You are in: eMedicine Specialties > Radiology > OBSTETRICS/GYNECOLOGY GastroschisisArticle Last Updated: May 23, 2008AUTHOR AND EDITOR INFORMATIONAuthor: Ali Nawaz Khan, MBBS, FRCS, FRCP, FRCR, LRCP, Chairman of Medical Imaging, Professor of Radiology, NGHA, King Fahad National Guard Hospital, King Abdulaziz Medical City, Riyadh, Saudi Arabia Ali Nawaz Khan is a member of the following medical societies: American Institute of Ultrasound in Medicine, Radiological Society of North America, Royal College of Physicians, Royal College of Physicians and Surgeons of the United States, Royal College of Radiologists, and Royal College of Surgeons of England Coauthor(s): Nigel Thomas, MBBS, Vice-Chair, Manchester (North) Research Ethics Committee; Honorary Lecturer, Visiting Professor, University of Salford, UK; Sumaira MacDonald, MBChB, PhD, MRCP, FRCR, Lecturer, Sheffield University Medical School; Endovascular Fellow, Sheffield Vascular Institute; Zahida Sabih, MBBS, MSc; Durre Sabih, MBBS, MSc, Visiting Faculty, Department of Nuclear Medicine, Pakistan Institute Applied Sciences and Nishtar Medical College; Director, Multan Institute of Nuclear Medicine and Radiotherapy Editors: Harris L Cohen, MD, FACR, Vice Chairman/Associate Chairman (Research Activities), Director, Division of Body Imaging, Professor of Radiology, Stony Brook School of Medicine; Visiting Professor of Radiology, Johns Hopkins School of Medicine; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; Karen L Reuter, MD, FACR, Professor, Department of Radiology, Lahey Clinic Medical Center; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; Eugene C Lin, MD, Clinical Assistant Professor of Radiology, University of Washington Medical School Author and Editor Disclosure Synonyms and related keywords: omphalocele, exomphalos, paromphalocele, embryonal ruptured omphalocele, laproschisis, abdominoschisis, full-thickness abdominal fusion defect, abdominal herniation INTRODUCTIONBackgroundGastroschisis represents a herniation of abdominal contents through a paramedian full-thickness abdominal fusion defect. The abdominal herniation is usually to the right of the umbilical cord. No genetic association exists. A gastroschisis usually contains small bowel and has no surrounding membrane. The herniated bowel is not rotated and is devoid of secondary fixation to the posterior abdominal wall. Gastroschisis usually is detected in the second trimester using antenatal sonography.1, 2, 3, 4, 5, 6, 7, 8, 9 The maternal serum alpha-fetoprotein (AFP) level is elevated in 77-100% of mothers. The mortality rate is approximately 17%. Surgical repair should be offered within the first day after delivery to avoid infection. The outcome is no different in infants delivered in tertiary obstetric centers than in infants delivered in smaller peripheral hospitals, although delivery within easy access of a neonatal surgical unit is advised. Cesarean delivery is performed in many mothers of fetuses with gastroschisis, although this does not convey any advantage over vaginal delivery. Related Medscape topics: PathophysiologyControversy exists regarding the cause of gastroschisis. Some authorities suggest that the defect is caused by abnormal involution of the right umbilical vein, resulting in rupture of the anterior abdominal wall at a point of weakness. Others suggest that gastroschisis results from rupture of an exomphalos. Rupture of a small omphalocele and transformation into a gastroschisis has been described in utero. This observation has led to speculation that gastroschisis could represent an omphalocele that ruptures before the somatic components of the anterior abdominal wall become folded. However, the much-increased incidence of associated anomalies in patients with omphalocele does not support this theory. Another theory for the etiology of gastroschisis is premature interruption of the right omphalomesenteric artery, which results in ischemic injury to the anterior abdominal wall through which herniation of abdominal contents occurs. This artery persists under normal circumstances. The use of recreational drug use has been quoted as a significant risk factor for gastroschisis.10 Maternal hair analysis proved an acceptable and valuable method of independently verifying recreational drug use. A bowel diameter greater than 17 mm usually represents significant bowel dilatation, and diameters greater than 11 mm are usually associated with a greater number of postnatal bowel complications. Sonographic findings of bowel abnormalities are associated with difficult abdominal wall repair and an increased incidence of complications. Tibboel and associates reviewed a number of studies in which prenatal and postnatal autopsy material showed no evidence of abnormal histologic results in ganglion cells or in the myenteric nervous system to explain the motility disorder