Multimodality Imaging of Pancreatic Arteriovenous Malformation

Arteriovenous malformation of the pancreas (PAVM) is a very rare entity, although it may be increasingly diagnosed with the expanding use of cross-sectional imaging of the abdomen. PAVM is characterized by a network of tangled vasculature within and surrounding all or part of the pancreas, resulting in the shunting of the arteries of the pancreas directly into the portal venous system. Here, we present a patient with chronic abdominal pain and pancreatitis found to have PAVM, based on the findings of computed tomography, magnetic resonance imaging, endoscopic retrograde cholangiopancreatography, and angiography. Differential considerations are discussed. Although PAVM is uncommon, it should be considered in the differential of patients with recurrent abdominal pain or gastrointestinal bleeding.

Introduction

Pancreatic arteriovenous malformation (PAVM) is a vascular abnormality in which blood bypasses the capillary bed of the pancreas and flows directly from the pancreatic arterial vessels into the portal venous system. All or part of the pancreas may be involved.1, 2 PAVMs are quite rare, with fewer than 100 case reports in the English-language literature.1, 3 Symptomatic and asymptomatic patients have been reported. When symptoms are present, the most common presenting symptoms are gastrointestinal (GI) bleeding and abdominal pain.1, 2, 4

PAVM may be demonstrated with several modalities, including contrast-enhanced computed tomography (CT), magnetic resonance imaging (MRI) with or without contrast, angiography, transabdominal ultrasound (US), endoscopic US, endoscopic retrograde cholangiopancreatography (ERCP), and scintigraphy. On CT, PAVM is characterized by arterial-phase enhancement of multiple feeding arteries with early filling of draining veins, including the splenic and portal vein. In addition to these findings, dynamic contrast-enhanced MRI may also demonstrate signal voids on noncontrast sequences, owing to high-velocity flow through the dilated vessels. MRI also shows diffusely lower T1 signal of the pancreas, which is normally slightly brighter than the liver on noncontrast T1-weighted images. Angiography typically shows a racemose vascular network with multiple dilated feeding arteries, and early opacification of the draining portal or splenic vein. Gray-scale US findings include hypoechoic vascular structures, whereas color Doppler US findings include a characteristic “mosaic” pattern of intermixed vessels with varying angles of flow. Waveforms in the splenic or portal veins may be pulsatile or arterialized owing to the increased flow through the PAVM.⁵ ERCP can reveal associated ductal abnormalities, including filling defects along the walls of the ducts owing to impressions and areas of mass effect from adjacent, dilated vessels.⁶ Distribution of PAVM may be focal or diffuse, although the focal form of PAVM is much more common.⁴

The most common differential consideration would include a vascular tumor, which can be difficult to differentiate from the focal form of PAVM. Other diagnostic considerations would include chronic pancreatitis, which can produce similar ductal abnormalities on ERCP, and an intrapancreatic splenule, which usually appears as an early-enhancing nodule in the distal pancreas.⁷ Careful evaluation of cross-sectional images can usually enable confident exclusion of a focal mass, however, and can usually provide definitive diagnosis of PAVM.

Here, we report a case of a patient with extensive PAVM affecting the entire pancreas. Companion images are shown.