I'm very sorry about your dog.

Gastric Dilatation and Volvulus, also known as "Bloat", is a potentially fatal condition. Even with dogs who receive treatment, as many as 25% to 40% die.

Gastric dilation starts with a distended, swollen stomach. The stomach is usually full of air, and is so full that the dog can't empty it's contents by belching, vomiting, or digestion.

The condition is called gastric torsion when the stomach suddenly twists up to 180 degrees. At this point the twisting causes damage to tissues and organs.

Gastric volvulus is when the stomach twists from 180 to 360 degrees. At this point the stomach is closed off at the esophagus and the small intestine. Ischemia, the lack of blood flow, quickly causes necrosis (death) of tissue. Soon bacteria from the dead tissue gets into the blood stream and causes massive infection or septic shock. The stomach is still distended, which puts pressure on the lungs, causing difficulty breathing. The distension also puts pressure on the blood vessels, which slows the blood return to the heart, resulting in lowered blood pressure. As there is less blood volume for the heart to pump, heart function is compromised and arrhythmias may occur.

The spleen can begin to bleed because the twisting of the stomach causes it to separate from the stomach. This may cause clotting abnormalities to develop, and the dog can bleed to death very quickly.

When Gastric Dilatation and Volvulus occurs, it can take less than an hour or up to 36 hours for it to result in death.

Since in your dogs case, her spleen was folded upon itself, it must have separated from the stomach, causing her to "bleed out", which can quickly result in death. If I had to guess, and it really would be a guess, I'd say she would have died within an hour from her spleen separating from her stomach.

Vets do not really understand what causes GDV in the first place. All dogs swallow air, but for some reason dogs that develop GDV cannot release this swallowed gas. GDV is more prevalent in some breeds than others, although all dogs can get it. (English Bulldogs are not one of the breeds it is commonly found in.)

I had never heard of GDV following a caesarean, but after doing some research I found an article about the risk of GDV developing after the use of a specific anesthesia during surgery. These were the results of the study:

A recent study has described the development of gastric dilation due to aerophagia (excessive swallowing of air) during the recovery of a dog anaesthetised with tiletamine/zolazepam.
http://www.provet.co.uk/health/diseases/bloatanaesthesia.htm

I would ask your vet what anesthesia he used. GDV is just not common after c-sections or surgery. I think your vet should also explain to you how he thinks the GDV occured, and why it wasn't noticed post-op. There may be legitimate explanations for these questions, I just think you have the right to understand what happened.

Again, I'm very sorry about your dog, and I hope this information helps. Don't hesitate to ask if you have anymore questions.

See:
http://www.peteducation.com/article.cfm?cls=2&cat=1571&articleid=402
http://www.globalspan.net/bloat.htm
http://www.animalclinic.com/bloat.htm
http://www.provet.co.uk/health/diseases/bloatanaesthesia.htm
http://www.eclipse.net/~bobaloo/bloat.htm
http://www.triplecrownkennel.com/bloat.html

Susan is offline now so I thought I'd add some information for you.
This is what I know both from dealing with bloat in dogs and in having c-sections done on them.
The torsion is the big issue - dogs can survive bloat but when the stomach twists nothing can escape from it.
If your dog was in labor before having the c-section contractions could have influenced a torsion.
Anesthesia as the dogs thrash when coming around from it can also influence a torsion.
Removing the pups also leaves a lack of tension in the abdominal organs which could influence torsion.
In my experience the most likely dogs to torsion seem to be dogs that are easily emotionally stressed.
Everything may have been fine when your vet stitched her up. At the point you were leaving the vet should have re-examined her before letting her leave with a change like that in shape.
This site covers what should have been done
http://www.marvistavet.com/html/body_bloat.html
Now you have seen it you won't mistake it again.
Hopefully that is true of your vet too.
The spleen folding has to do with the torsion too and organs being pushed out of place by pressure. If the spleen had shown signs of bleeding then that would have been a reasonable cause of death as its a very vascular organ and dog bleeds out rapidly from it.
In this case it sounds like the blood flow to heart and brain were interupted by the bloat and torsion.
Not every vet knows everything and vets can get tired too. But personally I think you might want to seek out a different vet for tricky care cases (and bulldogs are always tricky) if there is one you can go to.
Are your pups doing OK? I find hand raising on goats milk works pretty well if you add a daily dose of liquid puppy vitamins to it.
And its awful losing a dog because you bred her and the vet messed up (had it happen to one of mine and I became a much more demanding owner advocating my pets since then). If you have not seen www.petloss.com and the rainbow bridge story it might bring a little comfort.
Hope this helps you!

Thanks for adding some information, Nancy.

Stress does contribute to the original condition of gastric dilatation, but once that condition occurs torsion usually follows.

I think it was negligent of the vet not to have checked her out when you pointed out how bloated she was. The average person might notice it and not think it was significant, but it should have made the vet stop and think when you brought it to his attention. GDV is the second leading cause of death in dogs after cancer, so he had to be familiar with the symptoms.

It sounds like when your dog laid down with her pups, the change is position probably cut off the remaining blood flow since she died so fast.

I'm sorry your vet acted like you were at fault. That's usually the attitude of someone who know's he's missed something but doesn't want to admit it. I think going to a different vet, if another is available, is a good idea, too.

I'm sorry in addition to the loss of your dog you have to deal with your vet not explaining things to you, or even giving you an apology. It makes things so much harder.