Pediatric Surgery

Chapter 67 Pediatric Surgery




Pediatric surgery remains as a true general surgical specialty, providing total care for infants and children of all ages. The range of clinical pathology is broad and not limited to specific anatomic organ systems. Pediatric surgeons are challenged by dealing with a wide spectrum of pathologies involving multiple organ systems from neonates to young adults. Although the pathogenesis of many pediatric surgical conditions remains unknown, there have been recent significant basic science and clinical advances in pediatric surgery, which have resulted in improvement in the management of complex pediatric surgical conditions. This chapter highlights common and unique pediatric surgical conditions.



Newborn Physiology


The newborn infant is physiologically distinct from the adult patient in many respects. The smaller size, differing volume capacities, and functional immaturity of organ systems present unique challenges in the management of surgical conditions.




Pulmonary System


The lungs are not fully matured at birth and continue to form new terminal bronchioles and alveoli until about 8 years of age. In premature infants, lung immaturity is one of the greatest contributors to morbidity and mortality. Immature lungs have fewer type II pneumocytes and a lower production of surfactant, which is critical for reducing alveolar surface tension and thereby increasing functional residual capacity. Hence, premature infants are at significant risks for alveolar collapse, hyaline membrane formation, and barotrauma. Surfactant is a lipoprotein mixture of phospholipid, protein, and neutral fats. Lecithin, the most predominant phospholipid, can be measured in amniotic fluid, and the lecithin-to-sphingomyelin ratio is used to determine fetal lung maturity. In addition to pulmonary parenchymal issues, the airway of the newborn is small (tracheal diameter = 2.5 to 4 mm) and easily plugged with secretions. The respiratory rate for a normal newborn may range from 40 to 60 breaths/min, with a tidal volume of 6 to 10 mL/kg. Nasal flaring, grunting, intercostal and substernal retractions, and cyanosis constitute symptoms of respiratory distress. Infants are obligate nasal and diaphragmatic breathers and any condition that obstructs the nasal passages (including the nasogastric tube) or interferes with diaphragmatic function may result in severe respiratory compromise. A major contributor to the treatment of premature infants, therefore, has been the ability to provide exogenous surfactant. This has resulted in improved survival and decreased incidence of bronchopulmonary dysplasia, a condition characterized by oxygen dependence, radiologic abnormality, and chronic respiratory symptoms beyond the first 28 days of life. The administration of inhaled nitric oxide, a potent inducer of vascular smooth muscle relaxant, has also proven useful in neonates with PPHN.





Fluids, Electrolytes, and Nutrition



Fluid Requirements


Fluid and electrolyte therapy in pediatrics requires careful assessment of fluid intake, fluid losses, and electrolyte abnormalities prior to initiating fluid management. It also requires frequent monitoring during the course of therapy to assess the adequacy of treatment. Accurate estimation of IV fluid and electrolytes is critical, especially in small infants with a narrow margin of error. Because of increased insensible water losses through thinner immature skin, fluid requirements for premature infants are substantial. Insensible water losses are directly related to gestational age, ranging from 45 to 60 mL/kg/day for premature infants weighing less than 1500 g to 30 to 35 mL/kg/day for term infants. Other factors, such as radiant heat warmers, phototherapy for hyperbilirubinemia, and respiratory distress, further increase losses. In the first 3 to 5 days of life, there is a physiologic water loss of up to 10% of the body weight of the infant. As such, fluid replacement volumes are less over the first several days of life. These fluid volumes are regarded as estimates and may change according to differing patient factors.


Fluid requirements are calculated according to body weight (Table 67-1). During the first few days of life, the fluid recommendations are conservative; however, most neonates require 100 to 130 mL/kg/day for maintenance fluids by the fourth day of life. Neonates with conditions that are associated with excessive fluid losses (e.g., gastroschisis) can require as much as 1.5 times maintenance volume. The two best indicators of sufficient fluid intake are urine output and osmolarity. The minimum urine output in a newborn and young child is 1 to 2 mL/kg/day. Although adults can concentrate urine in the range of 1200 mOsm/kg, an infant responding to water deprivation is only able to concentrate urine to a maximum of 700 mOsm/kg. Clinically, this indicates that greater fluid intake and urine output are necessary to excrete the solute load presented to the kidney during normal metabolism. In general, the daily requirements for sodium and potassium are 2 to 4 and 1 to 2 mEq/kg, respectively. These requirements are usually met with a solution of 5% dextrose in 0.45% normal saline with 20 mEq KCl/liter at the calculated maintenance rate. Fluid losses from gastric drainage, ostomy output, or diarrhea should also be carefully assessed and replaced with an appropriate solution. Gastric losses should be replaced in equal volumes with 0.45% NS with 20 mEq KCl/liter. Diarrheal, pancreatic, and biliary losses are replaced with isotonic lactated Ringer’s solution. Acutely hypovolemic patients requiring rapid volume expansion should be treated with an IV bolus of 10 to 20 mL/kg body weight of whole blood, plasma, or 5% albumin. Transfusions of packed red blood cells are given in increments of 5 to 10 mL/kg.


