Bloated guinea pig - Now passed away

Hello, we had a 1yr 6 month old male guinea pig who showed symptoms of bloat within an hour. Within 20 minutes of  the forst sign of swelling, we took him straight to the vets. The swelling got worse and he was in immense pain. The xray the vet did is attached. She didnt really have a definitive answer as to what caused this. He was still passing faeces and urinating (though she never asked us this question) she said the only option MAY have been surgery but likely to be unsuccessful. She didnt suggest anything else. He had ongoing urinary issues for around 6 months. We had tried 2 courses of antibiotics for the urine issues (apparently he had bladder sludge) and he was on 1/4 of a Catease capsule once daily to try and line his bladder to protect it from crystals. He was on 0.4ml of metacam twice a day and his last recorded weight was 1.06g. We really just wanted a second opinion on the xray as to what could have caused this. Could it have been stomach twist? Or would that have been apparent on an xray? He was eating and pooping mormally the hour before his belly started swelling and it wasnt swollen for long before we took him to vets. 

Hello!  - I have a soft spot for guinea-pigs and I'm so sorry that you lost yours.  Guinea-pigs, like us, have a gasterointestinal tract that only flows in one direction - but more so, because while we can vomit or burp to remove food or gas that's causing pressure, a guinea-pig can't;  once it's in there, food can only progress in one direction.  Therefore, if for any reason the tract gets narrowed or blocked, or twists, or foods produce excessive gas in the gut, or if the tract simply stops moving (eg the guinea pig gets a sore tooth or jaw and doesnt eat for a day, so the guts stop propelling food forwards) the consequence is often bloating.  It is a very common secondary condition - always caused by something else - and frequently fatal.  Sending warm thoughts your way at this tine.