Clinical History
A 25-year-old farmer from India, on anti-tuberculosis treatment for 2 months presented with acute onset dyspnoea, chest pain and acute onset copious whitish sputum stained with blood. Rhonchi were auscultated in right apex and bronchial breath sounds in left lower zone. Sputum analysis was positive for acid-fast bacilli.
Imaging Findings
Chest X-ray and Scanogram of thorax demonstrated a well-defined cavity in the left lower zone with membrane-like structures within. Right apical segment delineated multiple cavities. Few fine fibrotic lines were noted in both the lung fields, predominantly in right hemithorax. Right upper zone appeared collapsed with ipsilateral tracheal traction and right middle and lower zone were collapsed with elevation of the diaphragm.
HRCT thorax, axial, sagittal and coronal reformatted images clearly depicted a well-defined spherical cavity in the basal segment of the left lower lobe, with collapsed membranes within. Cavitatory and fibrotic changes noted on chest X-ray were confirmed.
Discussion
A. Tuberculosis in the tropics is rampant, and so is echinococcosis. And co-existence of both, although rare in Western countries, is more frequent in endemic areas. [1] Unhygienic rearing of animals is an important predisposing factor. Incidence of human echinococcosis is closely related to the prevalence of the disease in domestic animals. E. granulosis causes cystic echinococcosis and is endemic in the Mediterranean, Middle East, and Latin America. E. multilocularis causes alveolar echinococcosis and is endemic in Alaska, central Europe, Turkey and China. Humans become exposed to eggs of tapeworm after close contact with dogs. Typically larvae that pass through the liver are trapped in pulmonary arterial capillaries and develop into hydatid cysts. [2]
Cystic echinococcosis most commonly affects liver followed by lung. Pulmonary hydatid disease affects the right lung in 60% cases, mostly in the lower lobes. [3]
B. Symptomatology of both diseases is essentially the same - mild cough with or without expectoration, chest pain and haemoptysis. Differentiating one from the other clinically is far-fetched. Rupture is often accompanied by expectoration of copious amount of salty expectoration. Symptomatic hydatid disease of lung follows rupture of the cyst. [3]
Serological diagnosis for either of the two diseases may not be confirmatory [4]. Due to a wide spectrum of presentation, false negative serological tests are common.
C. Radiological features are conclusive with CT leading the investigation protocol. [4]
Diagnosis of intact hydatid cyst is usually based on a suspicion resulting from an unexpected finding on routine chest radiographs in a patient from an endemic area. Radiographically, it appears as a homogeneous spherical opacity with definite edges. Calcification is rare. Even the availability of a basic chest X-ray in the periphery would point the clinician towards a presumptive diagnosis and referral of these patients to the nearest tertiary equipped centre.
Cyst rupture is the commonest complication of pulmonary hydatidosis. The characteristic “serpent sign” can be noted due to collapsed membranes within the cyst.
Fluoroscopy and CT demonstrate “water lily sign” due to membranes seen floating in the cyst's fluid. Air lining between the pericyst and endocyst is appreciated on CT as “cumbo sign”.
D. Surgical enucleation or pericystectomy is the treatment of choice. It is imperative to continue medical treatment post-operatively. [4]
E. Teaching points:
• Unhygienic rearing of animals in tropics is a common predisposing factor (Occupational history).
• False negative serology maybe seen.
• CT is the imaging modality of choice.
• Serpent sign is classical for ruptured hydatid cyst.
Differential Diagnosis List
Spontaneously ruptured pulmonary hydatid cyst with concomitant tuberculosis.
Fungal colonisation of tuberculous cavities
Tuberculous lung abscess
Final Diagnosis
Spontaneously ruptured pulmonary hydatid cyst with concomitant tuberculosis.