Table 67-1 Daily Fluid Requirements for Neonates and Infants


















WEIGHT VOLUME
Premature infants <2 kg 140-150 mL/kg/day
Infants, 2-10 kg 100 mL/kg/day for first 10 kg
Children, 10-20 kg 1000 mL + 50 mL/kg/day for weight 10-20 kg
Children >20 kg 1500 mL + 20 mL/kg/day for weight >20 kg


Nutrition




Caloric Requirements


Energy requirements vary significantly from birth to childhood and also under different clinical conditions (Table 67-2). The parameter that is most indicative of sufficient delivery of calories in neonates is weight gain. Total daily caloric requirements and the expected daily weight gain decrease with age. Neonates have the highest energy requirements necessary to maintain growth. Almost 50% of the energy used in term infants younger than 2 weeks and 60% of energy intake in premature infants weighing less than 1200 g is devoted to growth. A general guideline for enteral caloric requirement for neonate is 120 calories/kg/day to achieve an ideal growth of 25 to 35 g/kg/day of weight gain (≈1% body weight gain/day). Most standard infant formulas, as well as breast milk, contain 20 calories/ounce. Formulas with higher caloric density are available for neonates who are unable to consume sufficient volumes to meet their caloric requirements and/or require fluid restriction. Breast milk or a protein hydrolysate formula (e.g., Pregestimil, Alimentum) should be used when beginning feedings in neonates with compromised gut functions (e.g., necrotizing enterocolitis [NEC]) or short gut caused by massive bowel resection. In general, continuous feedings are initiated for infants with a stressed gut and transition to bolus feedings is made later. Enteral feeding tolerance is carefully monitored by assessing for abdominal girth, gastric residuals, and stool or ostomy output.


Table 67-2 Average Caloric and Protein Requirement by Age



























AGE (yr) CALORIES (kcal/kg/day) PROTEIN (g/kg/day)
0-1 90-124 2.0-3.5
1-7 75-90 2.0-2.5
7-12 60-75 2.0
12-18 30-60 1.5
>18 25-30 1.0





Neck Lesions



Cervical Lymphadenopathy


Enlarged lymph nodes is one of the most common pediatric conditions, resulting in frequent referral to a surgeon for biopsy and/or resection. They occur usually along the sternocleidomastoid muscle border, often presenting in clusters. The cause is multifocal but often thought to be infectious. A careful history and physical examination are typically sufficient to determine surgical indications; however, the use of diagnostic ultrasound has significantly increased in recent years. In most healthy children, cervical lymphadenopathy presents as a small, mobile, rubbery, palpable mass in the anterior cervical triangle. However, relatively fixed, nontender, progressively enlarging nodes in the supraclavicular region should raise suspicion for more serious underlying conditions. Other associated symptoms, such as night sweats and a history of weight loss, should also be thoroughly investigated. Chest radiography is often performed as a screening method to detect mediastinal adenopathy. If enlarged anterior mediastinal nodes are seen, a computed tomography (CT) scan of the chest is obtained to assess nodes better and identify potential airway compression. Patients with acute, bilateral cervical lymphadenitis are usually managed nonoperatively because respiratory viral infectious causes (e.g., adenovirus, influenza virus, respiratory syncytial virus) are common. S. aureus and group A streptococci are responsible for most cases of acute pyogenic lymphadenitis. When nodes become fluctuant because of a central area of liquefying necrosis, needle aspiration or incision and drainage should be performed.


Cat scratch disease is a self-limiting infectious condition characterized by painful regional lymphadenopathy. Bartonella henselae, a gram-negative bacillus, is responsible for most cases. A history of exposure to cats is helpful, but not always present. Indirect immunofluorescent antibody testing has only moderate specificity and, therefore, the use of the polymerase chain reaction assay from a lymph node biopsy is more useful for diagnosis. There is no specific treatment for cat scratch disease because it is usually self-limited. A less common infectious cause for cervical lymphadenitis is nontuberculous mycobacterial infection.1 In general, the nodes are fluctuant, with a violaceous appearance of the overlying skin. The diagnosis is typically made by positive cultures for nontuberculous acid-fast bacilli, along with a tuberculin skin test. Surgical excision is usually indicated because most nontuberculous mycobacteria are resistant to conventional chemotherapy.



Cystic Hygroma


Cystic hygromas are multiloculated cystic spaces lined by endothelial cells; they occur as a result of lymphatic malformation. Most cystic hygromas involve the lymphatic jugular sacs and present in the posterior neck region. The other common sites are the axillary, mediastinum, inguinal, and retroperitoneal regions, and approximately 50% of them present at birth. Cystic hygromas usually present as soft cystic masses that distort the surrounding anatomy, including the airway, which can result in acute airway obstruction. Prenatal recognition of a large cystic mass of the neck is associated with a significant risk to the airway, greater association with chromosomal abnormalities, and higher mortality rates. Advanced prenatal imaging modalities allow for careful coordination of surgical intervention at the time of delivery.


Aside from distorting adjacent normal structures, cystic hygromas are prone to infection and hemorrhage within the mass. Imaging studies, such as magnetic resonance imaging (MRI), can play a crucial role in preoperative planning. In general, complete surgical excision is the preferred treatment. However, this may be difficult because of the intimate involvement with surrounding vital structures. Resections are generally tedious, requiring careful isolation and ligation of lymphatic branches. Aggressive blunt and electrocautery dissections can lead to inadequate control of lymphatics, often resulting in recurrence and/or infection caused by accumulation of the lymphatic leak. Radical resection with sacrifice of vital structures is not advocated. Injection of sclerosing agents such as bleomycin or OK-432, derived from Streptococcus pyogenes, has been reported to be effective in the nonoperative management of cystic hygromas.2



Thyroglossal Duct Cyst


A thyroglossal duct cyst is a midline neck lesion that originates at the base of the tongue at foramen cecum and descends through the central portion of the hyoid bone. It is one of the most common midline neck lesions presenting in preschool-aged children (Fig. 67-1A). Although thyroglossal duct cysts may occur anywhere from the base of the tongue to the thyroid gland, most are found at or just below the hyoid bone. The standard operation for thyroglossal duct cysts has remained unchanged since it was described by Sistrunk in 1928. It involves complete excision of the cyst in continuity with its tract, the central portion of the hyoid bone, and the tissue above the hyoid bone, extending to the base of the tongue (see Fig. 67-1B). Failure to remove these tissues will result in a high risk for recurrence because multiple sinuses have been histologically identified in these locations. Embryologically, a thyroid diverticulum develops as a median endodermal thickening at the foramen cecum. As the embryo develops, the thyroid diverticulum descends in the neck and remains attached to the base of tongue by the thyroglossal duct. Also, as the thyroid gland descends to its normal pretracheal position, the ventral cartilages of the second and third branchial arches form the hyoid bone—hence, the intimate anatomic relationship of the thyroglossal duct remnant with the central portion of the hyoid bone. Normally, the thyroglossal duct regresses by the time the thyroid gland reaches its final position. When the elements of the duct persist despite complete thyroid descent, a thyroglossal duct cyst may develop. Failure of normal caudal migration of thyroid gland results in a lingual thyroid, in which no other thyroid tissue is present in the neck. Ultrasound or radionuclide imaging may provide useful information to identify the presence of a normal thyroid gland within the neck.