that accompanies some cases of gastroschisis.12 Tibboel et al also showed that a fibrous peel surrounds the herniated bowel beginning at approximately 30 weeks' gestation. Ischemic changes in the bowel loops are usually not seen in fetuses with gastroschisis who were aborted before 30 weeks' gestation. However, ischemic changes are seen in postnatal infants who have hypoperistalsis, which suggests that bowel vascular compromise may occur at the abdominal wall defect late in pregnancy. The cause of bowel injury in gastroschisis has been controversial for several years. Experimental animal models have shown that when bowel is exposed to allantoic contents, it thickens, becomes edematous, and develops a fibrous peel, whereas bowel exposed to amniotic fluid alone develops normally. Results from animal models have led to the suggestion that the urine in amniotic fluid causes the bowel damage.13 The fibrous peel consists of type 1 collagen and fibrin, and it usually dissolves after surgical repair. Some authors suggest that the peel itself may cause the bowel motility disorder. Another animal study showed that bowel damage in gastroschisis at least partially depends on meconium exposure in utero.14 The authors of this study suggested that the increasing evidence of physiologic in utero defecation supports the hypothesis that bowel damage in gastroschisis may be meconium dependent. Gastroschisis is classified as an open fetal defect by virtue of the finding that it is not covered by skin. Open fetal defects allow diffusion of AFP from the fetal circulation into amniotic fluid. Because the fetal AFP level is 200-300 times as high as the concentration in amniotic fluid, the diffusion is not only reflected as higher amniotic fluid AFP levels, but it is also reflected in higher maternal serum AFP levels, albeit to a lesser degree. Major malformations and chromosomal anomalies are common in association with omphalocele. However, these anomalies are rare in gastroschisis, with the exception of intestinal atresia, which appears to be a direct consequence of in utero herniation. Bowel anomalies occur in 5% of patients with gastroschisis and include intestinal atresia or stenosis resulting from vascular compromise. Rarely, ectopia cordis has been recorded.6 Chromosomal anomalies in gastroschisis are extremely rare, and most centers do not recommend karyotyping in infants with gastroschisis. FrequencyUnited StatesThe incidence of gastroschisis is 1.75-2.5 cases per 10,000 live births. Most cases are sporadic, although a few familial cases have been reported. Occurrence in twins has been reported. InternationalThe incidence is the same as in the United States. Mortality/MorbidityAlthough reported survival rates are good in gastroschisis, the postoperative hospital stay is often lengthy, and complications occur frequently, especially complications related to the gastrointestinal tract.15 Evidence of bowel damage, such as atresia, necrosis, or severe dilatation or thickening of the bowel, or the inability to close the abdominal defect primarily indicates a poor prognosis. Prenatally, bowel obstruction, peritonitis, bowel perforation, prematurity, and fetal growth restriction may be complications of gastroschisis. Postnatally, malrotation, small bowel atresia or stenosis, bowel infarction, prolonged intestinal motility dysfunction, necrotizing enterocolitis, chronic short-gut syndrome, and hyperalimentation hepatitis may occur. Deformations of the fetal urinary tract can develop secondary to gastroschisis. These do not represent separate malformations, and karyotyping is not indicated. When hydronephrosis is present, ongoing urologic evaluation of the neonate is indicated. Survival rates after surgery are 87-100%. Mortality rates are 17%, and most deaths occur as a result of premature delivery, sepsis, and bowel infarction. The clinical outcome cannot be correlated with the size of the abdominal defect as estimated using sonography or with the known time of exposure to amniotic fluid. Gastroschisis diagnosed antenatally can resolve in utero—causing necrosis of portions of the small and large bowel, leading to short-bowel syndrome and increased mortality and morbidity rates. Spontaneous resolution of gastroschisis and closure of the anterior abdominal wall defect have been described.16, 17, 18, 19 Associated anomalies are more uncommon than in omphalocele. The reported overall incidence of associated anomalies is 7-30%. The anomalies are not related directly to the defect and include anencephaly, cleft lip and palate, ectopia cordis, atrial septal defect, diaphragmatic hernia, scoliosis, syndactyly, and amniotic band. These anomalies add to the morbidity. Improvements in short-term results of gastroschisis treatment can be attributed to more recent developments in prenatal diagnosis and the advancements of centralized