Introduction

  Hydatid cyst, or Echinococcosis, is an important helminthic zoonotic disease in humans that commonly affects liver and lungs. This disease result in high morbidity rates particularly in endemic regions. In Tunisia, this disease is endemic and the surgical incidence is 15/ 100000 habitants [1]. Hydatic cyst disease may cause atypical clinical and radiological features and complications that cause difficulties in diagnosis [2]. It can be asymptomatic or present with complications such as infection and perforation [3]. Hydatid cysts can be diagnosed by various imaging methods such as direct chest radiography and thoracic computed tomography (CT) [4]. Uncomplicated hydatid cysts, seen as round opaque lesions on chest radiography, are easily diagnosed, whereas complicated cysts (infected or/ and perforated) may change the radiographic appearance of the hydatid cyst, causing an incorrect diagnosis and delayed treatment.[5]. Here, we are reporting a patient of complicated hydatic cyst resembled a pneumonia.

Case presentation

  A 20-year-old female with no past medical history presented to our Emergency Department (ED) with complaints of sudden dyspnea and fever. Her general physical examination showed altered facies. She was febrile, alert with a pulse rate of 96/min, respiratory rate of 28/min and blood pressure of 110/76 mmHg. Examination of all other organs were essentially normal. Examination of the respiratory system revealed a decreased vesicular breath sounds and vocal resonance and an impaired percussion note in the right lower lung field. Complete blood count (CBC) came with a high white blood cell (WBC) count of 13 600 cells/L with 73% being neutrophils. Chest X-Ray (CXR) showed an atypical right basal triangular opacity with an outer vertex and an inner base with excavated density associated with an overlying focus of alveolar condensation (Figure 1). Initially, the patient was treated for pneumonia with antibiotic. CT scan demonstrated a complicated hydatic cyst partially ruptured in the right lobe (Figure 2). There was no other detectable lesion in the liver or any other organ. Further, there was no history of any pet dog. On the basis of clinical and radiological findings, she was diagnosed as having a complicated hydatid cyst. Surgery was indicated and the patient was admitted in “the thoracic surgery department”. 

Discussion

  Pulmonary hydatid disease is a serious problem in many countries, including several Mediterranean countries, New Zealand, Australia, North America, South America, Central America, and Asia [6]. The majority of hydatid cyst diseases are caused by the larval stage of Echinococcus Granulosus affecting mostly the liver and lungs, respectively [7,8]. In 60% of the cases, it is located in the right lung and in 20% of the cases the lesions are bilateral [9]. In our case, the lesion was unilateral and located in the right lung. The growth of hydatid cysts is slow and may remain undiagnosed for long periods [6]. Hydatid cysts have many presentations although the majority are asymptomatic and hence found incidentally [10]. However, they can rupture, which can cause symptoms of productive cough, coughing out cystic contents, hemoptysis and chest pain. The diagnosis is usually easy by typical radiological findings, especially if they are accompanied with hepatic hydatid cysts [10]. Uncomplicated cysts, seen as round opaque lesions on chest radiography, are easily diagnosed. However, infected and or perforated cysts, known as “complicated” cysts, may change the radiographic appearance of the hydatid cyst, causing an incorrect diagnosis and delayed treatment [11]. Imaging modalities and serology establish the diagnosis in most cases. However, when they are complicated with infection, the diagnosis can be quite challenging as the clinical and radiological findings become atypical [11]. Routine hematological and biochemical tests are unsupportive in the diagnosis of hydatid disease [12]. In diagnosis of hydatid cyst, tests such as indirect hemaglutination or indirect fluorescent antibody can be applied [13]. In our case, serological test was not done. Since the clinical and laboratory findings are not specific in the diagnosis of hydatid cyst, radiological scan gains importance at the diagnosis stage. Cysts that are not complicated are seen as well demarcated round or homogeneous masses in computer tomography and lung graphics. Larger cysts can result in atelactasy in lungs, mediastinal shift or pleural effusion depending on the level of the pressure on the neighbouring tissue. Lung graphics of the complicated cysts can show air-fluid level, water lily or meniscus signs. Ruptured cysts can appear as mass or abscess in computer tomography. In another study conducted on this issue, it was reported that hydatid cyst disease can easily be confused with thoracic empyema, mediastinal mass, tuberculosis pleurisy and thoracic wall tumour [14].

It should be kept in mind that pulmonary hydatid cyst in endemic regions clinically and radiologically can mimic lung infection when complicated.

Conclusion

  Due to their varied presentations, pulmonary hydatid cyst may imitate other chest diseases espacially when complicated and the diagnosis imposes major challenges. The disease should be considered especially in endemic regions.

References

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