasonography; D055815:Young Adult