Pulmonary cystic echinococcosis

Abstract

Purpose of review: Pulmonary cystic echinococcosis, a zoonosis caused by the larvae of the dog tapeworm Echinococcus granulosus, is considered as a major public health problem in countries where dogs are used to care for large herds. Despite its frequency and widespread endemicity, the literature on pulmonary cystic echinococcosis is scarce and not systematic. We aimed to summarize currently available information to provide a comprehensive overview for clinicians facing cases of pulmonary cystic echinococcosis.

Recent findings: Despite discrepancies in the literature, some patterns can be discerned. The ratio of lung:liver involvement is higher in children than in adults. Most pulmonary cases are discovered incidentally on routine radiograph evaluation; also most infected individuals remain asymptomatic until the cyst enlarges sufficiently to cause symptoms. Symptoms are usually caused by mass effect from the cyst. Complications (cyst rupture, aggregated infection) change the clinical presentation, producing cough, chest pain, hemoptysis, or vomica. Diagnosis is obtained by chest radiographs or computed tomography, and supported by serology. Presurgical chemotherapy reduces the chances of seeding and recurrence. Treatment with benzimidazoles is an option when surgery is unavailable or complete removal is unfeasible.

Summary: Diagnosis of pulmonary cystic echinococcosis is primarily made by imaging, and surgery remains the main therapeutic approach.

Figure 1

Life cycle of E. granulosus, adapted from reference 3

Figure 2

Scheme of a hydatid cyst: A) pericyst membrane (inflammatory host reaction); B) laminated layer (parasite origin); C) germinal layer; D), E). Daughter cyst.

Figure 3

Posteroanterior and lateral chest X rays showing lung cysts: A) Big cyst that is occupying the majority of right lung; B)Two cysts located in lower and middle lobe of right lung; C) Complicated (broken) cyst located in lower lobe, arrow indicates “camalote” or “water lily” sign ruptured cyst.

Figure 4

CT imaging in lung cystic Echinococcosis: A) Complicated cysts located posteriorly in the superior segment of the superior lobe with “mass within a cavity” sign. B) Complicated (broken) cyst located posteriorly in left lung, arrow indicates the communication between cyst cavity and bronchial tree. C) Complicated cyst located in the superior segment of inferior lobe in right lung, arrow indicates the appearance of “mass within a cavity” sign with air and air-fluid level.