Gastroschisis

Definition

Gastroschisis, which literally means "split abdomen," is a hernia (open fissure) in the muscle and skin of the abdominal wall that allows the contents of the abdominal cavity to be exposed to the outside of the body. The opening is usually 2–5 in (5–12.7 cm) long and located in the median plane of the abdomen to the right of the umbilical cord.

Gastroschisis appears during the fetal period and causes the fetal intestines to be exposed to the amniotic fluid with no covering sac. Because amniotic fluid contains the urine of the fetus, this exposure may irritate the fetal intestines, causing swelling and shortening during development. As fetal development progresses, the opening becomes smaller relative to the size of the intestines. Consequently, the bowel may either become strangulated or malrotated. After the infant is born, the intestines are placed back inside the abdominal cavity and the opening is closed surgically. However the intestines may still pose long-term functional problems because of the previous irritation and formation of adhesions.

Description

Gastroschisis is caused by a defect in the normal fetal developmental pattern. In fetal development, the midgut (intestines) loops out of the abdominal cavity in a normal process known as physiological umbilical herniation. This process begins in the sixth week of fetal development because there is not enough room in the abdominal cavity for the growing liver, kidneys, and intestines. By the tenth week of fetal development, the liver and kidneys have decreased in size and the abdominal cavity has grown. In a normal fetus the intestines return to the abdominal cavity at this time, and the abdominal wall forms around them. In a fetus with gastroschisis, the return of the intestine to the abdominal cavity fails to occur. The pancreas, stomach, liver, spleen, bladder, uterus, ovaries, or fallopian tubes are rarely also herniated. The cause of the failure of the intestines to return to the abdominal cavity is unknown. The attachment of the umbilical cord is normal.

Genetic profile

The cause of gastroschisis is unknown; no definite genetic association has been determined. Chromosomal abnormalities are rarely associated with gastroschisis, and familial occurrence is exceptionally rare. Most genetic centers do not recommend the testing of infants with isolated gastroschisis. The familial cases that have been reported include occurrence in twins. Gastroschisis is not usually seen in association with other types of birth defects. Deformations of the fetal urinary tract can develop because of gastroschisis. These do not represent separate malformations, and genetic testing is not indicated.

A genetically associated issue that may arise is the misdiagnosis of gastroschisis for the distinct condition known as omphalocele . This misdiagnosis occurs in 5% of patients with omphalocele and has serious implications because omphalocele is often associated with chromosomal abnormalities and additional non-gastrointestinal malformations.

Demographics

Gastroschisis is not a common birth defect. It occurs in approximately two infants per 10,000 live births in the United States and internationally. Most cases of gastroschisis are sporadic with no familial association. Abnormalities of the intestines as a direct consequence of gastroschisis are seen in 5% of patients. Gastroschisis occurs slightly more often in males than in females. Young maternal age, maternal drug usage, and origination from a socially or economically disadvantaged background all increase the risk of gastroschisis. Very low maternal weight is associated with three times increased risk for gastroschisis. High maternal intake of nitrosamines found in preserved meat and beer doubles the risk of gastroschisis. High maternal weight reduces risk. A low maternal intake of chemicals called carotenoids found in many fruit and vegetables or glutathione from animal protein causes three to four times increased risk for gastroschisis. Carotenoids and glutathione are antioxidants that have a protective effect on the fetus and decrease oxygen stress or oxygen deprivation. Any factor that reduces blood flow to the fetus, thereby causing oxygen stress, can be a factor in the development of gastroschisis. Maternal intake of aspirin or ibuprofen (found in Advil) causes four to five times increased risk for gastroschisis. Both medications are inhibitors of the cyclooxygenase enzyme and influence blood flow to the fetus. Acetaminophen (found in Tylenol) has no demonstrated association with gastroschisis. Decongestants, especially pseudoephedrine and phenylpropanolamine, more than double the risk because they cause constriction of blood vessels and decrease blood flow to the fetus. Illness and fever have no association with the development of gastroschisis.

Signs and symptoms

A mother carrying a fetus with gastroschisis will not experience any unusual signs or symptoms in early pregnancy.

Gastroschisis may be suspected when maternal serum screening, which is typically performed at 15-20 weeks of gestation, reveals an elevated alpha-fetoprotein level (AFP). Gastroschisis is an open defect in the fetal abdominal wall which allows the leakage of AFP from the fetal tissues into the amniotic fluid. The increased amount of amniotic fluid AFP is absorbed into the maternal circulation and can be easily measured in a maternal serum screening test. An elevated AFP level detected in maternal serum is not indicative of gastroschisis specifically, but this does alert the obstetrician that a detailed ultrasound of the fetus is indicated. An elevated maternal serum AFP level is present in approximately 75 to 80% of cases of gastroschisis. Gastroschisis may also be incidentally detected in the second trimester during routine ultrasonography.

Diagnosis

Ultrasonogram is the primary method of diagnosis for gastroschisis because it is noninvasive, rapid, and allows for real-time fetal monitoring. Gastroschisis is often diagnosed before 20 weeks of gestation by an ultrasonogram that may show some or all of the following: loops of fetal intestines floating exposed to amniotic fluid with or without other organs, signs of intestinal obstruction, or a defect in the middle of the abdominal wall to the right of a normal umbilical cord.

With a transvaginal sonogram, the diagnosis has been made as early as 12 weeks of gestation. The diagnosis may be made difficult by flexed fetal limbs. The detection rate in the United States is approximately 75% with the use of ultrasonogram. Frequent ultrasonograms may be necessary to monitor potential injury to the fetal intestines as the pregnancy progresses. A blood clot around the umbilicus as a result of a traumatic amniocentesis or premature detachment of the placenta may mimic gastroschisis on an ultrasonogram.

Once the infant is born and has received corrective surgery, radiographs and bowel contrast studies may be necessary to diagnose intestinal complications. While these procedures are noninvasive, they expose the infant to a degree of radiation. A computed axial tomography (CAT) scan is not considered a medically suitable method by which to diagnose gastroschisis. Magnetic resonance imaging (MRI) is not usually used for diagnosis due to high expense and limited availability.

Treatment and management

In cases of gastroschisis, the infant is usually delivered in a hospital with a neonatal intensive care unit. If the infant's other organs are mature enough, the child is often delivered at 36, often using a Caesarian section. At birth, infants with gastroschisis die without immediate corrective surgery and intensive hospital care. The infant is given intravenous fluids, and the intact intestinal contents are temporarily placed in a surgical plastic clinging film attached to the infant's stomach. The plastic film helps to prevent infection, heat loss, and dehydration.

If the fissure and intestinal spillage is small to medium, the intestines are re-inserted into the abdominal cavity and the fissure is surgically closed within 12–24 hours after birth. If the fissure is large or complicated then the procedure may occur in stages over several days. A silastic bag (silicone plastic called a silo) is used to gradually return the intestines to the abdominal cavity at each stage. Finally the silo is removed and the skin is surgically closed.

Approximately 48% of infants with gastroschisis are small for gestational age. During the recovery period the infants receive nutrition and fluids intravenously. Once the intestines are able to receive food, infants may begin breast- or bottle-feeding. Normal feedings usually begin by the fourth week from delivery date. However, some infants with gastroschisis have associated complications that require months of intravenous feeding. Infants are discharged from the hospital once they are attaining sufficient weight gain and are followed closely over several months.

Prognosis

The overall prognosis for an infant with gastroschisis without extensive complications is very good. Most deaths occur as a result of premature delivery, infection, and bowel necrosis. The clinical outcome is not correlated with the size of the hernia as estimated using ultrasonography or with the known time of exposure to amniotic fluid. Although the survival rate is high, the postoperative hospitalization is often lengthy with complications. If the intestines sustained damage from exposure to amniotic fluid or from twisting, then the prognosis is of poorer quality. Complications that negatively influence prognosis include intestinal damage, prematurity, fetal growth restriction, and shortening of the gut secondary to irritation. Gastroschisis diagnosed prenatally may resolve in utero, causing the death of portions of the intestines. This may result in a condition known as chronic short gut syndrome with a poor prognosis, including problems with diarrhea, slow weight gain, vitamin or mineral deficiencies, and increased mortality. Spontaneous resolution of gastroschisis and closure of the abdominal hernia have been reported. Gastroschisis may also cause deformations of the fetal urinary tract, resulting in a poor prognosis.

Resources

BOOKS

Moore, Keith L., and T. V. N. Persaud. The Developing Human, Clinically Oriented Embryology, Seventh Edition. New York: Elsevier Science, 2003.

ORGANIZATIONS

Office of Rare Diseases National Institutes of Health 6100 Executive Boulevard, 3B-01 Bethesda, Maryland 20892-7518. (301) 402-4336. Patient Support Groups. <http://ord.aspensys.com/asp/resources/pat_supgrp.asp>.

WEB SITES

California Birth Defects Monitoring Program. California State Health Department and March of Dimes (March 22, 2005). <http://www.cbdmp.org/index.htm>.

Children's Hospital of Philadelphia Center for Fetal Diagnosis and Treatment. (March 22, 2005.) <http://fetalsurgery.chop.edu/gastroschisis.shtml>.

Gastroschisis. Children's Hospital of Boston (March 22, 2005). <http://www.childrenshospital.org/cfapps/A2ZtopicDisplay.cfm?Topic=Gastroschisis>.

Gastroschisis. E Medicine (March 22, 2005). <http://www.emedicine.com>.

Gastroschisis. Medline Plus (March 22, 2005). <http://www.nlm.nih.gov/medlineplus/ency/article/000992.htm>.

National Center for Birth Defects and Developmental Disabilities Conference. Centers of Disease Control and Prevention 2004 (March 22, 2005). <http://www.cdc.gov/ncbddd/conference/NCBDDD%20Program%20Book.pdf>.

Omphalocele and Gastroschisis E Medicine (March 22, 2005). <http://www.emedicine.com>.

Surgeon General's Report 2004—Health Consequences of Smoking. (March 22, 2005.) <http://www.cdc.gov/tobacco/sgr/sgr_2004/pdf/chapter5.pdf>.

University of California San Francisco Fetal Treatment Services. (March 22, 2005.) <http://www.ucsfhealth.org/childrens/medical_services/fetal_treatment/index.html>.

Maria Basile, PhD