Giant splenic artery aneurysm rupture mimicking a pancreatic pseudocyst: a diagnostic pitfall on non-contrast computed tomography.

Splenic artery aneurysm (SAA) rupture is a rare but life-threatening cause of acute abdominal pain, with mortality exceeding 25% in undiagnosed cases. This report describes a giant SAA rupture that was initially misdiagnosed as a pancreatic pseudocyst on non-contrast computed tomography (CT), highlighting a critical diagnostic pitfall. A 49-year-old hypertensive male presented with sudden-onset left upper quadrant pain and nausea. Initial non-contrast CT showed cystic lesions with peripheral calcification, which were radiologically interpreted as a pancreatic pseudocyst. The patient subsequently developed hemodynamic collapse due to a "double rupture" phenomenon. Emergency CT angiography revealed a ruptured giant SAA (5.2 cm). Emergency laparotomy and splenectomy were performed successfully. This case illustrates the limitations of non-contrast CT in differentiating SAAs from cystic pancreatic lesions and reinforces the necessity of a low threshold for CT angiography in unexplained upper abdominal pain.