An older adult experiences abdominal pain radiating to the back, nausea, vomiting, and elevated serum amylase. What is the most likely diagnosis?

The symptoms presented — abdominal pain radiating to the back, nausea, vomiting, and elevated serum amylase — align closely with a diagnosis of acute pancreatitis. The radiating abdominal pain, particularly if it is severe and located in the upper abdomen, is a classic presentation for pancreatitis, which can often extend to the back due to the anatomical location of the pancreas.

Elevated serum amylase is another significant indicator; this enzyme is typically elevated in cases of acute pancreatitis as the pancreas undergoes inflammation or necrosis. The combination of these symptoms helps to establish a strong correlation with the diagnosis.

While other conditions may exhibit similar gastrointestinal symptoms, the specific combination of factors such as the pain pattern, elevated amylase levels, and systemic manifestations like nausea and vomiting provide a clearer indication of acute pancreatitis over the other listed possibilities, which may not consistently include elevated amylase or the characteristic pain radiation.