These four cases illustrate the rare location of hydatid cyst.
computed tomography plays a crucial role for the early diagnosis,
assessment of the lesions and follow-up after surgical treatment.
- Hydatidosis is an endemic zoonosis due to the larva of Echinococcus granulosus.
It can be seen worldwide but it is more prevalent in the Mediterranean region (Fig 1).
- It is endemic in the north part of Morocco ,
and our university hospital is a referral hospital in this region.
- The life cycle of E granulosus involves two hosts (Fig 2).
The definitive host is usually a dog but may be some other carnivore.
- Human infection is caused by contaminated food or by direct contact with infected canine.
Hydatid cyst located in the interventricular septum
Two patients had the lesion in the interventricular septum,
presenting with recurrent chest pain and asthenia.
Location
Cardiac hydatid cyst is a very rare entity.
Areas of cardiac involvement in hydatid disease include the left ventricle (60% of cases),
right ventricle (10%),
pericardium (7%),
pulmonary artery (6%),
and left atrial appendage (6%); involvement of the interventricular septum is rare (4% of cases).
Clinical presentation
Although cardiac hydatid cysts are in general asymptomatic,
serious complications can happened such as syncope,
atrioventricular block,
pericarditis,
stenosis in cardiac valve,
and sudden death may develop caused by the cyst localion and its size.
Serologic tests
Are always useful for diagnostic purposes.
Radiographic features
Plain film
Chest radiographs usually show a normal cardiothoracic ratio,
but may show regular mass scattered throughout the lung field,
so it varied according to the sites of the cysts.
Echocardiography
Echocardiography is simple and useful in the diagnosis of cardiac hydatid cyst,
it can show the cystic nature of the mass and its relationship to the cardiac chambers.
Multidetector CT
Computed tomography provide further information,
such as the anatomic extent,
the position of the cyst and its relationships to the cardiac cavity.
In our case,
CT Scan studies revealed a multiloculated cystic lesion with well-defined borders and parietal calcifications,
located in the apical part of the interventricular septum (Figure3).
MRI
The MRI appearance of a hydatid cyst is usually a characteristic oval lesion that is hypointense on T1-weighted images and hyperintense on T2-weighted images with a hypointense peripheral ring (a dense fibrous capsule from the reactive host tissue).
Differential diagnosis
Differential diagnosis must be considered with a variety of cystic tumors located in the interventricular septum and with congenital pericardial cyst.
Treatment
Surgical excision is the preferred treatment.
However,
adhesion to vital structures sometimes makes this impossible and patients require long-term therapy with albendazole.
Hydatid cyst in the pulmonary artery and the inferior vena cava
A hydatid cyst in the pulmonary artery is very rare disease but it can occur secondary to embolization of a cardiac hydatid cyst or by the passage of the hydatid cyst from the liver into the inferior vena cava and right heart chambers into the pulmonary artery.
Also,
the hydatid cyst can penetrate the arterial wall through little cracks in the intima layer of the wall or can be localized within an aneurysm.
In our cases,
one patient had a cystic lesion in both the lower lobe pulmonary artery (Figure.
4) and the last one had a lesion in the left main pulmonary artery and the inferior vena cava (Figure.
5).
Both patients were followed for their hepatic hydatic cyst.
So,
some hepatic cysts extended into the inferior vena cava and we assumed that the larvae of Echinococcus granulosus entered the systemic circulation and ended up in the pulmonary artery.
Clinical presentation:
Hemoptysis is the most frequent sign of hydatid pulmonary embolism,
the presenting symptoms included dry cough,
fatigue,
dyspnea and sudden chest pain.
The possible occurrence of complications can be seen such as anaphylactic reactions including fever,
eruptions,
or even circulatory collapse secondary to the cyst ruptures.
Serologic tests
Are always useful for diagnostic purposes.
Radiographic features
Plain film
Plain chest radiograph most of time,
did not show any pathology.
Echocardiography
Echocardiography is the investigative procedure of choice for studying cardio pericardial hydatidosis but it rarely enables direct visualization of the pulmonary embolus.
Transesophageal echocardiography (TEE) may show no lesion in the cardiac chambers or visualized a cystic lesion and massive emboli in the pulmonary artery.
Multidetector CT
Angio-Computed tomography of the chest revealed a cystic structure with well defined margins in the pulmonary artery and its branches also in the inferior vena cava (Figure.
4,5).
MRI
On magnetic resonance imaging,
a hydatid cyst is observed as an oval lesion that is hypointense on T1- weighted images and hyperintense on T2-weighted images(Figure.
4).
Computed tomography or magnetic resonance imaging for follow-up is important to search for recurrences or any complications.
Differential diagnosis
Differential diagnosis with a pulmonary intra-arterial lesion,
such as pulmonary thromboembolism and a primary arterial neoplasm.
Treatment
Surgical treatment combined with medical treatment may improve the prognosis.
Surgical intervention included longitudinal incision of the distal portion of the pulmonary artery under the superior vena cava and then puncture and aspiration of the cyst content,
irrigation with hypertonic solution,
and extraction of the cyst as far distally as possible.