Alejandro Garcia, MD and William Middlesworth, MD

Prenatal Consultation and Fetal Interventions

Numerous structural congential malformations can be detected prenatally, including the following: anencephaly, encephalocele, spina bifida, hydrocephalus, transposition of the great arteries, hypoplastic left heart syndrome, limb reduction defect, bilateral renal agenesis, diaphragmatic hernia, omphalocele, and gastroschisis. Prenatal diagnosis of gastrointestinal atresia and obstruction is suggested by the presence of polyhydramnios and dilated bowel loops, which develop proximal to the obstructed site. The overall prenatal detection rate for gastrointestinal obstruction is 34%; it is 52% for duodenal, 40% for small intestine, 29% for large intestine, 25% for esophageal, and 7% for anal atresia.

Congenital diaphragmatic hernia (CDH): A few centers are reporting early trials using techniques that permit expansion of the affected lung prenatally. Most trials involve internal or external obstruction of the trachea, which allows expansion of the lungs in utero. Trials have been limited by concerns regarding maternal safety, premature labor, and miscarriage. The results of recent randomized control trials using tracheal occlusion show survival benefits for fetuses with severe CDH compared with those receiving standard postnatal management, but with higher rates of premature rupture of membranes and preterm delivery. Multicenter trials of temporary tracheal occlusion are planned.

Myelomeningocele: Prenatal repair for myelomeningocele reduced the need for shunting and improved motor outcomes at 30 months but was associated with maternal and fetal risks.

Twin-twin transfusion syndrome: In monochorionic twins with evidence of unequal distribution of blood flow between fetuses, fetoscopic laser surgery can be performed to disconnect some of the communicating blood vessels in utero. This procedure stops the flow of blood from the donor to the recipient and halts the progression of twin-twin transfusion. Occasionally, one twin is lacking a functioning cardiac system, and reversed arterial perfusion occurs, with blood flow traveling from the normal twin to the abnormal twin leading to cardiac failure in the normal twin; this is known as the twin reversed arterial perfusion (TRAP) sequence. Fetal laser surgery can be used to interrupt blood supply to the nonviable twin.

Congenital cystic adenomatoid malformation (CCAM): Infants with prenatally diagnosed CCAM with hydrops are at very high risk for fetal or neonatal demise. This has led to the performance of either fetal surgical resection of the massively enlarged pulmonary lobe (fetal lobectomy) for cystic or solid lesions or thoracoamniotic shunting for lesions with a dominant cyst. It was discovered that administration of betamethasone, performed preoperatively to induce fetal lung maturity, also caused regression of these lesions. The role for fetal intervention in fetuses with CCAM and hydrops refractory to medical treatment is currently unknown.

Sacrococcygeal teratoma: Fetuses with evidence of hydrops have been treated with trials of radiofrequency ablation of feeding vessels or fetal resection of the teratoma. The benefit of these treatment modalities is unknown. ¹²³⁴⁵

Congenital Diaphragmatic Hernia (CDH)

The posterolateral portion of the diaphragm is the last to form, when the pleuroperitoneal canal closes. If it has remained open by the time the extruded midgut returns to the peritoneal cavity between the ninth and tenth weeks of gestation, the viscera will pass into the chest, and a CDH will result.

Although affected infants will occasionally be asymptomatic, they usually present with moderate to severe respiratory distress. There are diminished breath sounds on the side of the hernia and usually a shift of the heart and trachea to the opposite side. The abdomen is characteristically scaphoid. Increasingly, CDH is being diagnosed in utero by antenatal ultrasound.

Many studies have looked at lung-to-head ratio (LHR, the ratio of contralateral lung diameter to head circumference measured during 24-28 weeks’ gestation), liver position, and mediastinal shift as tools to predict mortality. Although reports have been conflicting, LHR is increasingly used to predict mortality in infants with left-sided CDH. Recent studies of infants with left-sided CDH have shown that an LHR value of less than 0.85 carries a very poor prognosis and is predictive of mortality 95% of the time. An LHR greater than 1.4, however, is virtually always associated with survival. ⁶⁷

The most useful tool is a chest x-ray, which will usually demonstrate air-filled intestinal loops in the chest (once the baby has had time to swallow air); the diaphragmatic contour on the affected side is obliterated, and the mediastinum is often shifted to the opposite side ( Fig. 19-1). In babies with the less common right-sided CDH, the findings may be more confusing, with opacification of the right lower chest from the herniated liver; in these cases, ultrasonography will provide clarification.

