ISPUB.COM The Internet Journal of Thoracic and Cardiovascular Surgery Volume 7 Number 2 1 of 4 The Diagnostic Value Of The "Air Bubble Sign" In Complicated Pulmonary Hydatid Cysts G Yuncu, S Örs Kaya, S Sevinc, N Karabulut, H Alper Citation G Yuncu, S Örs Kaya, S Sevinc, N Karabulut, H Alper. The Diagnostic Value Of The "Air Bubble Sign" In Complicated Pulmonary Hydatid Cysts. The Internet Journal of Thoracic and Cardiovascular Surgery. 2004 Volume 7 Number 2. Abstract The aim of this study was to investigate the utility of the "air bubble sign" in infected hydatid cysts. We reviewed the computed tomography findings in 35 patients with surgically proven infected hydatid cysts, of whom 13 cases did not have correct diagnosis preoperatively. We also assessed the CT findings in a randomly chosen 30 patients with various benign and malignant pulmonary diseases. We found the air bubble sign to be present in overall 30 of 35 cases (sensitivity of 85.7%) with infected hydatid cysts and in one of the randomly chosen 30 cases in the control group with various lung diseases (specificity of 96.6%). High accuracy rate of air bubble sign may help the correct diagnosis of complicated hydatid cysts in equivocal cases and preclude unnecessary investigations and invasive diagnostic procedures. INTRODUCTION Hydatid disease is prevalent and widespread in most sheep and cattle raising countries throughout the world. Pulmonary hydatid cyst is one of the most common diseases seen in thoracic surgical centers in Turkey with an incidence of 20 per 1.000.000 [ 1 ]. Pulmonary involvement occurs in approximately 15% of cases being the second most frequent site after liver [ 2 ]. A variety of signs denoting different appearances of the hydatid cysts have been described on chest radiographs and CT. In uncomplicated hydatid cysts, radiologic diagnosis is relatively easy. CT provides further information in equivocal cases by revealing the fluid density of an intact cyst and the air-fluid density of a ruptured cyst. However, infection of the cyst may increase the attenuation values and a produce a solid appearance, which may hamper the correct diagnosis. Such a complicated cyst, in the absence of positive history, serologic tests and other radiologic signs, may simulate a malignant tumour, tuberculosis, abscess and other infected cystic lesions of the lung. The “air bubble sign” was described in complicated cysts and reported to be an important clue in the differentiation of hydatid cysts from other disease processes [ 3 ]. This study aimed to assess the diagnostic value of the air bubble sign in the diagnosis of ruptured pulmonary hydatid disease. MATERIAL AND METHODS In the past five years, 35 consecutive patients (17 males, 18 females) who underwent surgical treatment for ruptured and infected hydatid cysts were included in the study. The patients ranged in age from 14-69 years (mean, 36.2 years). All patients had preoperative CT examinations which were reported as solid lesions measuring >20 HU in density. The correct preoperative diagnosis was not established in 13 cases based on radiologic and serologic findings. The control group consisted of 30 cases (16 males, 14 females; mean age 52 years, range 23-69 years) with pathologically proven 20 malignant (13 squamous cell carcinoma, four adenocarcinoma, one large cell carcinoma and two small cell carcinoma) and 10 benign (four tuberculosis, four pneumonia, one pulmonary embolism and one lung abscess) pulmonary diseases which may radiologically simulate complicated hydatid cysts. In all patients in the study and control groups, final histopathological diagnoses were available. CT examinations of both groups were re-evaluated in retrospect and reported by the two radiologists, first without taking account of, then considering the air bubble sign. The final decision was established by consensus. Data were statistically evaluated with the chi-square test using Statistical Package for the Social Sciences (SPSS , 11.0, Chicago, I11).