Although many of the principles involved in managing infants and children with surgical diseases are similar to those for adults, three important differences justify the special field of pediatric surgery:

  1  Most of the congenital anomalies that require surgery in children have no counterpart in older individuals. In fact, many would be lethal if not corrected promptly in early childhood.

  2  Physiologically, young children are not merely small adults! They have unique metabolic demands and often limited reserves that require special attention to maintain their physiologic parameters within the narrow range of normality. On the other hand, children have a tremendous capacity for repair and regeneration. They are usually not afflicted by many of the preexisting chronic illnesses that affect older people. If handled with great care and skill, these young patients have the resiliency to recover rapidly from even major surgical procedures and subsequently live long, productive lives.

  3  Children with surgical illness, and often moreso their parents, have special emotional needs and require extra support during what is often a trying time for the entire family.

This chapter describes (a) the perioperative management of the pediatric patient, (b) surgical conditions common to neonates (apparent at birth or within the first 30 days), (c) surgical conditions common to older children, (d) malignancies found in children, and (e) principles of trauma care in children and how they differ from those in adults.

PERIOPERATIVE MANAGEMENT OF THE PEDIATRIC SURGICAL PATIENT

Fluids and Electrolytes

Fluid and electrolyte management in pediatric patients must be extremely precise because the margin between dehydration and fluid overload is narrow. Compared with adults, infants and children have greater metabolic demands, and because they turn over body water and electrolytes so rapidly, pediatric patients may undergo rapid, major shifts in body fluid compartments. The immature neonatal kidney has limited concentrating and diluting capacities and therefore cannot be entirely relied upon to compensate for a deficiency or overabundance of fluids and electrolytes. Although children’s needs may be estimated according to standard formulas, there is no substitute for frequent adjustments based on careful monitoring of the patient’s condition.

Neonates have a significantly greater proportion of total body water than do adults because newborn infants have a larger pool of extracellular fluid (ECF) (Fig. 2-1). This fluid compartment is increased further in extremely premature infants (<30 weeks’ gestation). At birth the ECF is even more expanded, and as much as 10% of birth weight is lost during the first week as this surplus water is excreted.

Figure 2-1   Body fluid compartments in very premature infants, term infants, and adults. Unshaded areas show the percentage of body weight as total body water. ECF, extracellular fluid; ICF, intracellular fluid.

In calculating fluid and electrolyte requirements for children who cannot receive enteral feeds, the following quantities must be considered:

  1  Maintenance requirements

  2  Replacement of preexisting deficits

  3  Replacement of ongoing abnormal losses

Maintenance Requirements

Maintenance fluids and electrolytes are the quantities that must be provided to compensate for normal renal excretion and insensible losses through the skin and lungs. Table 2-1 provides guidelines for calculating the amounts of water and electrolytes required. In addition, a minimal quantity of glucose is included to provide for some protein sparing and to avoid hypoglycemia. These constituents can all be provided by D10% in 1/4 normal saline + 20 mEq/L KCl in infants and D5% in 1/2 normal saline + 20 mEq/L KCl in older children at the infusion rate calculated in Table 2-1. Calcium gluconate should be added for premature infants, who are calcium deficient.

Preexisting Deficits

Children with acute surgical illness may have significant fluid and electrolyte deficits from poor oral intake, vomiting, diarrhea, peritonitis, sepsis, burns, or hemorrhage. Intravascular volume must be rapidly restored to maintain adequate tissue perfusion for normal organ function, particularly if the child requires an urgent operation. Most surgical diseases cause isotonic dehydration. Instead of basing rehydration calculations on imprecise estimates of percentage of dehydration, fluid deficits are best corrected empirically in stages, as outlined in Table 2-2.

Children who are significantly anemic or actively bleeding may require blood transfusions. There is no arbitrary value of hemoglobin below which a transfusion is indicated, and each child must be individually assessed to optimize oxygen delivery. Volumes used for pediatric “units” are provided in Table 2-3.

Abnormal Ongoing Losses

Abnormal losses include measurable and immeasurable third-space fluid losses. Measurable losses refer to abnormal external drainage. In the surgical patient, these losses usually arise from the gastrointestinal tract or from various drainage tubes and are most accurately replaced on a volume-for-volume basis. Gastric drainage is approximated as D5% in 1/2 normal saline + 10 mEq/L KCl. Alimentary tract losses distal to the pylorus are replaced as lactated Ringer’s solution.

