Ruptured Pulmonary Hydatid Cyst Complicated by Tension Pneumothorax: A Rare Case Report

Introduction

Hydatid cyst (HC) is a zoonotic disease known since the time of Hippocrates. It commonly occurs in regions where agriculture and animal husbandry are prevalent, particularly in the absence of adequate preventive measures. The disease is caused by Echinococcus granulosus, a cestode parasite. ¹ It primarily affects the liver and lungs, with a prevalence of 5% to 10% in endemic areas of Asia. ² In the lungs, hydatid cysts typically present with nonspecific symptoms such as cough (60%), chest pain (45%), dyspnea (25%), and hemoptysis (12%). The most diagnostic feature of excitation of cyst fluid or membranes is pathognomonic but rare, observed in only 7% of cases.^1,3 Radiological imaging, particularly computed tomography (CT) and magnetic resonance imaging (MRI), plays a central role in the diagnosis of pulmonary cystic echinococcosis (CE), while serological tests can offer supportive evidence. ⁴ Rupture of pulmonary hydatid cysts presents a diagnostic challenge, as it can mimic recurrent pneumothorax radiologically. The reported incidence of rupture ranges from 2.4% to 6.2%. ⁵ Rupture may occur spontaneously, after trauma, or in some cases be triggered by a forceful cough. ⁶ We report the case of a 20-year-old female from Syria who presented with a ruptured pulmonary hydatid cyst complicated by tension pneumothorax and pleural effusion. The work has been reported in line with the SCARE criteria. ⁷

Case Presentation

We report the case of a 20-year-old female from Syria who presented to the emergency department with sudden-onset severe shortness of breath, right-sided pleuritic chest pain, palpitations, and a dry cough. Notably, she had experienced intermittent right-sided chest pain and dry cough for approximately 2 months prior to presentation, which partially improved with over-the-counter analgesics. She denied fever, chills, weight loss, night sweats, hemoptysis, or other systemic symptoms. On physical examination, the patient appeared in respiratory distress. Vital signs showed tachypnea (RR: 30 breaths/min), tachycardia (HR: 120 bpm), hypotension (BP: 90/60 mmHg), and oxygen saturation of 95% on room air. Chest examination revealed asymmetrical chest wall movement, absent breath sounds, and decreased tactile fremitus on the right lung field. The remainder of the physical exam was unremarkable.

An urgent chest X-ray showed a massive right-sided pneumothorax with complete collapse of the right lung and mediastinal shift to the left (Figure 1). A well-defined rounded opacity with a visible air–fluid level and the Water Lily sign was identified in the lower zone of the right lung, suggestive of a ruptured pulmonary hydatid cyst. A follow-up chest CT confirmed a large ruptured hydatid cyst in the right middle lobe associated with a moderate pleural effusion and tension pneumothorax (Figure 2). An emergent needle decompression was performed through the second intercostal space at the midclavicular line, followed by insertion of a 28 Fr chest tube, which drained approximately 1 l of clear fluid along with continuous air leak. The patient’s respiratory and hemodynamic status improved markedly after decompression.

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Figure 1.

Initial chest X-ray showing massive right-sided pneumothorax with complete lung collapse, mediastinal shift to the left, and a rounded opacity in the right lower zone with air–fluid level and a visible Water Lily sign.

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Figure 2.

Chest CT scan confirming the presence of a large ruptured hydatid cyst in the right middle lobe, associated with tension pneumothorax and moderate pleural effusion.

Definitive surgical management was carried out 2 days later via right posterolateral thoracotomy through the sixth intercostal space under general anesthesia. Intraoperatively, a ruptured hydatid cyst was found occupying the middle lobe. The germinative membrane was carefully removed, the cavity was thoroughly irrigated with normal saline, bronchial fistulas were individually closed, and capitonnage was performed. A 28 Fr chest tube was reinserted, and complete lung re-expansion was confirmed intraoperatively.

Postoperative recovery was uneventful. The chest drain was removed after 72 hours once output had decreased to 25 ml/24 hour with no air leak, and imaging confirmed full lung expansion. The patient was discharged in stable condition. At follow-up, a chest X-ray taken 4 months later showed complete recovery with no signs of residual disease or recurrence.

Discussion

Cystic echinococcosis (CE), also known as hydatid disease, is a parasitic infection caused by Echinococcus granulosus, with dogs serving as the definitive hosts. It remains an underrecognized global public health concern, particularly affecting rural and livestock-raising communities. ⁸ Hydatid cysts are composed of 3 distinct layers: an outer host-derived fibrous layer known as the pericyst, and 2 inner parasite-derived layers the laminated membrane (exocyst) and the germinal layer (endocyst). The germinal layer is responsible for producing protoscoleces and daughter cysts. ⁹ Cystic echinococcosis (CE) is transmitted to humans through the ingestion of Echinococcus eggs present in dog feces, typically via contaminated food, water, or direct contact with infected dogs. Once ingested, the embryos (oncospheres) hatch in the small intestine, penetrate the intestinal wall, and enter the portal circulation. Most are filtered and deposited in the liver, but some may bypass the hepatic barrier via the hepatic sinusoids and reach the lungs or other organs through the systemic circulation. Alternatively, embryos may reach the lungs via lymphatic spread or, less commonly, through direct inhalation of air contaminated with Echinococcus eggs, potentially entering the tracheobronchial tree.^9-11 Cystic echinococcosis (CE) is often asymptomatic and frequently detected incidentally during imaging studies. It typically presents as a solitary cyst; however, multiple cysts or involvement of multiple organs may occur. The presence of multiple cysts can result from hematogenous dissemination or secondary to the rupture of a pre-existing cyst. The liver is the most commonly affected organ, accounting for approximately 70% of cases, followed by the lungs in 10 to 30% of cases.^9,11 Pulmonary hydatid cysts (PHCs) are predominantly unilateral in approximately 80% of cases and most commonly involve the lower lobes, particularly the right lower lobe, in around 60% of patients. ¹² In contrast, our patient presented with a ruptured hydatid cyst located in the right middle lobe, a less commonly affected site.

Symptomatic presentations often arise from cyst rupture or from compressive effects of large cysts typically those exceeding 5 cm in diameter on adjacent structures. ¹³ Rupture may occur spontaneously or be triggered by trauma, often manifesting with sudden-onset cough, chest pain, or fever. Expectoration of cyst contents may lead to a characteristic salty or peppery taste. In addition, rupture can provoke hypersensitivity reactions, including urticarial rash, fever, wheezing, or even anaphylaxis. Other potential complications of PHCs include secondary bacterial or fungal infections, pneumothorax, hemoptysis, hematogenous spread leading to new cysts in distant organs, and rarely recurrent pulmonary embolism due to cyst migration into vascular structures. ⁹ In our case, the patient presented with sudden respiratory distress and a large tension pneumothorax, which was later attributed to spontaneous rupture of a middle lobe hydatid cyst an example of a life-threatening but rare complication.

The diagnosis of PHC is usually based on a combination of epidemiological risk factors, imaging and serology. Uncomplicated PHCs appear on chest X-ray as homogenous, sharply defined, round or oval opacities. On CT they appear as cystic lesions with smooth walls of variable thickness with homogenous internal contents with fluid density.^9,13 When partial evacuation of the cyst fluid occurs, the collapsed germinal membrane (endocyst) may detach and float on the remaining fluid, creating the characteristic “Water Lily sign” (also known as the “Camelotte sign”) on imaging. ¹⁴ In our case, the presence of the Water Lily sign on the initial chest X-ray provided strong radiological evidence of cyst rupture, which facilitated prompt diagnosis and expedited surgical management.

Serologic tests demonstrate a sensitivity of 85% to 95% for hepatic hydatid cysts, but their sensitivity drops to approximately 50% to 60% in pulmonary cases. Therefore, serology serves as a confirmatory tool rather than a reliable rule-out test in the diagnosis of pulmonary hydatid cysts.^15,16 Enzyme-linked immunosorbent assay (ELISA) and indirect hemagglutination assay (IHA) are the most commonly employed serological methods for detecting anti-Echinococcus antibodies. Among them, IgG ELISA is reported to be the most sensitive technique for diagnosing hydatid disease. ¹⁷ The differential diagnosis of pulmonary hydatid cysts includes lung abscess, cavitary tuberculosis, infected benign cysts, and cavitating pulmonary neoplasms. In such conditions, rupture into the pleural cavity can similarly result in hydropneumothorax or pyopneumothorax, making imaging interpretation more challenging. ¹⁸ Pulmonary hydatid cysts (PHCs) can be treated medically or surgically depending on cyst size, location, and symptom severity. Medical therapy, using benzimidazoles like albendazole, is typically reserved for small cysts (<5 cm) or inoperable cases. Albendazole is preferred for its superior bioavailability, given at 400 mg twice daily in adults, with treatment lasting at least 3 to 6 months.^19,20 Surgery remains the definitive treatment for operable cases, especially when complications are present. Intraoperative precautions such as injecting scolicidal agents (eg, 20% hypertonic saline, povidone-iodine, ethanol) and isolating the field are essential to prevent spillage and recurrence.^21-23 In our case, surgery was clearly indicated due to the cyst’s large size, its middle lobe location, and serious complications including tension pneumothorax and pleural effusion following rupture.

Limitations

This report describes a single patient; therefore, the findings cannot be generalized or used to establish causality. In addition, serology may be less sensitive in pulmonary echinococcosis and was not relied upon as a standalone diagnostic tool. Finally, follow-up was limited to 4 months, which may not fully capture late recurrence.

Conclusion

Pulmonary hydatid disease remains a significant diagnostic and therapeutic challenge, especially when complicated by cyst rupture. This case underscores the importance of high clinical suspicion in endemic regions, as well as the need for rapid stabilization and definitive surgical management. A multidisciplinary approach involving imaging, surgery, and antiparasitic therapy offers the best chance for complete recovery and prevention of recurrence.