Endotracheal intubation with mechanical ventilation, supplemental oxygen, and orogastric decompression are used immediately in the presence of respiratory distress. Positive pressure ventilation through a face mask is not recommended because gas will enter the gastrointestinal tract and further compress the lungs. Exogenous surfactant, high-frequency ventilation, and inhaled nitric oxide are occasionally used but have no proven benefit. Barotrauma to the lungs caused by aggressive ventilation should be avoided. The level of PCO₂ may be allowed to rise to 50 to 60 mmHg (permissive hypercapnia) as long as the arterial pH remains greater than 7.25. The arterial PaO₂ should be kept between 50 and 80 mmHg but not above 100 mm Hg. ⁸⁹¹⁰

ECMO, the use of a modified heart–lung machine to provide cardiorespiratory support independent of the lungs, may be used before or after corrective surgery if the baby does not respond to the ventilatory therapy described previously. Supporting an infant on ECMO and delaying surgery allow time for pulmonary hypertension to improve while avoiding lung damage caused by barotrauma and excessive oxygen concentrations from the ventilator. The availability of ECMO may be associated with an increased chance of survival among infants with CDH. ¹¹

CDH was once thought to be a surgical emergency, but now repair is deferred intentionally to allow for normal physiologic changes to occur in the postnatal circulation. Current recommendations are for resuscitation followed by a period of stabilization until the neonate’s clinical condition improves. If the baby requires ECMO preoperatively, surgical repair is usually delayed until the ECMO settings have been lowered and the patient is considered ready to come off ECMO, but before decannulation. ¹²¹³

Several institutions are now reporting survival rates of 80% to 90% (compared with historical survival rates of 50% to 60%) for infants with left-sided CDH and approximately 55% for right-sided CDH. Most of the improvement is believed to be attributable to referral to high-volume tertiary care centers for management of these babies, as well as minimization of iatrogenic pulmonary injury through the avoidance of high ventilatory settings. However, many single institution–based reports are confounded by case selection bias, which fails to consider those CDH patients who do not reach referral centers. This is referred to as the “hidden mortality” of CDH. ^14151617

ECMO

ECMO support can provide heart–lung bypass (venoarterial support) or simply lung bypass (venovenous support). For infants with signs of hemodynamic instability such as in sepsis, heart failure, or CDH, venoarterial support is most commonly used. A cannula is placed into the right atrium via the right internal jugular vein for venous return, and a second cannula is placed into the aortic arch by way of the right common carotid artery for arterial delivery. In cases of isolated respiratory failure such as in meconium aspiration, venovenous support can be used. A double-lumen cannula is placed into the right internal jugular vein, and the tip of the cannula lies in the right atrium. Blood is removed from the right atrium, gas exchange occurs in the ECMO circuit ( Fig. 19-2), and the blood is returned to the right atrium.

The selection of neonates as potential ECMO candidates remains controversial and varies according to the institution. Relative contraindications that must be considered are the presence of an irreversible cardiopulmonary disorder, coexisting anomalies incompatible with life (e.g., trisomy 13 or 18), uncorrectable bleeding diathesis, and existing intracranial hemorrhage (above grade II). Infants who are younger than 35 weeks’ gestation are at a high risk of developing intracranial hemorrhage with systemic heparinization.

Vascular Anomalies

Vascular anomalies represent a spectrum of conditions that result from focal aberrations of blood vessel development. According to the International Society for the Study of Vascular Anomalies (ISSVA), vascular anomalies are classified as hemangiomas (proliferating endothelial tumors) and congenital vascular malformations ( Table 19-1). Hemangiomas are proliferative lesions that typically undergo periods of rapid growth and involution after birth. Hemangiomas can be distinguished from congenital vascular malformations by immunoreactivity for the glucose-1 transporter (GLUT-1). Congenital vascular malformations have been defined as lesions that are present at birth that do not further proliferate postnatally, although more recent data suggest that remodeling and growth can occur in some settings. Congenital vascular malformations can be subclassified further according to hemodynamic characteristics. Fast-flow lesions include arteriovenous fistulas and malformations, and slow-flow lesions include venous, lymphatic, and mixed malformations. ¹⁸¹⁹²⁰

Formerly known as cystic hygromas, lymphatic malformations are congenital vascular anomalies that can develop in areas of lymphatic drainage and are occasionally diagnosed in utero. Lymphatic malformations are hypothesized to develop from primitive lymphatic sacs that arise from mesenchyme or embryologic endothelial networks. Contraction of thickened muscular linings may increase intramural pressure and cause cystic dilation. Children can present with macrocystic or microcystic disease or a mixture of the two. Lymphatic malformations most commonly occur in the cervicofacial and cervicothoracic regions, although they can arise in virtually any location. They can cause complications such as obstruction of airway or vital organs, recurrent infection, bleeding, destruction of involved bones, and disfigurement.