perinatal care. There has also been considerable improvement in long-term results of babies treated for gastroschisis. The initial gastrointestinal problems and developmental delays are made up during the first 2 years of life, and therefore, a more optimistic prenatal counseling can now be given. SexA slight male predilection exists. AgeThe diagnosis can often be made by using antenatal sonography before 20 weeks' gestation. With transvaginal sonograms, the diagnosis has been made as early as 12 weeks' gestation. AnatomyThe anterior abdominal wall and umbilical cord insertion are readily recognized on antenatal scanning because the wall provides a direct interface between itself and the amniotic fluid. The anterior abdominal wall is best demonstrated by axial scans. Assessment of the lower anterior abdominal wall is occasionally made difficult by flexed fetal limbs. The inner aspect of the anterior abdominal wall is difficult to see because its echodensities are identical to the remainder of the abdominal viscera unless fetal ascites is present. Gastroschisis results from herniation/evisceration of small bowel into the amniotic cavity through a small defect (2-5 cm) in the right paraumbilical region. Reportedly, the defect can be located in the left paraumbilical region, but this site is extremely rare. No covering membrane exists. The large bowel (common), pancreas, stomach, liver (rare), spleen, bladder, uterus, ovaries, and fallopian tubes may also be herniated. The attachment of the umbilical cord is normal. Clinical DetailsGastroschisis is found incidentally or because of an elevated maternal AFP level. Rarely, polyhydramnios may prompt an antenatal sonographic examination. Fetal growth restriction is a frequent association. Oligohydramnios is rare. Chromosomal anomalies are not associated with gastroschisis, and familial occurrence is exceptionally rare. Approximately 50% of fetuses with gastroschisis are small for their gestational dates. Fetal abdominal circumference, which is regarded as a standard reference for assessment of fetal size, does not apply to this group of fetuses; therefore, obstetric management may be difficult. The presence of the bowel in amniotic fluid may affect cardiotocographic monitoring. As a result of the difficulty in monitoring fetal maturity and fetal well-being, cesarean delivery is performed with many fetuses, although this does not convey an advantage in terms of fetal mortality or morbidity. Postnatal management requires a sterile covering of cling film over the herniated viscera to prevent infection, heat and evaporative loss, and the need for immediate transfer to a neonatal surgical unit.23 Hospital stays for these infants are lengthy, and although most of these infants are usually on normal feedings by 4 weeks from the date of delivery, many affected infants require months of intravenous feeding because of the many bowel complications associated with gastroschisis. Preferred ExaminationAntenatal sonography is the key imaging examination available, with detection rates of 70-72%. Prenatal sonography is the primary imaging modality in pregnancy because it is noninvasive, is rapid, and allows real-time fetal examination. Plain radiographs and bowel contrast studies may be indicated in the postnatal postoperative period to assess bowel complications. Limitations of TechniquesSonography remains operator dependent, and artifacts are a problem. Despite the straightforward nature of the defect, a diagnosis of gastroschisis can be missed. Misdiagnosis of exomphalos as gastroschisis has occurred in 5% of patients. This misdiagnosis has serious implications because exomphalos is often associated with chromosomal and other severe anomalies and karyotyping is not performed in patients with gastroschisis. In one case series, gastroschisis was misdiagnosed as exomphalos at a rate of 14.7%. This misdiagnosis results in unnecessary amniocentesis, which exposes the fetus to the risks involved in amniocentesis and which also exposes the mother to psychological trauma. Assessment of fetal size by using abdominal circumference measurements is difficult in the presence of gastroschisis. Postnatal plain radiographs and bowel-contrast studies lack specificity and expose the infant to a radiation burden. However, Siemer et al have developed a sonographic weight formula for fetuses with abdominal wall defects.11 The authors evaluated their formula in a group of 97 fetuses with either gastroschisis or omphalocele and concluded that it provided a significantly greater accuracy in estimating fetal weight than a more commonly used formula. More data will be necessary to determine the utility of Siemer et al's formula. DIFFERENTIALSIleal Atresia Omphalocele Other Problems to Be ConsideredPhysiologic bowel herniation Physiologic herniation occurs at 10-13 weeks. The best method for differentiating this from an omphalocele is to obtain a repeat sonogram after 15 weeks' menstrual age. A large defect with the liver exteriorized indicates an omphalocele at any gestational age. Omphalocele Omphalocele is herniation of a variable amount of abdominal viscera through a defect (2-10 cm) at the base of the umbilical cord. A membrane covers the herniation, differentiating it from gastroschisis, and the umbilical vessel inserts into the apex. Association with liver herniation, ascites, cardiac defects, and chromosomal anomalies is frequent. Association with holoprosencephaly and limb anomalies is occasional. The incidence of chromosomal abnormalities is high at approximately 33%. The prognosis is related to the karyotype, associated abnormalities, and contents of the omphalocele.24 Umbilical hernia Umbilical hernia results from a defect in the linea alba; the protruding bowel is covered by subcutaneous tissues and skin. Umbilical hernia is common in the first months in 20% of black neonates and in 3% of white neonates, as well as common in premature infants, namely, in more than 5% of premature infants weighing less than 1500 g. Sonographic findings include a prominent bulge of the anterior abdominal wall that may contain omentum and/or bowel, which may protrude into the umbilical cord. Amniotic fluid AFP levels may be elevated when the bowel is herniated into the umbilical cord. Amniotic band syndrome Amniotic band syndrome (ABS) is a common cause of an abdominal wall defect. Involvement of the abdominal wall may produce appearances similar to gastroschisis. However, an atypical location of the abdominal wall defect suggests the diagnosis of ABS. Membranes contiguous with such a defect may be identified. Bladder extrophy Sonographically, bladder extrophy may present as an external, well-defined, solid or complex mass immediately superior to the fetal genitalia. Prolonged and repeated scans fail to reveal the fetal bladder. The renal collecting system and ureters need not be dilatated, and unilateral or horseshoe kidneys may be found. Uterine and adnexal anomalies are relatively frequent. The pubis is abnormally wide, and the umbilical cord insertion may be abnormal. Cloacal extrophy Cloacal extrophy consists of a low omphalocele; bladder or cloacal extrophy; and, frequently, other caudal anomalies. These other conditions may include meningomyelocele anal atresia and lower limb anomalies. Most affected fetuses have a single umbilical artery. Sonographic findings include a low anterior abdominal mass below the umbilical cord that is associated with an absent urinary bladder. Limb-body-wall complex Limb-body-wall complex (LBWC) is a lethal condition with a severe anterior abdominal wall defect. The defect is placed laterally and involves the size of the umbilical cord insertion. The abdominal contents lie outside within a sac of amnion and mesoderm. Association with congenital heart defects (CHDs), cranial anomalies (encephalocele), limb abnormalities, and scoliosis is frequent. Chromosomal defects are usually not present. Cavernous hemangioma Cavernous hemangiomas are most frequently found over the lower body and are often associated with Klippel-Trenaunay-Weber syndrome, which is diagnosed in the presence of multiple surface masses, producing limb hypertrophy. Hydrops may occur. Thoracoabdominal pentalogy of Cantrell Ectopia cordis associated with a ventral wall defect should prompt the diagnosis of pentalogy of Cantrell. The syndrome is often associated with other anomalies. Blood clot A blood clot around the umbilicus secondary to traumatic amniocentesis or abruptio placenta may mimic gastroschisis. RADIOGRAPHFindingsConventional radiography is no longer used in the assessment of fetal abnormalities because this imaging modality exposes both the mother and fetus to an unnecessary radiation burden. However, conventional radiology does have a role in postnatal evaluations, particularly in infants in the postoperative period. A minority of infants develop complications, such as necrotizing enterocolitis, short-bowel syndrome, persistent bowel dysfunction, and cholestatic jaundice. Investigation by means of plain imaging, contrast studies, and sonographic examinations are necessary and helpful in these patients. Plain images reveal bowel-wall thickening, luminal dilatation, and generalized abdominal distention. A small-bowel enema is considered superior to conventional follow-through in distinguishing mechanical obstruction from functional obstruction in infants with persistent bowel dilatation.25 Degree of ConfidenceConventional radiographs demonstrate poor resolution between maternal parts and fetal parts, and they have no place in antenatal management. Plain-film and contrast radiography are excellent noninvasive procedures for use in the investigation of the postoperative persistent