Ch11-F07416.qxd 8/28/06 10:38 AM Page 223 Abdominal and abdominal-wall 11 abnormalities C H A P T E R David W. Pilling ■ Introduction Adrenal masses Adrenal haemorrhage ■ Normal appearances Neuroblastoma ■ Normal variants, pitfalls and artefacts Extralobar pulmonary sequestration Uterus and vagina ■ Anterior abdominal-wall appearances Bowel abnormalities List of conditions Stomach Exomphalos Duodenal atresia Gastroschisis Jejunal and ileal atresia Limb–body-wall complex Meconium ileus Ectopia cordis Meconium peritonitis Cloacal and bladder exstrophy Large bowel pathology ■ Abdominal abnormalities Persistent cloaca Normal anatomy Hirschsprung’s disease Bright bowel ■ Intra-abdominal abnormalities Megacystis microcolon intestinal hypoperistalsis Liver syndrome (MMIH) Gall bladder Sacrococcygeal teratomas Choledochal cysts Ascites Spleen Intra-abdominal calcification Intra-abdominal cysts Posterior abdominal-wall tumour INTRODUCTION been undertaken in virtually all ultrasound departments using routine serum alphafetoprotein Abdominal-wall abnormalities are one of the screening. Even though the primary aim of this commoner fetal abnormalities demonstrated by screening was to exclude neural-tube defects, ultrasound. They were recognized early in the anterior abdominal-wall defects as a group are the development of fetal ultrasound because disturbance second commonest anatomical cause for raised of the abdominal-wall contour in the region of the serum alphafetoprotein. The spectrum of anterior cord insertion was demonstrated even by static abdominal-wall defects extends from the very B-mode scanning before real time was available. minor exomphalos with bowel herniating into the Since many of these abnormalities cause a rise in base of the cord to the most major defects, including the serum alphafetoprotein, a specific search for the pentalogy of Cantrell and body-stalk defect or abdominal-wall abnormalities as a cause for this has early amnion rupture sequence. 223 Ch11-F07416.qxd 8/28/06 10:38 AM Page 224 NORMAL APPEARANCES ANTERIOR ABDOMINAL-WALL APPEARANCES The anterior abdominal wall is best demonstrated in axial section.The anterior abdominal wall is clearly List of conditions outlined by amniotic fluid on its external surface with the site of the cord insertion being clearly • Exomphalos demonstrated. The lowest part of the anterior • Gastroschisis abdominal wall is sometimes obscured by the flexed • Limb–body-wall complex/early amnion rup- legs with assessment of the anterior abdominal ture sequence wall below the cord insertion sometimes being • Ectopia cordis (including pentalogy of extremely difficult, whatever approach is utilized. A Cantrell) midline, sagittal view of the fetus will sometimes • Cloacal and bladder exstrophy. give better views of this area but this is not always feasible. The internal aspect of the anterior abdominal wall can be difficult to see clearly Exomphalos because of the similar echodensities of the anterior abdominal wall and adjacent liver and bowel. This Exomphalos occurs in about 0.1 to 0.3% of becomes more clearly identified as the pregnancy pregnancies,1,2 the incidence increasing with advances. maternal age. • Abdominal and abdominal-wall abnormalities Exomphalos is an incomplete return of the abdominal contents to the abdominal cavity in early 11 pregnancy. In its minor form this can consist of NORMAL VARIANTS, PITFALLS herniation of a small loop of bowel into the base of AND ARTEFACTS the cord and can be extremely difficult to diagnose. Any transonic area at the base of the cord that is not By 12 weeks’ gestation, the bowel has returned to a blood vessel is almost certainly a small loop of the abdomen so that any herniated abdominal con- bowel in a minor exomphalos.The umbilical arteries tents are abnormal after this time.The exclusion of are seen coursing around the sac and its contents in abnormality of the anterior abdominal wall is diffi- contradistinction to gastroschisis. The most major cult in certain circumstances, particularly where the exomphalos may,indeed, be larger in cross-sectional anterior abdominal wall of the fetus lies adjacent to area than the abdomen.The sac of an exomphalos, the maternal uterus or placenta.This is not a major which consists of peritoneum and amnion, may difficulty with adequate amounts of liquor in the contain any of the abdominal organs, although first and second trimesters since the fetus will usually bowel is most commonly present, but the stomach, turn given time so that the anterior abdominal wall liver and spleen may be partially or entirely present can be checked. With severe oligohydramnios and within the exomphalos. Exomphalos containing anhydramnios and, in particular, with the reduced only bowel are in the minority (10–25%).3,4,5 The mobility of the fetus in the third trimester, exclusion relatively thick sac wall restricts the ‘leakage’ of of an anterior abdominal-wall defect can be very alphafetoprotein and levels are not as raised as in difficult. With