Читать книгу Clinical Pancreatology for Practising Gastroenterologists and Surgeons - Группа авторов - Страница 84

MDCT is the most common imaging modality utilized to distinguish vascular complications associated with AP. It identifies peripancreatic vascular structures and involvement. Peripancreatic venous thrombosis of the splenic, portal, and/or superior mesenteric veins occurs as a result of stasis from spasm and mass effect from the surrounding pancreatic inflammation. Splanchnic vein thrombosis is the most common vascular complication of AP given that the splenic vein runs posteriorly and adjacent to the body and tail of the pancreas. It is seen in about 1.7% of all patients undergoing abdominal contrast‐enhanced cross‐sectional imaging [33] and 22.6% of patients with AP [34] and in 50% of patients with ANP [35]. It is often an incidental finding and may lead to severe complications such as mesenteric ischemia, non‐cirrhotic portal hypertension, and/or gastrointestinal bleeding. Splanchnic vein thrombosis can lead to engorgement of the short gastric vessels, leading to gastric varices with 12% risk of gastrointestinal bleeding [34]. On CT imaging, venous thrombosis is established by the presence of an enlarged vein with low attenuation in the center and does not enhance with the injection of intravenous contrast. There may also be extensive irregular enhancing vessels around the portal or splenic vein suggesting collateral formations. Focal segmental peripheral areas of lower attenuation may also be seen in the hepatic parenchyma that do not enhance with intravenous contrast, suggesting ischemic changes as a result of portal vein thrombosis [36,37].

Figure 5.3 Infected walled‐off necrosis: the arrow depicts the encapsulated collection of heterogeneous necrosis as well as air bubbles in the dependent portion of the collection.

Source: courtesy of Elham Afghani.

Arterial pseudoaneurysms are late complications of AP. The incidence is approximately 1.3–10% and can occur weeks to months after the onset of AP [36]. If not recognized early, it has up to a 90% mortality from hemorrhagic complications [37]. It occurs as a result of erosion of the wall of the vessel by the autodigestive action of proteolytic enzymes. On CT imaging, the pseudoaneurysm may appear as a saccular structure with an enhancing component and a possible thrombus. Pseudoaneurysms will enhance on arterial but not venous phase. Unenhanced images may suggest a pseudoaneurysm by a lesion with increased attenuation due to thrombosis. Pseudoaneurysms most commonly form in the splenic artery. Other locations include the gastroduodenal, superior mesenteric, pancreaticoduodenal, and hepatic arteries [36]. Pseudocysts can transform into pseudoaneurysms by mass effect and erosion into the surrounding arteries. On CT imaging, the pseudocyst/pseudoaneurysm does not appear cystic, but is dense on non‐contrast images and enhances on arterial and venous phases [36,38].