Immeasurable third-space losses are fluids and electrolytes that are pathologically sequestered within the body and are neither in equilibrium nor available to the intravascular space. In children with surgical diseases, such fluid can accumulate in the gastrointestinal tract from obstruction and inflammation, in body cavities as ascites and pleural effusions, and diffusely as edema from the leaky capillary syndrome that accompanies shock. Operative manipulation can cause edema in tissues as a result of direct trauma. Because third-space losses cannot be measured directly, their intravenous replacement is approximated. Sequestered fluid is almost always isotonic and is replaced as balanced salt solution. Although one common approach is to provide for the expected regional fluid loss from operative trauma by running intravenous fluids at 1.5 to 2 times the maintenance rate for the first 24 hours postoperatively, this method may give patients too much free water. It is preferable to administer boluses of isotonic normal saline or lactated Ringer’s solution in 10 to 20 mL/ kg aliquots as directed by the patient’s clinical condition.

The adequacy of intravenous fluid therapy can be determined only by monitoring the patient’s response. Useful parameters are level of activity, color, skin turgor and temperature, heart rate, and blood pressure. Most helpful is the urine output, which should exceed 1 to 2 mL/kg/hr in infants and 0.5 mL/kg/hr in adolescents. Children who receive fluids solely as intravenous infusions should have serum electrolytes measured at least every other day.

Nutrition

The well-nourished child who will be eating within 3 to 4 days does not need nutritional support other than the basic fluids and electrolytes as outlined above. On the other hand, if feedings must be withheld longer, if the child is under significant stress, or if the child is premature, enteral or total parenteral nutrition (TPN) may be critical for survival. Compared with adults, growing children have increased nutritional demands, but often limited nutritional reserves. When compounded by the increased metabolic requirements imposed by surgical illness, the risks for malnutrition are considerable. Significant consequences of malnutrition include lack of growth, impaired organ function, immunologic incompetence, and the inability to heal wounds.

Enteral Nutrition

The provision of nutrients through the intestinal tract is ideal. Compared with TPN, enteral feeding is more physiologic, less prone to complications, and far less costly. A lack of enteral feeds leads to atrophy of the intestinal microvilli and to stagnation of the enterohepatic circulation. In critically ill patients it can also lead to translocation of bacteria across the intestinal mucosa, resulting in sepsis. Even if full enteral feeds cannot be tolerated, the provision of small, “trophic” amounts of enteral nutrition may counterbalance some of these problems. The common enteral feeds used for infants are summarized in Table 2-4.

If a baby cannot suck but has an otherwise functional intestinal tract, a small nasogastric or orogastric tube may be inserted for gavage feedings. Nasojejunal tubes may be used for individuals at high risk for aspiration (e.g., those with delayed gastric empyting or gastroesophageal reflux). A child who requires prolonged tube feedings (e.g. one who cannot swallow because of neurologic disease) is best served by a gastrostomy tube because nasogastric tubes are irritating, are easily displaced, and can promote aspiration. A number of Silastic low-profile tubes and buttons are available.

Parenteral Nutrition

Many children with major surgical disorders require TPN while the gastrointestinal tract is temporarily nonfunctional. All nutrient requirements are supplied intravenously by the administration of carbohydrates, proteins, fats, electrolytes, trace elements, and vitamins. Intravenous nutrition may be infused through either a peripheral or a central vein. Advantages of peripheral venous nutrition are ease of catheter placement and fewer catheter complications. Glucose can be administered up to a concentration of 12.5%. The rest of the required calories are supplied as emulsified fat. More hypertonic solutions (up to 25% glucose) may be delivered centrally through the superior or inferior vena cava. The umbilical vein can often be utilized for the first 1 to 2 weeks following birth. Thin, Silastic percutaneously inserted central catheters (PICCs) are inserted centrally through a percutaneously accessed extremity vein. When peripheral veins are scarce, central access is achieved percutaneously through the subclavian vein or by a cut-down procedure in the neck or groin. A silicone catheter with a tunneled Dacron cuff (of the Hickman or Broviac type) is preferred because it is minimally thrombogenic and tends to resist infection.

The nutritional needs of each child who is receiving TPN are calculated daily and the appropriate solution is prepared. TPN is infused at maintenance fluid rates by an infusion pump. Concentrations are gradually increased over several days until daily requirements are achieved. All children who receive TPN are monitored closely. Weight is recorded daily, urine is monitored for glucose, and blood is analyzed periodically for glucose, electrolytes, lipids, bilirubin, and liver enzymes.