Branchial Cleft Remnants


The branchial cleft remnants typically present as a lateral neck mass on a toddler. The structures of the head and neck are derived from six pairs of branchial arches, their intervening clefts, and pouches. Congenital cysts, sinuses, or fistulas result from failure of these structures to regress, persisting in an aberrant location. The location of these remnants generally dictates their embryologic origin and guides the subsequent operative approach. Failure to understand the embryology may result in incomplete resection or injury to adjacent structures. All branchial remnants are present at the time of birth; however, they are often not recognized until later in life. These lesions may present as sinuses, fistulas, or cartilaginous rests in infants. However, they occur more commonly as cysts in older children and adolescents. The clinical presentation may range from a continuous mucoid drainage from a fistula or sinus to the development of a cystic mass that may become infected. Branchial remnants may also be palpable as cartilaginous lumps or cords corresponding with a fistulous tract. Dermal pits or skin tags may also be evident.


First branchial remnants are typically located in the front or back of the ear or in the upper neck near the mandible. Fistulas typically course through the parotid gland, deep or through branches of the facial nerve, and end in the external auditory canal. Remnants from the second branchial cleft are the most common. The external ostium of these remnants is located along the anterior border of the sternocleidomastoid muscle, usually in the vicinity of the upper half to lower third of the muscle. The course of the fistula must be anticipated preoperatively because stepladder counterincisions are often necessary to excise the fistula completely. Typically, the fistula penetrates the platysma, ascends along the carotid sheath to the level of the hyoid bone, and turns medially to extend between the carotid artery bifurcation. The fistula then courses behind the posterior belly of the digastric and stylohyoid muscles to end in the tonsillar fossa. Third branchial cleft remnants usually do not have associated sinuses or fistulas and are located in the suprasternal notch or clavicular region. These most often contain cartilage and present clinically as a firm mass or subcutaneous abscess.




Extracorporeal Life Support


Extracorporeal life support (ECLS) is a form of cardiopulmonary bypass that provides temporary support for the critically ill patient with acute refractory respiratory and/or cardiac failure. In general, ECLS delivers sufficient gas exchange and maintains circulatory support, thus allowing for physiologic recovery. The largest experience with ECLS has been with respiratory failure in newborns; however, it is applicable for various clinical conditions resulting in respiratory and/or cardiovascular failure in pediatric and adult patients. Since its first reported neonatal case in l976, the use of ECLS has now become the standard therapy option for refractory neonatal respiratory failure unresponsive to maximum conventional medical treatment. There are over 170 centers around the world contributing to the Extracorporeal Life Support Organization database.



Indications


The major indications for neonatal ECLS include meconium aspiration, respiratory distress syndrome, PPHN, sepsis, and congenital diaphragmatic hernia (CDH). Neonates with complex congenital cardiac defects may be supported with ECLS perioperatively. Meconium aspiration is the most common indication for neonatal ECLS and is associated with the highest survival rate (>90%). Selection criteria for the initiation of neonatal ECLS vary slightly among institutions. Generally, an infant must have at least an 80% predicted mortality with continued conventional medical treatment to justify ECLS therapy. Two guidelines have been historically used as a means to predict survival without ECLS. The alveolar-arterial difference in the partial pressure of oxygen (PAO2 − PaO2 [also known as AaDO2]) is calculated as follows:



AaDO2 more than 610 for longer than 8 to 12 hours, and AaDO2 more than 620 for 6 hours associated with extensive barotrauma and severe hypotension requiring inotropic support, are considered to be criteria for ECLS. The oxygen index (OI) is calculated as the fraction of inspired oxygen (usually 1.0) multiplied by the mean airway pressure ×100 divided by PaO2. An 80% mortality is noted with an OI more than 40. Exclusion criteria include gestational age less than 34 weeks, birth weight less than 2 kg, and a nonreversible pulmonary pathology. Additional exclusion criteria include the presence of cyanotic congenital heart disease or another major congenital anomaly that precludes survival, intractable coagulopathy or hemorrhage, sonographic evidence of a significant intracranial hemorrhage (higher than a grade I intraventricular hemorrhage), and more than 10 to 14 days of high-pressure mechanical ventilatory support. Before the initiation of ECLS, all infants must undergo echocardiography to rule out congenital heart disease and cranial ultrasound to exclude the presence of significant intracranial hemorrhage.



Physiologic Considerations


The basic concept of ECLS is to drain venous blood, remove carbon dioxide, add oxygen through the artificial membrane lung, and then return warmed blood back into the circulation. Venoarterial bypass provides cardiac and respiratory support, whereas venovenous bypass provides only respiratory support. Venoarterial bypass is used most commonly; the right internal jugular vein and common carotid artery are typically chosen for cannulation because of their vessel sizes, accessibility, and adequate collateral circulation. The ECLS circuit is composed of a silicone rubber bladder, which collapses when venous return is diminished, roller pump, membrane oxygenator, heat exchanger, tubing, and connectors. Venous blood from the right atrium drains through the venous cannula to the bladder and is pumped to the membrane oxygenator, where carbon dioxide is removed and oxygen is added (Fig. 67-2). The oxygenated blood then passes through the heat exchanger and is returned to the patient through the arterial cannula. The patient is systemically anticoagulated to prevent clotting of the ECLS circuit; hence, patients are at risk for bleeding complications. As such, hematocrit values, platelet counts, and fibrinogen levels must be closely monitored and maintained at acceptable ranges. Cranial ultrasound is performed for the first few days of ECLS to monitor for hemorrhage and then done on an as-needed basis. Extracorporeal flow is gradually weaned as native cardiac or pulmonary function improves. Indicators of lung recovery include an increasing PaO2, improved lung compliance, and clearing of the chest x-ray. Once the extracorporeal flow rate reaches minimal levels, the patient is trialed off bypass by temporarily clamping cannulas. If tolerated, the patient is taken off ECLS support on moderate conventional ventilatory settings.





