**6. Radiological features**

The plain chest radiograph is very helpful in diagnosis of pulmonary hydatid cyst. In un‐ complicated hydatid cysts, radiologic diagnosis is relatively easy and is identified on routine chest radiograph incidentally. Unruptured pulmonary hydatid cyst shows one or more ho‐ mogenous round or oval wellshaped masses with smooth borders surrounded by normal lung tissue on chest radiograph. It can access large volumes and compress to the adjacent structures. (Fig 6, 7, 8)

leading to effective treatment. On the other hand, one should bear in mind the possibility that carcinoma may rarely have clinical, radiological, and serological features, similar to those of a hydatid disease. It is uncommon for the diagnosis to be made from the microscop‐ ic discovery of hooklets in respiratory secretions, highlighting the value of close liaison with

Most serodiagnostic techniques have been evaluated for diagnosis of cystic hydatid dis‐ ease caused by Echinococcus granulosus. Formerly, the laboratory diagnosis of echinococ‐ cosis has been based chiefly on the results of the Casoni intradermal (ID) or the complement-fixation (CF) test. The CF test has a limited sensitivity, while the ID test may be unreliable since, once acquired, skin sensitivity may persist for life. After, the findings of Garabedian et al and Kagan et al [7,8] reported that indirect haemagglutina‐ tion (IHA) was more sensitive to formers tests but there were some limitations with the practical aspect of IHA, for example false positive reactions with other helminthic infec‐

Actually, the most sensitive technique in detecting pulmonary hydatid disease is immu‐ noglobulin G enzyme-linked immunosorbent assay (ELISA) test, with a sensitivity of 85.3%; it's a quantitative serodiagnostic method that specific IgG ELISA kit was available commercially. It was a better test for initial screening of suspected cases of human hyda‐ tidosis and was more acceptable due to its higher sensitivity and simplicity in practice [9]. Our data showed that ELISA is more sensitive than IHA for initial screening of sus‐

Serological tests are often helpful, but measurable immunological responses do not develop in some patients, essentially in lung hydatid cyst contrary to liver localization, where it seems that it has more supply antigenic stimuli to host tissues. Laboratory testing should be used either in highly suspicious cases or for postoperative follow-up of pulmonary hydatid cyst disease. Antibody production is elevated during the first 4 - 6 weeks after surgical inter‐ vention, followed by a decrease during the next 12 - 18 months. In patients who have a re‐ currence before 2 years, antibody production remains similar to pre-operative levels [8, 9]. Eosinophilia is 10-30% positive in hydatid cyst disease. Eosinophilia increases if cyst rupture

The plain chest radiograph is very helpful in diagnosis of pulmonary hydatid cyst. In un‐ complicated hydatid cysts, radiologic diagnosis is relatively easy and is identified on routine chest radiograph incidentally. Unruptured pulmonary hydatid cyst shows one or more ho‐ mogenous round or oval wellshaped masses with smooth borders surrounded by normal lung tissue on chest radiograph. It can access large volumes and compress to the adjacent

microbiological staff.

200 Principles and Practice of Cardiothoracic Surgery

**5.1. Laboratory tests**

pected cases of hydatidosis.

**6. Radiological features**

structures. (Fig 6, 7, 8)

tions, cancers and chronic immune complex disease.

and it is also high in countries where parasitosis is endemic [10].

**Figure 6.** Chest radiograph showing large hydatid cyst right upper lobe causing mediastinal shift to opposite side

**Figure 7.** CT appearance of an uncomplicated giant hydatid cyst of the right lung.

If the hydatid cyst is infected or ruptured, the radiological appearance may become atypical and it may cause incorrect and delayed diagnosis.

Complicated, a variety of signs denoting different appearances of the hydatid cysts have been described. During enlargement, the cyst can erode into the bronchus and air can enter between the pericyst and endocyst leading to the thin crescent (meniscus) sign (fig 9)

**Figure 8.** CT scan showing two well-circumscribed homogenous cysts over right and left lower lobes

**Figure 10.** Combo sign (Double air layer appearances

foration which necessitates further use of CT.

cyst form the serpent sign. (Fig 11)

id. (Fig 12, 13)

in the cavity. (Fig 14)

pleurisy, and empyema.

After the contents of the cyst are partially expectorated, collapsed membranes inside the

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Another pathognomonic sign is the water lily sign which occurs after the endocyst de‐ taches completely and the layer caves into the cyst cavity, floating freely on the cyst flu‐

In pulmonary hydatid disease, the radiologial signs are usually precise contrary to the clini‐ cal presentation. The appearance of a pulmonary hydatid cyst may change secondary to per‐

Rupture, with an incidence of 49%, is the most frequent complication of pulmonary hydatid disease. Communicating rupture occurs when the cyst contents escape via bronchial radicles which are incorporated in the pericyst. Rupture of the hydatid cyst into the bronchus occurs due to the degeneration of the membranes and manifests as coughing and expectoration of a large amount of salty sputum containing mucus, hydatid fluid, and rarely fragments of the laminated membrane. Thereby, solid remnants of the collpased parasitic membrane are left

In the other hand, pulmonary hydatid cyst may mimic a variety of clinical and radiologi‐ cal problems including tuberculosis, primary and secondary tumors, lung abscess, bron‐ chopulmonary infections, Wegener's granulomatosis, bronchiectasis, pneumothorax,

**Figure 9.** The pulmonary meniscus sign (arrow): crescent-shaped inclusion of air surrounded by consolidated lung tis‐ sue

As the air continues to enter this space, the cyst ruptures and air fills the endocyst. The air fluid level in the cyst and air like onion peel between pericyst and endocyst is called the Cumbo sign (Fig 10)

**Figure 10.** Combo sign (Double air layer appearances

**Figure 8.** CT scan showing two well-circumscribed homogenous cysts over right and left lower lobes

**Figure 9.** The pulmonary meniscus sign (arrow): crescent-shaped inclusion of air surrounded by consolidated lung tis‐

As the air continues to enter this space, the cyst ruptures and air fills the endocyst. The air fluid level in the cyst and air like onion peel between pericyst and endocyst is called the

sue

Cumbo sign (Fig 10)

202 Principles and Practice of Cardiothoracic Surgery

After the contents of the cyst are partially expectorated, collapsed membranes inside the cyst form the serpent sign. (Fig 11)

Another pathognomonic sign is the water lily sign which occurs after the endocyst de‐ taches completely and the layer caves into the cyst cavity, floating freely on the cyst flu‐ id. (Fig 12, 13)

In pulmonary hydatid disease, the radiologial signs are usually precise contrary to the clini‐ cal presentation. The appearance of a pulmonary hydatid cyst may change secondary to per‐ foration which necessitates further use of CT.

Rupture, with an incidence of 49%, is the most frequent complication of pulmonary hydatid disease. Communicating rupture occurs when the cyst contents escape via bronchial radicles which are incorporated in the pericyst. Rupture of the hydatid cyst into the bronchus occurs due to the degeneration of the membranes and manifests as coughing and expectoration of a large amount of salty sputum containing mucus, hydatid fluid, and rarely fragments of the laminated membrane. Thereby, solid remnants of the collpased parasitic membrane are left in the cavity. (Fig 14)

In the other hand, pulmonary hydatid cyst may mimic a variety of clinical and radiologi‐ cal problems including tuberculosis, primary and secondary tumors, lung abscess, bron‐ chopulmonary infections, Wegener's granulomatosis, bronchiectasis, pneumothorax, pleurisy, and empyema.

Fig 11: Lung involvement in a child with previous episodes of cough and expectoration. Collimated lateral chest radiograph shows an intracystic serpentine structure representing

Figure 12 (a) Postero-anterior and lateral (b) chest radiographs showing a cavitary lesion located at the left paracardiac region in the left hemithorax with an air-fluid level having a

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Thoracic Hydatid Cyst: Clinical Presentation, Radiological Features and Surgical Treatment

Fig 13:CT Scan of thorax showing the torn germinal layer in the Left hydatid cyst: the 'water-

collapsed membranes (serpent sign) (arrows).

a b

lily sign.'(Arrow)

convex serpinginous margin with hetrogenous contents

**Figure 13.** CT scan of thorax showing the torn germinal layer in the right hydatid cyst: the 'water-lily sign.'

**Figure 14.** Chest X-ray showing a large cavity with a germinative layer in the left lung

not, however, be mistaken as cavitations or pseudocavitations. (Fig 15)

However, CT scan can display the cystic appearance of a pulmonary mass lesion and help localize the cystic lesion for surgical purposes. CT provides further information in equivocal cases by revealing the fluid density of an intact cyst and the air-fluid density of a ruptured cyst. However, infection of the cyst may increase the attenuation values and a produce a sol‐ id appearance, which may hamper the correct diagnosis. Such a complicated cyst, in the ab‐ sence of positive history, serologic tests and other radiologic signs, may simulate a malignant tumor, tuberculosis, abscess and other infected cystic lesions of the lung [11].

The "air bubble sign" was described in complicated cysts and reported to be an important clue in the differentiation of hydatid cysts from other disease processes. Air bubble sign is best demonstrated in mediastinal window settings as single or multiple small, rounded radi‐ olucent areas with very sharp margins within solid media or pericystic areas. They should

**Figure 11.** Lung involvement in a child with previous episodes of cough and expectoration. Collimated lateral chest radiograph shows an intracystic serpentine structure representing collapsed membranes (serpent sign) (arrows).

