So he really hasn't eaten since Thursday? That is a huge red flag.
The only way to tell if they is an obstruction is an Xray and/or ultraound of the abdomen. Based on his symptoms, I don't see how they can rule it out.
And I say this of the owner/parent of a Golden Retriever who had two major surgeries for obstructions and fortunately puked up two other potential obstructing items. Ben almost died from the first obstruction. The vets kept saying he was okay (three vets in two states, over a long Christmas holiday weekend), I knew he wasn't okay. Within an hour of arriving at the surgeon, they had him in surgery.
Good luck and positive thoughts.
Skin kids - Jason, Kevin, Allison
Canine kids - Bennett & Bailey (always in our hearts), Riley, Banker, Rogue and Boz
Feline kids - Zoey, Talley and Abra