Differential Diagnosis for Right Lower Quadrant Abdominal Pain

The differential diagnosis for right lower quadrant (RLQ) abdominal pain is broad and includes various conditions. Here's an organized approach to considering these diagnoses:

• Single Most Likely Diagnosis

  • Appendicitis: This is often the first consideration for RLQ pain, especially if the pain is acute, starts near the umbilicus, and then localizes to the RLQ. Appendicitis is a common cause of acute abdominal pain requiring surgical intervention.

• Other Likely Diagnoses

  • Ovarian Cyst or Torsion: In females, ovarian cysts can cause RLQ pain, especially if they rupture or torsion occurs. The pain can be severe and is often accompanied by nausea and vomiting.
  • Ectopic Pregnancy: Another consideration in females, especially if there's a history of missed periods or positive pregnancy test. Ectopic pregnancy is a medical emergency.
  • Diverticulitis: Although more common on the left side, diverticulitis can occur on the right and cause RLQ pain, especially in individuals with a history of diverticular disease.
  • Intestinal Obstruction: Can cause RLQ pain, especially if the obstruction is in the ileum. Symptoms include severe abdominal pain, vomiting, and constipation.
  • Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease can cause chronic or acute RLQ pain, depending on the disease activity and location.

• Do Not Miss Diagnoses

  • Ectopic Pregnancy: As mentioned, this is a medical emergency that requires immediate attention.
  • Ruptured Aneurysm or Aortic Dissection: Although these conditions typically present with back or abdominal pain, they can sometimes cause RLQ pain and are life-threatening if not promptly diagnosed and treated.
  • Pneumonia: Basilar pneumonia, especially if it involves the right lower lobe, can cause referred pain to the RLQ.
  • Ureteral Colic: A stone in the right ureter can cause severe, colicky pain that may radiate to the RLQ.
  • Mesenteric Ischemia: This condition, which involves insufficient blood flow to the intestines, can cause severe abdominal pain, including in the RLQ, and is a medical emergency.

• Rare Diagnoses

  • Yersinia or Other Infectious Ileitis: Certain infections can cause inflammation of the ileum, leading to RLQ pain.
  • Meckel's Diverticulum: A congenital anomaly of the small intestine that can cause pain, especially if it becomes inflamed or if there's a complication like intestinal obstruction or bleeding.
  • Carcinoid Tumor: Rare tumors that can cause abdominal pain, including in the RLQ, often accompanied by other symptoms like flushing or diarrhea.
  • Right Lower Lobe Pulmonary Embolism: Although less common, a pulmonary embolism can cause referred pain to the abdomen, including the RLQ, especially if the embolism involves the lower lobes.

Each of these diagnoses has distinct clinical features and may require specific diagnostic tests for confirmation. A thorough history, physical examination, and appropriate imaging or laboratory tests are crucial for making an accurate diagnosis.