**Figure 12.** (a) Postero-anterior and lateral (b) chest radiographs showing a cavitary lesion located at the left paracar‐ diac region in the left hemithorax with an air-fluid level having a convex serpinginous margin with hetrogenous con‐ tents

Figure 12 (a) Postero-anterior and lateral (b) chest radiographs showing a cavitary lesion

Fig 11: Lung involvement in a child with previous episodes of cough and expectoration. Collimated lateral chest radiograph shows an intracystic serpentine structure representing

collapsed membranes (serpent sign) (arrows).

Fig 13:CT Scan of thorax showing the torn germinal layer in the Left hydatid cyst: the 'water-**Figure 13.** CT scan of thorax showing the torn germinal layer in the right hydatid cyst: the 'water-lily sign.'

lily sign.'(Arrow)

a b

**Figure 14.** Chest X-ray showing a large cavity with a germinative layer in the left lung

**Figure 11.** Lung involvement in a child with previous episodes of cough and expectoration. Collimated lateral chest radiograph shows an intracystic serpentine structure representing collapsed membranes (serpent sign) (arrows).

(a) (b)

**Figure 12.** (a) Postero-anterior and lateral (b) chest radiographs showing a cavitary lesion located at the left paracar‐ diac region in the left hemithorax with an air-fluid level having a convex serpinginous margin with hetrogenous con‐

tents

204 Principles and Practice of Cardiothoracic Surgery

However, CT scan can display the cystic appearance of a pulmonary mass lesion and help localize the cystic lesion for surgical purposes. CT provides further information in equivocal cases by revealing the fluid density of an intact cyst and the air-fluid density of a ruptured cyst. However, infection of the cyst may increase the attenuation values and a produce a sol‐ id appearance, which may hamper the correct diagnosis. Such a complicated cyst, in the ab‐ sence of positive history, serologic tests and other radiologic signs, may simulate a malignant tumor, tuberculosis, abscess and other infected cystic lesions of the lung [11].

The "air bubble sign" was described in complicated cysts and reported to be an important clue in the differentiation of hydatid cysts from other disease processes. Air bubble sign is best demonstrated in mediastinal window settings as single or multiple small, rounded radi‐ olucent areas with very sharp margins within solid media or pericystic areas. They should not, however, be mistaken as cavitations or pseudocavitations. (Fig 15)

Figure 15: Mass with few air bubbles (arrows) **Figure 15.** Mass with few air bubbles

The hydatid cysts can grow more easily and faster in the lungs because of the elastic struc‐ ture of the lungs compared to the liver. For this reason, the growth rate of cysts in the lungs is estimated to be at least 5-fold higher than in the liver [12]. It has been noted that the per‐ centage of pulmonary cysts larger than 10 cm (huge cyst) is 21.9%-25% [13, 14]. We also not‐ ed that huge pulmonary cysts occur more often in children than in adults.

**Figure 17.** Contrast-enhanced CT scan obtained at the level of the dome of the diaphragm shows a partially calcified cyst originating in the posterior segment of the right hepatic lobe and growing through the diaphragm into the lung

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During the natural course of infection, the fate of the hydatid cysts is variable. Some cysts may grow (average increase: 1–30 mm per year) and persist without noticeable change for many years. Others may spontaneously rupture or collapse and can completely disappear. Calcified cysts are not uncommon. Spillage of viable protoscoleces after spontaneous or traumatic cyst rupture, or during interventional procedures, may result in secondary echi‐

Initially, the surgical treatment of pulmonary hydatidosis involved the marsupialization of the cyst when it was attached to the wall, or an atypical pulmonary resection consist‐ ing of two stages: first pleurodesis was produced, followed by marsupialization in a sec‐ ond procedure. Evidently, these techniques have since been abandoned exceptly when the diagnosis of hydatid cyst rupture was carried later. We have treated young women with chronic pleuritis by marsupialization discovered one month after hydatid cyst rup‐

(arrows). The cyst has the characteristic hourglass shape.

**8. General principles of the treatment**

**7. Evolution**

nococcosis.

**8.1. Surgery methods**

ture. (Fig 18, 19, 20)

*8.1.1. Conventional surgery*

Rarely, expectoration of the cystic fluid and germinative membrane may lead to spontane‐ ous healing of the residual cavity in some of the small cysts. (Fig 16)

**Figure 16.** CT scan of the chest showing an empty cavity with thin walls after complete evacuation of hydatid mem‐ brane

The simultaneous involvement of the liver and lung is quite uncommon but when it occurs, the right lung is involved in 97% of the cases [15]. Transdiaphragmatic hydatid disease has been very seldom reported. (Fig 17)

**Figure 17.** Contrast-enhanced CT scan obtained at the level of the dome of the diaphragm shows a partially calcified cyst originating in the posterior segment of the right hepatic lobe and growing through the diaphragm into the lung (arrows). The cyst has the characteristic hourglass shape.
