What is the most likely diagnosis for a boy who presents with fever, abdominal pain, and distension, particularly on the right side, after a fall onto his right side, and is found to be pale and hypertensive?

Most Likely Diagnosis: Liver Contusion

The most likely diagnosis is liver contusion (Option A), given the history of blunt trauma to the right side, right-sided abdominal distension, pallor (suggesting blood loss), and hypertension (which can occur as a compensatory response to hemorrhage in children).

Clinical Reasoning

Trauma History as the Key Discriminator

• The fall onto the right side one day prior is the critical historical element that distinguishes traumatic injury from spontaneous pathology 1
• Liver contusion from blunt abdominal trauma presents with delayed symptoms as bleeding accumulates, explaining the progression from initial injury to next-day presentation with distension 2
• The right-sided location of both the trauma and the distension directly correlates with liver anatomy in the right upper quadrant 3

Supporting Clinical Features

• Pallor indicates significant blood loss from hepatic injury, which can be substantial given the liver's high vascularity 2
• Hypertension in a pale child represents a compensatory catecholamine surge attempting to maintain perfusion despite hemorrhage—this is a classic pediatric response to blood loss before decompensation occurs 2
• Fever can occur with liver contusion due to blood resorption, tissue necrosis, or developing hematoma, typically appearing 24-48 hours post-injury 1
• Abdominal distension, particularly localized to the right side, suggests either subcapsular hematoma or intraperitoneal bleeding from hepatic injury 2, 4

Why Other Options Are Less Likely

Pyelonephritis (Option B)

• While pyelonephritis causes fever and flank pain, it does not explain the traumatic mechanism, pallor, or right-sided abdominal distension 1
• Pyelonephritis typically presents with dysuria, frequency, and costovertebral angle tenderness rather than abdominal distension 3

Neuroblastoma (Option C)

• Neuroblastoma is an abdominal mass that develops over weeks to months, not acutely after trauma 2
• The temporal relationship between fall and symptoms makes traumatic injury far more likely than coincidental tumor presentation 1
• Hypertension can occur with neuroblastoma due to catecholamine secretion, but the acute post-traumatic presentation argues against this diagnosis 3

Wilms Tumor (Option D)

• Wilms tumor presents as a gradually enlarging abdominal mass, not acute post-traumatic distension 2
• While Wilms tumor can cause hypertension through renin secretion, the acute traumatic context and pallor suggesting hemorrhage make this diagnosis unlikely 3
• Fever is uncommon in Wilms tumor unless there is tumor necrosis or infection 2

Critical Clinical Pearls

• In any child with abdominal pain, distension, and pallor following trauma, solid organ injury (especially liver or spleen) must be the primary consideration 2, 1
• Hypertension in a pale, potentially hemorrhaging child is a compensatory mechanism that can precede cardiovascular collapse—this requires urgent imaging and resuscitation 2
• The combination of fever, abdominal distension, and systemic signs developing 24-48 hours after trauma is classic for evolving hepatic injury with hematoma formation 1, 4
• Immediate contrast-enhanced CT imaging is indicated to assess for hepatic laceration, subcapsular hematoma, or intraperitoneal hemorrhage 2, 3