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Tex Heart Inst J. 2009; 36(3): 230–233.
PMCID: PMC2696497

Primary Intrathoracic Extrapulmonary Hydatid Cysts

Analysis of 14 Patients with a Rare Clinical Entity

Abstract

Primary hydatid cysts very rarely form in intrathoracic yet extrapulmonary sites. Accurate preoperative diagnosis in such cases is difficult, and corrective surgical procedures necessarily differ from those that are used to treat the far more typical pulmonary or hepatic hydatid cysts. We retrospectively evaluated the diagnostic and operative characteristics of intrathoracic extrapulmonary hydatid cysts, and we examined the outcome of aggressive surgical interventions that went beyond conventional parenchymal-sparing procedures.

From 2003 through 2007, 14 patients (mean age, 39.14 ± 16.8 yr) underwent surgical treatment in our hospital for primary intrathoracic extrapulmonary hydatid cysts. These cysts were variously in the diaphragm, chest wall, mediastinum, pleura, and pericardial cavity. All patients underwent cystectomy, decortication, resection, and repair of the adjacent structure. No complication, recurrence, or death occurred in the follow-up period of 15 ± 18.1 months (range, 2–52 mo).

In order to achieve complete resection and to avoid recurrence of disease from intrathoracic extrapulmonary hydatid cysts, the thoracic surgeon should forgo cystotomy and capitonnage in favor of cystectomy with a wide resection and reconstruction of surrounding tissues. Postoperatively, patients should adhere to a regimen of anthelmintic therapy.

Key words: Anthelmintics/therapeutic use, echinococcosis/complications/diagnosis/radiography/surgery, incidence, recurrence, retrospective studies, thoracic diseases/diagnosis/parasitology/surgery, thoracic surgical procedures, operative/methods, treatment outcome, Turkey/epidemiology

Hydatid cyst disease, or echinococcosis, is a parasitic disease that has been known since the time of Hippocrates. It remains endemic in Turkey and other countries. Although the liver and the lungs are the usual sites of the disease, cysts can also form elsewhere in the body.1,2 It is not difficult to diagnose typical pulmonary or hepatic hydatid cysts. Conversely, when cysts appear intrathoracically but in extrapulmonary locations, crucial diagnostic difficulties may occur, with atypical clinical and radiologic signs. Cysts in such sites can lead to fatal complications, such as bronchial rupture, fistulas to the pleural and pericardial cavities, and severe bleeding.3,4 Difficulties in diagnosis notwithstanding, corrective surgical treatment differs from that of pulmonary or hepatic hydatid surgery.

In this retrospective analysis, we evaluated the characteristics of intrathoracic extrapulmonary hydatid cysts and sought to confirm the most appropriate surgical interventions. This study was approved by our institution's ethics committee.

Patients and Methods

From 2003 through 2007, 160 patients with thoracic echinococcosis underwent surgical treatment in our department. All were evaluated retrospectively as to age, sex, symptoms, diagnostic procedures, anatomic location of cysts, surgical procedures and complications, and outcomes. Of the 160 patients, 116 had cysts in the pulmonary parenchyma only, and another 30 had cysts within the lungs or the liver. Fourteen patients (8.75%) had intrathoracic cysts in extrapulmonary locations. This last group of patients constituted our study group.

An intrathoracic-yet-extrapulmonary cyst was defined as a cyst that was found in intrathoracic extrapulmonary tissues with no involvement of the pulmonary parenchyma and with no transmission of disease from the abdomen to the thorax. We excluded patients who had a parenchymal cyst that had perforated to the pleura and patients who had experienced transdiaphragmatic transmission, because such cysts were assumed to have occurred as a sequela of extrapulmonary cystic involvement (such as perforation) from primary organs.

Results

Age, Sex, and Symptoms of the Patients. The study group comprised 8 men and 6 women whose mean age was 39.14 ± 16.8 years (range, 16–69 yr). All were symptomatic, most commonly with chest pain.