Congenital Diaphragmatic Hernia


Despite early prenatal detection of CDH, it remains one of the most challenging conditions to manage in pediatric surgery. CDH is a relatively common cause of neonatal respiratory distress, with an overall incidence of 1 in 2000 to 5000 live births. Most CDH defects occur on the left side (80%); bilateral condition is extremely rare. A hernia sac is present 20% of the time. Despite recent innovative treatment strategies, such as fetal hernia repair or tracheal occlusion, extracorporeal membrane oxygenation, inhaled nitric oxide, partial liquid ventilation, and respiratory management protocol of permissive hypercapnea, the overall survival rates have not changed significantly and remain in the range of 70% to 90%. Accurate determination of true survival is complicated by the fact that many infants with CDH are stillborn, and many reports tend to exclude infants with complex associated anomalies from survival calculations.






Treatment


The open fetal surgery for CDH has failed to show significant overall survival advantage. Occlusion of the fetal trachea, resulting in accumulation of lung fluid to stimulate lung growth, has garnered significant recent interest. A laparoscopic approach has also been used to apply external clips or place balloons and sponges to occlude the fetal trachea. However, the fetal occlusion technique has not significantly influenced the overall survival rate with CDH, and fetal interventions for CDH remain limited to a few centers. The postnatal management of CDH is directed toward stabilization of the cardiorespiratory status while minimizing iatrogenic injury from therapeutic interventions. Immediate securing of the airway with endotracheal intubation is critical. Excessive mean airway pressure ventilation can result in pneumothorax and compromised venous blood return to the heart. An orogastric tube is placed to prevent gastric distention, which may worsen the lung compression, mediastinal shift, and ability to ventilate. The use of tolazoline, a nonselective α-adrenergic blocking agent, as a pharmacologic pulmonary vasodilator has not produced clinically significant results. Inhaled nitric oxide is used by most centers as a pulmonary vasodilator. Surfactant administration and high-frequency ventilation have also resulted in variable overall outcome for CDH infants. However, the recent use of gentle ventilation with permissive hypercapnia and stable hypoxemia has resulted in a significantly higher survival rate (≈75%) for CDH infants.



Surgical Repair


It has been well established that CDH repair should be delayed for 2 to 4 days until cardiopulmonary stabilization has occurred. The preferred operative approach for a posterolateral CDH is through a subcostal abdominal incision. The viscera are reduced into the abdominal cavity and the posterolateral defect in the diaphragm is closed using interrupted nonabsorbable sutures. When present (10% to 15% of cases), a hernia sac should be excised. Typically, the hernia defect is large, with only a small anteromedial leaflet of diaphragmatic tissue present. A number of reconstructive techniques and materials are available for the repair of large hernia defects. The surgical technique of abdominal or thoracic muscle flaps can be considered, but the use of prosthetic material (e.g., Gore-Tex, W.L. Gore, Elkton, Md) has become more widespread. The advantages of a prosthetic patch are shorter operative time and a tension-free repair. However, the major potential problems with prosthetic patches are the risks of infection and recurrence of the hernia. Recently, the use of regenerative extracellular matrix biomaterials has garnered significant interest as an ideal biodegradable patch to repair diaphragmatic hernia defects. At times, the abdominal cavity may be too small to accommodate the reduced viscera from the thoracic cavity. A temporary abdominal silo may be considered, but allowing for an incisional hernia with skin-only closure until the definitive fascia closure can be performed is an alternative surgical option. The timing of CDH repair relative to ECLS remains controversial. A recent CDH study group report has suggested that CDH repair after ECLS therapy is associated with improved survival when compared with repair while on ECLS.3




Bronchopulmonary Malformations


Bronchopulmonary malformations are congenital abnormalities of the airway, such as bronchogenic cysts, intralobar and extralobar sequestrations (ELSs), congenital pulmonary airway malformations (CPAMs), and congenital lobar emphysema (CLE). Their natural histories vary widely. In the perinatal period, these lung lesions can result in pleural effusions, polyhydramnios, hydrops, and pulmonary hypoplasia with subsequent respiratory distress and airway obstruction. If severe enough, fetal demise can ensue. With increasing importance placed on prenatal care, many of these lesions are being diagnosed prenatally with serial imaging. Fetal surgery has been pursued when fetal viability is at risk. Although these congenital abnormalities are often asymptomatic and may even spontaneously regress, there is concern that these anomalies may cause recurrent infections and exhibit long-term malignant potential.



Bronchogenic Cyst


Bronchogenic cyst is the most common cystic lesion of the mediastinum. The cyst wall consists of fibroelastic tissue, smooth muscle, and cartilage, whereas the cyst itself is lined with respiratory tract epithelia (ciliated columnar cells). It can also contain mucus-producing cuboidal cells, which contribute to enlargement of the cyst with mucus. They may occur anywhere along the tracheobronchial tree but are usually found around the carina and right hilum. Less frequently, they present in the neck, lung, pleura, pericardium, or below the diaphragm. When the cysts are large, they can compress surrounding vital structures, including the airway. Infants are particularly at risk because of their narrow, easily compressible airway. Bronchogenic cysts can also cause dysphagia, pneumothorax, cough, and hemoptysis or become infected, which is how older children present. Often picked up on postnatal chest x-ray, the diagnosis is confirmed by CT as a spherical nonenhancing mass. It is fluid- or mucus-filled, although an air-fluid level is apparent if the cyst communicates with the airway. Cysts within the pulmonary parenchyma typically communicate with a bronchus, whereas those in the mediastinum usually do not. Bronchogenic cysts are routinely resected even if asymptomatic, although recently there have been debates on observation alone for this condition.4 Rare cases of malignant transformation have been reported. Resection is performed by video-assisted thoracic surgery (VATS) or thoracotomy.



