My Dad - diarrhoea after op

This is a long story but it is about my dad. He fell off a ladder just over 18 months ago and was in critical/intensive care and recovered fine, but during numerous scans it showed up a hiatus hernia but as he was so fragile at the time they couldn't do it. Fast forward and once he has recovered, they had him in at Christmas to do the hiatus hernia operation. It ended up being more complex as the hiatus hernia was actually his stomach! It was literally in his chest, which explained the years of heartburn, acid indigestion, noisy digestive system etc. As long as I can remember my dad always had Rennie tablets in his pocket! They moved his stomach down from his chest and what followed was weeks of soft food etc...

It's now heading to 6 months since his op and my dad curses the day they did it. Since then he has had constant wind, belching, what he describes as bubbling and diarrhoea, sorry for the vulgar description but my dad describes it as brown water. He has lost over two stone since the op (my dad is 62) and he wasn't obese before. He has been back to the hospital numerous times and the most recent thing that has happened is they gave him a CAT Scan but the consultant advised as far as they are concerned the operation was a success. There is no issues as far as they can see on the scan.

He has had tablets incase it was some kind of gastric bug (made no difference), and various other tablets to treat the gas, alongside things like buscopan etc.. and he has now been referred back to the GP who has now taken a stool sample (that was difficult) and he is waiting for the results alongside blood tests.

Thanks consultant have the GP a list of meds they wanted dad to take and he will see him in a month but the GP won't prescribe all these yet until she has had the stool sample results and blood tests as she feels she wants to know for sure there is nothing on these before prescribing a range of drugs which I guess is wise.

Dad is getting depressed and whilst he knew he really has to have the op - he was told if ever he had a chest infections etc he would have probably died as his stomach was preventing his lungs from working at full capacity. Obviously it was never addressed before as my dad had just ignored it and he is not one for going to the doctors.

Has anyone experienced anything similar? I just want to share this with my dad and explore other options and I'd anyone has had similar it would be helpful to know.

My dad has been in tears today, he rung the GP for his results and the receptionist said "it's all clear carry on as normal". He was very patient in trying to explain that he hasn't been normal for months. He has to ring the GP tomorrow. So all we know is the operation was a success, his stool and blood samples are all fine and on paper everything is fine. No one can say why he is suffering with the wind, gas, diarrhoea etc.

He had already been treated for intestinal infection 'just incase' to no success previously so it certainly isn't this or any other bug. To have it consistently since he had the op on 31 December 2016 cannot be normal. Mum is going to the GP with him tomorrow.