Differential Diagnosis for Abdominal Pain

The differential diagnosis for abdominal pain is broad and can be categorized based on the likelihood and potential impact of missing a diagnosis. Here's a structured approach:

• Single Most Likely Diagnosis
  • Gastroenteritis: This is often the most common cause of abdominal pain, especially if the pain is accompanied by symptoms like diarrhea, vomiting, and fever. The justification for this being the single most likely diagnosis is its high prevalence in the general population and the broad range of pathogens that can cause it.
• Other Likely Diagnoses
  • Irritable Bowel Syndrome (IBS): A common condition characterized by chronic abdominal pain, bloating, and alteration of bowel habits, without any mechanical, inflammatory, or biochemical abnormalities.
  • Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease and ulcerative colitis can cause chronic abdominal pain, diarrhea, weight loss, and sometimes blood in the stool.
  • Peptic Ulcer Disease: Ulcers in the stomach or duodenum can cause abdominal pain, typically in the upper abdomen, and can be exacerbated by food or improved by antacids.
  • Constipation: Can cause significant abdominal discomfort and is very common.
• Do Not Miss Diagnoses
  • Appendicitis: Although not the most common cause, appendicitis is a surgical emergency that requires prompt diagnosis and treatment to prevent perforation and peritonitis.
  • Ectopic Pregnancy: A life-threatening condition in women of childbearing age presenting with abdominal pain and possibly a missed period.
  • Ruptured Aortic Aneurysm: A catastrophic condition that presents with severe abdominal and/or back pain and is often fatal if not immediately treated.
  • Mesenteric Ischemia: A condition where there's insufficient blood flow to the intestines, which can lead to tissue death and is a medical emergency.
• Rare Diagnoses
  • Intussusception: A condition where a part of the intestine slides into an adjacent part, potentially cutting off blood supply, more common in children but can occur in adults.
  • Volvulus: A twisting of a portion of the intestine that can cut off blood flow and require emergency surgery.
  • Pancreatic Cancer: Although rare, it can present with abdominal pain, weight loss, and jaundice, and is important to consider in the differential, especially in older patients with risk factors.
  • Porphyrias: A group of rare genetic disorders that can cause severe abdominal pain, among other symptoms.

Each of these diagnoses has a unique set of clinical features, risk factors, and diagnostic approaches. A thorough history, physical examination, and judicious use of diagnostic tests are crucial in narrowing down the differential diagnosis and guiding management.