Portal Vein Invasion Secondary to Hepatic Hydatid Disease: A Rare Case Report

Abstract

Background

Hydatid cyst disease is a zoonotic parasitic infection caused by Echinococcus species and remains endemic in many regions worldwide, particularly in North Africa and the Mediterranean basin. The liver is the most commonly affected organ due to portal dissemination of the parasite. Although hepatic hydatid cysts are frequently encountered, vascular complications are uncommon, and portal vein invasion represents an exceptionally rare manifestation. This complication may lead to portal vein thrombosis, cavernous transformation, portal hypertension, and potentially life-threatening complications including anaphylaxis.

Case Presentation

We report the case of a 56-year-old male with a prior history of surgery for hepatic hydatid disease who presented with portal vein invasion mimicking portal vein thrombosis. Imaging studies revealed a hydatid cyst located in segment IV of the liver associated with portal venous obstruction and cavernomatous transformation. Color Doppler ultrasonography demonstrated absence of blood flow within the portal vein and collateral venous circulation consistent with portal cavernoma. Contrast-enhanced computed tomography clearly demonstrated communication between the multiloculated hydatid cyst and the portal vein, with multiple daughter vesicles extending from the portal trunk to the segmental portal branches causing vascular occlusion. Despite evidence of intraportal rupture, the patient did not develop anaphylactic shock or systemic allergic manifestations.

Discussion

Portal involvement in hepatic echinococcosis may occur through extrinsic compression, inflammatory invasion of the vascular wall, or direct rupture of the cyst into the portal circulation. Although all echinococcus larvae initially pass through the portal venous system, portal vein invasion remains exceedingly rare, likely due to the high pressure within the portal circulation. Chronic portal obstruction may result in extrahepatic portal vein obstruction, portal hypertension, and cavernous transformation. Radiologic imaging, particularly contrast-enhanced computed tomography, plays a crucial role in differentiating portal hydatid disease from conventional portal vein thrombosis by demonstrating intravascular daughter cysts and direct cysto-portal communication. Surgical management remains the treatment of choice and should address both the hydatid cyst and complications related to portal hypertension.

Conclusion

Portal vein invasion by hydatid cysts is a rare but serious complication of hepatic echinococcosis that may mimic portal vein thrombosis. Recognition of this entity is essential, particularly in endemic regions and in patients with previous hydatid surgery, in order to optimize diagnosis and management. Early identification through advanced imaging modalities may help prevent severe complications and improve clinical outcomes.

Introduction

Hydatid cyst disease is a zoonotic condition caused by the Echinococcus parasite and can affect virtually any organ in the body. However, the liver, lungs, and nervous system are the most frequently involved sites. ¹ Liver hydatidosis caused by echinococcosis remains endemic in Maghreb countries and continues to represent a significant public health concern. ²

The parasite requires two mammalian hosts to complete its life cycle. Dogs serve as the definitive host, whereas sheep and other domestic herbivores function as intermediate hosts, with humans representing accidental intermediate hosts. Adult worms develop in the small intestine of the definitive host, producing eggs that are excreted in feces. Following ingestion, the embryos are released in the duodenum of the intermediate host, penetrate the intestinal wall, and disseminate through the portal circulation. The larval stage develops most commonly in the liver, where protoscolices are produced and later ingested by carnivorous definitive hosts. Humans become infected by consuming contaminated food or through direct contact with infected definitive hosts.

Patients with hepatic hydatid disease are often asymptomatic. When symptoms occur, they are usually nonspecific and include vague abdominal pain, secondary liver abscess formation, cholestatic jaundice, or cyst rupture with or without anaphylaxis. Hydatid cysts may cause serious and potentially life-threatening complications including rupture, bacterial superinfection, and compressive mass effects. ³

Portal vein involvement represents one of the rarest complications of hepatic echinococcosis. Several mechanisms have been proposed to explain vascular involvement, including extrinsic compression, inflammatory invasion of the vessel wall mimicking thrombosis, and direct rupture into the vascular lumen. The inflammatory reaction caused by external compression may facilitate the development of a cyst-portal fistula, permitting passage of daughter cysts into the portal circulation. Cyst rupture occurs in approximately 50–90% of cases. Lewall and McCorkell classified echinococcal cyst rupture into three types: direct, contained, and communicating rupture. The communicating type involves tearing of the endocyst membrane with leakage through biliary radicles or bronchioles. ⁴ Although communication with the portal vein has not been formally described in this classification, findings from our case and the autopsy report by Buyuk et al. ⁵ suggest that portal venous communication should also be considered.

