Introduction

Cystic Echinococcosis is a zoonotic parasitic infection caused by the larval stage of Echinococcus granulosus, a tapeworm commonly found in regions with extensive livestock farming. Although it is globally distributed, it is more frequently observed in rural and endemic areas, with a reported incidence of 1:2000 in our country.^{Reference Akar, Eryilmaz and Yazicioğlu1} The disease most commonly affects the liver (over 65% of cases) and lungs, with these two organs together accounting for at least 90% of all hydatid cyst localisations.^{Reference Banisefid, Baghernezhad and Beheshti2} Cardiac involvement by hydatid cysts is exceedingly rare, occurring in only 0.5–2% of all cases.^{Reference Yaman and Sirlak3} Within the heart, the left ventricle is most commonly involved (60%), followed by the right ventricle (10%), pericardium (7%), left atrium (6–8%), interventricular septum (3–4%), and the right atrium (4%).^{Reference Vahidshahi, Tahouri, Farahmandi and Hekmat5}

The clinical manifestations of cardiac hydatid disease are highly variable and influenced by the age of the patient, cyst size, location, and the disease stage.^{Reference Al-Dairy and Abo Kasem6} While many patients remain asymptomatic, the most commonly reported symptoms include dyspnoea, chest pain, palpitations, and cough.^{Reference Jamli, Cherif and Ajmi4} More critically, rupture of the cyst—especially when subendocardial—can release antigenic material into the circulation, potentially resulting in life-threatening complications such as anaphylactic shock, pulmonary or systemic embolism, acute coronary syndrome, or malignant arrhythmias.^{Reference Al-Dairy and Abo Kasem6} Transthoracic echocardiography remains the primary diagnostic modality due to its non-invasive nature and high sensitivity. However, CT and MRI may provide complementary anatomical and structural insights.^{Reference Jamli, Cherif and Ajmi4} Although medical therapy alone is insufficient to cure the disease, it is essential both pre- and post-operatively to reduce recurrence and improve survival outcomes.^{Reference Al-Dairy and Abo Kasem6}

Case presentatıon

We report the case of a 6-year-old girl from a rural area with no known prior medical history, referred to our hospital with a suspicion of a cardiac mass consistent with a hydatid cyst.

Upon admission, her general condition was poor, though her vital signs remained within normal limits. Laboratory evaluation showed a normal eosinophil count (1.2%). A chest X-ray revealed mild cardiomegaly, and electrocardiogram findings were unremarkable. Transthoracic echocardiography demonstrated a 2 cm pericardial effusion, primarily localised near the right ventricle, along with a large echogenic, thick-walled cystic lesion (30 x 25 mm) in the right atrium, situated above the tricuspid valve. The cyst mildly obstructed inflow and was adherent to the lateral wall of the right atrium.

Further evaluation with CT revealed a bilobulated cystic mass measuring 60 x 42 x 43 mm, with a thick, double-layered wall (up to 3 mm) extending into the right atrial appendage and towards the atrioventricular valve. Indirect haemagglutination serology was strongly positive (1/2560), confirming the diagnosis. Abdominal and brain MRIs showed no extracardiac cysts (Figures 1 and 2).

Figure 1.

Left: Transthoracic echocardiogram (apical four-chamber view) showing a large, thick-walled cystic lesion (blue arrows) adherent to the lateral wall of the right atrium (RA). Also visible: right ventricle (RV), left atrium (LA), and left ventricle (LV). Right: Axial CT image demonstrating a bilobulated cystic mass (asterisk) with a thick wall in the right atrium, extending towards the atrial appendage and atrioventricular valve.

Figure 2.

Intraoperative image showing the excised hydatid cyst during open-heart surgery.

Based on these findings, oral albendazole treatment (15 mg/kg) was initiated, adrenaline, oxygen and intubation equipment were prepared at the patient’s bedside in case of anaphylactic shock due to possible cyst rupture, and surgical excision was planned.