Diagnostic Procedures. In all 14 patients, chest radiography, computed tomography, and thoracic and abdominal ultrasonography had been performed preoperatively. All had also undergone bronchoscopy and spirometry. An enzyme-linked immunosorbent assay test, which had been performed in 9 of the 14 patients, had rendered true-positive results in 5 patients and false-negative results in 4. Echocardiography had been used in 1 patient to determine the contiguity of the cyst to the pericardium, and magnetic resonance imaging had been used in 2 patients to determine cystic contiguity to the mediastinum.

Locations of the Cysts. The patients' hydatid cysts were in the diaphragm (Fig. 1), chest wall (Fig. 2), pleura (Figs. 3, ,4,4, and and5),5), pericardium, and mediastinum. The clinical characteristics of the patients are shown in Table I. All cysts had been treated surgically.

Table thumbnail
TABLE I. Clinical Characteristics of the 14 Patients
figure 9FF1
Fig. 1 Computed tomography shows a diaphragmatic hydatid cyst.
figure 9FF2
Fig. 2 Preoperative magnetic resonance imaging shows hydatid disease in the chest wall of a patient who consequently underwent resection and reconstruction of the chest wall.
figure 9FF3
Fig. 3 Computed tomography shows multiple cysts filling the entire pleural area.
figure 9FF4
Fig. 4 Photograph shows the macroscopic characteristics of hydatid cysts that were evacuated from the pleura.
figure 9FF5
Fig. 5 Photograph shows resected pleural layers that were massively invaded by hydatid cysts.

Diagnoses, Surgical Procedures and Complications, and Outcomes. In most patients, the preoperative diagnosis was not identical to the postoperative diagnosis. One patient with a diaphragmatic cyst had undergone surgery for a hepatic cyst in a general surgical clinic at another hospital. At our hospital, this patient underwent exploration via thoracotomy, followed by cystectomy and diaphragmatic resection and repair (Fig. 1). As a result of the diagnostic lessons that were learned, diagnostic thoracotomy was used in all 13 subsequent patients.

Cystectomy and wide resection were the chief operative procedures. Costal resection was performed in 3 of the 5 patients who had cysts of the chest wall; in the other 2, the surrounding soft tissues were resected. We refrained from cystotomy because of the risk of spillage, and we performed no capitonnage. Table II shows the surgical and additional procedures that were performed.

Table thumbnail
TABLE II. Surgical and Additional Procedures Performed in the 14 Patients

Albendazole (10 mg/kg) was prescribed to all patients for as long as 3 months postoperatively. No complication, recurrence, or death occurred during the follow-up period of 15 ± 18.1 months (range, 2–52 mo).

Discussion

Although echinococcosis has been rare in developed countries, greater population mobility and migration may portend an increase in the frequency of this clinical entity.5 Echinococcosis remains a substantial public-health problem in many countries, such as Turkey,3,6 where the incidence is 1 in 2,000.6

Hydatid cysts can be found in various tissues. Although the liver and the lungs are the usual locations, the brain, heart, kidney, spleen, uterus, fallopian tubes, mesenteric region, diaphragm, and muscles may be affected.7–9 Intrathoracic yet extrapulmonary locations are infrequent, with an occurrence rate of 7.4%.1,3 Pulmonary sites are the most common site of intrathoracic hydatid cyst development; there, they are called pulmonary hydatid cysts. Conversely, cysts in the diaphragm, pleura, mediastinum, pericardium, myocardium, fissures, and chest wall are called intrathoracic extrapulmonary cysts,3,10 and they can cause a variety of symptoms. Ten of our 14 patients had cysts in the diaphragm or the chest wall.

Although hydatid cysts usually produce various symptoms, they can be asymptomatic.11 Intrathoracic extrapulmonary cysts may produce compression symptoms in surrounding vital structures.4 Our patients chiefly experienced chest pain (in 70%) and dyspnea consequent to lung compression.

