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Congenital cystic adenomatoid malformation of lung--differential diagnosis and management.

Congenital cystic adenomatoid malformation (CCAM) of the lungs is a developmental abnormality (hamartoma) (1). The clinical presentation, usually respiratory distress, and the chest X-ray findings may be confused with congenital diaphragmatic hernia (CDH) which is a commoner lesion. The importance of differentiating these conditions is highlighted by the case of CCAM we present, as the surgical approach, thoracotomy for CCAM and laparotomy for CDH differs.

A 26-day-old 2.2 kg male baby was referred to from a peripheral hospital with a diagnosis of CDH. The child presented with a history of laboured breathing for 10 days. On examination he was tachypnoeic with intercostal and subcostal recession. Auscultation revealed decreased air entry over the left hemithorax and heart sounds shifted to right. On chest X-ray, the left hemidiaphragm was not well visualised. This seemed to confirm the diagnosis of CDH and the child was booked for an exploratory laparotomy.

In the operating room, after securing intravenous access and routine monitors, the baby was preoxygenated and anaesthesia was induced with halothane in oxygen via facemask followed by 1 mg meperidine intravenously. The trachea was intubated orally. Anaesthesia was maintained with 1% halothane in oxygen and muscle relaxation achieved with vecuronium bromide.

Laparotomy demonstrated an intact diaphragm with normal placement of the bowel, liver and spleen thus excluding the diagnosis of CDH. The abdomen was closed and neuromuscular blockade was reversed. Adequate spontaneous ventilation was not established and the patient was transferred, still intubated, to the neonatal intensive care unit (NICU) for ventilatory support.

Case review and repeat chest X-ray after inserting a nasogastric tube showed the nasogastric tube in the abdomen, the stomach bubble present and the left hemithorax contained cystic gas-filled shadows. A diagnosis of CCAM was made. The following day at left thoracotomy, after a similar anaesthesia sequence as used for the laparotomy, the entire left lower lobe was found to be replaced by a cystic mass and left lower lobectomy performed. After an essentially uneventful intraoperative course and demonstration that adequate spontaneous respiration was again not achievable, the patient was transferred ventilated to the NICU. Postoperative chest X-ray showed good expansion of the right lung, minimal compensatory emphysema of the left upper lobe and the mediastinum still shifted slightly to the right.

On the second postoperative day, while still ventilated in the NICU, the patient developed a high fever. Despite a range of interventions, septic shock ensued and the sepsis syndrome progressed. The patient died on the 10th postoperative day.

In congenital cystic adenomatoid malformation, an absence of bronchial cartilage leads to air trapping. This may lead to airway collapse. The diagnosis of CCAM is suggested from clinical findings, chest radiograph and CT scan but can be confirmed only at surgery. The radiologic appearance of lesions can vary over time due to the variation in gas trapping, retained fluid secretions or superinfection (2). CT scan can detect areas of consolidation with heterogenous attenuation on enhanced scans and areas of low attenuation around cystic lesions (3). The differential diagnosis of CCAM includes diaphragmatic hernia, cystic bronchiectasis, congenital lobar emphysema, intrapulmonary bronchogenic cyst, prior infection with pneumatocoele formation and other foregut malformations.

Patients with CCAM usually present with gradually progressive respiratory distress as the lesion enlarges postnatally due to air-trapping (4,5). There is often an associated pulmonary hypoplasia in the remaining ipsilateral and contralateral lung induced by compression. The hypoplastic lung is excessively fragile and hence susceptible to barotrauma, resulting in alveolar rupture, with progression to pulmonary interstitial emphysema, pneumomediastinum and pneumothorax and even, on rare occasions, surgical emphysema and air embolism. This pattern or presentation and progression may mimic CDH.

An abdominal X-ray in patients with CCAM will usually demonstrate a normal abdominal gas pattern and exclude CDH. Passing a nasogastric tube and observing its position on X-ray may be helpful but a nasogastric tube will not always pass into the herniated stomach in CDH, leaving some doubt. In our case, the chest X-ray diagnosis suggested CDH and inability to pass the nagogastric tube in the first instance was attributed to this.

The treatment of symptomatic CCAM is excision of the affected lobe or lobes. When preoperative stabilisation is required it is essential to try to avoid positive pressure ventilation as this will risk further air-trapping and may result in rapid deterioration. The risk of air-trapping also affects anaesthetic management and, if possible, the baby should be allowed to breathe spontaneously until the chest is opened. Nitrous oxide should be avoided as it may cause expansion of air filled cysts. CCAM may have an anomalous vascular supply, so surgical mobilisation of the affected lobe should take this into account.

No attempt should be made at the end of the surgery to expand the ipsilateral lung to fill the hemithorax, as this manoeuvre may cause pneumothorax. There have been reports that avoiding postoperative pleural drainage may increase survival. If the baby has required preoperative ventilatory support or if the operation has been performed within 24 hours of birth, postoperative ventilation should be electively continued and weaning deferred for at least 24 hours (14).

Clinical manifestations and X-ray appearance of CCAM and CDH may be similar. Distinguishing the conditions is important to avoid a futile laparotomy as occurred in our case.

References

(1.) Stocker JT, Madewell JE, Drake RM: Congenital cystic adenomatoid malformation of the lung. Classification and morphologic spectrum. Hum Pathol 1977; 8:155-171.

(2.) Winters WD, Effmann EL, Nghiem HV, Nyberg DA. Disappearing fetal lung masses: importance of postnatal imaging studies. Pediatr Radiol 1997; 27:535-539.

(3.) Kim WS, Lee KS, Kim IO, Suh YL, Yeon KM, Chi JG et al. Congenital cystic adenomatoid malformation of the lung: ct-pathologic correlation. AJR Am J Roentgenol 1997; 168:47-53.

(4.) Cloutier MM, Schaeffer DA, Hight D. Congenital cystic adenomatoid malformation. Chest 1993; 103:761-764.

(5.) Al-Bassam A, Al-Rabeeah A, Al-Nassar S, Al-Mobaireek K, Al-Rawaf A, Banjer H et al. Congenital cystic disease of the lung in infants and children. Eur J Pediatr Surg 1999; 9:364-368.

R. GARG

A. BHALOTRA

M. ARYA

P. BHADORIA

G. MANCHANDA

New Delhi, India.
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Title Annotation:Correspondence
Author:Garg, R.; Bhalotra, A.; Arya, M.; Bhadoria, P.; Manchanda, G.
Publication:Anaesthesia and Intensive Care
Article Type:Case study
Geographic Code:9INDI
Date:May 1, 2008
Words:1008
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