Congenital Pulmonary Airway Malformation


CPAMs have been controversially described as hamartomatous lesions in which a multicystic mass replaces normal lung tissue. They are connected to the tracheobronchial tree and its blood supply is pulmonary. Although they are usually unilateral and unilobar, they can present in the immediate perinatal period with life-threatening respiratory distress. If asymptomatic during this time, infants and older children can go on to present with fevers, persistent cough, and recurrent pneumonia. CPAMs can undergo malignant transformation; rhabdomyosarcoma has been reported. They are classified based on their appearance on imaging and confirmation is made by pathologic examination. According to the Stocker classification, type I lesions account for almost 75% of all cases and consist of a small number of large, 2- to 10-cm cysts that can compress normal lung parenchyma. Type II lesions have numerous cysts, usually measuring less than 1 cm in diameter. Type III lesions are rare and appear to be only a few millimeters in diameter.5 However, they are associated with mediastinal shift, hydrops, and a poor prognosis.


Ultrasound and, less commonly, MRI, are used to locate the lesion, characterize its appearance, determine its blood supply and venous drainage, and evaluate whether there is any displacement of other thoracic structures. Also, when there is any uncertainty, prenatal MRI has been used to differentiate CPAM from other congenital thoracic abnormalities. Postnatally, a chest radiograph is usually diagnostic, revealing a mass with a possible mediastinal shift and air-fluid levels, but a chest CT is frequently obtained for confirmation. When fetal distress occurs in utero, options include fetal thoracotomy and thoracoamniotic shunting (if the fetus is <32 weeks). Most fetuses with a prenatally diagnosed CPAM experience partial regression in the third trimester and can be treated with expectant management. They can then undergo postnatal resection at 5 to 8 weeks of life.4 Postnatal management of the symptomatic patient necessitates resection via a thoracotomy or VATS. The treatment of asymptomatic patients is more controversial but it is generally agreed that they should be resected, given the risk of infection and malignancy.



Pulmonary Sequestration


Bronchopulmonary sequestrations (BPSs) are nonfunctional nests of microcystic pulmonary tissue that have no connection to the tracheobronchial tree but are fed by an aberrant systemic artery. There are two types, intralobar (IL) and extralobar (EL); the former is contained within normal lung parenchyma and the latter is separate and encased by its own pleura.4 ELSs occur predominantly in males and, in 40% of cases, other congenital anomalies, such as posterolateral diaphragmatic hernia, pectus excavatum and carinatum, and enteric duplication cysts, can be found.


Lacking a communication to the airway, sequestrations do not form enlarged cysts or cause spontaneous pneumothoraces. They can, however, infarct, become infected, and cause hemoptysis. It has been reported that ELSs can undergo torsion as well. Because of their aberrant systemic vascular supply (Fig. 67-4), BPSs can result in significant left-to-right shunting in infants, who are then susceptible to high-output cardiac failure.6 For an initial evaluation, Doppler ultrasound may reveal a systemic arterial supply from the infradiaphragmatic or thoracic aorta. The lesion itself may appear solid, but can also be cystic. CT or MRI can aid in further defining the vascular anatomy. Accounting for 75% of all BPSs, intralobar sequestrations (ILSs) are found within the medial or posterior segments of the lower lobes, more on the left side. Most ELSs are found posteromedially in the left lower chest but can occur within or below the diaphragm. Air within an ILS usually signifies infection, whereas the same finding in an ELS suggests the presence of a fistulous connection with the esophagus.4



If a BPS is identified on prenatal ultrasound, the fetus is followed with serial ultrasound, looking for mass enlargement and the development of complications such as hydrops, pleural effusion, or polyhydramnios.6 BPS has been reported to spontaneously regress. In fact, it is estimated that 68% of BPSs undergo spontaneous regression before birth as they become isodense with the surrounding lung. The involution may occur as the lesion outgrows its blood supply. Because of the risk for infection and bleeding, ILSs are usually resected by segmentectomy or lobectomy. ELSs are usually asymptomatic and, because there is generally no tracheobronchial communication, the risk of infection is low. As such, many of these lesions can be observed.



Congenital Lobar Emphysema


CLE describes a progressively distended, hyperlucent lobe caused by abnormal bronchopulmonary development. Air trapping in the emphysematous lobes occurs with intrinsic or extrinsic obstruction, which includes endobronchial obstruction from mucosal proliferation and extrinsic compression from vascular anomalies. In over 90% of cases, it involves the left upper or right middle lobe. CLE is rarely diagnosed prenatally, but its prevalence is 1 in every 20,000 to 30,000 deliveries.4 It tends to present in the first few days of life and as late as 6 months after birth. On ultrasound, CLE appears as an echogenic homogenous lung mass. When CLE is discovered in an asymptomatic patient, observation is recommended because these lesions have a tendency to regress. A chest radiograph is customarily diagnostic because it reveals overdistention of the involved lobe. Importantly, the lucency should not be mistaken for a pneumothorax, and positive-pressure ventilation should be used with caution because of the propensity of these patients to undergo auto-PEEP (positive end-expiratory pressure; auto-PEEP is defined as the end-expiratory intrapulmonary pressure that develops as a result of dynamic airflow resistance during mechanical ventilation). When the CLE progresses to the point that it causes mediastinal shift and worsening symptoms, an open thoracotomy with lobectomy is indicated.