Prior surgery or percutaneous treatment for echinococcosis may predispose patients to this complication, increasing the incidence up to 50% in these settings. ⁶ Although all echinococcus larvae pass through the portal circulation during dissemination, portal vein invasion remains extremely uncommon, likely due to the high intravascular pressure within the portal system. ⁷

Compression or invasion of the portal vein by a hydatid cyst may lead to portal vein thrombosis or extrahepatic portal vein obstruction (EPVHO). ⁸ In rare instances, this may progress to cavernous transformation and portal hypertension. ⁹ A portal cavernoma consists of a network of porto-portal collateral dilated tortuous veins within the hepatoduodenal ligament that develops secondary to portal vein obstruction. ¹⁰

Another important feature of hydatid cyst disease is the allergenic nature of the cyst fluid. Rupture into body cavities or vascular structures may precipitate severe anaphylactic reactions and even death. ¹¹ Buyuk et al reported fatal anaphylaxis following intravascular rupture of a hydatid cyst after liver trauma. ⁵ Similarly, Marriott et al described a case of anaphylaxis caused by intraportal venous rupture, with identification of a hydatid protoscolex within a hepatic venule, indicating intravascular exposure to parasitic material. ¹²

Given the rarity and potentially fatal complications of portal hydatid disease, accurate recognition is essential to distinguish it from conventional portal vein thrombosis and optimize patient management, especially in endemic regions. We report a rare case of portal vein invasion by hepatic hydatid disease associated with portal cavernomatosis and portal hypertension.

Case Presentation

A 56-year-old male from an endemic region for echinococcosis presented for evaluation of progressive abdominal discomfort and imaging findings suggestive of portal vein thrombosis. His medical history was significant for prior surgery for hepatic hydatid cyst disease performed several years earlier. No other significant comorbidities were reported. The patient denied recent abdominal trauma, fever, hematemesis, melena, or weight loss. There was no known history of chronic liver disease, viral hepatitis, alcohol abuse, or prothrombotic disorders.

On physical examination, the patient was hemodynamically stable and afebrile. Abdominal examination revealed mild right upper quadrant tenderness without signs of peritoneal irritation. No palpable abdominal mass was identified. There were no clinical signs of hepatic failure. Examination did not reveal jaundice, ascites, or lower limb edema. Mild splenomegaly was suspected on abdominal palpation. Importantly, no signs of acute allergic reaction or anaphylaxis were observed despite evidence of intravascular extension of the hydatid cyst.

Initial laboratory investigations demonstrated preserved liver function with no significant elevation in serum bilirubin or liver enzymes. Inflammatory markers were not markedly elevated. Coagulation parameters were within normal limits. Serologic findings were compatible with previously treated hydatid disease. Due to the patient’s prior history of hepatic echinococcosis and suspicion of portal venous pathology, further radiologic assessment was undertaken.

Abdominal ultrasonography revealed a heterogeneous cystic lesion within segment IV of the liver, containing internal septations and daughter cysts suggestive of recurrent hydatid disease. The lesion appeared adjacent to the portal venous bifurcation. Color Doppler ultrasonography demonstrated absence of normal blood flow within the main portal vein and revealed multiple periportal collateral vessels consistent with cavernomatous transformation. Features of portal hypertension were also identified, including splenomegaly and porto-portal collateral circulation. The previously operated hydatid liver cyst was visualized with postoperative changes surrounding the lesion.

Subsequent contrast-enhanced computed tomography (CT) provided a more detailed characterization of the lesion and vascular involvement. CT demonstrated a multiloculated cystic lesion within the fourth hepatic segment communicating directly with the portal venous system. Multiple daughter vesicles were identified extending into the portal trunk and segmental portal branches, producing near-complete occlusion of the portal vein lumen. The lesion displayed characteristic imaging findings of hydatid disease, including hypointense rim appearance and internal daughter cysts. The portal vein showed complete obstruction with development of extensive collateral venous circulation consistent with portal cavernoma formation (Figure 1).

Figure 1.

Contrast-enhanced computed tomography (coronal reconstruction) demonstrating portal cavernoma with occlusion of the portal venous system by hydatid disease extending from the portal trunk to the segmental portal branches

The imaging findings strongly suggested portal vein invasion secondary to hepatic hydatid disease rather than conventional bland portal vein thrombosis. The direct continuity between the cyst cavity and the portal venous system was particularly evident on CT sequences, supporting the diagnosis of intraportal rupture of the hydatid cyst.

Despite intravascular extension of hydatid material, the patient did not experience signs of systemic hypersensitivity, anaphylactic shock, or embolic complications. No evidence of secondary bacterial infection of the cyst was observed. Endoscopic evaluation was considered to assess potential complications related to portal hypertension, particularly esophageal varices.

