PULMONARY CYSTIC ECHINOCOCCOSIS

Abstract

TOPIC: Chest Infections TYPE: Medical Student/Resident Case Reports INTRODUCTION: A lung nodule in an elderly patient almost always raises concern for lung cancer, irrespective of risk factors. While lung cancer remains foremost in the clinicians mind, a thorough occupational history may provide clues implicating a different diagnosis of more uncommon etiologies of lung nodule, such as in our case. CASE PRESENTATION: A 74 year old male with a history of hypertension and prostate cancer in remission presented to his primary care physician with 3 months of dry cough and chest pain. He had no smoking history. Vital signs showed a blood pressure of 170/93 mmHg, with other vital signs within normal limits. Physical examination and laboratory analysis was unrevealing. A chest radiograph showed a 2.9 centimeter (cm) left lower lobe nodule. Computerized tomography scan (CT) of the chest demonstrated a lobular left lower lobe lung nodule measuring 3x2x2 cm with smooth margins. Fluorodeoxyglucose (FDG)-positron emission tomography (PET) scan failed to reveal any other avid regions. A robotic left lower lobe wedge resection was performed, revealing a cystic membranous spherical lesion that spilled fluid when incised. Frozen section pathology showed a hydatid cyst containing innumerable Echinococcus granulosus organisms. He was started on albendazole therapy. It was later discovered that the patient was in the Army and deployed to rural southern Vietnam for 5 months in his youth, where he was working in farms and with wild animals, swimming through dirty water and drinking contaminated water. When back in the United States, he did cross country trips, riding mules in Utah. He also lived in Hawaii for 3 years with a dog. Echinococcus serology was negative. Repeat CT scan showed no other hydatid lesions and no other liver lesions. The patient completed 1 month total of albendazole and has recovered. DISCUSSION: Only a minority of lung involvement in E. granulosus infection coincides with liver cysts (20-40%). The lower lobes of the lung are commonly involved (60%). Patients may be asymptomatic, have cough, hemoptysis or even anaphylaxis (1). Differentiating an unruptured cyst from other pulmonary pathology such as malignancy, can be difficult radiographically. One Turkish study reports 7 patients in a 4 year span who had surgical removal of a presumed malignancy but were found to have a hydatid cyst (2), and can be a common occurrence in endemic areas. Chest imaging usually reveals a homogenous well-circumscribed lesion with smooth lobulated margins. If the bronchus is eroded, air is introduced into the cyst and may appear as a crescent of air (crescent sign) (3). CONCLUSIONS: Obtaining an extensive travel and exposure history may substantially alter the differential diagnosis of such lesions, and assist in diagnostic and management considerations. REFERENCE #1: Morar R, Feldman C. Pulmonary echinococcosis. Eur Respir J. 2003 Jun;21(6):1069-77. doi: 10.1183/09031936.03.00108403. PMID: 12797504. REFERENCE #2: Çobanoğlu U, Aşker S, Mergan D, Sayır F, Bilici S, Melek M. Diagnostic Dilemma in Hydatid Cysts: Tumor-Mimicking Hydatid Cysts. Turk Thorac J. 2015 Oct;16(4):180-184. doi: 10.5152/ttd.2015.4606. Epub 2015 Oct 1. PMID: 29404100. REFERENCE #3: Garg MK, Sharma M, Gulati A, Gorsi U, Aggarwal AN, Agarwal R, Khandelwal N. Imaging in pulmonary hydatid cysts. World J Radiol. 2016 Jun 28;8(6):581-7. doi: 10.4329/wjr.v8.i6.581. PMID: 27358685. DISCLOSURES: No relevant relationships by Oleg Epelbaum, source=Web Response No relevant relationships by Daniel Greenberg, source=Web Response No relevant relationships by Ravi Manglani, source=Web Response No relevant relationships by Fouzia Shakil, source=Web Response No relevant relationships by Helena Tomac Pavosevic, source=Web Response