My 2year old lab (up to date with vaccines, wormed regularly and spayed) developed a severe swollen abdomen so I rushed her to the vets. She went sort of sausage shaped and could only just lay on her side witout rolling. Her breathing was affectd also. They did blood tests, x-rays etc couldn't see any reason for it and the swelling just gradually went away. She was back to normal and now 2 weeks later it's happenned again !! Anyone had this happen?

It sounds like she had the early symptoms of bloat (torsion) one of flatcoats did this a couple of times, my vet reccommended giving her milk of magnesia if I saw it happening as it prevented it going further as quickly as it would otherwise. As it turned out she did recover and pass the gas by belching and breaking wind after having the milk of magnesia, so it never got to be the full blown torsion, which would have needed urgent veterinary intervention.

This seems to be the same thing my little Ollie suffered from. This was controlled by keeping him very calm for at least an hour after feeding and prescribed Tagamet. (probably similar to milk of magnesia). This expelled all the gases (from both ends).  He was in severe pain and the risk of torsion was high, as the air in the stomach left room for the spleen and gut to twist. All was resolved quite simply by keeping him calm after meals

For this reason it is very good policy in all breeds to not excersise an hour before or after feeding.  As my freind has dobes and hgas always foillowed this precaution, I feel it does no harm to do likewise even though in my breed it is very rare, and in the cases I ahve heard of was the result fo gorging on a bag of dry feed to bursting point.

Gorging on dried food was how it started in my flatcoat. She managed to open the door to the food store in the night! I now feed more fresh foods so hopefully it won't happen again.
Tagamet is similar to milk of magnesia, but was not on the market when my bitch was alive.