Table 2-5 summarizes the complications of TPN. Mechanical complications are most common with centrally placed catheters. Catheter sepsis is also a major hazard with central catheters, and can be minimized by scrupulous surgical and nursing techniques. Bacterial contamination is often treated successfully with antibiotics administered through the catheter, whereas life-threatening infections or fungal sepsis usually necessitate catheter removal. Liver damage may occur in any patient who is receiving TPN, but preterm infants are most susceptible. The precise etiology is unknown, but the cause is probably multifactorial and may include absence of enteral feeding, injurious components in the TPN, or essential components missing from TPN. Cholestasis is initially identified by rising serum bilirubin and alkaline phosphatase levels. It usually reverses when TPN is discontinued, but may progress to cirrhosis and hepatic failure.

Respiratory Management

Respiratory failure, or the inability to maintain adequate gas exchange through the lungs, is common in surgically ill children. Infants have high oxygen requirements, are obligate nasal breathers, and depend almost exclusively on their diaphragms rather than on chest wall muscles for air movement. As a result, they have a limited safety margin before respiratory insufficiency develops. Even moderate increases in intra-abdominal pressure can cause respiratory distress. Table 2-6 lists the common causes of respiratory failure in children, the clinical signs, and the steps in management.

Endotracheal intubation provides the most secure airway. It is always necessary for prolonged mechanical ventilation, and it may facilitate pulmonary suctioning and physical therapy. The size of the tube to be inserted may be estimated from the diameter of the child’s external nares or little finger, or for children over 2 years of age using the formulas Age (years)/4 + 4 for uncuffed tubes or Age (years)/4 + 3 for cuffed tubes. The pediatric airway is short; to avoid inserting the tube into a bronchus, bilateral equality of the breath sounds must be verified.

The two types of mechanical ventilators available are the volume- and pressure-modulated varieties. Volume ventilators deliver a preset tidal volume, regardless of pulmonary compliance, and are used in most patients beyond the newborn period. Pressure ventilators deliver breaths up to a preset pressure and are preferred for infants, in whom the very low lung volumes involved compared with the dead space would prevent accurate delivery of a preset volume to the lungs. The ventilator should be adjusted to its lowest possible settings consistent with adequate gas exchange. Oxygen levels must not be excessive, particularly in preterm neonates, who are at high risk for retinal damage and pulmonary toxicity that can lead to chronic fibrosis (bronchopulmonary dysplasia).

Pneumothorax is common in children who receive positive pressure ventilation and should be suspected whenever there is sudden deterioration in the respiratory status. The diagnosis is confirmed by chest x-ray or transillumination (a point source of light applied to the chest wall and lights up that entire side of the chest). Definitive treatment is the placement of an intercostal chest tube, but expeditious needle aspiration can provide immediate relief.

High-frequency ventilation is an innovation in which very low tidal –volumes are directed down the trachea at extremely rapid rates (150–2,500 breaths/min). When very high ventilatory settings are needed, this technique may allow adequate gas exchange to occur at lower airway pressures than with conventional rates, producing less trauma to the lungs.

Extracorporeal membrane oxygenation (ECMO) is a form of prolonged cardiopulmonary bypass in which gas exchange occurs in an external circuit that contains the patient’s flowing blood and is utilized only when all forms of positive pressure ventilation are inadequate. ECMO can provide complete respiratory support, independent of the lungs, and thereby allows the lungs to rest and recover while organ function is well maintained. ECMO is reserved for the most desperately ill infants because it requires cannulation of major vessels and systemic anticoagulation. Overall survival in newborn infants treated with ECMO is approximately 80%, depending on the cause of respiratory failure. The survival rate for older children and adults is approximately 50%.

Preoperative Evaluation and Preparation

All children who undergo surgery require a careful history and a thorough physical examination, but laboratory studies are not routinely necessary in healthy children. When indicated, complete blood count (CBC), urinalysis, coagulation parameters, blood typing and crossmatching, serum electrolyte and arterial blood gas determinations, electrocardiogram, and x-rays films are obtained.

Children must be in the best possible condition at the time of operation. A child with an upper respiratory infection should have elective surgery postponed until the infection is resolved. A patient who is in shock should be resuscitated as completely as possible before even an urgent operation.

Many operations on infants can be performed on an outpatient basis, starting at 3 months of age for term babies and at approximately 52 weeks after conception for premature infants. Because the respiratory center is immature before that time and there is a risk of apnea after general anesthesia, elective operations should be delayed. After emergency procedures, close postoperative monitoring in the hospital for 24 hours or longer is mandatory.

Preoperative NPO guidelines differ from those of adults, and are outlined in Table 2-7.

