What are the indications for abdominal X-ray in emergency settings, aside from intestinal obstruction?

Indications for Abdominal X-Ray in Emergency Settings (Beyond Intestinal Obstruction)

Abdominal X-ray has very limited utility in modern emergency practice and should only be ordered for suspected perforated viscus, urinary tract stones, or ingested foreign bodies when CT scan is unavailable. 1, 2

Primary Indications When CT is Unavailable

Suspected Perforated Viscus

• Abdominal X-ray can detect pneumoperitoneum (free air under the diaphragm) with 92% positive predictive value for perforation 3, 4
• However, sensitivity is poor (74-84%) and specificity is only 50-72% for confirming the diagnosis 1
• CT scan remains vastly superior with 93-96% sensitivity and 93-100% specificity, and should be obtained in stable patients even after positive X-ray findings 1, 3
• The World Society of Emergency Surgery emphasizes that if diffuse peritonitis is clinically evident, imaging should not delay surgical intervention 1

Urinary Tract Stones

• Plain radiography can identify radiopaque stones in the urinary tract 1
• This indication is reasonable when ultrasound or CT are not immediately available 1

Ingested Foreign Bodies

• Abdominal X-ray is appropriate for detecting radiopaque foreign bodies in the gastrointestinal tract 1
• This represents one of the few scenarios where plain films provide unique diagnostic value 1

Limited Role in Other Conditions

Bowel Distension Assessment

• X-ray may reveal bowel distension or fluid levels when CT is unavailable 1
• However, ultrasound is superior (88% sensitivity, 76% specificity) and should be preferred over X-ray when CT is not accessible 1

Post-Bariatric Surgery Complications

• The World Society of Emergency Surgery notes that abdominal X-ray has limited diagnostic value in post-bariatric patients 1
• Point-of-care ultrasound or CT with oral contrast should be used instead 1

Critical Evidence Against Routine Use

Multiple studies demonstrate that plain abdominal radiography has no place in the routine workup of acute abdominal pain in current emergency practice 2:

• Low sensitivity and accuracy across most acute abdominal conditions 2
• CT provides superior decision-making for management and surgical planning 2
• Plain films expose patients to significant radiation without adequate diagnostic yield 5

Recommended Imaging Algorithm

For acute abdominal pain in the emergency department:

1. CT scan with IV contrast is the first-line imaging study (93-96% sensitivity, 93-100% specificity) 1, 6
2. Point-of-care ultrasound when CT unavailable (88% sensitivity for fluid, abscesses, distention) 1
3. Plain X-ray only if both CT and ultrasound are unavailable AND there is specific suspicion for perforation, stones, or foreign body 1, 2

Common Pitfalls to Avoid

• Never delay surgical exploration based on negative X-ray findings when clinical suspicion is high 1, 6
• Do not order routine abdominal X-rays for undifferentiated abdominal pain - they rarely change management 2, 5
• Remember that X-ray cannot identify the cause (0% sensitivity) or site (60% sensitivity) of obstruction or perforation 1
• In pregnant patients, ultrasound and MRI should be used instead of X-ray to limit radiation exposure 1, 6