gaseous distention in infants, and plain radiography remains the most useful noninvasive procedure in the radiographic diagnosis of small bowel obstruction despite its limited sensitivity (50-66%). When plain radiographic findings are combined with the clinical history and results of physical and laboratory examinations, a confident diagnosis of small bowel obstruction can usually be made. False Positives/NegativesPlain radiographs cannot always be used to differentiate mechanical obstruction from functional obstruction. Differentiating an adynamic ileus from a mechanical small bowel obstruction may be particularly difficult, especially in the immediate postoperative period. Eventually, most intestinal obstructions (especially when strangulation is present) may lead to an adynamic ileus, which is associated with perforation and peritonitis. Under these circumstances, gas may appear in the small bowel proximal to the obstruction or may be retained in the atonic colon, leading to diagnostic confusion. Little or no gas within the small bowel may lead to a false-negative diagnosis. CT SCANFindingsThe computed tomography (CT) scan appearance of fetal gastroschisis discovered as an incidental finding was reported in a 25-year-old woman who was pregnant and who underwent CT scanning for blunt abdominal trauma.26 However, the high radiation burden makes CT scanning unsuitable for use in the assessment of fetal anomalies. MRIFindingsIn general, magnetic resonance imaging (MRI) has not been used in the diagnosis of gastroschisis, partly because MRI is time consuming, expensive, and limited in availability. Moreover, to date, the image quality has been poor. Some of these problems have been overcome with the use of ultrafast sequences; therefore, MRI can be used as an adjunct to sonography, especially in patients in whom sonographic findings are unclear or degraded as a result of obesity or oligohydramnios.1, 27, 28, 29, 30, 31 MRI findings frequently add information beyond that available with sonograms. This information commonly changes patient counseling and, at times, patient treatment.1, 27, 28, 29, 30, 31 MRI does provide a global view of the fetus and analysis of the anatomy in multiple planes. This imaging modality is useful in the diagnosis of intestinal obstruction and detection of microcolon, malrotation, and volvulus. Degree of ConfidenceFetal MRI during the first trimester remains controversial secondary to biosafety issues, and its use is limited because of the diminutive fetal size. However, fetal abdominal masses are well depicted on MRIs, and the performance of MRI is not affected by diminished amounts of amniotic fluid. False Positives/NegativesSufficient experience has not yet been gained in the diagnosis of anterior abdominal wall defects with MRI to determine the existence of false-positive findings. ULTRASOUNDFindingsPrenatal sonography is the primary imaging modality in pregnancy because it is noninvasive and rapid, and because it allows real-time fetal examination. In suspected gastroschisis, the following sonographic features suggest the diagnosis:
Related eMedicine topics: Degree of ConfidenceThe sensitivity of abnormality detection using sonography is 75% for gastroschisis and 77.3% for omphalocele. Ultrasound sensitivity in the diagnosis of gastroschisis has improved considerably over the past 2 decades. False Positives/NegativesOther anterior abdominal wall defects may mimic gastroschisis, but with the use of modern ultrasound equipment, confusion should not arise. When the liver is intra-abdominal in an omphalocele, a false diagnosis of gastroschisis may be entertained; however, the many anomalies associated with omphalocele should indicate the correct diagnosis. Bladder extrophy, body-stalk anomaly, and periumbilical blood clots are other mimics of gastroschisis (see Differentials and Other Problems to Be Considered). INTERVENTIONAmniocentesis may be required in patients in whom omphalocele cannot be differentiated from gastroschisis. This is particularly the case when liver herniation occurs in gastroschisis. Amniocentesis may also be performed for karyotyping in the unusual event that other anomalies are present in association with gastroschisis. Amnioinfusion has been used to improve the outcome in fetuses affected by gastroschisis.33 The mechanism by which this improvement results from a reduction of inflammatory change remains to be proved. Another indication for amnioinfusion is in fetuses with gastroschisis complicated by oligohydramnios.34 This is a particularly high-risk group in which serial sonography and computerized fetal heart rate monitoring are necessary during the third trimester. In selected fetuses with gastroschisis and severe oligohydramnios, serial amnioinfusion may be beneficial. Medical/Legal Pitfalls
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