Operative Care and Monitoring

The ability to perform major surgery successfully on preterm infants is a recent development and is largely the result of increased understanding of neonatal physiology and advances in technology. Even extremely premature neonates can be safely brought through surgery, provided that the anesthesiologist is knowledgeable and attentive to their special needs and the surgeon handles the fragile tissues with the utmost gentleness and skill.

Although general anesthesia is used for almost all children who undergo operations, supplementation with regional or local blocks (such as epidural, ilioinguinal/iliohypogastric, penile, and intercostal infusions) can lower intraoperative requirements of potent general agents and diminish postoperative pain and discomfort. Epidural catheters can be left in place for several days.

During the course of an operation, the clinical condition of a small child who is almost completely covered with drapes can change rapidly. The endotracheal tube can become blocked, slip out of the trachea, or migrate down a mainstem bronchus. Close monitoring is essential and should always include an electroencepahlogram (ECG), precordial or esophageal stethoscope, blood pressure cuff, temperature probe, pulse oximeter, and end-tidal CO₂ monitor for measurement of the adequacy of ventilation. Additional options can include a urinary catheter and arterial access (usually with an umbilical artery catheter in neonates) for frequent blood sampling and arterial pressure measurement. Central venous catheters (which may be inserted through the umbilical vein in neonates) can be used to estimate left ventricular filling pressures and help guide intravenous fluid requirements. Swan-Ganz catheters, which are more accurate in the presence of cardiopulmonary disease, are used much less often in children than in adults. They are cumbersome to insert and have relatively high complication rates in small patients.

Infants can rapidly become hypothermic in the operating room, leading to greatly increased metabolic demands, peripheral vasoconstriction, acidosis, and even death. Premature infants have a surface area that is up to 10 times that of adults per unit weight. In addition, they have little subcutaneous tissue for insulation and rely on the metabolism of brown fat for heat generation, which may be rendered inactive by anesthetic agents or depleted by poor nutrition. In the operating room, heat loss is exacerbated as body cavities are exposed and anesthesia abolishes muscular activity and causes vasodilatation. Children are kept warm by adequately heating the operating room; using radiant heaters, warming mattresses, and circulating warm air; covering the extremities and head; and warming all solutions and intravenous fluids used to prepare them for surgery.

Allowable blood loss is generally 15% to 20% of estimated blood volume, depending on patient stability. Greater losses generally require transfusions with packed red blood cells.

Postoperative Care and Pain Management

Close monitoring is most essential during the immediate postanesthesia recovery period, because children are especially prone to respiratory and cardiovascular complications at this time. Although most children can be extubated at the conclusion of the operative procedure, those who are critically ill or prone to apnea should remain ventilated until stabilized. Following extubation, supplemental oxygen should be given and pulse oximetry monitored to prevent hypoxia, which may temporarily occur postoperatively even after relatively minor operative procedures.

The most common cause of hypotension or oliguria in the postoperative period is hypovolemia secondary to inadequate resuscitation or third-space losses. A fluid challenge of 10 to 20 mL/kg of isotonic fluid should be given and the clinical response monitored.

Nutrition must be started postoperatively as soon as possible. In many situations, a regular diet may be offered as soon as the child is awake. Following gastrointestinal surgery or if the child is critically ill, parenteral nutrition may be necessary until the gastrointestinal tract has recovered. Nasogastric tube decompression may avoid gastric distention, which can compromise respiration and lead to aspiration.

Postoperative pain is often inadequately managed because children may be unable to clearly express their complaints and because of exaggerated concerns by health care workers about narcotic addiction and respiratory depression. As mentioned, long-acting local nerve blocks can be given during general anesthesia to limit postoperative pain for hours, and epidural catheters may be left in place for several days. Narcotics should be administered intravenously rather than intramuscularly because of the pain and unpredictable pharmacokinetics of intramuscular injection. Because apnea is a concern in children younger than 6 months of age, narcotics should be given only in a carefully monitored setting. For children older than 5 years, patient-controlled analgesia, in which the patient triggers the infusion of intravenous medication within preset limits, provides superior pain relief with less total narcotic than with traditional pain control methods. Nonsteroidal anti-inflammatory drugs can be used to reduce narcotic dosages and side effects postoperatively. Table 2-8 provides dosages for commonly used analgesics.

Emotional Support

Even the most routine operation is often a major traumatic event for patients and their families. Children between the ages of 1 and 4 years are aware enough to be afraid, although they cannot understand the bewildering events going on around them. Older children and adolescents are particularly fearful of physical injury and mutilation. Parents are often devastated at the prospect of their child having to undergo an operation, with the dread of general anesthesia often superseding that of the operative procedure itself.

