Differential Diagnosis for Diffuse Abdominal Pain in a Patient with a History of Cholecystectomy

Single Most Likely Diagnosis

• Irritable Bowel Syndrome (IBS): Given the history of cholecystectomy, which might have been performed for gallstones, and the presentation of diffuse abdominal pain, IBS is a common condition that could explain the symptoms, especially if the patient has a history of bowel habit changes or stress.

Other Likely Diagnoses

• Gastroesophageal Reflux Disease (GERD): Symptoms can include abdominal pain, especially if the pain is more upper abdominal and associated with eating or lying down.
• Peptic Ulcer Disease: Although less common without a gallbladder, peptic ulcers can still occur and cause abdominal pain, often localized to the upper abdomen.
• Small Intestine Bacterial Overgrowth (SIBO): This condition can cause diffuse abdominal pain, bloating, and changes in bowel habits, and might be considered, especially if the patient has had alterations in bowel anatomy or motility issues.
• Adhesions or Bowel Obstruction: Although less common, these can occur after any abdominal surgery, including cholecystectomy, and cause diffuse or localized abdominal pain.

Do Not Miss Diagnoses

• Appendicitis: Although the appendix is typically located in the lower right abdomen, atypical presentations can occur, and missing appendicitis can have severe consequences.
• Pancreatitis: This condition can cause severe, diffuse abdominal pain and is a medical emergency. A history of gallstones (which might have led to the cholecystectomy) increases the risk.
• Mesenteric Ischemia: A condition where blood flow to the intestines is blocked, causing severe abdominal pain out of proportion to physical examination findings. It's rare but life-threatening.
• Perforated Viscus: Any condition leading to a hole in the stomach, small intestine, or colon can cause severe abdominal pain and is a surgical emergency.

Rare Diagnoses

• Carcinoid Syndrome: Rare tumors of the neuroendocrine system can cause abdominal pain, flushing, and changes in bowel habits.
• Eosinophilic Gastroenteritis: A rare condition characterized by eosinophilic infiltration of the gastrointestinal tract, causing abdominal pain, nausea, and vomiting.
• Abdominal Angina: Rarely, chronic mesenteric ischemia can cause postprandial abdominal pain due to insufficient blood flow to meet the increased demand of the intestines during digestion.

Each diagnosis should be considered based on the patient's full clinical presentation, including history, physical examination, and diagnostic tests as appropriate.