A 48-year-old man with a 10-year history of recurrent acute pancreatitis presents with hematemesis and melena. On examination, he has splenomegaly and left upper quadrant fullness, but no ascites or stigmata of chronic liver disease. Liver function tests are normal. Contrast-enhanced CT abdomen shows the finding marked **A** in the diagram, with prominent gastric varices along the greater curvature. Which of the following is the most appropriate definitive management for this patient?