Given the rarity and complexity of portal hydatid disease, a multidisciplinary discussion involving radiologists, hepatobiliary surgeons, and gastroenterologists was undertaken. Therapeutic management was directed toward both the hydatid cyst and the associated portal hypertension. Surgical intervention was considered the most appropriate treatment strategy due to the extensive vascular involvement and risk of progressive portal hypertension-related complications.

The patient underwent exploratory laparotomy with partial pericystectomy of the recurrent hepatic hydatid cyst. Intraoperatively, communication between the cyst cavity and the portal vein was confirmed. The cyst contents and daughter vesicles were carefully evacuated, and the cysto-portal communication was managed surgically. The residual cavity was treated according to standard surgical principles. Postoperatively, the patient received albendazole therapy and recovered without major complications. The postoperative course was uneventful. Albendazole therapy was continued for 6 months. At 6-month follow-up, the patient remained asymptomatic, with no radiological evidence of recurrent hydatid disease and stable portal hypertension.

Discussion

Hydatid disease remains an important parasitic infection in endemic regions, particularly in North Africa, the Mediterranean basin, the Middle East, and South America. Hepatic involvement is the most common presentation because the liver acts as the first filter for embryos entering the portal circulation after intestinal absorption. ¹ Although hepatic hydatid cysts are frequently encountered in clinical practice, vascular complications remain uncommon, and direct portal vein invasion represents one of the rarest manifestations of the disease.

The pathophysiology of portal vein involvement in hepatic echinococcosis is complex and multifactorial. Several mechanisms have been proposed, including progressive external compression by enlarging cysts, inflammatory infiltration of the vessel wall, and direct rupture into the portal venous system. ⁴ External compression may initially impair portal blood flow and predispose to thrombosis, whereas chronic inflammation around the cyst can weaken the vascular wall and facilitate communication between the cyst cavity and the portal lumen. In advanced cases, daughter vesicles may migrate into the portal circulation and produce complete vascular obstruction, as demonstrated in our patient.

Despite the fact that all echinococcus embryos pass through the portal circulation during their life cycle, portal venous invasion remains extremely rare. ⁷ This rarity has been attributed to the relatively high intraluminal pressure and continuous blood flow within the portal system, which likely prevent implantation and growth of parasitic elements within the vessel lumen. Consequently, only isolated cases of portal hydatid disease have been reported in the literature.

Our patient had a prior history of surgery for hepatic hydatid disease, which may have contributed to the development of portal invasion. Previous surgical or percutaneous interventions are recognized risk factors for complicated hydatid cyst rupture and may increase the incidence of cysto-vascular fistulization. ⁶ Postsurgical adhesions, altered local anatomy, and chronic inflammatory changes may facilitate erosion into adjacent vascular structures over time. This observation emphasizes the importance of long-term follow-up in patients previously treated for hepatic echinococcosis.

The radiologic findings in this case were particularly characteristic and played a crucial role in establishing the diagnosis. Doppler ultrasonography demonstrated absence of portal venous flow and features of cavernomatous transformation, while CT clearly identified communication between the hydatid cyst and the portal venous system with intraluminal daughter vesicles. CT remains one of the most valuable imaging modalities for evaluating complicated hydatid disease because it provides excellent soft tissue contrast and allows detailed assessment of vascular and biliary involvement. The identification of daughter cysts within the portal lumen is highly suggestive of hydatid invasion and may help differentiate this condition from conventional bland portal vein thrombosis or tumor thrombosis.

Differential diagnosis of portal vein obstruction includes thrombotic disease related to cirrhosis, malignancy, inflammatory disorders, and hypercoagulable states. In endemic regions, however, hydatid disease should also be considered when portal vein thrombosis occurs in association with cystic hepatic lesions. Failure to recognize this rare complication may lead to inappropriate treatment strategies, such as isolated anticoagulation therapy, while delaying definitive management of the underlying parasitic disease.

One of the most significant consequences of portal vein invasion is the development of extrahepatic portal vein obstruction and portal hypertension. ⁸ Chronic obstruction of the portal vein leads to the formation of porto-portal collateral veins surrounding the occluded segment, resulting in cavernous transformation. Portal cavernoma is defined as a network of dilated tortuous collateral veins within the hepatoduodenal ligament that bypass the obstructed portal vein. ¹⁰ Although cavernomatous transformation serves as a compensatory mechanism to maintain hepatic perfusion, it also predisposes patients to complications of portal hypertension, including esophageal varices, gastrointestinal bleeding, splenomegaly, ascites, and hypersplenism.

