Hydatid disease is a zoonosis caused by Echinococcus spp. Seen worldwide, E. granulosus is the most common, and is endemic in Spain. 1 Hepatic disease is the most frequent presentation, with approximately 65 to 75% of hydatid cysts located in the liver, whereas 15 to 25% of cases are observed in the lungs. Only 10% of cases are located in other organs. 1,2
Few symptoms are observed in the lungs and diagnosis is uncommon before the rupture of the cyst toward adjacent structures such as bronchi or pleura has occurred. In such cases the clinical presentation is variable and unspecific. The most frequent symptoms are cough, fever, hemoptysis, and chest pain. Radiologic findings of pulmonary nodules or masses is common. 3,4
We report an exceptional case of pulmonary hydatidosis that presented clinically as pneumonia secondary to atelectasis due to an endobronchial tumor.
A 37-year-old woman with a 2-month history of productive cough was admitted to the regional hospital. She had no previous systemic or pleuropulmonary disease. She was a nonsmoker with no history of drug abuse.
After 2 months of experiencing chronic cough, she presented with hemoptoic sputum production, mild pleuritic chest pain, weakness, and fever (38.6°C). Physical examination revealed hypoventilation at the base of the left lung. No other pathologic signs were observed.
On the day of admission, laboratory tests revealed a leukocyte count of 13,300 cells/μL (85% neutrophils, 7% lymphocytes, 7% monocytes, 1% LUC); erythrocyte sedimentation rate, 93 mm/hour; hemoglobin, 12.5 g/dL; hematocrit, 40%; and mean corpuscular volume, 87 fL. The routine blood chemical analysis was normal and included glucose, sodium, potassium, urea, creatinine, uric acid, cholesterol, total bilirubin, total proteins, albumin, alanine aminotransferase, aspartate aminotransferase, gamma-glutamyl transpeptidase, alkaline phosphatase, and lactate dehydrogenase. The blood coagulation parameters were also within normal values. The chest radiograph showed focal consolidation of the left lower lobe with loss of the cardiac silhouette accompanied by pleural effusion. Chest computed tomography (CT) revealed a left pleural effusion with secondary atelectasis of the left lower lobe and lingular consolidation with air and low-attenuation areas (Fig. 1). Examination of the sputum showed an intense, unspecific cell inflammatory reaction with the absence of neoplastic cells and without evidence of alcohol acid-resistant bacilli in Ziehl–Nielsen preparations. In the acute phase, the serologic studies for atypical microorganisms (Mycoplasma pneumoniae, Chlamydia pneumoniae, Legionella) were negative.
The patient was diagnosed with community-acquired pneumonia and treated with amoxicillin–clavulanic (875 mg/125 mg orally every 8 hours) with good clinical and radiologic response. The fever and chest pain disappeared, and the pulmonary infiltrate and pleural effusion improved with complete resolution in 1 week. The patient remained in good clinical status and was followed as an outpatient.
Several months later, the patient underwent 2 episodes of hemoptoic sputum production after exercise. An additional chest CT scan including high abdominal sequences showed a persistence of atelectasis of the lower lingular segment (Fig. 2). A flexible bronchoscopy was indicated, revealing the presence of a mucus plug in the inferior segment of the lingula that could not be aspirated. Upon suspicion of a subjacent endobronchial tumor (bronchial adenoma) with a high risk of bleeding after biopsy, only an adjacent bronchial mucosa biopsy and a bronchoaspirate were performed. The analysis revealed unspecific chronic inflammation without malignant cells or alcohol-acid resistant bacilli.
Due to these inconclusive results, the patient was transferred to our hospital to undergo further bronchoscopic evaluation. After the mucus plug was completely eliminated, a complete obstruction of the lower segmental bronchus of the lingula by a yellowish tumor surrounded by hyperemic bronchial mucosa was observed (Fig. 3). Several biopsies were obtained from tumor without significant bleeding. Anatomic pathologic examination revealed a hydatid cyst. Cyst lesions were not observed in the liver. The patient underwent a subsequent lingulectomy due to the presence of subjacent suppurative disease with destroyed lung parenchyma. The postoperative course was uneventful and, at present, the patient remains asymptomatic.
