Portal Vein Aneurysm (PVA)

Portal Vein Aneurysm: Comprehensive Overview

A portal vein aneurysm (PVA) is a rare vascular abnormality defined as a focal dilatation of the portal venous system, typically involving the main portal vein but also potentially occurring in the intrahepatic or extrahepatic branches. Although often asymptomatic and discovered incidentally, it can occasionally lead to serious complications.

1. Cause and Etiology

Portal vein aneurysms are classified as congenital or acquired, depending on their origin.

Congenital PVAs

Believed to result from developmental weakness in the vessel wall due to incomplete regression of embryonic vitelline veins or failure of normal vascular remodeling.
May be associated with connective tissue disorders such as Ehlers-Danlos syndrome or other vascular malformations.

Acquired PVAs

These typically occur due to:

Portal hypertension (the most common acquired cause) usually results from liver cirrhosis.
Trauma or surgery involving the portal venous system (iatrogenic).
Pancreatitis or cholangitis with associated inflammation or thrombosis leading to vessel wall weakening.
Neoplasms causing extrinsic compression or direct invasion of the portal vein.
Infections (e.g., hepatitis, pyogenic liver abscess) damage the vessel wall.

2. Pathophysiology

The exact pathophysiological mechanism depends on the etiology:

Congenital PVAs: Weakness in the venous wall due to defective collagen or elastic tissue leads to progressive dilatation under normal portal venous pressure.
Acquired PVAs:

Increased intraluminal pressure (as in portal hypertension) results in venous dilatation.
Chronic inflammation or thrombosis can lead to focal wall damage, resulting in aneurysmal outpouching.
Over time, aneurysms may become predisposed to complications like thrombosis, rupture, or compression of adjacent structures.

A true aneurysm involves all layers of the vessel wall, while a pseudoaneurysm is a contained rupture without an intact wall, typically due to trauma or surgery.

3. Epidemiology

Extremely rare, with fewer than 200 cases reported in the literature.
Prevalence: Unknown due to rarity and incidental nature; some studies suggest the prevalence of <0.5% in imaging series.
Age: Can occur at any age, but is most frequently detected in middle-aged and older adults.
Gender: No clear gender predilection, although some reports show a slight male predominance.
Increasing detection due to widespread use of cross-sectional imaging (e.g., CT, MRI, Doppler ultrasound).

4. Clinical Presentation

Asymptomatic in most cases and discovered incidentally on imaging.
When symptomatic, patients may present with:

Right upper quadrant or epigastric pain
Nausea and vomiting
Symptoms of portal hypertension (if aneurysm compresses adjacent structures or is associated with liver disease)
Palpable abdominal mass (rare)
Gastrointestinal bleeding, if an aneurysm ruptures or causes varices
Portal vein thrombosis symptoms are if complicated by clot formation

5. Imaging Features

Accurate diagnosis relies heavily on imaging. Common modalities include:

Ultrasound (US) with Doppler:

First-line modality due to accessibility and non-invasiveness.
Shows a well-defined, anechoic, cystic mass in the region of the portal vein with internal blood flow on color Doppler.
“Yin-yang” sign may be seen on Doppler due to turbulent flow.

Computed Tomography (CT):

Demonstrates a focal, contrast-enhancing dilatation of the portal vein.
Provides excellent anatomical detail, helping differentiate from cysts or solid tumors.
Can detect associated thrombosis or compression of nearby structures.

Magnetic Resonance Imaging (MRI) / MR Angiography (MRA):

On 10 mm-thick maximum intensity projection CT images, aneurysmal dilatation of the right (yellow arrow) and left (red arrow) portal veins, predominantly right-sided diffuse calcification, and partial thrombosis of the portal vein are observed.

Helpful in characterizing flow dynamics and soft tissue contrast.
Visualizes thrombus and aneurysm wall more clearly than CT.

Criteria for Diagnosis:

Diameter > 15 mm in the main portal vein (some use >19 mm for extrahepatic and >7 mm for intrahepatic veins).
Fusiform or saccular dilatation.

6. Treatment

Treatment depends on the size, symptoms, and complications.

Conservative Management:

Asymptomatic and stable PVAs are usually managed with observation and periodic imaging.
Anticoagulation may be considered if thrombosis is present or if the patient is at high risk.

Surgical or Interventional Treatment:

Indicated for:

Symptomatic aneurysms
Rapidly enlarging aneurysms
Thrombosed aneurysms
Compression of adjacent structures
Rupture (very rare)

Options include:

Aneurysmectomy: Surgical removal.
Porto-systemic shunt: In cases with portal hypertension.
Endovascular approaches: Rare, but may include stenting or embolization.
Liver transplantation: In cases of severe liver disease with complex portal venous anatomy.

7. Prognosis

Generally good in asymptomatic, stable cases with no complications.
Excellent prognosis with conservative management in most congenital or incidentally discovered aneurysms.
Prognosis worsens with complications like:

Thrombosis → portal hypertension, mesenteric ischemia.
Rupture → rare but potentially fatal.
Compression of the bile ducts or duodenum.

