What is the initial workup for a patient with suspected ileus?

Initial Workup for Suspected Ileus

The initial workup for a patient with suspected ileus should include a CT scan of the abdomen and pelvis, laboratory tests (complete blood count, electrolytes, BUN/creatinine, CRP, lactate), and plain abdominal radiography to differentiate between functional ileus and mechanical obstruction. 1

Clinical Assessment

When evaluating a patient with suspected ileus, focus on:

• Abdominal distention: A key physical finding in ileus
• Bowel sounds: Assess for absence or hypoactivity
• Passage of flatus or stool: Determine if there is complete cessation
• Nausea and vomiting: Common symptoms that may indicate proximal obstruction
• Weight gain: Can indicate fluid retention and third spacing

Diagnostic Testing

Imaging Studies

1. CT Scan of Abdomen and Pelvis

   • Gold standard for differentiating between functional ileus and mechanical obstruction 2
   • Sensitivity and specificity approaching 100% for distinguishing postoperative ileus from complete mechanical small-bowel obstruction 2
   • Can identify the cause, location, and severity of obstruction
   • Superior to plain radiographs which have limited sensitivity (60-70%) 3

2. Plain Abdominal Radiography

   • Often used as first-line imaging but has limited diagnostic value (sensitivity 60-70%) 3
   • May show dilated bowel loops and air-fluid levels
   • Cannot reliably determine the cause or location of obstruction

3. Water-Soluble Contrast Studies

   • Consider if CT findings are equivocal
   • Has both diagnostic and potential therapeutic value 3

Laboratory Tests

1. Complete Blood Count

   • To assess for leukocytosis with left shift (suggesting inflammation or ischemia) 3

2. Electrolytes, BUN/Creatinine

   • To evaluate for dehydration and electrolyte imbalances 3, 1

3. CRP and Lactate

   • Elevated values may indicate inflammation, peritonitis, or bowel ischemia 3
   • Normal values cannot exclude ischemia 3

4. Stool Studies

   • Consider if infectious etiology is suspected (e.g., C. difficile testing) 3

Differentiating Functional vs. Mechanical Ileus

CT scan is the most reliable method to distinguish between:

• Functional (paralytic) ileus: Generalized bowel dilation without a transition point
• Mechanical obstruction: Dilated bowel proximal to a transition point with collapsed bowel distally 2

Special Considerations

• Intra-abdominal hypertension: A potential complication of ileus found in up to 20% of critically ill patients 4
• Inflammatory markers: Elevated CRP, leukocytosis with left shift, and elevated lactate might indicate peritonitis or bowel ischemia, but normal values cannot exclude ischemia 3
• Comorbidities: Assess for conditions that may predispose to ileus (recent surgery, medications, metabolic disorders)

Management Considerations

Once ileus is diagnosed:

• Implement nasogastric tube drainage if vomiting persists or significant abdominal distention is present 1
• Provide intravenous fluids for hydration 1
• Monitor for complications such as electrolyte imbalances and malnutrition 1

Pitfalls to Avoid

• Relying solely on plain radiographs for diagnosis (limited sensitivity)
• Failing to differentiate between functional and mechanical ileus (different management approaches)
• Overlooking signs of peritonitis or bowel ischemia which require urgent surgical intervention
• Delaying CT scan when clinical suspicion for mechanical obstruction is high

By following this systematic approach to the initial workup of suspected ileus, clinicians can efficiently diagnose the condition, determine its cause, and initiate appropriate management to reduce morbidity and mortality.