Do you order a small bowel series for patients with suspected ileus?

Small Bowel Series for Ileus: Not Recommended

No, you should not order a small bowel series for ileus. Ileus is a functional disorder of intestinal motility, not a mechanical obstruction, and small bowel series (barium studies) are neither indicated nor helpful for diagnosing or managing ileus.

Understanding the Clinical Context

The key distinction is between mechanical small bowel obstruction versus paralytic ileus:

• Ileus is a functional disorder where bowel motility is impaired without mechanical blockage 1
• Mechanical obstruction involves physical blockage of the intestinal lumen requiring different management 2
• Clinical and plain film findings alone are often inconclusive in distinguishing these entities, with plain films being non-diagnostic in 20-52% of cases 3

Appropriate Imaging for Suspected Ileus

First-Line Imaging: CT Abdomen and Pelvis

CT is the imaging modality of choice when ileus versus mechanical obstruction needs to be differentiated 4, 2:

• CT has 100% sensitivity and specificity for distinguishing complete mechanical small bowel obstruction from paralytic ileus 5
• CT correctly identified the diagnosis in all cases except one when differentiating obstruction from ileus 2
• CT is superior to traditional clinical-radiographic evaluation, establishing diagnosis in 100% of cases versus 46% sensitivity with clinical-plain film combination 3

When Small Bowel Series Has Limited Role

Small bowel follow-through or enteroclysis may have a role in specific scenarios that are NOT ileus 4, 6:

• Low-grade or partial mechanical obstruction where contrast reaching the cecum within 4 hours correctly identified "insignificant obstructions" in 18 of 19 patients 6
• Intermittent mechanical obstruction with indolent presentation requiring provocative bowel distention 4
• CT should still be performed first, with small bowel follow-through reserved for cases where CT is not diagnostic 6

Why Small Bowel Series Fails in Ileus

Fundamental Limitations

• Small bowel barium studies assess for structural/mechanical abnormalities, not functional motility disorders 4
• In ileus, the problem is impaired peristalsis, not anatomic obstruction—barium will show dilated loops without a transition point, which doesn't change management 1
• Barium studies have low sensitivity and specificity for small bowel pathology in general, with some groups reporting poor diagnostic accuracy 4

Practical Disadvantages

• Delays definitive diagnosis: Adding a small bowel series when CT is needed wastes 12-72 hours, increasing morbidity and mortality 3
• Cannot identify complications: Unlike CT, barium studies cannot detect bowel ischemia, perforation, or other complications requiring urgent intervention 2, 6
• May be misleading: Plain radiographs and contrast studies were misleading in 20-40% of patients with suspected obstruction 4

Clinical Algorithm for Suspected Ileus

Step 1: Clinical Assessment

• Identify risk factors for ileus: recent surgery, medications (opioids), electrolyte abnormalities, systemic illness 1
• Distinguish from mechanical obstruction: ileus typically has diffuse abdominal distention, minimal pain, and absence of peritoneal signs 1

Step 2: Initial Imaging

• Plain abdominal radiographs may be obtained initially but have limited diagnostic value 4, 3
• If clinical picture suggests true ileus with clear etiology and benign examination, supportive management without advanced imaging may be appropriate 1

Step 3: When Diagnosis is Uncertain

• Order CT abdomen/pelvis with IV contrast (oral contrast optional) 2, 3, 5
• CT will definitively distinguish ileus from mechanical obstruction and identify complications 2
• CT changed management in 21% of patients by correctly modifying erroneous clinical diagnoses 2

Step 4: Management Based on CT Findings

• If ileus confirmed: Supportive care (NPO, IV fluids, electrolyte correction, treat underlying cause) 1
• If mechanical obstruction identified: Surgical consultation and intervention as indicated 3

Common Pitfalls to Avoid

• Ordering small bowel series reflexively without considering that it provides no useful information for functional ileus 4, 6
• Delaying CT when clinical picture is unclear, as this increases risk of complications from unrecognized mechanical obstruction or strangulation 3
• Relying on plain films alone when they are inconclusive in 20-52% of cases 3
• Failing to recognize that ileus rarely requires surgery—supportive measures based on etiology usually suffice 1