In hydatid disease produced by E. granulosus, the adult parasite lives on the intestinal wall of its definitive host (dogs or any other related canine) fixed by a double crown of hooks. The third segment of the parasite contains a great number of eggs that are passed in the feces of the infected animal, thereby infesting the environment. After the human ingestion of contaminated food or close contact with an infested dog, the eggs reach the duodenum, where they rupture. The freed embryo then penetrates the intestine wall to the portal venous system. The sinusoid capillaries of the liver can retain this embryo or, if it escapes, it can remain in the lung, where capillaries prevent further migration. More than 85% of hydatid cysts are located in the liver or the lung.
The pulmonary hydatid cyst presents few symptoms, and diagnosis is based on clinical and radiologic findings. 3,4 A significant number of cases are discovered in the asymptomatic stage due to the minimal pulmonary reaction of the cyst. This allows the cyst to grow (intact hydatid cyst stage) with the subsequent compression of adjacent structures. The consistency of the bronchus prevents cyst growth but the bronchial structure is compressed and the cartilaginous and muscular tissues of the bronchial wall are transformed into sclerotic tissue that favors its perforation. As a result of bronchial perforation, air enters the cyst, subsequently impairing nutrition of the cyst and leading to its rupture (complicated hydatid cyst). This finding is considered pathognomonic of a ruptured cyst with expulsion of its content: a watery fluid and the so-called hydatid sand formed by scolices and the remains of membranes that can be seen during bronchoscopy. Although typical, the expulsion of the cyst by coughing is observed in a small number of patients, approximately 9 to 17% of cases. 3–6 In some cases, pulmonary hydatidosis is presented as unresolved pneumonia 7 and is more rarely manifested as a cyst with intrabronchial growth and obstructive atelectasis.
The bronchial obstruction in our patient was observed in both the bronchoscopic examination and the chest CT scan. In the latter, the lumen of the lingular bronchus was found to have narrowed with an intrabronchial lesion obstructing the airway (Fig. 1). Once the obstructive pneumonitis was resolved with appropriate antibiotic treatment, the loss of volume was manifested as the typical triangular image of atelectasis and remained present in the chest CT (Fig. 2). The image was significantly different from that of a ruptured hydatid cyst. 8
In the intact cyst stage, typical radiologic findings include the presence of a smooth-edged mass, which is more prevalent in the periphery of the lower lobes. 3,6,9 In complicated cysts, the presence of air lamina between the cyst and its adventitia is considered a pathognomonic radiologic finding (meniscus sign). When the cyst is ruptured, an irregular fluid level may be seen in the cavity (water lily sign).
The bronchoscopic image was unusual in our patient. In general, endoscopic exploration is indicated for diagnostic purposes when the cyst is ruptured. 6,10 More frequently, a hyperemic bronchial mucosa, purulent secretions, and membranes can be observed. The endoscopic appearance of a hydatid cyst as an intrabronchial tumor has been described previously. 4,11 However, they were larger cysts with highly suggestive radiologic findings, and in no case were they described as atelectasis and obstructive pneumonia. Because this presentation is rare, we did not suspect hydatidosis and performed a biopsy of the lesion for diagnosis. The bronchoaspirates obtained during bronchoscopy were subsequently reexamined without evidence of scolices, stressing the indemnity of the cyst despite the biopsies obtained.
Surgery is the treatment of choice. 3,8,9,12 In our patient, a lingulectomy was performed due to the nonviability of the lung parenchyma secondary to the subjacent prolonged suppurative pulmonary lesion. The patient recovered satisfactorily and, at present, is asymptomatic and in a good state of health.
In summary, we report an exceptional presentation of a hydatid cyst with intrabronchial growth and obstructive atelectasis, as opposed to the more common presentation in which the clinical and radiologic findings are typical. 3,8,9,13 With the establishment of more adequate sanitary measures, the incidence of pulmonary hydatidosis has decreased over the last decade. However, this disease should be taken into account in patients with a pulmonary mass who come from endemic areas. In this context, the chest CT scan is helpful and can elucidate a diagnostic suspicion. During flexible bronchoscopy, biopsy of the endobronchial mass should be avoided whenever possible due to the risk of cyst rupture with subsequent bronchogenic dissemination and possible anaphylactic reaction.
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