Gastric varices are fed by the short gastric veins.
https://www.sciencedirect.com/science/article/pii/B9781437707748100764
The question says GASTRIC varices, not ESOPHAGEAL varices. My stupid brain. Plus I'm assuming left gastroepiploic would be a correct answer if it was listed.
Right gastroepiploic V can also be drained into its counterpart on the left, but short gastric V does not have anastomoses, so the varices of short gastric V leads to bleeding.
More fully: Afferents to gastric varices. The afferents to GV come from left gastric vein, short gastric veins and posterior gastric vein the left gastric vein mainly contributes to formation of cardiac varices whereas the short gastric vein and posterior gastric vein contribute to formation of fundal varices. Isolated gastric varices are more likely to be related to gastroepiploeic veins.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3940321/
submitted by saifshaikh(13)
There is splenic vein thrombosis. The short gastric veins normally drain into the splenic vein. Due to the thrombosis, there may be fluid backup and increased pressure, resulting in varices.