Much can be done to alleviate the anxiety of both children and parents. The approach must be individualized, depending on the age of the child and the temperament of the patient and family. Honest and open explanations are best. The child should be included in the discussions and provided with ample opportunity for questions. Videos, booklets, and a tour of the clinical facility can transform an alien, hostile setting into a familiar, friendly one. Even when procedures are unpleasant or painful, children fare better when they know what to expect. For the parent, an excellent relationship with the surgeon and a clear understanding of the events is important because parents often transmit their own feelings to their children. Informed parents can do much to prepare children at home.

Separation from parents should be minimized. Preoperative workups are usually done before hospital admission, and children should be discharged postoperatively as soon as medically indicated. Parents can remain with their child until the last moment before the child enters the operating room and may be present in the postanesthesia care unit (PACU) when their child awakens.

Premedications are often given to allay anxiety and should be administered orally because an injection would defeat this purpose. In the operating room, anesthesia induction in younger patients is performed with a face mask, which can be flavored. Older children can choose between mask and intravenous induction.

NEONATAL SURGICAL CONDITIONS

Birth defects are the most common cause of perinatal mortality and a major source of morbidity in the United States. In most instances, the etiology of these malformations is unknown and likely results from a combination of genetic and environmental factors. Many of these defects require surgical intervention for either cure or palliation. With the increasing use of antenatal screening modalities, particularly ultrasonography, more anomalies are being discovered in utero. For a limited number of conditions (e.g., hydronephrosis, hydrocephalus, space-occupying lesions of the chest), intrauterine operations may be beneficial, but these are still experimental procedures and are performed in only a few specialized centers. Nevertheless, prenatal diagnosis allows for family counseling regarding management of the pregnancy and planning of the timing, mode, and location of delivery. Most important, personal relationships can be established between the parents and the health care team at an early stage.

Congenital Diaphragmatic Hernia

A congenital diaphragmatic hernia (CDH) is a condition in which the absence of a portion of the diaphragm can lead to life-threatening respiratory compromise. It occurs in 1:4,000 live births and serves as a prototype for surgical causes of neonatal respiratory distress. As a result of recent advances in management, the survival rate has steadily improved. The opening in the diaphragm can vary in location and size (Fig. 2-2). By far the most common type is the Bochdalek hernia, which is a defect of the posterolateral diaphragm, usually on the left. Morgagni hernias, which are retrosternal defects, do not often present as emergencies in the newborn period.

Figure 2-2   Locations of congenital herniations in the diaphragm.

Embryology

The etiology of CDH is unknown. Embryologically, the extruded midgut normally returns to the abdominal cavity between the 9th and 10th weeks of gestation. If the pleuroperitoneal canal through the posterolateral portion of the diaphragm remains open, the viscera will pass into the chest and compress the developing lungs. The resulting pulmonary hypoplasia and abnormalities of the pulmonary vasculature affect both lungs, but are more severe ipsilaterally. The timing and severity of the pulmonary compression determine the physiologic consequences.

Pathophysiology

A CDH causes respiratory distress by a combination of physical compression of the lungs by the herniated viscera, pulmonary hypoplasia, and pulmonary hypertension. Although the mechanical lung compression is relieved by surgery, the pulmonary hypoplasia can be fatal if severe. Pulmonary hypertension results from the abnormally high pulmonary vascular resistance caused by the paucity of pulmonary arterioles and the abnormal vascular reactivity of the vessels that are present. This increased pulmonary vascular resistance causes right-to-left shunting of desaturated blood across the foramen ovale and ductus arteriosus, exacerbating the hypoxemia.

Clinical Presentation and Evaluation

A newborn with a CDH has a variable degree of dyspnea and cyanosis. There are diminished breath sounds on the side of the hernia and a shift of the heart to the opposite side. The abdomen is characteristically scaphoid. The diagnosis is confirmed by a chest x-ray that shows air-filled loops of bowel in the chest (or opacity in the right chest if the liver is involved), loss of the diaphragmatic contour, and mediastinal deviation (Fig. 2-3).

Figure 2-3   Congenital diaphragmatic hernia in a neonate. Intestinal loops are seen in the left side of the chest, with mediastinal displacement to the right.

Treatment

Initial resuscitation of a newborn with a CDH includes supplemental oxygen and usually endotracheal intubation with mechanical ventilation. Positive pressure ventilation through a face mask is contraindicated because gas will enter the gastrointestinal tract and further compress the lungs. A nasogastric tube is placed to minimize gastric distension.

