Painfull defecation

I have a 2 year old NI
He has been in pain when going to the toilet (for a poo) For months and months on and off. The vets first thought it was a enlarged prostate he had xrays and scan endiscope and had cells taken for the prostate to check for anything nasty.(All clear) They gave him antibiotics and he seemed to get better then in october was really not right in himself I took him the the vets who felt up him bum and said he felt really infected and sore up there and the prostate was huge and that was the likely cause of pain he was sent home on antibiotics and pain meds. And booked into be castrated the next week. The castration went well and he was given more antibs to help the prostate to go down 10 days after he had another scan and the prostate had shrunk by 2cm already ,it was 6 cm at its biggest another 3weeks and it had gone down to 2.5 and in normal range. he was still crying when doing a poo on and off then he started really screaming took him back to the vets his anal glads where full one was hard to express the other had thickening around it he was given more pain meds and sent home( vet said to think about anal glad removal if they are giving him alot of pain.) he is still not right and in alot of pain when going to the toilet.
He has gone back in today for another scan and his anal gland are fine so we are now at another dead end. They are getting a urine sample at the moment to test that but I am not sure they know what to do next.

Can anyone throw a few ideas at me. Really getting fed up now

Hi, I had had something similar with a previous gsd of mine, I too had been advised it may be due to prostate troubles and also to have him castrated. Luckily I didn't go ahead and it turned out to be a colitis which can be very nasty and painful. I remember giving him olive oil to help lubricate his system and got him on a course of sulphasalasine which took a grip of the condition, after all manner of diet changes and other drugs which hadn't helped. Maybe some olive oil in his diet for a while may help.

Thank you
Just off to google

Hi Did your dog have normal poo ?
As mine does he never has mucus or blood in it which i have read are clasic signs of colitis.

Poor fellow. Is his poos normal, or does he get the runs? What do you feed him on?

He is fed JWB. He never has the runs or blood or anything he has fine normal poo. Even if he has something different it wouldn't upset his stomach he is the sort of dog that can eat anything. Not that he does he has JWB and I even buy the mini jacks to treat him on through out the day.
He has paddywack the odd pressed raw hide bone and raw pigs trotter now and then when go out I always leave him with one of the above to chew on.

Strange one that, colitis wuld be the runs etc.. Im going to ask my friend for you, she's "into" diet etc.. and I think she has a dog with a dicky tummy too, Ill let you know what she says.

Thanks
I am off to ghet him from the vet in a bit poor boy has been in there all day.

Your poor boy, good luck when you pick him up. I'm wondering about those Paddywacks you give him, they have some seriously sharp splinters don't they???? Maybe, just maybe he might have got one stuck sideways somewhere along the line??? I wonder if some type of scan would show something like that up???

He has only recently been having the odd paddywhack and this problem has been going on for months so it can not be that.

I have him back from the vets and just the vet nurse handed him over they still hadn't got a urine sample so took him right outside and he did one for me right away.
They will call me when they get the sample back which has to be sent away so will be a few days.
They have left me with prednisalone and oxycare tablets.
So I am none the wiser.