Treatment of hemangiomas is selective, with intervention reserved for lesions that threaten vital functions, such as vision or respiration, or cause deformity or pain ( Box 19-1). Current first-line medical therapy for common hemangiomas of infancy has shifted in recent years from corticosteroids to beta blockers. The molecular mechanisms of response are still not fully defined, but both agents appear to induce or accelerate involution.

Treatment of congenital vascular malformations is highly dependent on the type of lesion and its location. Some lymphatic malformations, such as unilocular macrocystic malformations of the neck, may be amenable to surgical excision; other macrocystic lesions can often be treated successfully by sclerotherapy with doxycycline or other agents. Arteriovenous and venous malformations are generally treated using interventional radiologic techniques, such as transarterial embolization or sclerotherapy. Others, such as Klippel–Trénaunay–Weber syndrome, are in general treated conservatively and supportively. Current trials examining the role of oral therapy for diffuse, extensive, refractory, and recurrent lymphatic or mixed lesions with agents such as sirolimus [ http://clinicaltrials.gov/ct2/show/NCT00975819] and sildenafil are currently under way. ²¹²²

The ex utero intrapartum treatment (EXIT) procedure is available at selected centers for fetuses with evidence of airway compression in utero. A standard cesarean section is performed, and the baby is partially delivered but remains attached by its umbilical cord to the placenta. While the infant is maintained on placental circulation, an airway can be established, the mass resected, or extracorporeal life support can be initiated. Studies have shown that the EXIT procedure can be performed with minimal maternal morbidity and effective rescue of threatened infants. ²³

Congenital Lung Abnormalities

Increasingly, lung malformations are being discovered in utero by ultrasonography. These anomalies may be asymptomatic and discovered incidentally on an imaging study for another condition. They may produce symptoms related to respiratory compromise in neonates. Later in life, symptoms may be attributed to compression (e.g., chest pain, wheezing, dyspnea) or infection (e.g., chest pain, fever, cough, dyspnea). Occasionally, cross-sectional imaging is necessary because these lung malformations might be missed with traditional radiographs.

The treatment is almost always surgical excision, although the timing of surgery remains controversial. Increasingly, thoracoscopic resection is safe and feasible in infancy. CPAMs may resolve after a course of prenatal steroids with bethamethasone given during the second trimester. Some evidence suggests that CPAMs may develop into pleuropulmonary blastoma if left untreated. Asymptomatic congenital lobar emphysema may be observed, and many cases will regress over time. ²⁵

Esophageal Atresia and Tracheoesophageal Fistula

The precise etiology is unknown, but it is believed that the septation process that normally separates the foregut into the trachea and esophagus by the seventh week of gestation is incomplete. The more rapidly dividing trachea separates the upper and lower portions of the esophagus into discontinuous segments.

Esophageal atresia and tracheoesophageal fistula usually occur in combination but may occur in isolation.

VACTERL is an acronym for a combination of congenital abnormalities that frequently occur together; the presence of one or more should prompt a search for the others. These anomalies may involve the following structures:

Infants with esophageal atresia drool excessively because they cannot swallow their oral secretions. If feeding is attempted, the baby may develop respiratory distress as a result of aspiration from the blind-ending upper esophageal pouch. The clinician should attempt to pass a nasogastric tube, which will encounter resistance. A chest radiograph will demonstrate the tip of the tube coiled in the upper chest, confirming the diagnosis of esophageal atresia. Air visualized in the gastrointestinal tract indicates the presence of a fistula distal to the trachea, whereas a gasless abdomen implies an isolated esophageal atresia. Infants with an isolated tracheoesophageal fistula may exhibit symptoms later in life related to soiling of the lungs and respiratory distress.

The prevention of aspiration is most crucial. A nasogastric or orogastric sump tube is placed into the blind upper esophageal segment and connected to suction while the baby is maintained in a head-up position to minimize gastroesophageal reflux into the distal fistula. Intravenous fluids and broad-spectrum antibiotics are administered, and the baby is investigated for additional VACTERL abnormalities (see answer to Question 23). Positive pressure ventilation is not recommended because it can cause abdominal distention through the fistula.

If the baby is stable and the gap between esophageal segments is short, operative division of the fistula and a primary esophageal anastomosis is performed. When the infant is extremely premature or sick or has a long esophageal gap (as frequently occurs in isolated esophageal atresia without a fistula), the repair is done in stages. Division of any fistula and placement of a feeding gastrostomy are the initial procedures. Numerous classification systems have been developed to predict the outcome of infants with tracheoesophageal fistulas, such as the Waterson and Spitz criteria. Generally, infants weighing less than 1.5 kg and those with cardiac abnormalities carry a poor prognosis. Infants with one risk factor generally have good outcomes; those with both factors have a poor prognosis. ²⁶

Complications include anastomotic leak, stricture formation, recurrence of the tracheoesophageal fistula, and gastroesophageal reflux. Infants with evidence of reflux require acid suppression because of the long-term risk of esophageal cancer. These babies may also have underlying tracheomalacia.

