Abdominal X-Ray

A 65-year-old male presents to the emergency department with sudden onset severe abdominal pain, guarding, and rigidity. An erect abdominal X-ray is performed. Which of the following findings would be most indicative of a perforated viscus?

A 40-year-old female presents with colicky abdominal pain, vomiting, and obstipation for 2 days. An abdominal X-ray shows multiple dilated loops of small bowel arranged in a 'step-ladder' pattern with several air-fluid levels on erect views. These findings are most consistent with:

Which of the following acute abdominal conditions is least likely to be accurately diagnosed or ruled out by a plain abdominal X-ray?

On a plain abdominal X-ray, the psoas muscle shadows are typically visible bilaterally. Absence or obliteration of these shadows can be a non-specific sign of:

A 70-year-old male with a history of atrial fibrillation presents with sudden onset severe abdominal pain out of proportion to physical examination findings. An abdominal X-ray shows 'thumbprinting' of the colon and intramural gas (pneumatosis intestinalis). These findings are highly suggestive of: