Massive Inferior Vena Cava Thrombosis and Pulmonary Embolism Secondary to Hepatic Hydatid Cyst: A Fatal Case

Introduction

Hydatid disease, caused by Echinococcus granulosus, is an endemic parasitic infection that predominantly affects the liver. Although usually slow-growing and asymptomatic, large hepatic cysts can lead to catastrophic vascular complications such as inferior vena cava (IVC) thrombosis and pulmonary embolism (PE) [1].

The life cycle of Echinococcus granulosus involves a definitive host, typically a dog or other canid, which harbors the adult tapeworm in its small intestine [2,3]. Eggs are shed in the feces and ingested by intermediate hosts, such as sheep, cattle, or, accidentally, humans. Upon ingestion, the eggs hatch in the human small intestine, releasing oncospheres that traverse the intestinal wall to enter the portal venous system [4]. The liver acts as the primary physiological filter for these larvae, explaining why the right lobe of the liver is the site of infection in approximately 70% to 80% of cases [5].

The natural clinical history of hepatic cystic echinococcosis is characterized by an indolent course. The parasite develops into a fluid-filled cyst that grows at a rate of approximately 1 cm per year [6]. This slow growth often allows the host to remain asymptomatic for a long time, until the cyst reaches a massive size or a complication occurs [7]. Cysts are considered “giant” when they exceed 10 cm in diameter; these lesions are significantly more likely to cause mass effect-related complications in adjacent organs, including the gallbladder, stomach, and major vascular structures like the portal vein and the IVC [8].

The most common genotypes among canids are Echinococcus granulosus sensu stricto (G1–G3) and the G6/7 cluster of Echinococcus canadensis. The global prevalence of echinococcosis in canids reaches up to nearly 34% worldwide, with the highest prevalence reported in South America and the lowest in Europe, with a rate of nearly 66% and 19%, respectively [9]. In Africa, the overall prevalence in 14 countries was nearly 17%, with the highest prevalence in North Africa, with a rate of nearly 26% [10].

The intermediate host in Saudi Arabia varies among hosts according to site, season, animal age, and sex; the prevalence of infection is 32.9% in camels, 8.3% in cattle, 12.6% in sheep, and 6.56% in goats. It was reported that sheep and goats are the most important intermediate hosts of Echinococcus granulosus due to higher percentages of fertile cysts (47.67% in sheep and 23.99% in goats) [11].

Hepatic hydatid cysts result from infection with Echinococcus granulosus and can cause serious complications when expanding lesions compress adjacent structures such as the IVC [2]. Thrombosis can result from mechanical obstruction, inflammation, or direct fistulization into the venous system [5,11–13]. Patients with IVC thrombosis secondary to hydatid cysts often present with features of venous obstruction or embolic complications. Early recognition is crucial because these events are rare but potentially fatal [12,13].

Case Report

A 68-year-old woman with a history of paroxysmal atrial fibrillation presented to the emergency department with 3 months of right-upper-quadrant abdominal pain and recent worsening fever. She denied respiratory, urinary, or neurological symptoms. While in the waiting area, she suddenly collapsed, gasping for air. Her oxygen saturation dropped to 75% despite high-flow oxygen, and her Glasgow Coma Scale (GCS) score was 8/15. She was transferred to the resuscitation unit and intubated.

On examination, the abdomen was distended with palpable hepatomegaly. Air entry was decreased bilaterally. Both lower limbs were cold; the right leg was swollen with purple mottling. Venous blood gas analysis revealed severe metabolic acidosis. Laboratory tests are shown in Tables 1 and 2.

Contrast-enhanced computed tomography (CT) pulmonary angiography demonstrated segmental and subsegmental PEs, a giant (29 × 18 cm) right-lobe hepatic cyst, and mass effect on the right hemithorax with leftward displacement (Figure 1). Abdominal CT revealed extensive thrombosis extending from the infrarenal IVC to both external iliac veins, more pronounced on the right- prothrombotic state (Figure 2). Echocardiography showed a small pericardial effusion and extrinsic right-atrial compression without tamponade or pulmonary hypertension. The diagnosis of Echinococcus granulosus infection was primarily supported by the characteristic CT imaging findings. Owing to the patient’s critical emergency situation, there was insufficient time to perform the conventional laboratory serological tests before urgent intervention. Moreover, the surgical decision-making was substantially supported by the CT pulmonary angiography and CT abdomen. Abdominal ultrasound was not performed due to the emergency situation.