extreme oligohydramnios, the dis- gastroschisis.6 There is frequently some free fluid tortion of the anterior abdominal wall can often within the larger exomphalos, which obviously mimic a moderate-sized, anterior abdominal wall communicates freely with the peritoneal cavity defect. Defects in the infra-umbilical portion of the (Fig. 11.1).As the bowel is contained within a sac, it abdominal wall are difficult to exclude with flexion does not become exposed to amniotic fluid and of the fetal femora. Since many of these defects are thus does not become thickened. The relatively associated with bladder abnormalities, presence of wide neck to the sac (Fig. 11.2) seen in exomphalos a normal bladder, even in the absence of clear also contributes to the reduced incidence of bowel demonstration of the anterior abdominal wall, atresias compared with gastroschisis. excludes cloacal exstrophy and thus suggests an Other abnormalities are frequently associated intact lower abdominal wall, but will not exclude with exomphalos. Cardiac malformations are seen 224 exomphalos or gastroschisis. in up to 50%, limb abnormalities in about 30% and Ch11-F07416.qxd 8/28/06 10:38 AM Page 225 Anterior abdominal-wall appearances and is seen in 10% of cases. Other features include macroglossia, gigantism and cystic kidneys.Any fetus with exomphalos should be thoroughly examined for other abnormalities, particularly cardiac mal- formations. With larger exomphalos, the heart is Sac containing often difficult to examine comprehensively.This is free fluid due to the tendency of the heart to rotate, as much of the abdominal contents lie outside the normal abdomen. The fetus also tends to lie on its side, which makes an anterior approach to the heart Bowel quite difficult. The exomphalos itself may also loop impede the view of the heart to some extent. Umbilical cord cysts are sometimes associated with exomphalos and in such cases there is a very high Fig. 11.1 Axial section of the sac of an exomphalos, risk (44%) of trisomy 18. Diagnosis as early as 12 10 containing liver, a loop of bowel and some free fluid. weeks has been described with 3D ultrasound. Ultrasound diagnosed exomphalos in 66–75% of cases7,11 in two large British series from the late 1980s to early 1990s, but accuracy has increased in later years to as high as 86% in one American 12 L series. Misdiagnosis of exomphalos as gastroschisis occurred in 5%.7 In view of the high risk of chromo- some abnormalities all patients carrying a fetus with exomphalos should be offered karyotyping. B Polyhydramnios has been demonstrated in 30% Neck of of fetuses with exomphalos,13 but the cause, whilst sac sometimes related to other abnormalities, is not always clear. The fetus with exomphalos should be examined at intervals throughout the pregnancy, although complications such as bowel atresia are quite uncommon. Rupture of the sac in utero is rare.5,14,15 There is no evidence of improved outcome if the fetus is delivered by caesarean section16,17 and this Fig. 11.2 Sagittal section of fetus with exomphalos, should be reserved for those pregnancies with showing the wide neck of the sac containing liver and obstetric indications for such delivery. some loops of bowel. B, bowel; L, liver. In the absence of other abnormalities, the outcome for a fetus with exomphalos is good, with chromosome abnormalities in 28–36%, mainly surgical repair being feasible in most cases, although trisomies 13 and 18.7 The association of exomphalos sometimes complex, staged, abdominal-wall repairs with bladder exstrophy imperforate anus and spinal are required.The survival in exomphalos is strongly defects is well recognized (OEIS Complex) and is related to the incidence of associated anomalies and one of the rarer causes of nuchal thickening.8 this has to a large extent prevented an improvement Some authors quote a chromosome abnormality in survival in recent years. In the presence of a major rate of 61% at 11–14 weeks’ gestation.2 Chromosome associated anomaly, the survival can be as low as abnormalities are more frequently associated with 20%. Interestingly,whilst large size is associated with small exomphalos containing only bowel (67% a poorer prognosis, this is not a major factor. compared with 16% if liver is also present).1 It is Although in most cases the relative size of the important to differentiate a large exomphalos from exomphalos compared to the abdominal cross- limb–body-wall complex (see below). Exomphalos section remains unchanged, relative increase in size is a feature of the Beckwith–Wiedemann syndrome has been observed in some cases. Relative decrease 225 Ch11-F07416.qxd 8/28/06 10:38 AM Page 226 UC FT FT E E A B Fig. 11.3 (A) Axial section of fetus, showing fetal trunk (FT) with exomphalos (E). Note that the exomphalos is almost the same size as the fetal trunk. (B) Same fetus 4 weeks later, showing relative decrease in the size of the exomphalos (E). At birth, the exomphalos was very small and repair was delayed until 3 months of age.