Pathological finding of subclinical interstitial pneumonia as a predictor of postoperative acute respiratory distress syndrome after pulmonary resection.

OBJECTIVE Post-surgical interstitial pneumonia (IP) is a part of postoperative acute respiratory distress syndrome (ARDS). Some cases of ARDS may be an acute exacerbation of idiopathic pulmonary fibrosis (IPF) that is generally not recognised as IPF prior to surgery. In this study, we evaluated IP on preoperative computed tomography (CT) and histopathological findings in patients who underwent thoracic surgery, and attempted to identify high-risk patients who might develop postoperative ARDS. METHODS A retrospective review of preoperative CT and histopathological examination was performed in 487 patients who underwent lobectomy for primary lung cancer at our institute. RESULTS The incidence of ARDS was 2.05%, and histopathological finding of IP was the only predictor of ARDS (P = 0.038, odds ratio (OR) = 6.89). The incidence of IP on histopathological examination was 9.7% for all cases of lung cancer; and the incidence of ARDS in the IP-positive group (31.8%) was significantly different from that in the IP-negative group (1.5%) (P<0.05). However, in 85.7% of patients with ARDS, who were histologically IP-positive, IP was masked by emphysematous findings and thus not detected on preoperative CT. CONCLUSIONS In this study, histopathological finding of IP was the only predictor of ARDS; however, it was difficult to identify preoperatively because emphysematous change was also present in the majority of cases, which masks the findings of IP on CT. If identification of the high-risk case of ARDS is insisted upon, screening the presence or absence of IP (e.g., just in the patients with emphysema or IP finding on CT) by histopathological examination, as the need arises, after surgery using resected lung might be one of the additional methods of identifying those at high risk of ARDS.