A 42-year-old Hispanic woman presents to the primary care office complaining of 24 hours of steady epigastric and right upper abdominal pain with sudden onset and several episodes of nausea and vomiting. She has experienced similar painful episodes in the past, usually in the evening following heavy meals, but the episodes always resolved spontaneously within hours. This time the pain did not improve, so she sought medical attention. She has no medical history and takes no medications. She is married, has three children, and does not drink alcohol or smoke cigarettes.

a. Differential Diagnoses

1. Acute Pancreatitis: The patient's severe epigastric pain radiating to the back, nausea, and vomiting are classic symptoms of acute pancreatitis.
2. Cholecystitis: The right upper quadrant (RUQ) tenderness and history of pain after heavy meals suggest gallbladder disease.
3. Peptic Ulcer Disease: Epigastric pain and nausea could also be due to a peptic ulcer.

b. Most Likely Diagnosis

The most likely diagnosis is Acute Pancreatitis. The severe, steady epigastric pain radiating to the back, nausea, vomiting, and tachycardia are characteristic of this condition.

c. Underlying Etiology

The most common causes of acute pancreatitis are gallstones and alcohol abuse. Given the patient's history of pain after heavy meals (which can indicate gallstones) and her non-alcohol consumption, gallstones are the most likely etiology.

d. Complications of Acute Pancreatitis

1. Pancreatic Necrosis: This is a severe complication where parts of the pancreas die due to lack of blood supply.
2. Pancreatic Abscess: This is a collection of pus within the pancreas.
3. Pseudocyst Formation: This is a fluid-filled sac in the pancreas.

e. Causes of Acute Pancreatitis

1. Gallstones: These can block the pancreatic duct, causing inflammation of the pancreas.
2. Alcohol Abuse: Chronic alcohol consumption can lead to pancreatitis.
3. Hypertriglyceridemia: Very high levels of triglycerides in the blood can cause pancreatitis.

f. Management Plan

1. Pain Management: This is usually achieved with opioids such as morphine.
2. Fluid Resuscitation: Aggressive hydration, typically with lactated Ringer's solution, is crucial.
3. Nutritional Support: Initially, the patient may require fasting. Later, a low-fat diet is recommended.
4. Treatment of Underlying Cause: If gallstones are the cause, a cholecystectomy may be necessary.