The pulmonary embolism response team initiated intravenous heparin, albendazole, and broad-spectrum antibiotics. Vascular surgery advised conservative management as Doppler studies demonstrated triphasic arterial flow without ischemia. The patient was admitted to the intensive care unit with worsening acidosis (arterial blood gas results are shown in Table 3). She received vasopressors, sedation, piperacillin–tazobactam, vancomycin, meropenem, albendazole, and continuous renal replacement therapy for acute kidney injury.

Given persistent shock and concern for the infected cyst, bedside decompression was performed. Under ultrasound guidance, a 10-Fr catheter was inserted, draining 4 L of purulent material that cultured Bacteroides thetaiotaomicron. Following drainage, right-leg perfusion transiently improved. An IVC filter was inserted to prevent embolic events. Despite temporary hemodynamic stabilization, metabolic acidosis persisted, and continuous renal replacement therapy circuits repeatedly clotted. Anticoagulation was held because of a rising international normalized ratio. Re-accessing the cyst cavity was deemed unsafe. The patient developed refractory shock, severe hyperkalemia, bradycardia, and had cardiac arrest. Resuscitation was unsuccessful. Histopathological examination of the excised tissue confirmed the diagnosis of hepatic hydatid cyst of Echinococcus granulosus.

Discussion

This case highlights a rare but devastating complication of hepatic hydatid disease—IVC thrombosis with PE. The formation of a thrombus in the IVC is governed by the principles of Virchow’s triad: stasis, endothelial injury, and hypercoagulability [15]. In this case, all 3 elements of Virchow’s triad contributed to the development of IVC thrombosis [16]. First, stasis was present due to mechanical compression from a large cyst located on the retrohepatic segment of the IVC. Second, endothelial injury resulted from localized inflammation caused by an infected CE3b cyst. Third, hypercoagulability was driven by systemic sepsis, paroxysmal atrial fibrillation, and metabolic acidosis. These factors collectively created a profound prothrombotic state, culminating in the patient’s presentation.

Current recommendations suggest that in the presence of extensive IVC thrombosis, the filter should be placed before any invasive manipulation of the cyst [15,17]. Decompressing a giant cyst relieves the tamponade effect on the IVC. While this is necessary for restoring venous return, sudden restoration of flow through a previously compressed vessel can mobilize unstable thrombotic material or fragments of the cyst wall, leading to catastrophic pulmonary embolism [18].

The pathophysiology likely involves extrinsic compression by the enlarging cyst, compounded by inflammatory changes and infection. Similar cases have been reported, but the combination of massive cyst size (29 × 18 cm), septic thrombosis, and embolic phenomena underscores the clinical severity [14]. Mahajan et al described acute IVC thrombosis as an unusual manifestation of hydatid cysts [19], while Ismail et al reported direct cyst–IVC fistulization [12]. Our patient’s presentation was consistent with extrinsic compression rather than fistulization. Kantorová et al emphasized early recognition and surgical management in preventing fatal outcomes; however, our patient presented in extremis, precluding definitive surgery [13]. Management requires individualized multidisciplinary care. Surgical cyst excision is the standard treatment, but it may be infeasible in unstable patients. Percutaneous drainage can offer temporary decompression, as seen here, but carries risks of infection and recurrence [5,13]. Albendazole therapy and vigilant anticoagulation are essential adjuncts, but anticoagulation can be challenging in septic or coagulopathic patients.

Conclusions

Massive hepatic hydatid cysts can cause severe vascular complications, including IVC thrombosis and PE. Cyst complications arise because of the pressure effect of a large cyst on adjacent vascular structures, leading to mechanical obstruction and potentially triggering embolization. The potential life-threatening outcomes of a large hepatic hydatid cyst underscore the importance of vigilant clinical monitoring in affected patients.

Timely recognition of the vascular complications is essential. Early diagnosis enables prompt intervention, which may involve decompression procedures or definitive surgical management. Therefore, prompt action is critical to improving patient outcomes and survival. Multidisciplinary care is often required, and the approach should be tailored to the clinical status of the patient.