Congenital Obstruction of the Intestinal Tract

A careful history and physical examination is the next important step. A prenatal ultrasound may have demonstrated a dilated intestine proximal to an obstruction. Was prenatal genetic testing performed? (Down syndrome and other chromosomal abnormalities are associated with duodenal atresia and Hirschsprung disease.) Is there a family history of cystic fibrosis (which may point to meconium ileus) or siblings with intestinal atresia (which may be familial)? On examination the baby’s overall condition should be noted (sepsis is in the differential diagnosis and has several features in common with obstruction). Are there features of Down syndrome? Is there abdominal distention? Is the abdominal wall red? (This may signify an antenatal perforation.) Are there any palpable hernias? Is the anal opening in the normal location and patent?

Plain abdominal radiographs (supine and decubitus) are most useful and should be performed first. A normal gas pattern with no dilation of intestinal loops and air in the rectum lowers the likelihood of obstruction. A “double bubble” sign is pathognomonic for complete duodenal obstruction. Several dilated loops of intestine with air fluid levels and a lack of distal gas are indicative of a high intestinal obstruction. Many dilated loops of intestine suggest a distal small bowel or colonic obstruction.

In some instances contrast radiographs may be unnecessary—air is an excellent contrast medium, and if there is evidence of complete duodenal or jejunal obstruction on the plain films, further imaging studies are not necessary. If there is a dilated proximal intestine and some distal gas, suggesting a partial obstruction or a volvulus, an upper gastrointestinal tract contrast series is indicated. If there appears to be a distal obstruction, a contrast enema should be performed to differentiate meconium plug, meconium ileus, intestinal atresia, and Hirschsprung disease.

Duodenal obstruction is most commonly caused by atresia or congenital duodenal obstruction of malrotation. Atresia may take the form of stenosis, a web, or complete separation of the duodenal segments. One cause of atresia is the failure of complete recanalization of the lumen of the duodenum after the solid phase of embryologic development, when the epithelial lining occludes the lumen; another is an annular pancreas, wherein the ventral and dorsal pancreatic buds fuse around the duodenum and compress it during development. Most commonly, duodenal atresia occurs distal to the ampulla of Vater, accounting for the bilious nature of the vomiting.

Normal rotation consists of a 270-degree turning of the midgut on the axis of the superior mesenteric artery, resulting in the duodenojejunal junction being fixed in the left upper quadrant and the cecum attached in the right lower quadrant. In malrotation this process does not occur or is incomplete, resulting in a narrow base mesentery that puts the child at risk for development of a volvulus and obstruction ( Fig. 19-4).

The most common scenario is bilious vomiting for no apparent reason in an infant who has been otherwise well and has a flat abdomen. Clinical deterioration, acidosis, abdominal tenderness, and rectal bleeding are late and ominous signs.

Unexplained bilious vomiting in an infant is a surgical emergency until proved otherwise. If no other explanation is apparent (e.g., bilious vomiting with profuse diarrhea and fever may signify a systemic infection, such as gastroenteritis), an immediate evaluation for malrotation should be performed. Because plain abdominal radiographs are often nonspecific, an urgent upper gastrointestinal tract contrast study is mandatory to determine the position of the ligament of Treitz and look for a possible twist.

The twisting of the mesentery leads to vascular compromise and intestinal ischemia. Gangrene of the entire small intestine may occur within as short a period as several hours from the onset of symptoms.

The leading theory is that duodenal atresia results from a failure of recanalization in the eighth through tenth week of fetal development; there is no similar solid phase of development of the jejunum or ileum. Jejunal and ileal atresia are believed to result from an intrauterine vascular accident that produces infarction. Because there are no bacteria within the intestine at this time, gangrene and bacterial peritonitis do not develop and the involved segment atrophies, resulting in an atresia.

Meconium ileus is small bowel obstruction secondary to thick, tenacious meconium. Approximately 15% of infants with cystic fibrosis have meconium ileus at the time of birth.

Simple meconium ileus is the mechanical blockage of the distal ileum by the sticky, inspissated meconium characteristically found in babies with cystic fibrosis. Radiographs often demonstrate a foamy appearance of the dilated meconium-filled bowel loops and a lack of air-fluid levels. A barium enema will demonstrate multiple filling defects in the distal ileum and should be followed by the administration of Gastrografin. Its high osmolarity causes fluid to pass into the bowel lumen and will often relieve the obstruction nonoperatively.