Alimentary Tract



Esophageal Atresia and Tracheoesophageal Fistula


Esophageal atresia is a congenital condition of esophageal discontinuity that results in proximal esophageal obstruction. A tracheoesophageal fistula (TEF) is an abnormal fistula communication between the esophagus and trachea. Esophageal atresia and TEF can occur alone or in combination. The incidence of this anomaly is 1 in 1500 to 3000 live births, with a slight male predominance. Approximately one third of infants with esophageal atresia or TEF have a low birth weight, and 60% to 70% have associated anomalies. During the fourth week of gestation, the esophagotracheal diverticulum of the foregut fails to divide completely to form the esophagus and trachea. In 10% of patients, there is a nonrandom, nonhereditary association of anomalies referred to by the acronym VATER (vertebral, anorectal, tracheal, esophageal, renal or radial limb); an alternative acronym is VACTERL (vertebral, anorectal, cardiac, tracheal, esophageal, renal, and limb). Five anatomic variants of esophageal atresia are depicted in Figure 67-5. In the most common type (C lesion) of esophageal atresia with TEF, the proximal blind pouch ends approximately the distance of one to two vertebral bodies from the distal TEF. The distal TEF is typically located 1 cm above the carina in the membranous portion of the trachea.




Clinical Presentation and Diagnosis


The diagnosis of esophageal atresia is considered in an infant with excessive salivation along with coughing or choking during the first oral feeding. A maternal history of polyhydramnios is often present, more often in isolated proximal atresia (86%). In an infant with esophageal atresia and TEF, acute gastric distention may occur as a result of air entering the distal esophagus and stomach with each inspired breath. Reflux of gastric contents into the distal esophagus will traverse the TEF and spill into the trachea, resulting in cough, tachypnea, apnea, and/or cyanosis. The presentation of isolated TEF without esophageal atresia may be more subtle, often beyond the newborn period. In general, these infants have choking and coughing associated with oral feeding. The inability to pass a nasogastric tube into the stomach of the neonate is a cardinal feature for the diagnosis of esophageal atresia. If gas is present in the GI tract below the diaphragm, an associated TEF is confirmed (Fig. 67-6A). Conversely, the inability to pass a nasogastric tube in an infant with absent radiographic evidence of GI gas is almost diagnostic of an isolated esophageal atresia. The use of isotonic contrast by mouth to demonstrate the presence and/or level of the proximal esophageal atresia is strongly discouraged because of risk for aspiration. The diagnostic evaluation includes screening for other associated anomalies. Echocardiography and renal ultrasound are performed to evaluate for congenital heart defects (including aortic arch anomaly) and genitourinary malformations.




Treatment



Preoperative Management


Initial treatment includes decompression of the proximal esophageal pouch with a sump tube (e.g., Replogle tube) placed on continuous suction. The infant is positioned in an upright prone position to minimize GER and prevent aspiration. Broad-spectrum IV antibiotic coverage should be started empirically. Routine endotracheal intubation is avoided because positive-pressure ventilation may be inadequate to inflate the lungs because air is directed into the TEF through the path of least resistance. Ventilation may be compounded further by the resultant gastric distention. Gastrostomy to decompress the distended stomach should be avoided because it may abruptly worsen the ability to ventilate the patient. In these circumstances, manipulation of the endotracheal tube to be positioned distal to the TEF (e.g., right mainstem intubation) may minimize the leak and permit adequate ventilation. Furthermore, placement of an occlusive balloon catheter (Fogarty) into the fistula through a bronchoscope may be useful, but this maneuver can be risky. As a last resort, emergent thoracotomy with ligation of the fistula alone may be required. A preoperative chest radiograph and echocardiogram provide sufficient information to determine the side of the aortic arch. A right thoracotomy is performed for the operative repair in patients with a normal left-sided aortic arch. However, for infants with a right-sided arch, a left thoracotomy would be preferred. A higher incidence of aortic arch anomalies (e.g., vascular rings) and postoperative complications has been reported with right-sided aortic arch.7



Surgical Management


The typical surgical approach for the most common esophageal atresia with TEF involves an open thoracotomy, with an extrapleural approach through the fourth intercostal space. Bronchoscopy is routinely performed to determine the relative site of the fistula and exclude the presence of a second fistula (see Fig. 67-6B). After extrapleural dissection to expose the posterior mediastinum, the azygos vein is divided to reveal the underlying TEF. The TEF is dissected circumferentially and its attachment to the membranous portion of trachea is taken down. The tracheal opening is approximated using interrupted nonabsorbable sutures. The proximal esophageal pouch is then mobilized as high as possible to afford a tension-free esophageal anastomosis. The blood supply to the upper esophageal pouch is generally robust and is based on arteries derived from the thyrocervical trunk. However, the blood supply to the lower esophagus is more tenuous and segmental, originating from intercostal vessels. As such, significant mobilization of the lower esophagus is avoided to prevent ischemia at the esophageal anastomosis. The anastomosis is performed using a single- or double-layer technique (Fig. 67-7A). The rates of anastomotic leak are slightly higher with the single-layer anastomosis, whereas the rates of esophageal stricture are higher with the double-layer technique.



In case of a long gap between the two ends of the esophagus, there are several options. The first option is to suture the divided end of the distal esophagus to the prevertebral fascia, mark its location with a metal clip, and close the thoracotomy. Over a 2- to 3-month period, the proximal esophageal pouch may grow so that a subsequent primary esophageal anastomosis may be possible. Second, a circular or spiral esophagomyotomy of the upper pouch may be performed to gain esophageal length and facilitate a primary anastomosis. Another technique involves the placement of traction sutures through the proximal and distal ends of the esophagus, brought out through the chest. These sutures are then progressively tightened and a primary esophageal anastomosis is performed after several days.8 Alternatively, a cervical esophagostomy may be constructed and a formal esophageal replacement performed at a later date.


