Anatomical and Sonographical Studies on the Development of Fecal Continence and Sphincter Development in Human Fetuses

Abstract

The aim of this study was to specify the sonographic, anatomical and morphological aspects of the fetal anal sphincter and to compare them with pathological and physiological findings. The sphincter was examined by serial sectioning and staining of embryo and fetal tissue and by real-time ultrasound. Its function was analysed using amniotic fluid digestive enzyme assays in cases of anorectal atresia and cystic fibrosis. Morphological findings indicate that the functional components of the anal sphincter do not differentiate before 30 weeks and therefore do not account for the observed anal continence at 22 weeks. Ultrasound measurements of the sphincter indicate three developmental phases: 1) slow growth from 14 to 19 weeks; 2) rapid growth from 19 to 30 weeks; 3) subsequently, no further increase, but contractions indicative of peristaltism. Amniotic fluid digestive enzyme assays indicate that anal sphincter maturation begins with perforation of the anal membrane at 12 weeks. Comparison of pathological cases (anorectal atresia and cystic fibrosis) suggests two possible explanations of fetal anal obstruction: increasing viscosity of digestive secretion or the presence of the three anal sphincter muscles, even if still immature. Our results clarify the evacuation and retention of meconium during fetal life and the role of the terminal part of the digestive tract, notably the anal sphincter. Prenatal diagnosis of anorectal atresia is therefore possible before 20 weeks of gestation by measurement of amniotic fluid digestive enzymes and ultrasonography, thus enabling better neonatal management.

Development of the external anal sphincter with special reference to intergender difference: observations of mid-term fetuses (15-30 weeks of gestation)

“…Johnson (1914) described that the muscle coat of the anorectum becomes evident around 18 weeks of gestation. It seems to be almost consistent with sonographic observations (Bourdelat et al 2001). Using mid-term fetuses, Fritsch and Fröhlich (1994) demonstrated that fasciae along and around the levator ani became distinct, and that the funnel-shaped, three-dimensional extent of the levator began to show an intergender difference in shape.…”

Fetal extraperitoneal rectal perforation: a rare neonatal emergency

“…This concept has, in recent years, been extensively challenged, and there is now ample evidence that fetal defecation does indeed occur. This has been proven in animal studies using radioisotope labeling [10,11] as well as in human fetuses, using ultrasound [12,13]. Furthermore, the gross distension of the distal gut in cases of anorectal malformation and colonic atresia suggests that this is the sequel to obstructed fetal defecation.…”

Sonographic evaluation of the development of the fetal rectum and anal canal

“…Zalel et al 10 measured the fetal descending colon and rectum and reported a nonlinear relationship with menstrual age (R 2 of 0.848 and 0.831, respectively) with a maximum colon diameter of 18 mm. Bourdelat et al 15 also studied the US appearance of the fetal anal sphincter. US measurements and regression curves of the fetal anal canal and rectum indicated that these organs underwent a rapid growth in the second trimester and the early third trimester, but increased less rapidly afterwards.…”