How to approach a patient with fever and abdominal pain, and a USG (Ultrasonography) report suggestive of ileitis/enteritis with mild mural congestion of bowel loops and prominent bowel wall thickening of the ileo-caecal region?

Approach to Ileitis/Enteritis with Fever and Abdominal Pain

Immediately obtain a complete blood count (CBC) with differential to assess for neutropenia, followed by contrast-enhanced CT enterography or CECT abdomen to determine bowel wall thickness, rule out complications (perforation, ischemia), and establish the underlying etiology—this imaging is critical because mortality increases significantly if surgical disease is missed. 1

Initial Clinical Assessment and Laboratory Workup

Essential History and Physical Examination Points

• Assess for immunocompromised status: Recent chemotherapy (within 1-2 weeks), cancer diagnosis (especially leukemia or solid organ malignancy), HIV status, or immunosuppressive medications 1
• Evaluate for peritoneal signs: Abdominal rigidity suggests peritonitis requiring urgent surgical evaluation 1
• Check for systemic inflammatory response: Fever, tachycardia, tachypnea, and signs of hypoperfusion (oliguria, altered mental status, lactic acidosis) indicate sepsis 1
• Recent antibiotic exposure: Warrants testing for Clostridioides difficile 2
• Travel history and food exposure: Suggests infectious enteritis from Salmonella, Shigella, or parasites 2, 3, 4

Mandatory Laboratory Tests

• CBC with differential: Absolute neutrophil count is critical—neutropenia (<500 cells/μL) dramatically changes management 1
• C-reactive protein (CRP): Elevated levels support inflammatory/infectious etiology 1, 5
• Hepatobiliary markers, electrolytes, creatinine, glucose: Rule out cholecystitis, metabolic derangements 5
• Stool studies if diarrhea present: Multiplex antimicrobial testing preferred over traditional stool cultures 2
• Blood cultures: Essential if sepsis suspected or patient appears toxic 1

Imaging Strategy: The Critical Decision Point

When Ultrasound is Insufficient

Your USG shows bowel wall thickening but cannot definitively characterize the severity, extent, or complications—proceed immediately to contrast-enhanced CT. 1

• CT with IV contrast is the gold standard for evaluating ileitis/enteritis when diagnosis is uncertain or complications are suspected 1
• CT enterography specifically provides superior visualization of small bowel pathology and is "usually appropriate" for suspected enteritis 1
• Ultrasound limitations: Cannot reliably exclude perforation, ischemia, or accurately measure bowel wall thickness >10mm (a critical prognostic threshold) 1

Critical CT Findings That Determine Management

• Bowel wall thickness >10mm: Associated with 60% mortality in neutropenic enterocolitis vs. 4.2% if <10mm—this mandates aggressive medical management and close monitoring 1
• Signs of perforation or ischemia: Free air, pneumatosis intestinalis, portal venous gas, lack of bowel wall enhancement—these require emergency surgical consultation 1
• High-risk ultrasound/CT signs: Fluid-filled bowel, ascites, free fluid between loops, hyperechoic septa (necrotic mucosa) indicate impending complications 1

Differential Diagnosis and Management Pathways

If Patient is Neutropenic (ANC <500)

This is neutropenic enterocolitis (typhlitis) until proven otherwise—initiate broad-spectrum antibiotics immediately and manage non-operatively unless perforation/ischemia develops. 1

• Immediate antibiotic therapy: Monotherapy with anti-pseudomonal β-lactam (piperacillin-tazobactam) OR carbapenem as first-line per IDSA guidelines 1
• Bowel rest: NPO status with IV hydration 1
• Serial clinical assessment: Monitor for peritoneal signs, worsening sepsis, or failure to improve within 48-72 hours 1
• Surgery only for complications: Reserve operative intervention exclusively for documented perforation or bowel ischemia—mortality with surgery in neutropenic patients reaches 57-81% 1
• Expected recovery: 86% resolve with conservative treatment in 6-8 days; neutrophil count recovery correlates with symptom resolution 1

If Patient is Immunocompetent

Proceed with infectious workup while initiating empiric therapy based on severity. 2, 3, 5

Infectious Ileitis/Enteritis (Most Common)

• Bacterial causes: Salmonella, Shigella, Yersinia, Campylobacter, E. coli 2, 3, 4
• CT findings: Circumferential homogeneous thickening of terminal ileum (10-15cm segment), may have associated colonic involvement 4
• Management:
  • Mild-moderate symptoms: Oral hydration, antiemetics, antimotility agents (if no bloody diarrhea) 2
  • Severe symptoms or bloody diarrhea: Antimicrobial therapy guided by stool studies 2
  • Supportive care resolves most cases within 7 days 2, 4

Crohn's Disease (Chronic Presentation)

• Consider if: Symptoms >7 days, weight loss, extraintestinal manifestations, family history 3
• Requires: Ileocolonoscopy with biopsies for definitive diagnosis 3

Other Etiologies to Consider

• Medication-induced: NSAIDs cause subclinical ileitis 3
• Ischemic enteritis: Older patients, cardiovascular risk factors, severe pain out of proportion to exam 3
• Tuberculosis: Chronic course, endemic areas, systemic symptoms 1, 3

Red Flags Requiring Immediate Surgical Consultation

• Peritoneal signs: Rigidity, rebound tenderness, guarding 1
• Hemodynamic instability: Hypotension, tachycardia despite resuscitation, rising lactate 1
• CT evidence of perforation or ischemia: Free air, pneumatosis, lack of enhancement 1
• Clinical deterioration: Worsening pain, fever, or sepsis despite 24-48 hours of appropriate antibiotics 1

Common Pitfalls to Avoid

• Relying solely on ultrasound: USG cannot adequately assess bowel wall thickness >10mm or exclude complications—this threshold is life-or-death in neutropenic patients 1
• Delaying CT in unclear cases: Mortality increases when surgical disease is missed; liberal use of CT is advocated 1
• Operating on neutropenic patients prematurely: 86% resolve with medical management; surgery carries 57-81% mortality 1
• Missing immunocompromised status: Always check recent chemotherapy, HIV status, immunosuppressive medications 1
• Inadequate antibiotic coverage: Must cover Gram-negatives including Pseudomonas in neutropenic patients 1

Monitoring and Follow-up

• Serial abdominal exams: Every 4-6 hours initially if managed conservatively 1
• Repeat imaging if no improvement: Consider repeat CT at 48-72 hours if clinically worsening or not improving 1
• Neutrophil count recovery: In neutropenic patients, symptom resolution correlates with rising neutrophil counts 1
• Post-infectious complications: 9% develop post-infectious IBS; counsel patients about this possibility 2