The ventilatory management of CDH babies both preoperatively and postoperatively is most critical, as too-high ventilator settings will irreversibly damage the hypoplastic lungs. A strategy of “permissive hypercapnia” consists of strictly limiting the ventilatory pressures and oxygen concentrations while counterintuitively accepting some degree of hypercarbia and hypoxemia and has significantly improved survival. Adjuncts may include the administration of exogenous surfactant and inhaled nitric oxide (a pulmonary vasodilator) and the use of high-frequency ventilation. Finally, if all else fails, ECMO can provide complete respiratory support, allowing time for the pulmonary hypertension to improve while avoiding further lung damage by high ventilator settings.

The timing of the surgical repair of the CDH itself is no longer considered emergent, and there may be value in a delay of several days to stabilize the baby and improve the elevated pulmonary artery pressures. The operative approach is usually through the abdomen, although it may also be through the chest cavity. The viscera are reduced and the diaphragmatic defect is closed primarily or, if it is large, with a prosthetic patch.

Increasingly, CDH is being diagnosed by antenatal ultrasound. Delivery is then planned to take place in a specialized center. Although antenatal repair of the defect has not been successful technically, inducing lung growth by fetoscopic tracheal occlusion or the administration of pulmonary growth factors is being evaluated experimentally.

Prognosis

The survival of babies with CDH has improved from 50% to 80% with a combination of permissive hypercapnia, delayed surgery, and the judicious use of ECMO. Although most survivors have had little disability because the lungs continue to grow postnatally, as more severely affected CDH babies survive, more are showing evidence of long-term problems with pulmonary function, poor growth, and developmental delay.

Neonatal Thoracic Mass Lesions

Mass lesions in the chest cavity of newborns are infrequent but not rare and may be life threatening. These conditions include congenital lobar emphysema, cystic adenomatoid malformation, pulmonary sequestration, bronchogenic cysts, and foregut duplication cysts. The lesions may be asymptomatic or they may cause symptoms as a result of a primary compressive effect or secondary infection, including chest pain, wheezing, dyspnea, and fever. The malformation is usually visualized on a chest x-ray performed to evaluate these symptoms or is discovered coincidentally for another reason if the chest mass is not symptomatic. A computed tomography (CT) scan should be obtained if the findings on chest x-ray are not definitive.

Patients with congenital lobar emphysema (which represents hyperinflation of normal lung tissue) who are not significantly symptomatic may be observed. All other mass lesions of the thoracic cavity should be excised, although it is sometimes not possible to arrive at an exact diagnosis until the time of operation. When the lesion is within the lung, the involved lobe is usually resected.

Unborn infants with cystic adenomatoid malformation that causes hydrops have a very guarded prognosis because of the high rate of fetal demise, although recently antenatal resection or maternal treatment with steroids has shown some success in salvaging these individuals. Otherwise, infants and children tolerate thoracotomy and lobectomy extremely well, with little of the morbidity seen in adults. Even after pneumonectomy, the remaining lung usually grows and develops with few long-term respiratory problems.

Esophageal Atresia and Tracheoesophageal Fistula

Esophageal atresia (EA) is a congenital interruption in the continuity of the upper and lower portions of the esophagus (Fig. 2-4A). A tracheoesophageal fistula (TEF) is an abnormal communication between the trachea and esophagus (Fig. 2-4E). Either condition may occur alone, but they usually appear in some combination (Fig. 2-4B–D). The most common pattern is type C, in which the upper esophagus ends blindly and the lower portion communicates with the trachea. Overall, these anomalies are found in 1: 4,000 live births.

Figure 2-4   Anatomic patterns and approximate percentages of occurrence of esophageal atresia and tracheoesophageal fistula. A, Isolated esophageal atresia (8%). B, Proximal tracheoesophageal fistula (< 1%). C, Distal tracheoesophageal fistula (85%). D, Double fistula (< 1%). E, “H” type fistula (5%).

Pathophysiology

The etiology of EA and TEF is unknown, but it is believed that the septation process that normally divides the foregut into the trachea and esophagus by the seventh week of gestation is incomplete. In addition, the more rapidly growing trachea may partition the upper and lower esophagus into discontinuous segments. Neonates with EA and TEF often have certain other abnormalities, known as the VACTER association (vertebral, anal, cardiac, tracheal, esophageal, radial or renal). The presence of an anomaly of any of these structures should prompt a search for others.