In patients with pure esophageal atresia, primary anastomosis in the newborn period is not feasible because of a long gap between the two esophageal ends. Initially, a cervical esophagostomy for drainage of oral secretions and gastrostomy for enteral feeding access are performed. An esophageal replacement using the stomach, small intestine, or colon is then carried out at approximately 1 year of age. In some cases, the two ends of the esophagus may spontaneously grow so that a primary anastomosis may be accomplished by 4 months of age. The swallowing of saliva may actually promote elongation of the upper pouch, and an esophagostomy is therefore avoided. In patients with pure TEF, without esophageal atresia, the site of the TEF is usually in the region of the thoracic inlet. In this case, the surgical approach is through a cervical incision. At the time of surgical repair, it is often helpful to perform rigid bronchoscopy and cannulate the TEF with a guidewire to facilitate its identification. Recently, thoracoscopic repair has been described by several pediatric surgical centers (see Fig. 67-7B).9


The mortality rate of esophageal atresia or TEF is directly related to associated anomalies, particularly cardiac defects and chromosomal abnormalities. In the absence of these factors, survival of more than 95% of patients is expected. Postoperative complications unique to esophageal atresia or TEF include esophageal motility disorders, GER (25% to 50%), anastomotic stricture (15% to 30%), anastomotic leak (10% to 20%), and tracheomalacia (8% to 15%).



Gastroesophageal Reflux


GER is a common problem in infants and children. During the first year of life, infants normally experience some degree of vomiting, thought to be the result of an incompetent lower esophageal sphincter mechanism. This physiologic vomiting usually resolves spontaneously after 6 to 12 months. Pathologic GER can present with a spectrum of clinical symptoms. Although diagnostic studies can determine the presence of significant reflux, the patient’s symptoms remain as the most important factor in determining the surgical treatment of GER. Neurologically impaired children who are in need of enteral feeding access also have to be evaluated for concomitant reflux prior to gastrostomy placement. Today, a laparoscopic approach has become a standard for fundoplication with gastrostomy in pediatric patients.



Clinical Presentation


Pathologic symptoms of GER vary considerably, depending on the age of the patient and underlying associated medical conditions. Although vomiting is a common symptom, failure to thrive (FTT) as a result of caloric deprivation is one of the most critical complications of persistent GER in infants and children. Aspiration of gastric contents can also result in recurrent bronchitis or pneumonia, presenting initially with a chronic cough or wheezing. Reflux may stimulate vagal reflexes, producing laryngospasm or bronchospasm and leading to an asthma-like clinical picture.10 The significant airway spasm caused by reflux can result in apnea or choking spells, and may contribute to near-miss sudden infant death syndrome (SIDS). Irritability and crying in infants may also represent pain because of esophagitis induced by chronic reflux. Chronic acid insult to the lower esophagus can progress to the formation of stricture from chronic scarring and produce obstructive symptoms. Although rare in pediatric patients, chronic progressive esophagitis can lead to metaplastic replacement of normal lower esophageal squamous mucosa by columnar epithelium. This condition, known as Barrett’s esophagus, requires close surveillance to detect the progression of premalignant dysplastic changes.


Many children referred for antireflux surgery are neurologically impaired, usually secondary to such factors as metabolic conditions, head trauma, or birth asphyxia. Thus, most of these patients require permanent feeding access in the form of a gastrostomy tube, so antireflux surgery is often considered at the time of the gastrostomy placement, especially in patients who are unable to protect their airway reliably or who already have significant vomiting associated with intragastric tube feeding. However, the concept of prophylactic fundoplication at the time of gastrostomy in neurologically impaired children remains controversial. These patients are also at high risk for delayed gastric emptying because of upper gastroduodenal dysmotility. However, fundoplication alone may result in enhanced gastric emptying function.11



Evaluation


A detailed evaluation of the clinical history and associated symptoms will provide valuable guidance to determine the significance of GER. Clinical situations such as a near-miss SIDS episode or progressive neurologic disorders may indicate the desirability of performing an antireflux procedure, regardless of diagnostic study results. There are various diagnostic tools to objectively assess the presence of pathologic GER.


Barium esophagogram is used most frequently and provides anatomic and functional information about the esophagus and stomach. Esophageal stricture or mechanical evidence of gastric outlet obstruction, such as antral, duodenal web, or intestinal malrotation, can also be identified. Also, motility of the esophagus and gastric emptying function can be assessed by esophagography. However, one drawback is that this study lacks specificity. A 24-hour esophageal pH monitoring study remains as the gold standard test for diagnosing GER. It can determine the frequency and duration of acid reflux episodes and also provides significant information about reflux patterns, such as the total length of acid (pH < 4) reflux, duration of each episode, and longest continuous period of acid reflux. A gastric emptying scan is obtained when a radionuclide-labeled (99mTc sulfur colloid) liquid or semisolid food is used to assess gastric emptying quantitatively. This study can also identify the presence of GER. In general, approximately 50% of the isotope meal normally leaves the stomach within 60 minutes and approximately 80% empties by 90 minutes after ingestion of a labeled meal. Delayed gastric emptying may improve simply after an antireflux procedure alone.


Esophageal manometry measures the esophageal body and lower esophageal sphincter pressures and helps identify abnormal esophageal motility. Although relatively simple to perform, manometry is infrequently used to evaluate GER disorders in children. The severity of GER in infants does not always correlate with an incompetent lower esophageal sphincter mechanism. There has also been considerably less experience with manometric studies in pediatric patients. However, identifying patients with esophageal dysmotility may be important for selecting the appropriate antireflux procedure. Children with poor esophageal motility are prone to develop refractory dysphagia after complete wrap fundoplication. Endoscopic evaluation of the esophageal mucosa provides a gross and microscopic assessment of mucosal injury secondary to GER. Patients who present with hematemesis or dysphagia may have significant underlying esophagitis. Esophagoscopy can determine the spectrum of esophagitis from inflammation to ulceration to stricture, and is also helpful in identifying Barrett’s esophagus (columnar epithelium in the lower esophagus) via mucosal biopsy.




