Differential Diagnosis for RUQ Abdominal Pain and Right Lower Rib Pain

Single Most Likely Diagnosis

• Rib Fracture: Given the history of a fall from a horse 2 days prior, a rib fracture is a highly plausible cause for the right lower rib pain. The trauma from the fall could easily have resulted in a fracture, which would cause pain in the area of the fracture and potentially radiate or refer pain to the abdomen, especially if the fracture involves the lower ribs.

Other Likely Diagnoses

• Hepatic Contusion or Laceration: The right upper quadrant (RUQ) abdominal pain following a traumatic event like a fall from a horse raises concern for a liver injury. The liver is located in the RUQ and could be damaged in a fall, leading to pain in this area.
• Pneumothorax or Hemothorax: Although more commonly associated with chest trauma, a fall from a height like a horse could potentially cause lung injury leading to a pneumothorax (air in the pleural space) or hemothorax (blood in the pleural space), which could cause pain that might be referred to the abdomen.
• Musculoskeletal Injury: The trauma from the fall could result in muscle strains or bruises in the abdominal wall or back, leading to pain in the RUQ and right lower rib area.

Do Not Miss Diagnoses

• Splenic Rupture: Although the spleen is located on the left side, a severe traumatic event can cause multiple injuries, and splenic rupture is a life-threatening condition that requires immediate attention. It's less likely given the location of the pain but cannot be missed.
• Hemorrhage or Internal Bleeding: Any significant trauma can lead to internal bleeding, which is a medical emergency. The symptoms might not always be immediately apparent but can quickly become severe.
• Gallbladder Injury or Rupture: The gallbladder is located under the liver in the RUQ and could be injured in a traumatic event, leading to pain in this area.

Rare Diagnoses

• Diaphragmatic Rupture: This is a rare but serious condition where the diaphragm is torn, which can allow abdominal organs to herniate into the chest cavity. It's more commonly associated with severe blunt trauma to the chest or abdomen.
• Liver or Hepatic Artery Aneurysm: A pre-existing aneurysm that ruptures could cause sudden onset of RUQ pain, though this would be highly unusual and not directly related to the fall unless the aneurysm was somehow compromised by the trauma.