Overview
Congenital cystic adenomatoid malformation (CCAM) is one of a spectrum of congenital pulmonary lesions commonly seen by the pediatric surgeon. CCAM is characterized by a lack of normal alveolarization with an increased number of terminal bronchioles that are cystic in nature. These cystic lesions can range from less than 1 mm in size to greater than 10cm. Based upon the size of the lesions, CCAM’s can be described as macrocystic (lesions greater than 5.0cm) or microcystic radiographically. While the abnormal bronchioles do not participate in normal gas exchange, they maintain their connection with the normal tracheobronchial tree.1 This communication can lead to overinflation during aggressive attempts at resuscitation in the neonate. Additionally, inadequate clearing of normal respiratory bacterial pathogen may lead to recurrent pneumonias.1 The latter is the usual delayed presentation of children with CCAM not diagnosed prenatally or in infancy. Unlike bronchopulmonary sequestration (BPS), CCAM receive only blood supply from the pulmonary artery. CCAM’s may also show malignant degeneration if left unresected (pulmonary blastoma and rhabdomyosarcoma in infants and young children, bronchoalveolar carcinoma in older children).2
Prenatal Diagnosis
CCAM is routinely diagnosed on prenatal ultrasound. The differential diagnosis includes congenital diaphgramatic hernia, congenital lobar emphysema, bronchopulmonary sequestration, foregut duplication cyst and mediastinal cystic teratoma. Fetal MRI is used to differentiate between these lesions ultimately allowing for improved prenatal and postnatal care as well as prenatal counseling of the family.3 The size of the CCAM is significant prognostically. Compression of the esophagus may lead to polyhydramnios due to abnormal fetal swallowing of amniotic fluid. Compression of the mediastinum by a large CCAM may result in compression of the heart and great vessels ultimately leading to hydrops fetalis. CCAM volume ratio (CVR) can be determined using prenatal ultrasound by determining the CCAM volume and dividing by the head circumference to standardize for fetal size. A CVR greater than 1.6 is predictive of increased risk for hydrops.1 CVR can then be useful for determining which CCAM’s require increased level of surveillance prenatally. CCAM’s reach maximal growth before 28 weeks of gestation. Following this time period most CCAM’s either plateau in size or regress.1
Treatment
Treatment of CCAM is dependent upon the symptoms present. Prenatal management can consist of steroid treatment in fetuses with a CVR greater than 1.4. Betamethasone has been shown to arrest growth of CCAM with subsequent improvement in hydrops symptoms.1 A fetus that has been diagnosed with a macrocystic CCAM complicated by hydrops may be treated with thoracoamniotic shunting. Microcystic or solid CCAM’s that present with hydrops have been approached with fetal surgery. Late gestation fetus with hydrops may benefit from an ex utero intrapartum therapy (EXIT) approach.1 The fetus with a CCAM without hydrops should be managed with planned delivery and neonatal evaluation and surgery.
All newborns prenatally diagnosed with a CCAM should have a baseline radiograph at the time of birth. Surgical management should be based upon whether the newborn is symptomatic from the lesion. Persistent tachypnea, oxygen requirement, poor weight gain and inability to feed orally are indications for immediate resection. This has been classically performed through a posterolateral thoracotomy. Asymptomatic children may be discharged and followed up as an outpatient. At our institution, we typically perform preoperative imaging using computed tomographic scans at 3 months of age. CCAM’s are typically isolated to a single lobe, however, multilobar CCAM has been documented and will affect surgical decision making. Surgical resection, through a minimally invasive approach, is then carried out when the infant is 4 to 6 months old. Children who present with infected lesions are recommended to undergo adequate antibiotic therapy for the infection prior to the lesion. Minimally invasive approach is still a viable option in children who have had pneumonia; however, there has been a documented increase in conversion to open thoracotomy in these children.4
Minimally Invasive Approach
Preoperative imaging using computed tomographic scanning is obtained at 3 months of age as previously mentioned. The child should be placed in the lateral decubitus position with the affected side up. Central venous lines, arterial lines and bladder catheters are not required intraoperatively. Management of the airway requires an anesthesiologist experienced in pediatric airways to ensure adequate single-lung ventilation. Techniques available for isolating the contralateral lung include double lumen endotracheal tube in older children and adolescents. In younger children, a Fogarty balloon catheter (Edwards Lifesciences, Irvine, CA) may be used as an endobronchial blocker with placement of a single-lumen endotracheal tube. Infants may require mainstem intubation of the contralateral bronchus due to the narrow airway.4 Flexible bronchoscopy is necessary to ensure proper placement of the endotracheal tube and bronchial blocker during initial placement and after repositioning of the patient. We have not routinely placed epidural catheters preoperatively for pain management.
The surgeon and assistant both stand on the same side of the patient. We prefer to stand at the front of the patient with the monitor at the patient’s back. A veress needle is used to enter the chest cavity through a Step radially expanding sheath (USSC, Norwalk, CT). The hemithorax is then insufflated with low flow, low pressure carbon dioxide to aid in collapse of the affected lung. We typically preset our insufflations to 1 liter/minute with a pressure of 5 cm H2O. This initial entry site is typically through the 5th or 6th intercostal space in the mid-axillary line. Entry at this site will allow for visualization of the major fissure and the underlying pulmonary parenchyma.5 We typically use 3 5mm ports (2 working ports and 1 camera port). These ports are placed dependent upon the affected lobe and the location of the fissure to ensure adequate triangulation of the ports. A fourth stab incision for insertion of an instrument to assist with parenchymal retraction. Local anesthetic is infiltrated at each trocar site.
Resection of CCAM is typically through formal lobectomy. In the case of multiple CCAM’s affecting multiple lobes, segmental resection may be appropriate to preserve pulmonary parenchyma. The steps in dissection vary depending upon the affected lobe and follow the same principles as open thoracotomy.6 Completion of the major and minor fissure allows for visualization of the pulmonary vasculature and segmental artery branches. Division of the arterial branches is followed by division of the pulmonary vein. Initial division of the pulmonary artery prevents parenchymal congestion and preserves the intrathoracic work space. The Ligasure (Covidien Energy Devices, Boulder, CO) has proven to be an effective method of dividing pulmonary parenchyma to complete division of the fissure. This device has also been shown to be an effective method of division of pulmonary vessels. For larger vessels, control with an endoscopic hemoclip (Auto Suture ENDO CLIP, Covidien) or with intracorporeal suture ligation followed by division using an energy based sealing device has been described.4,7
Following division of the pulmonary vasculature, attention is turned to the segmental bronchus. In larger children, an endoscopic stapler can be utilized. In infants we prefer to use a locking hemoclip such as the Hem-o-lok system (Teleflex Medical, Research Triangle Park, NC). This ensures closure of the bronchus. The bronchus can also be divided and sutured with a monofilament, absorbable suture. After division of the bronchus, the specimen can then be removed by enlarging the most inferior trocar site. We do not routinely utilize an endoscopic pouch for specimen retrieval. After removal of the specimen an appropriately sized chest tube is placed in the most inferior incision. All wounds are then closed with absorbable sutures. The patient is extubated in the operating room and monitored overnight. We routinely remove the chest tube on the first post-operative day with discharge on the same day.
Summary
Thoracoscopic resection of CCAM is a safe alternative to open resection. Despite longer operative times, the minimally invasive approach has been shown in multiple studies to lead to decreased length of hospital stay, a shorter required time for chest tube and an overall lower postoperative complication rate.8,9,10 Current limitations for a thoracoscopic approach include patient size and inflammation from recurrent pneumonias making dissection more difficult. Additionally, newborn infants who present with symptomatic lesions are best treated with an open approach. Thoracoscopy in infants and children can be technically demanding but remains a viable option in the management of CCAM in the pediatric population.
References
1) Adzick NS, Farmer DL: Cysts of the Lungs and Mediastinum, in Coran AG, Caldamone A, Adzick NS, et al (eds): Pediatric Surgery, 7th edition, Mosby, 2012.
2) Chiu B, Flake AW: Congenital Lung Lesions, in Mattei P (ed): Fundamentals of Pediatric Surgery, Springer, 2011.
3) Pacharn P, Kline-Fath B, Calvo-Garcia M, et al. Congenital lung lesions: Prenatal MRI and postnatal findings. Pediatr Radiol 2013 Sep;43(9):1136-43.
4) Seong YW, Kang CH, Kim JT, et al. Video-assisted thoracoscopic lobectomy in children: Safety, efficacy, and risk factors for conversion to thoracotomy. Ann Thorac Surg 2013;95:1236-42.
5) Rothenberg SS. First decade’s experience with thoracoscopic lobectomy in infants and children. J Pediatr Surg 2008;43:40-45.
6) Waldhausen JA, Pierce WS, Campbell DB. Surgery of the Chest. St Louis, MO, Mosby Year-Book, 1995.
7) Bignon H, Buela E, Martinez-Ferro M. Which is the best vessel-sealing method for pediatric thoracoscopic lobectomy? J Laparoendosc Adv Surg Tech 2010;20(4):395-8
8) Vu LT, Farmer DL, Nobuhara KK, et al. Thoracoscopic versus open resection for congenital cystic adenomatoid malformations of the lung. J Pediatr Surg 2008;43:35-39.
9) Albanese CT, Syorak RM, Tsao KJ, et al. Thoracoscopic lobectomy for prenatally diagnosed lung lesions. J Pediatr Surg 2003;38:553-55.
10) Koontz CS, Oliva V, Gow KW, et al. Video-assisted thoracoscopic surgical excision of cystic lung disease in children. J Pediatr Surg 2005;40:835-37.
Robert Ricca, MD
Assistant Professor of Surgery, USUHS
Naval Medical Center
Portsmouth, VA
