Biliary Colic or Cholecystitis: The patient's symptoms of right upper quadrant (RUQ) pain radiating to the back and worsening over time are classic for biliary colic or cholecystitis, especially if the pain started after eating a fatty meal. The pain's radiation to the back and its worsening nature could indicate an inflamed gallbladder.

Peptic Ulcer Disease: Peptic ulcers can cause severe abdominal pain that may radiate to the back. The pain can be exacerbated by food or improved by antacids, which might help differentiate it from biliary causes.
Pancreatitis: Acute pancreatitis can present with severe abdominal pain radiating to the back, nausea, vomiting, and can be triggered by gallstones or alcohol use. The pain is often constant and severe.
Gastroesophageal Reflux Disease (GERD): While less likely to cause severe back pain, GERD can cause epigastric pain that radiates to the chest and, occasionally, to the back.

Myocardial Infarction: Although less common in women, myocardial infarction can present atypically with epigastric or back pain, especially in diabetic or postmenopausal women. It's crucial to consider cardiac causes, especially if the patient has risk factors.
Pulmonary Embolism: Severe, sudden-onset back or chest pain can be a presentation of pulmonary embolism, particularly if accompanied by shortness of breath or tachycardia.
Aortic Dissection: This is a medical emergency that can present with severe, tearing chest or back pain. It's more common in hypertensive patients or those with aortic pathology.
Ectopic Pregnancy: Although less likely in a 46-year-old, ectopic pregnancy can present with abdominal pain and should be considered in any female patient of childbearing age with abdominal pain, especially if there's a possibility of pregnancy.

Hepatic Artery Aneurysm: A rare cause of abdominal pain that can radiate to the back, often associated with a palpable mass.
Splenic Artery Aneurysm: Similar to hepatic artery aneurysm, this can cause left upper quadrant pain but is less likely to cause RUQ pain.
Diabetic Ketoacidosis: Can present with abdominal pain, but typically accompanied by other symptoms like hyperglycemia, ketosis, and altered mental status.