The Natural History of Portal Venous System Aneurysms.

Background: Portal venous system aneurysms (PVA) are increasingly diagnosed on cross-sectional computed tomography (CT) imaging. However, the natural history of these aneurysms is poorly understood and reports are limited to small case series.

Methods: Terms relevant to PVA were searched in radiology reports (2010-2022) with PVA presence confirmed by manual review. PVA were defined as a diameter greater than 1.5 cm in patients without cirrhosis and 1.9 cm in those with cirrhosis. Aneurysm growth was defined as greater than 20% increase in size while aneurysm regression as greater than 20% decrease in size. Patient demographics, comorbid conditions, and PVA outcomes were abstracted. Univariate statistics were used to compare groups.

Results: Thirty-eight aneurysms with radiographic follow up were identified in 35 patients, involving the portal vein (n=18, 47.4%), splenic vein (n=10, 26.3%), superior mesenteric vein (n=3, 7.9%), and portal confluence (n=7, 18.4%). While 12 (31.6%) were idiopathic, the remaining 26 (68.4%) were associated with portal hypertension (n=20, 52.6%) and prior liver transplant (n=4, 10.5%). The median growth was 0.2 cm (-2.6-2.4 cm) over median follow up over 5.0 years (0.3-16.6). Five (13.2%) PVA regressed and were largely idiopathic (80.0%, p=0.03). Thirteen (34.2%) PVA grew and were associated with portal hypertension (n=11, 84.6%, p=0.003) and thrombosis (n=6, 46.2%, p=0.05). Nine (23.7%) PVA thrombosed, predominantly in males (n=7, 77.8%). The median growth was 1.0 cm (-0.7-1.9 cm). Three patients (33.3%) were symptomatic from PVA thrombosis including abdominal pain (n=2, 22.2%), intestinal ischemia (n=1, 11.1%), and variceal bleeding (n=2, 22.2%). Four (44.4%) patients were treated with anticoagulation. No aneurysms ruptured. Of the 58 PVA initially identified with and without radiographic follow up, 5 (8.6%) underwent intervention with a median diameter of 4.0 cm (3.4-5 cm). Intervention included vein ligation (n=1, 20.0%), aneurysmorrhaphy (n=1, 20.0%) and aneurysmectomy (n=3, 60.0%). There was one case of aneurysm recurrence 20 years following resection and one post-operative mortality.

Conclusion: Two-thirds of PVA, including size greater than 3 cm, remain stable on surveillance. While annual surveillance is initially recommended to confirm PVA stability, interval imaging can be subsequently extended given low growth rates. Over 20% of PVA thrombosed but none ruptured. Although we did not observe any cases of rupture, the devastating consequences of rupture necessitate consideration of surgical intervention for large symptomatic PVA.