S3531 A Silent Threat Averted: Spontaneous Thrombosis of a Splenic Artery Pseudoaneurysm in Acute Pancreatitis

Introduction: Acute pancreatitis is a rare cause of pseudoaneurysms with an estimated incidence of 4.3-6.4%. They can be clinically silent; however, the most feared presentation is rupture, which can lead to fatal consequences. The splenic artery is the most common site for developing a pseudoaneurysm, yet they are extremely uncommon, with the incidence of splenic artery pseudoaneurysms (SAPA) around 0.01-0.2% per 100,000. We present a case of acute pancreatitis and an associated SAPA that spontaneously thrombosed. Case Description/Methods: A 38-year-old woman with a past medical history of alcohol abuse presented to the hospital with a chief complaint of abdominal pain. Laboratory evaluation was significant for lipase 292 U/L, hemoglobin 9.9 G/DL, and hematocrit 35.2%. A computed tomography abdomen demonstrated pancreatic atrophy and a 4.9 cm × 5.0 cm × 4.2 cm hyperattenuating collection surrounding a posterior 1.5 cm SAPA. Interventional radiology performed an angiogram that redemonstrated findings of SAPA and showed slow flow through the splenic artery, which was concerning for splenic artery thrombus. Gastroenterology was consulted for possible endoscopic ultrasound (EUS) and drainage, but deferred intervention due to concerns for pseudoaneurysm. Follow-up computed tomography angiography 24 hours later no longer visualized the SAPA and showed stability of the complex pseudocyst. The SAPA was determined to have spontaneously thrombosed, and the patient was managed conservatively with pain management and fluids. She was discharged home in a stable condition with plans for EUS surveillance as an outpatient. Discussion: Visceral pseudoaneurysms are formed through vessel wall destruction by the leakage of proteolytic enzymes in pancreatitis. SAPA is a rare yet potentially fatal complication with nearly 100% mortality if ruptured. Small pseudoaneurysms (<3 cm) thrombose spontaneously 87% of the time. Further management options depend on the patient's stability; if stable, endovascular treatment with coils, plugs, or thrombin injection can be pursued; however, if endovascular treatment fails or if patients are unstable, surgical exploration with ligation of SAPA with splenectomy and possible pancreatectomy is considered. EUS with drainage should not be attempted in patients with pseudoaneurysms with associated pseudocysts, as this can cause severe hemorrhage. EUS or radiographic surveillance after 4 weeks allows for encapsulation and better definition of pseudocyst margins to allow for safer drainage.