Final answer:
The most likely cause of diarrhea and cramping after meals in a post-gastric bypass patient is Dumping Syndrome, which leads to rapid movement of food into the small intestine and can also cause symptoms like nausea and stomach cramps.
Step-by-step explanation:
The possible cause of diarrhea and cramping 30 minutes after meals in a patient who recently underwent gastric bypass surgery could be Dumping Syndrome. This condition occurs when food moves too quickly from the stomach to the small intestine. Symptoms of Dumping Syndrome include diarrhea, nausea, stomach cramps, gas, and greasy stool. Other symptoms can include dehydration if severe, which may sometimes lead to malabsorption syndrome. While gastroenteritis, gallbladder disease, and pancreatitis could also cause similar symptoms, Dumping Syndrome is more specifically associated with the post-surgery patient experience.