Pitfall in necrotizing pancreatitis: Organized hematoma with arteriovenous fistula mimicking a splenic artery pseudoaneurysm

Splenic artery pseudoaneurysm is a rare vascular complication of necrotizing pancreatitis, carrying a significant risk of rupture and massive hemorrhage. Diagnosis and treatment are essential; however, imaging findings may occasionally mimic other vascular lesions, creating diagnostic challenges. We report the case of a patient with severe necrotizing pancreatitis in whom serial contrast computed tomography (CT) examinations demonstrated a hyperdense splenic hilar lesion in the arterial section, increasing from 22 to 54 mm over a short interval, highly suggestive of a splenic artery pseudoaneurysm. The lesion showed imaging characteristics and anatomical location typically associated with this vascular complication. In the follow-up CT scan, the lesion also filled in the venous phase, creating doubt about the previous diagnosis. Selective angiography further supported the diagnosis by demonstrating nodular opacification at the splenic hilum, and prophylactic proximal coil embolization of the splenic artery was performed. Despite treatment, follow-up multiphasic CT revealed persistent arterial flow beyond the embolization coils and arterial link, this finding led to the indication for splenectomy. Splenectomy ultimately revealed an organized hematoma associated with an arteriovenous fistula rather than a true pseudoaneurysm. Retrospective review of the imaging studies identified atypical features, including predominant portal venous phase and the absence of a clearly defined arterial communication on angiography, findings that may help differentiate these entities. This case highlights an important imaging pitfall in one of the most dangerous vascular complications of necrotizing pancreatitis and underscores the importance of correlating CT, angiographic, and surgical findings when the diagnosis remains uncertain.