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Difficulty: EasyInterpreting Imaging Results

A 71-year-old man presents to the emergency department with the sudden onset of severe, diffuse abdominal pain that began two hours ago. He has a 10-year history of severe osteoarthritis and takes high-dose naproxen daily. His temperature is 37.8°C (100.0°F), blood pressure is 100/60 mm Hg, pulse is 115/min, and respirations are 24/min. On physical examination, the patient appears acutely ill and is lying completely still on the stretcher. The abdomen is rigid with diffuse involuntary guarding and pronounced rebound tenderness. An upright chest radiograph is obtained and demonstrates a prominent, crescent-shaped radiolucency located immediately beneath the right hemidiaphragm, clearly separating it from the liver shadow. Based on the interpretation of this radiograph, which of the following is the most appropriate next step in management?

  1. Emergent exploratory laparotomyAnswer
  2. B
    Computed tomography of the abdomen and pelvis with intravenous contrast
  3. C
    Right upper quadrant ultrasonography
  4. D
    Intravenous proton pump inhibitor therapy and admission for observation
  5. E
    Administration of oral barium for an upper gastrointestinal series

Answer

Emergent exploratory laparotomy
The correct answer is emergent exploratory laparotomy. The patient's history of chronic NSAID use puts him at high risk for peptic ulcer disease. His sudden-onset severe pain, rigid abdomen with rebound tenderness, and hemodynamic instability strongly suggest an acute surgical emergency. The crucial diagnostic step here is interpreting the upright chest radiograph: a crescent-shaped radiolucency (air) beneath the right hemidiaphragm indicates pneumoperitoneum. In a patient with generalized peritonitis and free air on a radiograph, the diagnosis of a perforated hollow viscus is confirmed. The standard of care is immediate surgical exploration to identify and repair the perforation, control contamination, and wash out the peritoneal cavity. Delaying surgery for additional tests is life-threatening.

Step-by-Step Solution

1
Analyze the patient's history and physical examination findings.
The patient has a history of chronic NSAID use, presenting with sudden-onset severe pain and a rigid, peritonitic abdomen with tachycardia and borderline hypotension.
Identifying the clinical syndrome of an acute surgical abdomen is the first step in triaging the patient.
2
Interpret the specific imaging finding provided in the vignette.
A crescent-shaped radiolucency under the right hemidiaphragm on an upright chest radiograph is interpreted as free intraperitoneal air (pneumoperitoneum).
This radiologic sign confirms the presence of gas outside the bowel, indicative of a ruptured hollow viscus (likely a perforated peptic ulcer in this clinical context).
3
Determine the definitive management based on the diagnosis of a perforated viscus with peritonitis.
The patient requires immediate surgical intervention (exploratory laparotomy).
Delaying surgery for further imaging or attempting conservative management in a peritonitic patient with confirmed free air significantly increases mortality.

Key Concept

The radiographic finding of a crescentic radiolucency under the right hemidiaphragm indicates pneumoperitoneum, which, in the setting of acute peritonitis, mandates emergent surgical exploration.
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Topics

Interpreting Imaging Results

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