Differential Diagnosis for RLQ Pain at McBurney's Point

Single Most Likely Diagnosis

• Acute Appendicitis: The most common cause of right lower quadrant (RLQ) pain, especially when localized to McBurney's point, which is the anatomical location closest to the base of the appendix. The pain often starts around the navel and then moves to the RLQ.

Other Likely Diagnoses

• Mesenteric Lymphadenitis: Inflammation of the lymph nodes in the mesentery, often due to viral or bacterial infections, can mimic appendicitis in presentation.
• Ovarian Cyst or Torsion: In females, ovarian cysts can rupture or undergo torsion, leading to severe pain that may be localized to the RLQ.
• Ectopic Pregnancy: Though less common, ectopic pregnancy should be considered in females of childbearing age presenting with RLQ pain, especially if there's a history of missed periods or positive pregnancy test.
• Intestinal Obstruction: Obstruction of the small or large intestine can cause severe abdominal pain, which may be localized to the RLQ depending on the site of obstruction.

Do Not Miss Diagnoses

• Ruptured Ectopic Pregnancy: A life-threatening condition that requires immediate surgical intervention. Missing this diagnosis can lead to severe hemorrhage and death.
• Perforated Visculitis (e.g., Typhlitis): Inflammation of the cecum, often seen in immunocompromised patients, can lead to perforation and peritonitis if not promptly treated.
• Diverticulitis: Though more common on the left side, right-sided diverticulitis can occur and may present similarly to appendicitis.
• Inflammatory Bowel Disease (IBD) Flare: Conditions like Crohn's disease or ulcerative colitis can cause severe abdominal pain and may mimic appendicitis in their presentation.

Rare Diagnoses

• Meckel's Diverticulum: A congenital anomaly of the small intestine that can cause pain, bleeding, or obstruction, especially if it becomes inflamed or infected.
• Carcinoid Tumor: Rare tumors of the appendix or small intestine can cause abdominal pain, though they are less common and often present with other symptoms like flushing or diarrhea.
• Right Lower Quadrant Abscess: A collection of pus in the RLQ, which could be due to a variety of causes including diverticulitis, appendicitis, or other infections.
• Hernias (e.g., Spigelian or Obturator Hernia): Though rare, hernias can cause RLQ pain, especially if they become incarcerated or strangulated.