Complicated meconium ileus refers to an in utero perforation resulting from the initial intestinal obstruction, leading to meconium peritonitis, ascites, a meconium cyst, segmental volvulus, or intestinal atresia. Infants are usually distended at the time of birth (unlike with simple meconium ileus, in which distention is initially minimal and progresses over 24 to 48 hours). Infants with meconium peritonitis may have erythema of the abdominal wall and calcifications on abdominal radiographs.

Neonates with uncomplicated meconium ileus are initially treated with water-soluble contrast enema. Infants who have failed to respond to two or three therapeutic enemas require operative intervention. There is no place for attempted contrast treatment of complicated meconium ileus because urgent surgical exploration is required.

The hydrostatic pressure of the enema can perforate the intestine, so it is imperative that the procedure be performed by a radiologist who is skilled and experienced in treating newborn infants. Also, the fluid shift into the intestinal lumen from the hyperosmolar contrast can render the baby hypovolemic, and it is essential that the baby be well hydrated with intravenous fluids at the time of the procedure.

Duplications are endothelial-lined cystic or tubular structures found on the mesenteric side of the intestine that usually share a common wall. Mucous secretions or stool may accumulate in the duplication, causing it to distend, which may compress the adjacent bowel and cause obstruction.

Hirschsprung disease results when the parasympathetic nervous system fails to invest the entire digestive tract. During normal fetal development ganglion cells migrate cranially to caudally, so premature cessation of this process results in aganglionic bowel distal to the point where the process arrested.

The abnormally innervated distal bowel is unable to relax and propagate a peristaltic wave, producing a functional obstruction.

Two thirds of the time the transition zone is in the rectosigmoid region, but the zone of aganglionosis may involve the entire colon or even extend into the small intestine (i.e., total colonic Hirschsprung disease). Although Hirschsprung disease affects boys four times as often as girls, long-segment disease affects boys and girls equally.

Failure to pass meconium in the first 24 hours after birth is highly suggestive of Hirschsprung disease. There is a wide spectrum of presentations, ranging from complete functional distal obstruction with bilious vomiting and a distended abdomen to chronic constipation (in which case the diagnosis is usually not made until after the neonatal period). Sepsis resulting from enterocolitis can occur at any time.

The gold standard is a rectal biopsy that typically demonstrates an absence of ganglion cells and hypertrophy of parasympathetic nerve fibers, which stain intensively for acetylcholinesterase. This biopsy can be done at the bedside in the neonate. A contrast enema is suggestive of Hirschsprung disease if it shows a change in the caliber of the colon at the transition zone ( Fig. 19-5). It is important that the study be delayed if the baby has had an enema or a digital rectal examination or even if a rectal thermometer was inserted because any rectal manipulation may temporarily obliterate the radiographic appearance of the transition zone. The contrast enema may identify a transitional zone, which may be useful for operative planning.

Even in instances in which there is significant abdominal distention, the proximal intestine can almost always be decompressed by rectal irrigation and rectal exams, allowing time for a diagnostic work-up. Surgical repair involves resection of the aganglionic segment of bowel. Various surgical procedures have been developed to address this. The traditional surgical repair is a staged operation with a temporary diverting colostomy constructed above the transition zone, followed several months later by a “pull-through” operation in which the ganglionic bowel is brought down and anastomosed to the anal canal. In full-size babies without enterocolitis, the pull-through procedure is performed as a single operation, often with laparoscopic assistance.

Patients with Hirschsprung disease may develop enterocolitis, the precise cause of which is not well understood but which involves stasis, bacterial overgrowth, and translocation through the wall of the colon. Enterocolitis may be the first recognized manifestation of Hirschsprung disease but may also occur after surgery. It can be mild or severe with explosive diarrhea, dehydration, peritonitis, and sepsis. Enterocolitis is the most common cause of mortality from Hirschsprung disease. Treatment must be immediate and consists of bowel rest, broad-spectrum antibiotics, and thorough colonic irrigations.

Meconium ileus, as previously described, is obstruction of the distal ileum by thick and viscid meconium, which occurs in 10% to 20% of neonates with cystic fibrosis. Meconium plug is caused by meconium blocking the left colon in otherwise healthy babies. Small left colon syndrome is most common in infants of diabetic mothers and produces an obstruction from a temporarily dysfunctional, small-caliber left colon. A contrast enema with barium is usually diagnostic as well as therapeutic for both meconium plug and small left colon syndrome (through its mechanical effect), although subsequent testing for Hirschsprung disease or cystic fibrosis may be indicated.