Long-term monitoring is recommended to assess aneurysm size and complications.

Summary Table

Feature	Portal Vein Aneurysm
Etiology	Congenital (developmental defect), Acquired (cirrhosis, trauma, inflammation)
Pathophysiology	Focal dilatation due to wall weakness or increased portal pressure
Epidemiology	Rare; more common with increased imaging utilization
Clinical Presentation	Often asymptomatic; possible pain, mass, thrombosis, or GI bleeding
Imaging	US (anechoic cystic mass with flow), CT/MRI (enhancing dilatation of the portal vein)
Treatment	Observation if asymptomatic; surgery/intervention if symptomatic or complicated
Prognosis	Excellent if managed appropriately; complications can affect the outcome

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Case study: Postprandial Pain in a 58-Year-Old Woman

History and Imaging

A 58-year-old woman with a medical history of diabetes mellitus, hypertension, and dyslipidemia.
She previously underwent stent placement for bilateral cavernous internal carotid artery aneurysms.
She presented with recurrent periumbilical and right-sided abdominal pain that began two days ago, occurring primarily after meals.
Imaging studies were performed.

Quiz:

What is the most likely diagnosis?
(1) Pancreatic head cystic lesion (mucinous cystadenoma)
(2) Intraductal papillary mucinous neoplasm (IPMN)
(3) Vascular lesion (e.g., aneurysm)
(4) Choledochal cyst

Findings and Diagnosis:

Findings:

On grayscale abdominal ultrasound (a) and color Doppler ultrasound (b), a 3 cm anechoic cystic lesion was observed near the pancreatic head, with internal vascular flow noted. In contrast-enhanced CT during the portal venous phase (c), a focal dilatation of the main portal vein measuring 2.69 × 1.94 cm was identified.

Differential Diagnosis

Portal vein aneurysm (PVA)
Hypervascular pancreatic head lesion (e.g., neuroendocrine tumor or metastasis)
Mycotic portal vein aneurysm

Diagnosis

Portal vein aneurysm (sporadic/incidental; not mycotic)

Treatment

The patient was managed conservatively with symptomatic relief and regular surveillance of the aneurysm.

Discussion

Portal Vein Aneurysm (PVA)

The most common location for visceral venous aneurysms is within the portal venous system. Among PVAs, the main portal vein and the confluence of the splenic and superior mesenteric veins are the most frequently reported sites. A portal vein diameter exceeding 20 mm is generally accepted as diagnostic for extrahepatic PVA.

The exact etiology and pathogenesis of PVA remain unclear. However, portal hypertension and chronic liver disease are considered known risk factors. Other possible associations include pancreatitis, abdominal trauma, and a history of abdominal surgery.

The clinical presentation of PVA depends on factors such as aneurysm size, presence of complications (e.g., thrombosis, rupture), or comorbid conditions such as cirrhosis or portal hypertension. Small PVAs are frequently asymptomatic. When symptomatic, patients may present with recurrent epigastric or upper abdominal pain, jaundice, or, in rare cases, gastrointestinal bleeding.

Ultrasound is considered an accurate and reliable screening tool for PVA, as it typically appears as an anechoic mass with monophasic, non-pulsatile flow on color Doppler imaging. When the diagnosis is unclear, contrast-enhanced CT or MRI can be useful to differentiate between thrombosed and patent aneurysms.

In general, the presence of symptoms or thrombosis does not automatically indicate surgical intervention. Even large aneurysms or those extending into the splenic and superior mesenteric veins are primarily managed with conservative treatment and close follow-up, which remains the standard of care.

Learning Points

Recognition of PVA and its predisposing factors
Diagnostic, monitoring, and surveillance imaging strategies
A multidisciplinary and individualized approach is essential for the optimal management of each PVA case.

Reference

(1) Koc, Z., Oguzkurt, L., & Ulusan, S. (2007). "Portal vein aneurysms: Imaging, clinical findings, and a possible new etiologic factor." American Journal of Roentgenology, 189(5), 1023–1027. DOI: 10.2214/AJR.07.2266

(2) Lillemoe, K. D., Yeo, C. J., Talamini, M. A., et al. (1990). "Portal vein aneurysm: An unusual cause of portal hypertension."
Surgery, 108(5), 880–886.PMID: 2233790

(3) Laurenzi, A., Ettorre, G. M., Lionetti, R., et al. (2005). "Portal vein aneurysm: What to know." Digestive and Liver Disease, 37(10), 724–728. DOI: 10.1016/j.dld.2005.03.014

(4) Agarwal, A. K., Sharma, D., & Agarwal, S. (2015). "Portal vein aneurysm: A rare entity." Journal of Clinical and Diagnostic Research, 9(3), TD03–TD04. DOI: 10.7860/JCDR/2015/11371.5666

(5) Ghuman, S. S., Kaur, T., & Singh, K. (2019). "Portal vein aneurysm: A review." Journal of Clinical and Experimental Hepatology, 9(3), 373–377. DOI: 10.1016/j.jceh.2018.06.005

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