Clinical Presentation and Evaluation

An infant with EA, with or without a TEF, immediately chokes and regurgitates with feeding, as the blind-ending upper esophageal pouch rapidly fills. An alert nurse usually notes excessive drooling even earlier because the infant cannot swallow saliva. An attempt should be made to pass a nasogastric tube. Resistance is encountered, and an x-ray confirms that the tip is in the upper mediastinum. Air visualized in the abdomen confirms the presence of a TEF, because an isolated EA is associated with no gas in the gastrointestinal tract because air cannot be swallowed. Although contrast material may be instilled carefully to outline the upper esophageal pouch, this study is not necessary.

An isolated TEF, the “H” type fistula (Fig. 2-4E), is more insidious because the esophagus is patent. These individuals have recurrent aspiration pneumonia, and the diagnosis is established by endoscopy or contrast swallow.

Treatment

Immediate measures are taken to prevent aspiration. The baby is kept with the head elevated to minimize reflux of gastric contents through the fistula into the trachea. To avoid the accumulation of oral secretions, a double-lumen tube is placed in the upper pouch for suctioning. Intravenous fluids and broad-spectrum antibiotics are administered.

Most neonates with EA and TEF undergo primary repair, with division of the fistula and anastomosis of the upper and lower esophageal segments through a right thoracotomy. If the infant is extremely premature or has other major illnesses and cannot tolerate a lengthy procedure, or if the gap between esophageal segments is long, a staged repair is preferable. In that case, a gastrostomy is performed initially to keep the stomach empty and prevent aspiration. It is subsequently used for feeding after the TEF is ligated. Upper and lower esophageal segments may require several months to grow close enough to permit approximation. Only in rare instances is a colon or gastric interposition necessary to bridge the gap.

Common Complications

Postoperative complications include anastomotic leak, stricture, recurrent TEF, gastroesophageal reflux, and tracheomalacia. Tracheomalacia is caused by underdevelopment of the cartilaginous tracheal rings and may be manifested by noisy respirations, a barking cough, and apneic spells. Reflux is especially common and may require subsequent fundoplication.

Prognosis

Most neonates with EA and TEF have excellent results. Mortality is usually limited to those who are extremely premature or have other major anomalies.

Congenital Gastrointestinal Obstruction

Congenital gastrointestinal obstruction refers to an obstruction that is present at birth. The site of the obstruction may be anywhere from stomach to anus, and it can result from a wide variety of causes. These disorders should be managed with some urgency because the obstructed neonate can rapidly develop fluid and electrolyte derangements, may aspirate vomitus, and can acquire sepsis from perforation of the distended bowel or necrosis from an underlying volvulus.

Clinical Presentation and Evaluation

The clinical manifestations of congenital intestinal obstruction will vary depending on the site of obstruction. The four key signs are listed below.

  1  Polyhydramnios. The fetus swallows 50% of the amniotic fluid daily, which is largely absorbed in the upper intestinal tract. A high obstruction allows this fluid to back up and accumulate in excessive quantities.

  2  Bilious vomiting. Nonbilious vomiting is common in infants; bilious vomiting is much more often pathologic.

  3  Abdominal distention. Distention develops within 24 hours of birth in distal obstructions, as swallowed air accumulates above the blockage.

  4  Failure to pass meconium. Within 24 hours of birth, 95% of term babies pass meconium. A delay may signify obstruction.

If obstruction is suspected following a careful history and physical examination, plain x-rays are performed because swallowed air is an excellent contrast material. If a few dilated loops of bowel with air-fluid levels and no distal air can be seen (Fig. 2-5A), complete, proximal obstruction is diagnosed and no further imaging studies are needed. If the obstruction appears to be partial or is questionable, with some distal air visualized, an upper gastrointestinal contrast study is most useful. If many distended loops of bowel are seen, suggesting a distal obstruction (Fig. 2-5B), a contrast enema is indicated. Tables 2-9 and 2-10 compare features of the common causes of neonatal upper and lower gastrointestinal obstruction, respectively.

Figure 2-5   Congenital intestinal obstruction. A, Proximal obstruction from jejunal atresia. Air is visualized in the stomach and proximal jejunum only. B, Distal obstruction from ileal atresia. Multiple dilated bowel loops are seen.

Treatment

Initial management should always include nasogastric tube decompression, intravenous hydration, and prophylactic antibiotics. The need for and timing of surgery then depends on the nature of the obstruction and the overall condition of the baby.

Duodenal Obstruction

Duodenal obstruction is commonly caused by (a) atresia and (b) malrotation. Most obstructions of this type are distal to the ampulla of Vater, so the vomiting is bilious. Atresia may take several forms, including complete separation of the proximal and distal duodenal segments, stenosis, or a web across the lumen. During fetal development, the duodenal epithelium overgrows and transiently occludes the lumen. Failure of subsequent complete recanalization is believed to account for the various forms of atresia. There is a strong association of atresia with trisomy 21. An annular pancreas is frequently encountered, in which the ventral pancreatic bud fails to rotate around and become incorporated into the dorsal bud; the two instead fuse around the duodenum, creating a ring effect.