Anorectal Malformations

Anorectal malformations comprise a spectrum of disorders in which the rectum is deflected anteriorly and fails to reach its normal perineal termination. When the rectum and urinary system end in a blind pouch, this is classified as a cloaca. When the rectum ends above the levator muscles, the malformation is classified as high; when it passes through these muscles, the malformation is low. High lesions are more common in males; low lesions are more common in females.

The diagnosis is usually obvious on inspection of the perineum, which should be standard procedure for a newborn examination. Either no perineal opening is present or an external fistula is visible. In male newborns this fistula is usually a small opening anterior to the normal anal location in the perineum or as far forward as the scrotal raphe. Female newborns may also have an external fistula draining into the anterior perineum, or else in the posterior vulva behind the hymen (the vaginal “fourchette”). A single perineal opening signifies a cloaca, where the rectum, vagina, and urethra all open into one common chamber.

Inspection and urinalysis allow the clinician to determine the anatomy in most cases. A perineal fistula always means the lesion is low and a colostomy is not necessary. If such a fistula cannot be detected initially, there should always be a 16- to 24-hour waiting period to allow increased luminal pressure to force meconium through a possible fistula so that it becomes visible on examination. If there is meconium in the urine, an internal fistula to the urinary tract is confirmed. If there is no visible fistula, a cross-table lateral film with the baby in the prone position can be used to measure the most distal aspect of the rectum relative to the perineal skin. The work-up should also include a search for other possible components of the VACTERL association (see answer to Question 23).

If there is an external fistula to the perineum, or bucket-handle deformity in a male (i.e., a vertical raphe in the perineum with indentations on both sides), the lesion is low, and a primary anoplasty can be performed in the neonatal period. Otherwise, the lesion is probably high or intermediate, and an initial colostomy is recommended, followed by a pull-through procedure within the next several months. If there is a large fistulous opening only slightly anterior to the normal anal location (“anterior anus”), function may be normal and surgery may be unnecessary.

Alberto Peña devised the posterior sagittal anorectoplasty (PSARP) in which the anal and rectal sphincter muscles are divided posteriorly in the midline; this operative approach has become the standard procedure for the pull-through procedure because it allows for excellent visualization. Recently, a laparoscopic pull-through operation has become feasible.

Continence depends on the coordinated actions of the external sphincter, internal sphincter, and levator muscles. Because the levators are most important, infants with low lesions in whom the bowel has descended normally within the levator sling have an excellent functional outlook. Children with high anomalies frequently have underdeveloped sphincter muscles, and their results are mixed, with many having at least occasional soiling. Finally, children with a flat bottom (which implies very poorly developed muscles) without a developed gluteal fold and those having sacral anomalies on radiograph have the worst prospects for normal continence. These patients require a structured bowel management program, including daily enemas, to achieve “functional” continence. All children with anorectal malformations suffer from constipation, and parents must be informed of bowel regimens.

Necrotizing Enterocolitis (NEC)

NEC is a condition that most commonly affects premature infants after the institution of oral feedings; however, it also occurs in term babies who have other comorbidities (e.g., congenital heart disease). It is a hemorrhagic necrosis that initially affects the mucosa but may progress to involve full-thickness injury. Manifestations vary considerably, from mild abdominal distention with hematochezia to fulminant sepsis with necrosis of the entire intestinal tract.

Although the precise etiology is unknown, three factors seem to act in concert in promoting the development of NEC:

NEC may involve any portion of the gastrointestinal tract, but the ileocecal region is the most commonly affected.

No. Although affected patients may be clustered in place and time, no consistent agent has been isolated from all reported epidemics, and it is considered that a variety of the enteric flora may contribute to NEC’s pathogenesis.

Clinical signs are initially nonspecific and may consist of lethargy, apnea, temperature instability, and feeding intolerance. Gastrointestinal manifestations follow and include vomiting, bloody stools, abdominal distention, and abdominal tenderness. Generalized sepsis may supervene.

Although the diagnosis may be strongly suspected by the clinical findings outlined in the previous passages, the presence of bubbly lucencies in the intestinal wall on x-ray, called pneumatosis intestinalis, is pathognomonic. Pneumatosis represents gas in the bowel wall produced by enteric organisms and is seen in 80% of NEC cases ( Fig. 19-7). Other radiographic features may include irregularly dilated air-filled loops of bowel and the visualization of branching lucencies in the liver, which may signify gas in the portal venous system.

No. Most infants with NEC will respond to medical treatment consisting of withholding all enteral feeds, nasogastric decompression, broad-spectrum systemic antibiotics, and general supportive measures to optimize tissue oxygenation and perfusion. Frequent clinical examinations are mandatory, and serial abdominal radiographs are obtained to assess for static loops or perforation.