Dermal tests, biochemical tests, and imaging techniques are useful and are usually accurate in the diagnosis of hydatid disease. Although serologic tests are also used, they have lesser value in diagnosis because of false-negative and false-positive results.5,7 We found it possible to establish satisfactory and reliable diagnoses with the use of conventional radiography in concert with computed tomographic scanning and ultrasonography. In addition, the radiologic findings are helpful in the accurate planning of surgery, when that time arrives. Cystotomy and capitonnage are the standard treatments for typical hydatid disease.

Conversely, in the case of intrathoracic extrapulmonary cysts, preoperative diagnostic methods are not always reliable. Difficulties in diagnosis may lead to an incorrectly conceived initial surgical approach. Precise diagnosis usually occurs during surgical intervention. When an intrathoracic extrapulmonary cyst is identified, the surgeon should be aware that cystotomy and capitonnage are too conservative. More aggressive procedures, such as wide resections and reconstruction of surrounding tissues, can achieve complete extirpation without spillage and subsequent recurrence. We performed cystectomy and resection of the adjacent pericystic structures in all 14 of our patients who had intrathoracic extrapulmonary cysts.

Hydatid cysts rarely form in the chest wall. The ribs, sternum, or soft tissues of the chest wall may become a locus.10 The rate of overall bone involvement is 0.9% to 2%, which suggests that location in the thoracic cage is not common.12 Despite this, thoracic-cage involvement occurred in several of our patients. Costal destruction in 3 such instances showed that the cysts enlarged toward regions of least resistance and produced pressures that destroyed the bone.

Mediastinal hydatid disease has rarely been reported.13,14 Mediastinal cysts create pressure symptoms, such as dysphagia, because of esophageal compression.3 One of our patients experienced diaphragmatic eventration from compression of the phrenic nerve.

The diaphragm is another uncommon site for hydatid cysts.4 This region usually requires repair after the cysts are removed. Five of our patients had intradiaphragmatic cysts. After the cysts were removed, the defects were repaired primarily.

Previously reported pleural cysts have developed chiefly as a result of perforation of the cysts into the pleural area, and by diaphragmatic transmission.15 This is not actually pleural echinococcosis, but a complication thereof. The real clinical feature, as seen in our patient with the actual condition, is cystic location primarily in the pleural layers and the pleural region. In this patient, many cystic structures were drained, and complete decortication of the parietal pleura was performed. No effect on the pulmonary parenchyma was observed. However, the pleural layers are avascular, and a hydatid cyst may form and grow in this region because the structure of the laminated cyst membrane is permeable to calcium, potassium, chloride, water, and urea. Accordingly, these nutritional substances and others that may be useful to the parasite can traverse the membrane via diffusion. Active transport may also play a role.5

Although cardiac locations were not seen in our series, we performed cystectomy of a pericardial cyst in 1 of our patients.

Conclusion

Hydatid cysts can form in different anatomic sites, but extrapulmonary location within the thorax is very rare. This rarity may cause difficulties in diagnosis, followed by unexpectedly necessary wide resections and reconstructive procedures. Approaches that are too conservative may invite spillage and recurrence. The precise location of an intrathoracic extrapulmonary cyst is usually confirmed during surgical intervention. The corrective surgical procedures, which necessarily differ from those that are performed to treat a pulmonary or hepatic hydatid cyst, should be chosen in accordance with the site of the cyst. Total extirpation and reconstruction of the affected structures are preferable to cystotomy and capitonnage. To avoid recurrence, it is necessary to resect the affected tissues completely, and, postoperatively, to place patients on an anthelmintic medical regimen.

Footnotes

Address for reprints: Soner Gursoy, MD, 2040/7 sokak Albatros 10 Giris 4 D:47, Mavisehir, Bostanli, 35540 Izmir, Turkey. E-mail: moc.liamg@renossrg

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