The association between hydatid disease and portal cavernoma has only rarely been documented in the literature. The first reported case was described in 1998, ⁹ and only a few additional cases have subsequently been published. ⁷ Because of its rarity, the true incidence of this complication remains unknown. Nevertheless, increasing use of advanced cross-sectional imaging may improve recognition of portal vascular involvement in hepatic echinococcosis.

An additional major concern in cases of intravascular hydatid rupture is the risk of anaphylaxis. Hydatid cyst fluid contains highly antigenic material capable of triggering severe systemic hypersensitivity reactions. ¹¹ Rupture into vascular structures may result in widespread dissemination of parasitic antigens and sudden anaphylactic shock. Buyuk et al reported a fatal case of intravascular rupture following liver trauma with dissemination of cyst contents into the bloodstream. ⁵ Similarly, Marriott et al documented intraportal rupture associated with histologic identification of a hydatid protoscolex within a hepatic venule. ¹² Interestingly, despite clear evidence of portal venous rupture in our patient, no allergic manifestations or hemodynamic instability occurred. The absence of anaphylaxis may be related to slow chronic leakage of cyst contents into the circulation rather than sudden massive rupture. ¹³

Management of portal hydatid disease remains challenging because treatment must address both the parasitic lesion and the sequelae of portal hypertension. Surgical treatment remains the preferred therapeutic option in most reported cases. ¹⁴ The primary objectives include removal of the hydatid cyst, prevention of further vascular dissemination, and management of portal hypertension-related complications. Advances in hepatobiliary surgery and perioperative care have significantly reduced morbidity and mortality associated with hepatic resections. In selected cases, laparoscopic approaches may also be feasible.

Adjunctive antiparasitic therapy with benzimidazole derivatives such as albendazole may reduce recurrence risk and sterilize residual cystic components. However, medical therapy alone is generally insufficient in cases involving major vascular invasion. Endoscopic surveillance and treatment of esophageal varices may also be necessary in patients with established portal hypertension.

This case further supports the hypothesis that portal venous communication should be incorporated into the existing classification of hydatid cyst rupture proposed by Lewall and McCorkell. ⁴ Their classification includes direct, contained, and communicating rupture involving biliary or bronchial structures, but does not specifically address vascular communication. The findings observed in our patient, together with previous reports,^5,12 suggest that intravascular rupture represents a distinct and clinically significant subtype deserving formal recognition.

Additional evidence supporting the capacity of hydatid disease to involve major vascular structures was recently provided by Gökoğlu et al, who described an unusual case of temporal bone echinococcosis associated with obliteration of the transverse venous sinus. Although anatomically distinct from portal venous involvement, this report further demonstrates the potential of Echinococcus granulosus to cause clinically significant vascular obstruction in rare locations and highlights the diverse spectrum of vascular complications associated with hydatid disease. ¹⁵

Ultimately, this case highlights the importance of maintaining a high index of suspicion for vascular complications of hydatid disease, particularly in endemic regions and in patients with previous hepatic hydatid surgery. Early recognition through appropriate imaging is essential for accurate diagnosis, prevention of potentially fatal complications, and optimization of therapeutic management.

This report has several limitations. First, as a single case report, its findings cannot be generalized to the broader population of patients with hepatic hydatid disease. Second, the diagnosis of portal vein invasion was based primarily on characteristic imaging findings without histopathological or intraoperative confirmation of intravascular hydatid material. Although the radiologic features strongly supported the diagnosis, additional imaging modalities such as MRI or contrast-enhanced ultrasonography may have provided complementary information. Third, detailed laboratory parameters and long-term follow-up, including definitive surgical outcomes and progression of portal hypertension, were unavailable, limiting assessment of treatment efficacy and prognosis. Finally, the proposed modification of existing classifications of hydatid cyst rupture should be considered hypothesis-generating and requires validation through additional case reports and larger case series.

Conclusion

Portal vein invasion by echinococcal cysts is an exceptionally rare but serious complication of hepatic hydatid disease that may result in portal vein thrombosis, cavernous transformation, and portal hypertension. Recognition of this entity is essential because it may mimic conventional portal vein thrombosis while requiring a fundamentally different therapeutic approach. Imaging modalities, particularly CT, play a crucial role in demonstrating portal vein communication and intravascular daughter vesicles. Early diagnosis allows optimized management combining treatment of both hydatid disease and portal hypertension. Clinicians practicing in endemic regions should maintain a high index of suspicion for portal hydatid disease in patients presenting with portal venous obstruction and a history of hepatic echinococcosis.

ORCID iD

Karam Karam https://orcid.org/0009-0001-1914-320X

Ethical considerations

Case reports are exempted from ethical approval at our institution.

Consent to participate

A signed written informed consent was obtained prior to manuscript writing and submission.