The perforation of the duodenal ulcer led to the contents of the stomach being released into the peritoneal cavity. If you remember, the stomach contains acid, which will burn and irritate the surrounding tissues, and digestive enzymes. This caused the inflammation on the external surface of the liver.
As the gastric contents start to damage the bowel, the omentum moves over to form a shield, protecting the delicate structures beneath it by trying to contain the damage to a small area - hence the adhesions. However, gastric contents include of bacteria - this explains the gas release and the foul-smelling liquid - which proliferate in the peritoneal cavity and overwhelm the body's defences, leading rapidly to organ system failure and death.
Unless caught very quickly, the chances of surviving such a perforation are slim, as inflammation is so severe and rapidly progressive.