What are the diagnostic criteria and management options for paralytic ileus?

Diagnosis of Paralytic Ileus

Paralytic ileus is diagnosed clinically by the complete absence of bowel sounds on auscultation combined with abdominal distension, in the absence of mechanical obstruction confirmed by CT imaging. 1

Clinical Diagnostic Criteria

The diagnosis requires recognition of key clinical features:

• Complete absence of bowel sounds on auscultation is the hallmark physical examination finding that distinguishes paralytic ileus from mechanical obstruction 1
• Abdominal distension occurs in approximately 65% of cases and is a cardinal feature 1
• Absence of flatus and bowel movements combined with nausea and vomiting are additional diagnostic features 1
• Abdominal pain and tenderness are common but nonspecific symptoms 1

Imaging Studies

CT scan with IV contrast is the method of choice for confirming the diagnosis and excluding mechanical obstruction, with approximately 90% accuracy. 1, 2

• CT effectively distinguishes paralytic ileus from complete mechanical small-bowel obstruction with 100% sensitivity and specificity 2
• Plain abdominal radiographs alone are often confusing and nondiagnostic (sensitivity only 19%) and should not be relied upon exclusively 2
• CT findings in paralytic ileus show diffusely dilated bowel loops without a transition point, unlike mechanical obstruction which shows a clear point of obstruction 2

Laboratory Evaluation

Essential laboratory tests help identify underlying causes and complications:

• Complete blood count to assess for leukocytosis suggesting infection or peritonitis 1
• Electrolyte panel to identify hypokalemia, hypomagnesemia, or other metabolic derangements that can cause or perpetuate ileus 1
• Lactate levels to evaluate for bowel ischemia or sepsis 1

Special Diagnostic Considerations

In Patients Unable to Produce Stool

For patients with ileus who cannot produce stool specimens (relevant when infectious causes like C. difficile are suspected), PCR testing of perirectal swabs provides an acceptable alternative to stool specimen analysis 3

Warning Signs Requiring Urgent Evaluation

Certain clinical features indicate potential complications requiring immediate intervention:

• Fever, tachycardia, and confusion suggest sepsis or peritonitis 1
• Intense pain unresponsive to analgesics with diffuse tenderness, guarding, or rebound suggests perforation or ischemia 1
• Signs of shock including hypotension and oliguria indicate life-threatening complications 1

Differential Diagnosis

The key diagnostic challenge is distinguishing paralytic ileus from mechanical obstruction:

• Mechanical obstruction presents with high-pitched or hyperactive bowel sounds early, progressing to absent sounds only with complete obstruction 3
• Partial mechanical obstruction may be difficult to distinguish from ileus; CT is superior to clinical examination for this differentiation 2
• In the immediate postoperative period, CT should be obtained within 24 hours when the distinction between ileus and mechanical obstruction is unclear 2

Common Pitfalls

• Do not rely solely on plain radiographs in the postoperative setting, as they are frequently nondiagnostic 2
• Do not assume simple postoperative ileus when systemic symptoms (fever, altered mental status) are present, as these suggest complications 1
• In immunocompromised patients with ileus, consider strongyloidiasis hyperinfection syndrome as a potential cause 1, 4