Hydatid Cyst of the Lung
Echinococcal disease of the lung — diagnosis, imaging signs, and operative principles.
The lung is the second most common site of hydatid disease in humans after the liver. Echinococcosis is caused by the larval stage of the dog tapeworm Echinococcus granulosus (cystic echinococcosis — most common in humans). E. multilocularis causes alveolar echinococcosis.
Life cycle and pathogenesis
Adult E. granulosus inhabits the small intestines of primary hosts (dogs, canids) and releases eggs in faeces. Intermediate hosts (cattle, sheep) ingest eggs; oncospheres hatch and migrate via the circulatory system to form cysts in the liver and lungs. Humans are accidental dead-end hosts infected by contact with dogs, contaminated food, water, or soil.
Pulmonary hydatid occurs most commonly between ages 20–40. The cyst has three layers: an outer pericyst (host-derived fibrous tissue), a middle ectocyst (laminated membrane), and an inner endocyst (germinal epithelium).
Clinical features
Early cysts may be asymptomatic. Larger cysts cause cough, chest pain, and haemoptysis. Rupture into a bronchus produces hydatoptysis — expectoration of salty metallic fluid with grape-skin membranes and hydatid sand. Pleural rupture causes pneumothorax, effusion, or empyema. Cyst fluid is antigenic — rupture may cause anaphylaxis ranging from urticaria to full anaphylactic shock.
Imaging
| Sign | Appearance | Significance |
|---|---|---|
| Uncomplicated cyst | ||
| Cystic opacity | Well-circumscribed rounded/oval opacity | Intact cyst |
| Escudero–Nemerow sign | Change to oblong shape on deep inspiration | Confirms cystic nature |
| Bronchial communication / contained rupture | ||
| Meniscus / crescent sign | Thin rim of air on one side of cyst | Early communication |
| Cumbo sign / onion-peel | Separation of two cyst layers, ectocyst intact | Partial rupture |
| Complete rupture | ||
| Water-lily / Camelot sign | Collapsed membranes floating in cyst fluid | Complete rupture into bronchus |
| Whirl / serpent sign | Expectoration of fluid and collapsed membranes | Active drainage |
| Empty cyst sign | Pericyst outline with complete expectoration | Post-rupture cavity |
All patients should be screened for concomitant liver cysts. Serology (ELISA for E. granulosus IgG) provides complementary evidence but has lower sensitivity for lung than liver hydatid.
Treatment
Aspiration of pulmonary hydatid cysts is contraindicated — risk of puncture, spillage of cyst contents, anaphylaxis, pneumothorax, pleural contamination, and failure to address the bronchial communication or residual cavity.
Surgery — definitive treatment
Principles: (1) complete removal without spillage; (2) closure of bronchial communication; (3) obliteration of residual cavity; (4) preservation of normal lung parenchyma.
| Procedure | Technique | Advantage | Complication |
|---|---|---|---|
| Barrett's procedure (cystotomy with capitonnage) | Adventitial layer incised, laminated membrane extruded by PPV, bronchial openings repaired, residual cavity obliterated with purse-string sutures | Preserves lung parenchyma | Prolonged atelectasis |
| Perez-Fontana (pericystectomy) | Excision of cyst with pericyst; bronchial openings repaired; parenchyma approximated | Reduced recurrence | Air leak, BPF risk |
| Lobectomy | Excision of entire lobe | Cyst >50% of lobe, or when lobe unsalvageable | Parenchymal loss |
Scolicidal agents (hypertonic saline, povidone-iodine) are applied to the operative field to deactivate spilled fluid. For bilateral disease, the side with an intact cyst is operated first.
Medical treatment (adjuvant)
Albendazole is used perioperatively (4 days pre-operatively, continued 3–6 months post-operatively) and for: small cysts <10 mm, young children, disseminated disease, poor surgical risk, or intraoperative spillage. Monitor for hepatotoxicity and bone marrow suppression.
All clinical content should be verified against current guidelines before clinical application. This resource is intended for revision and educational purposes only.
Standard textbooks
- Shields TW, LoCicero J, Reed CE, Feins RH. General Thoracic Surgery. 7th ed. Lippincott Williams & Wilkins.
- Sellke FW, del Nido PJ, Swanson SJ. Sabiston & Spencer Surgery of the Chest. 9th ed. Elsevier.
- Pearson FG, et al. Thoracic Surgery. 3rd ed. Churchill Livingstone.