- Cyst – a round, parenchymal area of low attenuation with a thin wall (<4mm thick)
Pseudocyst of lung (acquired)
- Like a cyst but lacks epithelial/endothelial cells
- Fluid collection occurs as a result of exudation or degeneration
- Occurs in a cavity due to TB, lung abscess or staphylococcal pneumonia
Emphysematous cyst (acquired)
- Progressive disease of lung with rupture of alveolar wall and distension with air
- Cyst doesn’t have epithelial lining
- Compression of adjacent lung tissue occurs with poor gas exchange
- Clinical features – dyspnea, persistent cough
- Treatment – excision of cyst, lobectomy
- Complications – spontaneous pneumothroax, severe chronic bronchitis
Epithelial cyst (congenital)
- Developmental in origin
- Lined by respiratory epithelium
- Can be large single cyst or small multiple cysts
- Associated with cervical rib or cardiac anomalies
- More common in infants and children
- Clinical features
- Dyspnea, chest pain
- When cyst is infected – fever, cough, haemoptysis
- Treatment – excision of cyst, antibiotics
Echinococcal cysts (Hydatid cyst)
Epidemiology/etiology
- Echinococcus granulosus – most common in the Mediterranean, Middle East, Australia, S.Africa, S.America
- Definitive host – dogs, wolves, coyotes
- Intermediate host – sheep, goat, cattle, horses
- Cyst grows rapidly in lungs compared to other organs – as lungs have negative pressure
Clinical features
- Dyspnea, chest pain
- Haemoptysis, fever, cough
- Dark bloody sputum
- Rupture into alveolar tree – anaphylaxis
- Rupture – expectoration of fluid and grape skins
- Anorexia, WL
Complications
- Rupture of cyst
- Anaphylaxis
- Secondary infections
- Calcification of cyst
- Lung collapse, pleural effusion
- Secondary pleural hydatid formation
- Hepato-bronchial fistula – forms bilious sputum
Investigations
- CXR
- Dense homogenous opacity
- Water lily sign – collapsed laminated membrane produces an irregular projection in a fluid level
- Casoni’s test – intradermal injection of hydatid fluid; a wheal response at the injection site is considered positive
- Blood – eosinophilia
- Bronchoscopy – find laminated membrane and hooklets in bronchial aspirate
- PAIR – puncture, aspirate, inject NaCl (scolicidal agent), reaspirate
Treatment
- Chemotherapy if patient is unsuitable for surgery
- Albendazole 10mg/kg/d – 2 weeks
- Surgery
- Enucleation of cyst – Barret’s technique
- Resection only reserved for very large cysts
- Lobectomy – for cysts in >50% of lobe; cysts with severe pulmonary suppuration; other issues (pulmonary fibrosis, bronchiectasis, haemorrhage etc)
- Cyst rupture in pleura – medical emergency
- Treatment – irrigation and drainage