Differential Diagnosis for RLQ Pain

The differential diagnosis for right lower quadrant (RLQ) pain can be categorized into several groups based on the likelihood and potential severity of the conditions.

• Single Most Likely Diagnosis

  • Appendicitis: This is the most common cause of RLQ pain, especially in younger individuals. The pain often starts around the navel and then moves to the RLQ. Appendicitis requires prompt medical attention to prevent rupture and peritonitis.

• 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 condition in females, ectopic pregnancy can present with RLQ pain, vaginal bleeding, and symptoms of early pregnancy. It is a medical emergency.
  • Intestinal Obstruction: This can cause severe abdominal pain, including in the RLQ, along with nausea, vomiting, and constipation.
  • Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease and ulcerative colitis can cause chronic or recurrent RLQ pain, along with changes in bowel habits and weight loss.

• Do Not Miss Diagnoses

  • Ectopic Pregnancy: As mentioned, it's crucial to consider ectopic pregnancy in females of childbearing age presenting with RLQ pain due to its high mortality rate if not promptly treated.
  • Ruptured Aneurysm or Aortic Dissection: Although these conditions typically present with back or abdominal pain, they can sometimes cause RLQ pain and are medical emergencies with high mortality rates if not immediately addressed.
  • Pneumonia: Basilar pneumonia, especially if it involves the right lower lobe, can cause referred pain to the RLQ. This is more common in older adults or those with underlying lung disease.
  • Ureteral Colic: A stone in the right ureter can cause severe, colicky pain that radiates from the flank to the groin and may be perceived in the RLQ.

• Rare Diagnoses

  • Yersinia or Other Infectious Ileitis: These are less common causes of RLQ pain, often associated with infectious agents and can mimic appendicitis.
  • Meckel's Diverticulitis: A congenital anomaly of the small intestine, Meckel's diverticulum can become inflamed and cause RLQ pain similar to appendicitis.
  • Right Lower Lobe Pneumonia: As mentioned, pneumonia can cause referred pain, but it's less common to present primarily with RLQ pain.
  • Hernias: Incarcerated or strangulated hernias in the right lower quadrant can cause severe pain and are surgical emergencies.