Absolute indications for surgical intervention include pneumoperitoneum and intestinal gangrene (as demonstrated by abdominal wall erythema, unchanging bowel gas pattern, or failure to respond to medical therapy). Relative indications include progressive clinical deterioration, abdominal wall erythema, tender abdomen, metabolic acidosis, ventilatory failure, oliguria, thrombocytopenia, and portal vein gas.

Traditionally, a laparotomy is performed with inspection of the entire intestinal tract. Necrotic or perforated segments are resected, and an ostomy is performed. Bedside placement of an abdominal drain has been shown to have similar outcomes with regard to mortality, dependence on total parenteral nutrition, and length of hospital stay compared with laparotomy. Peritoneal drainage can be used as a temporizing procedure followed by subsequent operation. Close observation is required after any operative intervention. ²⁸

Ideally, stomas are reversed months later, when the patient is thriving and the elective procedure is very low risk. In reality, malabsorption or skin breakdown often necessitates earlier closure. A distal contrast study should always be obtained before reversing an ostomy to ensure that there is no silent stricture in the defunctionalized bowel. Approximately 10% to 15% of patients with NEC who do not develop full-thickness necrosis and perforation will develop an obstructive intestinal stricture.

Babies with SIP are generally younger (<1 week old) and more premature than NEC babies and often have not been fed. The exact etiology is unknown, but a very localized area of ischemia may be causative. Unlike with NEC, the surrounding bowel is not affected. Treatment consists of a localized resection with either an ostomy or possibly a primary anastomosis. ²⁹

Abdominal Wall Defects: Omphalocele and Gastroschisis

Between the fifth and tenth weeks of embryologic development, the intestine protrudes out of the umbilical ring and into the yolk sac. An omphalocele results when the lateral abdominal folds do not close and the exteriorized viscera remain in the sac ( Fig. 19-8). The etiology of gastroschisis is unknown. ( Table 19-2)

See Table 19-3.

The defects in the abdominal wall are generally larger in omphalocele than in gastroschisis. Extracelomic liver is almost always present with omphalocele.

Babies with an omphalocele have a higher incidence of associated anomalies, such as trisomy 13 and 18 syndromes, Beckwith–Wiedemann syndrome, pentalogy of Cantrell, bladder and cloacal exstrophy, and congenital cardiac abnormalities.

Gastroschisis is associated with younger maternal age but not associated with genetic syndromes. However, approximately 10% of these infants do have intestinal atresias, perhaps related to compression of the developing intestine against the edge of the abdominal opening.

Detection of abdominal wall defects in utero is important for several reasons. It can help prepare the family and assist in triaging the patient to a prenatal center. In the case of an omphalocele, associated defects can be searched for; their presence may affect prenatal care; timing and mode of delivery; and, in the case of multiple severe anomalies, potential termination of pregnancy.

Most studies show that cesarean section provides no significant advantage over vaginal delivery. One exception is the fetus with a very large omphalocele, for which several case reports have documented dystocia and liver damage during vaginal delivery.

Infants born with abdominal wall defects are prone to three serious problems: hypovolemia, hypothermia, and sepsis. Exposed bowel leads to increased loss of insensible fluid as well as heat loss. Immediate management includes placing the lower half of the infant, including exposed viscera, in a plastic wrapping or moist, sterile gauze; maintaining the infant in a warmer; initiating intravenous access and fluids; and providing nasogastric decompression to minimize bowel distention. Parenteral antibiotics are administered to decrease the risk of sepsis.

Babies with gastroschisis require urgent intervention because the viscera are exposed and vascular compromise may be present. In an infant with omphalocele, surgery is not urgent, and there is time for stabilization and evaluation of potential associated anomalies.

The two surgical options are primary closure or, if there is tension that might compromise respiratory function or the viscera itself, staged closure with a silo. A silo prevents dessication of the exposed viscera and resultant fluid losses.

Staged closure involves placing prosthetic material, usually a reinforced Silastic silo, over the viscera and attaching it to the fascia at the edges of the defect ( Fig. 19-11). The silo is manually compressed daily to gradually reduce the viscera and expand the peritoneal cavity. Most infants can be closed within 7 to 10 days with this method. Staged closure decreases the risk of long-term bowel dysfunction and need for reoperation. ³⁰

Yes. The omphalocele sac can be painted with an antiseptic, such as silver sulfadiazine or povidone-iodine. The sac will eventually epithelialize and contract, leaving a ventral hernia (which may be quite large) that can be repaired electively if the baby survives. This also allows for shorter duration of mechanical ventilator support and earlier feeds. ³¹

Abdominal Masses

More than half of all abdominal masses in neonates arise from the urinary tract.

