Louise Cortez was originally operated upon at Seattle Grace Mercy West to fix her chronic pancreatitis. The pancreas excretes enzymes that help digest food within the small intestine, but when someone has pancreatitis, the pancreas becomes inflamed and those enzymes damage the tissue of the pancreas. The Chief mentioned that Mrs. Cortez had a pancreatectomy, or a surgical removal of part of the pancreas. Mrs. Cortez had to be readmitted when she developed a pancreatic fistula — meaning those enzymes were leaking into the rest of her body, damaging the tissue of other organs.
The Middle Eastern leader's assistant revealed that his boss had an unruptured cerebral aneurysm. A cerebral aneurysm is a spot in one of the brain's blood vessels that is weakened so much that it balloons out and fills with blood, which can put pressure on nearby nerves or brain matter. If such an aneurysm ruptures, a hemorrhage occurs which could then lead to stroke, coma, or death.