Hypertrophic Pyloric Stenosis


Hypertrophic pyloric stenosis (HPS) is a disease of newborns, with an incidence of 1 in 300 to 900 live births. It is one of the most common GI surgical disorders in early infancy; it is most common between the ages of 2 and 8 weeks. Boys are affected four times as often as girls, with first-born male infants being at highest risk. Hypertrophy of the circular muscle of the pylorus results in constriction and obstruction of the gastric outlet, leading to nonbilious, projectile emesis, loss of hydrochloric acid with the onset of hypokalemic hypochloremic metabolic alkalosis, and dehydration. Although the exact cause for HPS remains unknown, a lack of nitric oxide synthase in pyloric tissue has been implicated.




Treatment: Surgical Management


The treatment of HPS is pyloromyotomy, consisting of incising through thickened pyloric musculature while preserving the underlying mucosa. This can be performed through a right upper quadrant or periumbilical incision. Recently, laparoscopic pyloromyotomy (Fig. 67-8) has gained popularity because of better cosmesis, with similar outcomes to those of the open technique.12 Before surgery, it is important that the infant be fully rehydrated with IV fluids to establish an adequate urine output and correct electrolyte disturbances such as metabolic alkalosis. Because the infant with underlying metabolic alkalosis will compensate with respiratory acidosis, postoperative apnea may occur. Thus, the serum HCO3 level needs to be normalized before surgery. Postoperatively, infants are usually allowed to resume enteral feedings. Vomiting after surgery occurs frequently but is generally self-limited. Potential complications include incomplete myotomy, mucosal perforation, and wound infection.




Duodenal Atresia


Duodenal atresia is thought to occur as a result of failure of vacuolization of the duodenum from its solid cord stage. The range of anatomic variants includes duodenal stenosis, mucosal web with intact muscular wall (so-called windsock deformity), two ends separated by a fibrous cord, and complete separation, with a gap within the duodenum. It is associated with several conditions, including prematurity, Down syndrome, maternal polyhydramnios, malrotation, annular pancreas, and biliary atresia (BA). Other anomalies, such as cardiac, renal, esophageal, and anorectal anomalies, are also common. In most cases, the duodenal obstruction is distal to the ampulla of Vater (85%), and therefore infants present with bilious emesis. In patients with a mucosal web, the symptoms of postprandial emesis may occur later in life.




Treatment: Surgical Management


The management is by surgical bypass of the duodenal obstruction as a side-to-side or proximal transverse to distal longitudinal (diamond-shaped) duodenoduodenostomy (see Fig. 67-9B). At the time of anastomosis, a concomitant distal intestinal atresia should be ruled out by injecting saline into a distal limb using a soft red rubber catheter. When the proximal duodenum is markedly dilated, a tapering duodenoplasty with staples or sutures should be considered to reduce the duodenal caliber, which may improve postoperative gastric emptying. In patients with a duodenal mucosal web, the web is excised transduodenally. Caution must be exercised to preserve the ampulla during the web excision.



Jejunoileal Atresia


Jejunoileal atresia is the most common GI atresia; it occurs in approximately 1 in 2000 live births. It is thought to occur as a result of an intrauterine mesenteric vascular occlusion. Atresias occur slightly more frequently in the jejunum than in the ileum. Jejunoileal atresias are classified as type I, a mucosal web or diaphragm (Fig. 67-10A), type II, with an atretic cord between two blind ends of bowel with intact mesentery, type IIIa, a complete separation of the blind ends of the bowel by a V-shaped mesenteric gap, and type IIIb, an apple peel or Christmas tree deformity with a large mesenteric gap (see Fig. 67-10B), in which the distal bowel receives a retrograde blood supply from the ileocolic or right colic artery. This tenuous blood supply has implications for reanastomosis and the potential for ischemic necrosis caused by an antenatal volvulus. Thus, many of these infants with this type of atresia are born with reduced intestinal length. Finally, in type IV, there are multiple atresias, with a string of sausage appearance.






Intestinal Malrotation and Midgut Volvulus


The actual incidence of rotational anomalies of the midgut is difficult to determine, but is estimated to occur in 1 in 6000 live births. The midgut normally herniates out of the coelomic cavity through the umbilical ring at approximately the fourth week of fetal development. By week 10 of gestation, the intestine begins to migrate back into the abdominal cavity in a counterclockwise rotation around the axis of the superior mesenteric artery (SMA) for 270 degrees. The duodenojejunal segment returns first and rotates beneath and to the right of the SMA to fix in the left upper quadrant at the ligament of Treitz. The cecocolic segment also rotates counterclockwise around the SMA to rest in its final position in the right lower quadrant. By the week 12, this process of intestinal rotation is complete and the colon becomes fixed to the retroperitoneum. An interruption or reversal of any of these coordinated movements implies an embryologic explanation for the range of anomalies seen.



Abnormal Intestinal Rotation


Complete nonrotation of the midgut is the most common anomaly and occurs when neither the duodenojejunal nor the cecocolic limb undergoes correct rotation. Consequently, duodenojejunal and ileocecal junctions lie close together and the midgut is suspended on a narrow SMA stalk, which can twist in a clockwise fashion to result in midgut volvulus. Nonrotation of the duodenojejunal limb, followed by normal rotation and fixation of the cecocolic limb, result in duodenal obstruction by abnormal mesenteric bands (Ladd’s bands) that extend from the colon across the anterior duodenum. In this anomaly, although obstructive symptoms may be severe, the risk of midgut volvulus is low because there is a relatively broad mesenteric base between the duodenojejunal junction and cecum. Normal rotation of the duodenojejunal limb with nonrotation of the cecocolic segment carries the same risk for midgut volvulus as a complete nonrotation anomaly. In this case, the risks for volvulus are high because of a narrow mesenteric base.


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Aug 1, 2016 | Posted by in CARDIAC SURGERY | Comments Off on Pediatric Surgery
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