Differential Diagnosis for Abdominal Pain in Adults

Abdominal pain is a common symptom with a wide range of possible causes. The differential diagnosis can be organized into several categories based on the likelihood and potential impact of missing the diagnosis.

• Single Most Likely Diagnosis

  • Gastroenteritis: This is often the most common cause of abdominal pain in adults, usually presenting with diarrhea, vomiting, and fever. It's typically viral in nature and self-limiting.
  • Irritable Bowel Syndrome (IBS): A chronic condition characterized by abdominal pain, bloating, and alteration of bowel habits without an identifiable cause. It's common and can be managed with lifestyle changes and medication.

• Other Likely Diagnoses

  • Urinary Tract Infection (UTI): Can cause abdominal pain, especially in the lower abdomen, accompanied by dysuria, frequency, and urgency.
  • Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease and ulcerative colitis can cause chronic abdominal pain, diarrhea, weight loss, and sometimes blood in stool.
  • Peptic Ulcer Disease: Gastric or duodenal ulcers can cause epigastric pain, especially related to eating.
  • Constipation: Can cause significant abdominal discomfort and is often associated with changes in bowel habits.

• Do Not Miss Diagnoses

  • Appendicitis: Although not the most common cause, appendicitis is a surgical emergency that can present with abdominal pain, initially diffuse or around the navel, then localizing to the right lower quadrant.
  • Ectopic Pregnancy: A life-threatening condition in women of childbearing age, presenting with abdominal pain and vaginal bleeding.
  • Ruptured Aortic Aneurysm: A medical emergency with severe abdominal or back pain, often described as tearing.
  • Mesenteric Ischemia: A condition where blood flow to the intestines is blocked, causing severe abdominal pain out of proportion to physical findings.
  • Pancreatitis: Inflammation of the pancreas, which can cause severe upper abdominal pain radiating to the back.

• Rare Diagnoses

  • Intussusception: A condition where a part of the intestine slides into an adjacent part, causing bowel obstruction and severe abdominal pain, more common in children but can occur in adults.
  • Celiac Disease: An autoimmune reaction to gluten, leading to small intestine damage and causing abdominal pain, diarrhea, and malabsorption.
  • Porphyrias: A group of disorders that can cause acute intermittent porphyria, leading to severe abdominal pain, neurological symptoms, and sometimes psychiatric disturbances.
  • Lead Poisoning: Can cause abdominal pain, constipation, and neurological symptoms, often related to occupational exposure or ingestion of contaminated substances.

Each of these diagnoses has distinct features and requires a thorough history, physical examination, and sometimes diagnostic tests to confirm. The key to managing abdominal pain effectively is to consider the broad range of possible causes and to prioritize those that are life-threatening or require urgent intervention.