Where is the problem?

This video clip requires no introduction. No other abnormality was found.
WHERE IS THE LIKELY SITE OF THE PROBLEM?

■ in the portal vein

Then you would expect BOTH oesophageal and fundal varices!

■ In the hepatic vein

In Budd-Chiary, there are no varices!

■ In the splenic vein

Isolated splenic vein varices - absolutely correct!

explanation

Quoting the 'Sarin Classification' of gastric varices, this is a case of an 'isolated fundal varix' (IGV1). In this case the underlying cause was splenic vein thrombosis following an admission for acute on chronic pancreatitis.  The precise distribution of the varices helps you to pinpoint the location of the thrombus. The infographic below from Song et.al is brilliant: 

Briefly, 
1) oesophageal varices with or without fundal varices points to portal vein thrombosis
2) fundal varices ALONE points to splenic vein thrombosis
3) antral and/or duodenal varices points to a thrombus in the gastro-epiploic vein

Brilliant !