Pediatric surgical image Localized persistent pulmonary interstitial emphysema Jagadish Rao, Mitchel I. Hochman, Grant G. Miller * Department of Surgery, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 4N3 A 3-week-old premature female infant was referred to our institution with progressively worsening respiratory distress. She was born at 29 weeks’ gestational age with radiologic evidence of mild respiratory distress syndrome. She required only minimal supplemental oxygen until her third week of life, when she developed worsening respiratory distress requiring mechanical ventilation. A new chest radiograph (Fig. 1) demonstrated hyperinflation of the left hemithorax with coarse reticular markings throughout the left lung. Computed tomography (CT; Fig. 2) revealed innumerable cystic spaces of varying sizes occupying the entirety of the left upper lobe, with no appreciable normal lung parenchyma interposed. She failed to wean from mechanical ventilation and underwent an urgent left thoracotomy. The entire upper lobe was grossly involved with cystic lung pathology (Fig. 3). This was treated by an uncomplicated left upper lobectomy, and the patient was weaned from mechanical ventilation over the next 3 days. The histopathology (Fig. 4) demonstrated cyst-like cavities lined by an irregular layer of cells within the lung parenchyma. These cells were mostly mononuclear admixed with foreign body–type multinucleated giant cells. The cysts were interspersed with essentially nor- mal-appearing pulmonary tissue. Occasional air spaces were questionably dilated, particularly at the periphery of the lung beneath the pleural surface. However, widespread emphysematous changes were not apparent; neither was there any significant intraalveolar or interstitial inflammatory cell infiltrate. These findings were diag- nosed as localized persistent pulmonary interstitial em- physema (PIE). Pulmonary interstitial emphysema is characterized by gas dissecting the interstitial tissues of the lung. It has 3 distinct forms: acute PIE, localized persistent PIE (LPPIE), and diffuse persistent PIE. This may occur as a result of increased intraalveolar pressure secondary to aspiration, partial bronchiole occlusion, or positive pressure ventilation and may cause overdistended pulmonary alveoli with resultant dissection of air into the interstitium. In acute PIE, the air tracks from the interstitium into adjacent spaces, causing pneumothorax, pneumomediastinum, or pneumo- pericardium. In persistent PIE, the air persists within the interstitium rather than tracking elsewhere. It may be localized to one lobe or diffusely present throughout the lung parenchyma. Acute PIE most often develops with hyaline membrane disease. It is less commonly associated with high ventilatory support provided to infants with obstructive air trapping secondary to meconium aspiration or pulmonary hypoplasia. Localized persistent PIE is also associated with hyaline membrane disease but can, as in this case, develop spontaneously. Diffuse persistent PIE is most commonly associated with bronchopulmonary dysplasia. These 3 forms of PIE can be distinguished radiograph- ically. On chest roentgenograms, LPPIE appears as a unilobar or multilobar multicystic, air-filled mass with mass effect. This may cause the contralateral lung to collapse, often increasing oxygen requirements and causing greater air trapping. Chest CT is helpful in differentiating LPPIE from other lesions, such as congenital cystic adenomatoid malformation or congenital lobar emphysema, as the abnormal air collection is in the interstitium and surrounds the bronchovascular bundles. The bronchovascular bundles 0022-3468/$ – see front matter D 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.jpedsurg.2006.01.071 * Corresponding author. Tel.: +1 306 966 8141; fax: +1 306 966 7988. E-mail address: miller@duke.usask.ca (G.G. Miller). Journal of Pediatric Surgery (2006) 41, 1191 – 1193 www.elsevier.com/locate/jpedsurg