This subject has come up a couple times recently, so I thought I would start a thread discussing it. I put it in first aid because though a dog can have a genetic predisposition to it, it cannot be directly transmitted or inherited so it is not properly a disease. It is a function of how the dog is structured, which is why it is more common in some breeds (in particular large breeds with deep chests) and why it can follow family lines (you are typically structured more similarly to your close relatives than to non-relations).
GDV happens when the stomach twists. Think of a peppermint in a cellophane wrapper. If you put the peppermint in a cellophane tube, it can slide out either end. But if you twist each side of the tube the peppermint can no longer escape. If you twist each end of the stomach, food and gasses cannot escape the stomach either. Gas can build up and the stomach can actually rupture (tear open). That is fatal.
Your digestive tract, and a dog's, is simply a very long tube from mouth to anus. It gets wider in some areas and narrower in others, but is still just a tube. If you block that tube, things start piling up. The place where it is easiest to get a twist cutting something off is at the entrance and exit of the stomach. The intestines are actually held together in a clump by a web of tissue called the mesentery. It would be really hard to twist the intestine, no matter how noodley it looks in pictures. When you take it out of the body, it comes out in one big clump.
Even if you get the stomach re-oriented correctly after it has twisted, there will be some damage done to the openings at either end of the stomach (from the esophagus and into the intestines). Pull that wrapper off the peppermint and try to flatten it out again. There are permanent "scars" on the wrapper from having been twisted. The same can be true of the dog's stomach. In fact, once a dog bloats he is more likely to do it again than the average population of dogs.
You can prevent bloat by tacking the stomach to the abdominal wall, and vets will sometimes do this during surgical intervention for bloat. However, the risk of bloat is generally not severe enough to justify subjecting the dog to this surgery as a preventive measure. Instead, you prevent bloat with some common sense management.
1. Do not exercise the dog on a full stomach.
2. Do not feed the dog when hot or right after exercise (more on this later).
3. Do not let him gulp food or water. Make him consume things calmly, even if it means stuffing his food in a kong and making him work to get out each mouthful.
The idea is not to combine a full stomach or a stomach fueled for producing gas with any physical activity that might cause the guts to move about inside him. So why worry about feeding him right after exercise if he's not going to exercise with a full stomach? Because the way we and dogs are designed, our bodies prioritize the allocation of resources. During physical exercise, adrenaline is released which improves the supply of resources to the muscles, AND removes those same resources from the digestive tract. Right after exercise a dog is not chemically capable of digestion. (No, it is not the same as dogs hunting in the wild, but that is more complicated than I want to go into right now. Just trust that it is true of pet dogs.) One of the results of the dog not being prepared for the chemical part of digestion is that extra gas will be produced, resulting in increased swelling of the stomach. A full stomach, be it full of food or gas, is a risk for bloat. A stomach twice as full because it has undigested food AND gas, is at a greater risk.
Here are some articles on GDV for further reading:
http://pethealthlibrary.purinacare.com/dogs/bloat-gastric-dilatation-volvulus/http://www.canismajor.com/dog/bloat.html