Physical examination may significantly narrow the diagnostic possibilities, even if it does not provide any absolute answer ( Table 19-4). The following are of particular note:

The management of ovarian cysts in a neonate is somewhat controversial. Most arise in response to antenatal hormonal stimulation and may subsequently resolve after birth. Potential complications such as torsion, hemorrhage into the cyst, and rupture are somewhat related to the size of the cyst; the risk of malignancy depends on whether the cyst is simple (homogeneous) or complex.

Most authors advise observation of simple cysts that are less than 5 cm in diameter with serial ultrasound exams. Excision is recommended for cysts that are larger than 5 cm, have solid components, or cause compressive symptoms. Cysts larger than 5 cm carry a higher risk of torsion. Many ovarian cysts are amenable to laparoscopic excision.

A plain abdominal radiograph might reveal a mass effect or bowel obstruction; can help localize the mass; and can sometimes provide useful information about the mass itself, such as the presence of calcifications or stool. An abdominal ultrasound is useful in the majority of cases because it can show whether the mass is cystic or solid, can reveal the effect on adjacent anatomic structures, and often can identify the exact anatomic location of the mass. Further information can be provided with abdominal computed tomography, magnetic resonance imaging, or urologic imaging.

Ultrasound appearance is characteristic and often diagnostic. Serum alpha-fetoprotein is usually elevated in hepatoblastoma. Small to moderate hemangiomas can be observed or treated medically with corticosteroids. Most large or symptomatic hemangiomas (causing pain, heart failure, thrombocytopenia) and all hemangioendotheliomas and hepatoblastoma require hepatic resection.

Hydronephrosis secondary to ureteropelvic junction obstruction or posterior urethral valves.

Sacrococcygeal teratomas are the most common congenital tumor ( Fig. 19-12). They can appear alarming because of their large size and compressive effects, but 90% are benign and can be completely resected. The Altman classification system is used to describe the morphology of the tumors relative to their location.

Hernias and Cryptorchidism

When the testes descend from the abdomen during embryologic development, there is a resulting communication between the scrotum and the peritoneal cavity, the processus vaginalis, which usually becomes obliterated between the seventh and ninth months of gestation. Failure of this processus to close allows viscera to protrude into the groin or scrotum as an indirect inguinal hernia. Premature infants are less likely to have had time for the processus vaginalis to close.

Yes. Inguinal hernias will not resolve spontaneously, and there is a serious risk of incarceration (inability to be reduced), which can lead to strangulation.

This issue is somewhat controversial. If an inguinal hernia is asymptomatic, some surgeons will wait several months until the baby is older, but most recommend repairing it before the baby’s discharge from the nursery to prevent complications. If the infant is premature and has diminished respiratory reserve (e.g., bronchopulmonary dysplasia), the operative procedure can be performed under spinal or epidural anesthesia, in most cases without having to intubate the baby.

The ovary is the most likely structure.

No. The vast majority of umbilical hernias will close spontaneously by 4 to 5 years of age. The risk of incarceration in the interim is extremely small, and recurrences for early repair are likely.

Undescended testes are very common in newborn males, especially when they are born prematurely. Observation only is indicated at this time. If the testicle cannot be brought down easily into the scrotum upon subsequent follow-up examinations, surgery can be performed between 9 and 15 months of age.

Urologic Conditions

The incidence of hypospadias is approximately 1 in 300 live male births. ³²

Epispadias, abnormal gait, anteriorly displaced anus, and vesicoureteral reflux are often associated with bladder exstrophy. ³³³⁴

Bladder exstrophy is caused by a persistence of the cloacal membrane after the fourth gestational week and a lack of medial migration of the lateral mesoderm. ³⁵

Prune-belly syndrome consists of deficient abdominal wall musculature, hydronephrosis, and undescended testes.

Renal agenesis is the most common malformation.

Approximately 90% of children with spina bifida have abnormal bladder innervation.

Circumcision

The undersurface of the foreskin is fused with the glans at birth, and it is not until later in childhood that the foreskin is truly retractable.

The Academy has recently revised its guidelines on circumcision, now favoring the procedure, though stopping short of recommending it for all male infants. The recent change has been prompted by growing evidence that favors several health benefits including prevention of urinary tract infections, human immunodeficiency virus (HIV), and penile cancer. Circumcision also prevents transmission of certain sexually transmitted infections, including HPV and herpes.

Advantages:

Disadvantages:

Neonatal circumcision should not be performed if the baby is otherwise ill or there are congenital anomalies of the penis (e.g., hypospadias, in which case the foreskin may be needed for eventual reconstruction).