What is the optimal diagnostic test for a middle-aged male patient with abdominal (abd.) pain, distension, and a liver percussion note that is not dull (resonant)?

Optimal Diagnostic Test for a Middle-Aged Male with Abdominal Pain, Distension, and Resonant Liver Percussion

The optimal diagnostic test for a middle-aged male patient with abdominal pain, distension, and a resonant liver percussion note is an erect abdominal X-ray (option C), as this would best detect free air under the diaphragm indicating a perforated viscus.

Clinical Significance of Resonant Liver Percussion

A resonant (non-dull) percussion note over the liver is highly significant as it suggests the presence of free air in the peritoneal cavity. Normally, the liver produces a dull percussion note due to its solid nature. When this area becomes resonant, it indicates:

• Replacement of the normal liver dullness with air
• Highly suggestive of pneumoperitoneum (free air in the peritoneal cavity)
• Most commonly caused by perforation of a hollow viscus (stomach, duodenum, or intestine)

Diagnostic Test Selection

Erect Abdominal X-ray (Option C)

• Best initial test for detecting free intraperitoneal air
• Can demonstrate air under the diaphragm (pneumoperitoneum)
• The erect position allows free air to rise and collect under the diaphragm, making it visible on X-ray
• Provides visualization of air-fluid levels if bowel obstruction is present

Why Other Options Are Less Appropriate:

1. Chest X-ray erect (Option A):

   • While a chest X-ray can detect free air under the diaphragm, it doesn't provide as complete a view of the abdomen
   • May miss smaller amounts of free air or other abdominal pathologies

2. Chest X-ray supine (Option B):

   • Significantly limited in detecting free air as air rises in the erect position
   • Cannot reliably demonstrate pneumoperitoneum

3. Abdominal X-ray supine (Option D):

   • Cannot reliably detect free air under the diaphragm
   • Free air distributes diffusely in the supine position, making it harder to visualize

Evidence-Based Considerations

While some recent guidelines suggest limited utility for plain radiography in general abdominal pain evaluation 1, 2, the specific clinical presentation described (resonant liver percussion) represents a classic indication for erect abdominal radiography to detect pneumoperitoneum.

The American Academy of Family Physicians acknowledges that conventional radiography may be appropriate for suspected perforated viscus 3, which is precisely what this clinical scenario suggests. The resonant percussion over the liver area strongly indicates free air in the peritoneal cavity.

Important Clinical Caveat

It's worth noting that modern practice is increasingly moving toward CT scanning for definitive diagnosis of perforated viscus, as it offers higher sensitivity (>95%) 3, 4. However, given the specific options presented and the classic clinical finding of resonant liver percussion, an erect abdominal X-ray remains the most appropriate choice among the given options.

Key Points to Remember

• Resonant percussion over the liver area is a red flag for pneumoperitoneum
• Erect positioning is crucial for detecting free air under the diaphragm
• While CT scanning is increasingly preferred in modern practice, among the options presented, erect abdominal X-ray is most appropriate
• Prompt diagnosis is essential as perforated viscus represents a surgical emergency requiring immediate intervention