How do you differentiate and manage ileus versus enteritis in a patient?

Differentiating and Managing Ileus versus Enteritis

Ileus is a functional or mechanical bowel obstruction characterized by absent bowel sounds, abdominal distension, and dilated bowel loops on imaging without mucosal inflammation, while enteritis is an inflammatory condition of the small bowel presenting with diarrhea, cramping, and evidence of mucosal inflammation on imaging or endoscopy. 1, 2

Clinical Differentiation

Key Clinical Features

Ileus presents with:

• Absent or hypoactive bowel sounds 1
• Abdominal distension with diffuse tenderness 2
• Nausea and vomiting (particularly with small bowel involvement) 2
• Obstipation (inability to pass stool or flatus) 1
• No fever unless complications develop (perforation, ischemia) 2

Enteritis presents with:

• Active, hyperactive, or normal bowel sounds 3
• Frequent watery or loose stools (≥3 stools in 24 hours) 3
• Cramping abdominal pain, often colicky 3
• Fever in infectious or inflammatory causes 3
• Localized tenderness (right lower quadrant in terminal ileitis) 4, 5

Critical Diagnostic Imaging Distinctions

On CT imaging, ileus shows:

• Dilated bowel loops (>3 cm small bowel, >6 cm colon) 1
• Air-fluid levels on upright films 2
• Transition point in mechanical obstruction 2
• Bowel wall thickness typically normal unless ischemia present 1
• No significant mucosal enhancement pattern 2

On CT/MRI enterography, enteritis shows:

• Wall thickening (3-5 mm or greater) 5
• Mucosal hyperenhancement with contrast 5
• High T2 intramural signal on MRI 5
• Mesenteric fat stranding and hyperemia 3
• Preserved or increased peristalsis 6

Diagnostic Algorithm

Step 1: Initial Assessment

• Obtain plain abdominal radiographs to identify dilated bowel loops and air-fluid levels suggesting ileus 2
• Check vital signs for fever (suggests enteritis or complicated ileus), tachycardia, and hypotension 3
• Assess stool pattern: obstipation favors ileus; diarrhea favors enteritis 3, 2

Step 2: Laboratory Evaluation

• Complete blood count: marked leukocytosis (>15 × 10⁹/L) suggests severe enteritis or complicated ileus 3
• CRP and ESR: elevated in enteritis, normal in uncomplicated ileus 3
• Lactate level: elevated (>5.0 mM) indicates bowel ischemia requiring urgent surgery 3
• Stool studies: cultures for bacterial pathogens, C. difficile toxin, and fecal calprotectin if diarrhea present 3, 5

Step 3: Advanced Imaging

• Contrast-enhanced CT scan is the most reliable exam for both conditions 3
• CT or MR enterography if terminal ileitis suspected to assess extent and differentiate Crohn's disease from infectious causes 3, 5
• Ultrasound can identify bowel wall thickening and hyperemia in enteritis but has lower sensitivity than CT 3

Step 4: Endoscopic Evaluation When Indicated

• Ileocolonoscopy with biopsies is the gold standard for diagnosing terminal ileitis and differentiating Crohn's disease from tuberculosis and other causes 4, 5
• Avoid endoscopy in suspected mechanical obstruction or toxic megacolon 3
• Multiple biopsies from visible lesions and normal-appearing mucosa are essential 5

Management Approach

Ileus Management

Conservative management is first-line for most cases: 2

• Bowel rest with nothing by mouth 3
• Nasogastric decompression if significant gastric distension or vomiting 3
• Intravenous isotonic fluids (lactated Ringer's or normal saline) for hydration and electrolyte replacement 3
• Correct underlying causes: discontinue opioids and anticholinergics, treat electrolyte abnormalities (hypokalemia, hypomagnesemia) 1, 2
• Prokinetic agents may be considered once mechanical obstruction excluded 3

Surgical intervention required when: 2

• Mechanical obstruction with complete blockage not resolving within 12-24 hours 2
• Signs of bowel ischemia (elevated lactate, peritonitis) 1
• Perforation or abdominal compartment syndrome (intra-abdominal pressure >20-25 mmHg) 1

Enteritis Management

Treatment depends on etiology identified:

For infectious enteritis: 3

• Most acute watery diarrhea requires no antimicrobials—supportive care only 3
• Oral rehydration solution (reduced osmolarity ORS) is first-line for mild-moderate dehydration 3
• Empiric antibiotics reserved for: immunocompromised patients, ill-appearing young infants, or those with recent international travel 3
• Avoid antimotility agents (loperamide) in children <18 years or when fever/bloody diarrhea present 3

For Crohn's disease (terminal ileitis): 4, 5

• 5-ASA compounds, immunomodulators, or biologics depending on severity 4
• Approximately 50% require surgery within 10 years due to complications 4, 5

For tuberculosis (endemic regions): 4, 5

• Standard anti-tubercular therapy for 6-9 months 4
• Always consider tuberculosis first in endemic regions before assuming Crohn's disease 5

For neutropenic enterocolitis (immunocompromised): 3

• Broad-spectrum antibiotics and bowel rest 3
• Surgery reserved only for perforation or ischemia 3

For C. difficile colitis: 3

• Oral vancomycin 125 mg four times daily for 10 days or fidaxomicin 200 mg twice daily 3
• Surgical consultation if systemic toxicity develops; subtotal colectomy for fulminant colitis 3

Critical Pitfalls to Avoid

• Do not assume all terminal ileitis is Crohn's disease—infectious causes (Yersinia, Salmonella, tuberculosis) are common and treatable 5, 6
• Do not perform appendectomy in the presence of terminal ileitis—this significantly increases risk of intra-abdominal septic complications and fistulas 5
• Do not give antimotility drugs when enteritis with fever or bloody diarrhea is suspected—risk of toxic megacolon 3
• Do not delay surgery in ileus with elevated lactate >5.0 mM—indicates ischemia requiring urgent intervention 3
• In immunocompromised patients, clinical signs are unreliable—contrast-enhanced CT is essential for accurate diagnosis 3
• Always test for C. difficile in patients with diarrhea and acute abdomen, especially if on immunosuppression 3