body stalk anomaly
incidence is about 1 in 14000 pregnancies. the anomaly arises from a failure of the body stalk to develop normally and the absence of umbilicus and umbilical cord leads to the hernial sac containing bowel, liver and other viscera being directly adherent to the placenta. the gross distortion of the spine and lower limbs is presumably secondary although other closure problems such as neural tube defects may be seen. the condition is fatal.
the appearances are typical with the fetus apparently adherent to the placenta. the most striking impression is of a fetus with a normal upper trunk but grossly abnormal appearance below the chest. the spine is frequently abnormally rotated along its axis, with marked lateral curvatures and/or severe scoliosis. hemivertebrae may be present. the extremities can adopt very abnormal positions and angles. different patterns of limb defects are seen, including amputations that resemble those of amniotic band syndrome. the defects are usually asymmetric, with the lower extremities more commonly involved that the upper ones. clubfeet are noted in half of the cases. elevated maternal serum alpha-fetoprotein levels are described.
it is important to distinguish anterior abdominal wall defects from body stalk anomalies. in gastroschisis the bowel lies free and other anomalies are very rare (5%), the umbilicus can be identified and the fetus is free floating in the amniotic cavity. isolated exomphalos does not cause distortion of the lower trunk and there is an obvious umbilical cord. in amniotic band syndrome disruptions of fetal anatomy occur but the abdomen is usually normal. in the pentalogy of cantrell the heart is also included and there is a diaphragmatic hernia.
the upper trunk and head seem normal but as the examination continues down the trunk the gross disruption from about mid- thorax becomes obvious
the spine is distorted over its lower half
hemivertebrae may be seen
the fetus appears adherent to the placenta
the umbilical cord is very short
the lower limbs are often rotated and difficult to trace
absent or hypoplastic limb bones
transverse limb amputations may be noted
- jauniaux e, vyas s, finlayson c, moscoso g, driver m, campbell s early sonographic diagnosis of body stalk anomaly prenat diag 10: 127-132
- allan ld, sharland g, cook a in: color atlas of fetal cardiology mosby-wolfe: london, p59-69