title: Sonographic evaluation of the development of the fetal rectum and anal canal.
abstract: OBJECTIVE
  To describe the sonographic (US) appearance of fetal anal canal and rectum and establish nomograms of their normal measurements.
  
  
  METHODS
  This was a prospective, cross-sectional study of 524 healthy women (mean age, 27 years; range, 21-37 years) with normal singleton pregnancy between 18 and 40 weeks of gestational age (GA). High-resolution transabdominal US was used to visualize and measure the normal fetal anal canal and rectum.
  
  
  RESULTS
  Satisfactory images and measurements of the fetal anal canal and rectum were obtained in 496 normal fetuses. The diameters of the normal anal canal and rectum were plotted as a function of GA in a sigmoid curve. The curve estimations were expressed by the following cubic regression equations with R(2) of 0.87 and 0.88, respectively (p < 0.001): anal canal diameter (mm) = 18.272 - 2.151 × GA + 0.0095 × GA(2) - 0.0011 × GA(3) , and rectal diameter (mm) = 18.545 - 2.543 × GA + 0.1237 × GA(2) - 0.0016 × GA(3) .
  
  
  CONCLUSIONS
  The fetal anal canal and rectum are visible sonographically between 18 and 40 weeks of GA. The knowledge of their normal US appearance and size from the second trimester of pregnancy onwards may help identify developmental anomalies.
authors: Department of Ultrasound, The First Affiliated Hospital of Fujian Medical University, Fuzhou, 35005, Fujian, PR China.
authors: Yi-Ming
authors: YM
authors: Su
authors: Zhen
authors: Z
authors: Ye
authors: Xiao-Yu
authors: XY
authors: Chen
authors: Xin-Xiu
authors: XX
authors: Liu
authors: Shu-Qiang
authors: SQ
authors: Chen
mesh_terms: D000328:Adult; D001003:Anal Canal / Q000000981:diagnostic imaging* / Q000196:embryology*; D003430:Cross-Sectional Studies; D005260:Female; D005865:Gestational Age; D006801:Humans; D011247:Pregnancy; D011446:Prospective Studies; D012007:Rectum / Q000000981:diagnostic imaging* / Q000196:embryology*; D012044:Regression Analysis; D016216:Ultrasonography, Prenatal / Q000379:methods*