On the sixth day of hospitalisation, the patient developed sudden haemodynamic instability, with an oxygen saturation of 56%, heart rate of 146 bpm, and blood pressure of 70/40 mmHg. The adrenaline prepared at the bedside was immediately administered intramuscularly, and the patient was transferred urgently to the paediatric intensive care unit with oxygen administered via a mask. Repeat Transthoracic echocardiography revealed a marked decrease in cyst size and inflow obstruction, suggesting cyst rupture. The eosinophil count had risen to 9%, indicating a hypersensitivity response. Suspecting an anaphylactoid reaction secondary to intracardiac cyst rupture, emergency surgery was performed.

Following cardiopulmonary bypass via median sternotomy, the cystic mass was visualised in the right atrium. A rupture was observed in the portion facing the vena cava inferior, with thrombus formation inside the cavity. The cyst was found to be extensively infiltrating the atrial wall and could not be separated en bloc. Therefore, the section extending towards the sinus venosus was excised along with part of the atrial wall. Histopathological analysis confirmed the diagnosis of a hydatid cyst. The patient recovered uneventfully and was discharged in the first postoperative week with ongoing albendazole therapy. The patient had no complaints during follow-up at the outpatient clinic after discharge. No recurrence was detected by echocardiography.

Discussion

Cardiac hydatid cysts are exceedingly rare, especially in paediatric patients. Within the heart, the right atrium is one of the least frequently involved sites. However, due to the delicate structure and low pressure of the right heart chambers, the risk of intracavitary rupture is relatively high.

Transthoracic echocardiography remains the gold standard for diagnosing cardiac hydatid disease due to its accessibility, safety, and capacity to provide real-time anatomical and functional information. In our case, transthoracic echocardiography clearly identified the cystic mass and helped monitor morphological changes post-rupture. CT and MRI can provide additional structural details, particularly in assessing wall thickness, extent, and involvement of surrounding tissues.

Intracardiac hydatid cyst rupture is a medical emergency. The right heart, especially the right ventricle, is the most common location for such ruptures, which may result in pulmonary embolisation, pulmonary hypertension, or even sudden death. Demirci et al. reported a fatal case of a 10-year-old girl who died suddenly due to a hydatid cyst located in the right ventricular apex.^{Reference Demirci, Gunaydin, Dogan and Toy9} Çetin et al. also reported pulmonary hypertension secondary to involvement of both pulmonary arteries as well as the right ventricle.^{Reference Çetin, Karaman, Özgökçe, Geylan and Yildizeli11} Additionally, H. Bouraoui et al. identified a right atrial hydatid cyst in a 6-year-old patient in Tunisia who was examined for exertional dyspnoea and chronic dry cough; however, the patient died on the first postoperative day due to right heart failure and severe tracheal haemorrhage.^{Reference Bouraoui, Trimech, Madhaoui, Ernez-Hajri, Jeridi and Ammar12} The morphology of the cyst—such as size, wall thickness, presence of septations, and proximity to vascular or valvular structures—can provide clues regarding rupture risk, though predicting the exact timing remains difficult.

In our patient, the bilobulated morphology, thin walls, and large size increased the rupture risk. Despite appropriate medical therapy and early surgical planning, the cyst ruptured before intervention, causing haemodynamic collapse and an anaphylactoid reaction. This highlights the importance of close and continuous monitoring, even in haemodynamically stable patients.

Several factors can predispose a cyst to rupture: large or rapidly growing cysts, superficial localisation near organ surfaces, intracardiac position, thinning or calcification of the wall, increased intracystic pressure due to daughter cysts, floating membranes (water lily sign), and trauma. Clinical indicators such as hypersensitivity reactions or acute cardiovascular deterioration may signal imminent rupture. These high-risk features warrant early surgical intervention in experienced centres, even in asymptomatic or minimally symptomatic patients.

Additionally, serial imaging to assess morphological changes in the cyst is crucial during follow-up. Alterations in wall thickness, shape, or internal content may indicate instability. Our experience underscores the necessity of combining imaging findings with clinical assessment for timely diagnosis and intervention.