Rotation of the intestine normally occurs in the fetus after the midgut (i.e., the bowel from the duodenum to the transverse colon) has returned to the abdominal cavity from the yolk sac. The vertical midgut rotates 270 degrees in a counterclockwise direction, placing the cecum in the right lower quadrant and the duodenojejunal junction in the left upper quadrant. Subsequently, the ascending and descending colon are fixed retroperitoneally by fibrous attachments that arise from the lateral abdominal wall. In malrotation, this process is incomplete. The cecum is located in the right upper quadrant or remains completely in the left abdomen, and the duodenojejunal junction is located to the right of the midline. This configuration allows the intestine, which is suspended between these closely fixed points, to twist as a midgut volvulus (Fig. 2-6A,B). Midgut volvulus may occur at any age in the presence of malrotation, but is most common in the first month of life. It is the most dangerous form of intestinal obstruction, potentially progressing to necrosis of the entire midgut if not urgently recognized and corrected.

Figure 2-6   A, Congenital malrotation of the intestine with a high cecum and right-sided duodenojejunal junction forming a narrow pedicle. B, The midgut has twisted as a volvulus. C, Ladd’s bands can also obstruct the duodenum in malrotation.

In infants with malrotation, the peritoneal attachments to the lateral abdominal wall, which normally fix the cecum retroperitoneally, now cross over the duodenum to reach the high, malrotated cecum. These attachments are called Ladd’s bands and may be another cause of partial or complete obstruction by compression of the duodenum. (Fig. 2-6C).

The diagnosis of complete duodenal obstruction at birth is established by visualizing a “double bubble” on x-ray, because air is present in the stomach and in the proximal, dilated duodenum, but none is seen distally (Fig. 2-7). If the obstruction is incomplete, some air will be noted below.

Figure 2-7   “Double bubble” sign in a neonate with duodenal atresia. Air is visualized in the stomach and proximal dilated duodenum only.

Duodenal obstruction demands expeditious surgery, unless midgut volvulus has been ruled out. For atresia with or without annular pancreas the obstruction is bypassed through an anastomosis between the proximal duodenal segment and the distal duodenum or a loop of jejunum (a gastrojejunostomy is poorly tolerated in infants). In malrotation, the volvulus (if present) is untwisted, Ladd’s bands are divided, and the base of the small bowel mesentery is widened. Because the bowel must be returned to the abdomen in the malrotated position, an appendectomy is also performed to avoid misleading presentations of appendicitis. The entire operation (termed a Ladd’s procedure) can now be performed laparoscopically.

Small Intestinal Obstruction

Congenital obstruction of the small intestine is usually caused by atresia, meconium ileus, and intestinal duplication. Like its duodenal counterpart, atresia of the small intestine may range from a web across the lumen (Fig. 2-8) to complete separation of the intestinal segments. The defects may be multiple. Unlike duodenal atresia, the proposed etiology is an in utero vascular accident, such as a localized twist or intussusception. Because there are no intraluminal bacteria antenatally, the resulting necrosis produces localized atrophy rather than bacterial peritonitis, occasionally leading to considerable loss of small bowel length.

Figure 2-8   Atresia of the small intestine caused by an intraluminal web. A size discrepancy between the dilated proximal and contracted distal bowel is seen.

Meconium ileus is caused by impaction of sticky, thick meconium in the distal ileum, the narrowest portion of the intestinal tract. It occurs in 15% of infants with cystic fibrosis, from the abnormally viscid enzymes secreted by the pancreatic and intestinal glands. A family history of cystic fibrosis, an autosomal recessive disorder, is suggestive, but is positive in only 25% of patients. X-rays often demonstrate a peculiar foamy appearance of the dilated meconium-filled bowel loops and a lack of air-fluid levels, as the thick meconium is mixed with air and fails to layer out. Calcification on abdominal x-ray indicates that an antenatal perforation has occurred.

Duplications are endothelial-lined cystic or tubular structures adjacent to any portion of the alimentary tract. They are found on the mesenteric side of the normal bowel, usually sharing a common wall with it, and may or may not communicate with the primary lumen. Mucous secretions or stool may accumulate in the duplication, causing it to distend. Obstructive symptoms from pressure on neighboring bowel or localized volvulus may appear during or after the neonatal period.

Atresias

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