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 with abdominal pain, distension, and resonant liver percussion is an erect abdominal X-ray (option C), as this would best detect free air under the diaphragm indicating a perforated viscus. 1, 2
Clinical Significance of Resonant Liver Percussion
When examining a patient with abdominal pain and distension, the liver percussion note is typically dull. A resonant percussion note over the liver area is highly suspicious for:
- Free intraperitoneal air (pneumoperitoneum)
- Displacement of the liver by air-filled bowel
This finding, particularly when accompanied by abdominal pain and distension, strongly suggests a perforated hollow viscus, most commonly a perforated peptic ulcer or perforated intestine.
Diagnostic Test Selection Algorithm
Resonant liver percussion + abdominal pain/distension:
- First-line test: Erect abdominal X-ray (option C)
- This view allows visualization of free air under the diaphragm
Why erect position is superior to supine:
- Free air rises to the highest point in the abdomen when the patient is upright
- Air collects under the diaphragm, creating a clear air-fluid level visible on erect films
- Supine films may miss small amounts of free air
Limitations of other options:
- Chest X-ray erect (option A): While useful for detecting free air under the diaphragm, it doesn't provide adequate visualization of bowel gas patterns
- Chest X-ray supine (option B): Cannot reliably detect free air as it doesn't allow air to collect under the diaphragm
- Abdominal X-ray supine (option D): May show abnormal gas patterns but is less sensitive for free air detection
Evidence-Based Considerations
While some recent guidelines suggest that conventional radiography has limited diagnostic value in most cases of abdominal pain 3, specific clinical scenarios like suspected bowel perforation (indicated by resonant liver percussion) remain appropriate indications for plain radiography.
The American Academy of Family Physicians notes that conventional radiography may be appropriate for select patients with suspected perforated viscus 4. When perforation is suspected based on physical findings like resonant liver percussion, an erect abdominal X-ray provides the most direct visualization of free air.
Important Clinical Caveat
Although some studies have questioned the routine use of erect abdominal radiographs 1, 2, the specific clinical scenario presented (resonant liver percussion) represents a high-risk situation where visualization of free air is critical for diagnosis. In this particular case, the erect abdominal X-ray remains the most appropriate initial test.
For a more comprehensive evaluation after the initial X-ray, CT with IV contrast would be recommended as it has superior sensitivity for detecting smaller amounts of free air and can better identify the cause of perforation 5.