The diagnosis of IPF depends on the correlation between clinical, radiological and pathological findings, after eliminating the known causes of interstitial lung disease, such as asbestosis that have similar pathological findings in the lung [6,10]. IPF has a heterogeneous clinical course, from an asymptomatic stable state to progressive respiratory failure or acute exacerbation. Smoking history has a strong association with IPF, especially the risk of heavy smokers was significantly elevated . Histologically, IPF is characterized by patchy interstitial fibrosis which is progressively worse with time variation. The interstitial fibrosis indicated an accumulation of extracellular matrix and fibroblasts in the distal airways [12, 13]. The chest computed tomography (CT) of IPF demonstrates reticular markings distributed in a bilateral and asymmetric pattern with predilection towards the lower lobes . High-resolution computed tomography (HRCT) is more accurate than chest roentgenogram in diagnosing IPF .
In our case, the patient showed no preoperative inflammatory signs and relevant respiratory symptoms. The preoperative chest roentgenogram showed slight interstitial change in bilateral lungs. The patient experienced an uneven postoperative recovery process with an increased HR, unstable BP, dyspnea, cyanosis, comatose, and reduced oxygen saturation. The mask oxygen inhalation, the oral trachea cannula and the nasal catheter oxygen inhalation were used to maintain oxygen saturation. The patient died in general ward after extubation eventually although he experienced full consciousness recovery and remained stable for one day after removal of the oral trachea cannula and assisted respiration. The autopsy showed significantly increased lung weight with tough texture and multifocal pulmonary interstitial fibrosis and thickening of pulmonary arteries in histology. No evidence of etiology associated with secondary pulmonary fibrosis was found. Based on the histological examination, chest roentgenogram and acute clinical deterioration, the cause of death was identified as AE-IPF after eliminating heart failure and acute lung injury of known cause such as infection and pulmonary embolism. Combined with the victim’s 20-year history of smoking, we thought the patient had IPF before surgery and AE have occurred in the early course of IPF.
AE-IPF was reported to occur after pertussis, influenza (H1N1) vaccination, accidental inhalation of waterproof’s vapor containing siloxanes [16-18]. In addition, post-operative stress might be also a causation of AE-IPF. Some studies have reported the occurrence of AE-IPF appeared after non-pulmonary surgery such as cholecystectomy and resection of lipoma in the neck . The inflammatory response to surgical intervention, exposure to a high concentration of oxygen, and overdistension of the lung by positive pressure ventilation are thought to be possible factors that trigger a rapid deterioration of IPF . Thus, we speculated that the surgery and general anesthesia were related to the deterioration of IPF in this case.
The present case is rare that AE occurred in symptomless IPF after non-pulmonary surgery. The medical personal should recognized that the localized interstitial pulmonary fibrosis might be symptomless and not detectable. We highlight that the physicians and pathologists should pay close attention to clinical, radiological and pathological characters of IPF.