Discussion
We reported a 17-year-old male presented with a large pulmonary hydatid
cyst (PHC). Spontaneous rupture of the cyst led to acute respiratory
distress syndrome requiring mechanical ventilation. Echinococcus
granulosus, a parasitic tapeworm is the pathogenic organism of hydatid
disease. This infectious disease is endemic in many parts of the world
such as Iran and it is considered a health concern in these countries.
While hydatid cysts could be produced in different organs, the liver and
lungs are the most frequently affected sites. The definite hosts of the
disease are carnivores such as dogs. Humans are defined as the
incidental intermediate host who is infected by direct contact with dogs
or ingestion of food contaminated by their feces. Echinococcal embryos
are released in the gastrointestinal lumen and reach the blood vessels
or lymphatics by penetrating the intestinal wall. Then they reach
different organs including the liver and lungs through the bloodstream
or lymphatics where they form hydatid cysts. As we mentioned in the case
presentation section our patient was a vegetable farmer and he might
have been infected by the ingestion of contaminated vegetables [3,
4].
Hydatid cyst remains asymptomatic during the first few years. Clinical
presentation depends on the location and size of the cysts. The most
frequently reported symptoms of pulmonary hydatid disease are cough,
chest pain, dyspnea, and hemoptysis. Rupture of the cysts or secondary
bacterial infection may occur. Rupture of the cysts either iatrogenic or
spontaneous may cause cough, chest pain, hemoptysis, emesis,
pneumothorax, pleural effusion, or empyema. Fever and hypersensitivity
reactions including anaphylaxis may occur as a consequence of cyst
rupture [3, 4].
Chest X-ray and chest CT scan are diagnostic tools for pulmonary hydatid
cysts. Similar to our case, on chest CT scans, PHCs are smooth-walled
cysts with variable thickness and contain soft tissue with the density
of water or near water. Leukocytosis, eosinophilia, and elevated ESR are
nonspecific laboratory features. The coexistence of pulmonary and liver
cysts is prevalent. Therefore, when PHC is diagnosed, additional imaging
like ultrasonography should be done to investigate possible liver cysts.
Surgery and medical treatment are two major therapeutic options. Surgery
is the treatment of choice. Medical treatment includes benzimidazoles
like mebendazole or albendazole which are administered orally and used
for specific indications such as disseminated disease, contraindication
for surgery, recurrent cysts, multiple cysts, or leakage of hydatid
fluid during operation [5, 6].
Fanne et al reported a 21-year-old female presented with productive
cough, dyspnea, and fever. Two cavitary lesions with air-fluid levels
were found on the chest X-ray. Five days after hospitalization she
developed eosinophilia, ARDS, and anaphylactic shock and was intubated.
Albendazole, praziquantel, and high doses of intravenous steroids were
administered. She improved after four weeks and underwent cyst resection
and lobectomy after discharge [7].
In conclusion, acute respiratory distress syndrome could be a possible
complication of a pulmonary hydatid cyst. Physicians should be aware of
this life-threatening complication for appropriate diagnosis and
treatment.