In a patient with five days of fever, CT demonstrates mild splenomegaly and a long segment of circumferential mural thickening of the terminal ileum and ileocecal junction with a few enlarged ileocolic lymph nodes—what is the likely diagnosis and what are the recommended next diagnostic and therapeutic steps?

CT Findings Commentary: Likely Diagnosis and Management

This CT presentation is most consistent with active inflammatory bowel disease, specifically Crohn's disease, though intestinal tuberculosis must be excluded given the fever and ileocecal involvement—proceed immediately with ileocolonoscopy and biopsy for definitive diagnosis. 1

Differential Diagnosis

The CT findings of long-segment circumferential mural thickening of the terminal ileum and ileocecal junction with enlarged lymph nodes and splenomegaly in a febrile patient create a specific differential:

Primary Considerations:

• Crohn's Disease: The long-segment involvement with circumferential wall thickening and ileocolic lymphadenopathy are characteristic features. 1 The asymmetric wall thickening and hyperenhancement seen on CT are specific for Crohn's disease when combined with these findings. 1

• Intestinal Tuberculosis: This is a critical differential, particularly in endemic areas. 2, 3 Ileocecal tuberculosis characteristically shows circumferential wall thickening of the terminal ileum and cecum, ileocecal valve thickening, and regional lymphadenopathy—often with low-density areas suggesting caseation necrosis. 2 The presence of fever for 5 days makes this diagnosis particularly important to exclude. 3

• Enteric Fever (Typhoid): Can present with fever, mesenteric lymphadenopathy, splenomegaly, and circumferential small bowel wall thickening. 4 However, this typically involves shorter segments and is less likely with such prominent ileocecal involvement.

Critical Next Steps

Immediate Diagnostic Workup:

Colonoscopy with ileoscopy and biopsy is mandatory and should be performed urgently. 1 This is the reference standard for evaluating ileocecal inflammation and can differentiate between the major diagnostic possibilities. 1

• Obtain multiple biopsies from the terminal ileum, ileocecal valve, and cecum for histopathology and mycobacterial culture. 1, 3
• Look for specific endoscopic features: Deep longitudinal ulcers and skip lesions favor Crohn's disease, while transverse ulcers and a patulous ileocecal valve suggest tuberculosis. 5
• Send tissue for acid-fast bacilli staining and TB culture to exclude tuberculosis. 2, 3

Additional Laboratory Evaluation:

• Blood cultures if not already obtained, given the persistent fever. 4
• Fecal calprotectin to assess inflammatory activity. 1
• Complete blood count, CRP, ESR to gauge inflammation severity. 1
• Tuberculin skin test or interferon-gamma release assay (QuantiFERON) to assess TB exposure. 3

Severity Assessment

The CT findings suggest active inflammatory disease based on: 1

• Long-segment involvement (suggesting more severe disease)
• Circumferential wall thickening
• Enlarged mesenteric lymph nodes
• Associated splenomegaly

Evaluate for complications that would require urgent intervention: 1

• Abscess formation
• Fistula or sinus tracts
• Bowel obstruction (assess for upstream dilation)
• Perforation risk

Management Approach Pending Diagnosis

While Awaiting Colonoscopy:

• Monitor closely for signs of complications: worsening abdominal pain, peritoneal signs, increasing fever, or hemodynamic instability. 1
• Avoid empiric immunosuppression until tuberculosis is definitively excluded, as this could be catastrophic if TB is present. 1, 3
• Supportive care: hydration, nutritional support, symptom management. 1

If Crohn's Disease is Confirmed:

The extent and severity of involvement will guide therapy: 1

• Moderate to severe ileocecal Crohn's: Consider systemic corticosteroids for induction, followed by immunomodulators or biologics (anti-TNF agents). 1
• Assess for penetrating complications (fistulas, abscesses) which may require surgical consultation. 1

If Tuberculosis is Confirmed:

• Initiate standard anti-tuberculous therapy immediately (rifampin, isoniazid, pyrazinamide, ethambutol). 2, 3
• Avoid corticosteroids unless there is significant obstruction, and only with concurrent anti-TB therapy. 3

Common Pitfalls to Avoid

• Do not assume Crohn's disease without excluding tuberculosis, especially in endemic areas or with travel history—the CT findings overlap significantly. 2, 3, 5
• Do not delay colonoscopy—imaging alone cannot definitively distinguish between these entities. 1
• Do not start immunosuppression empirically before obtaining tissue diagnosis and excluding infection. 1
• Recognize that mild splenomegaly can occur with both Crohn's disease and infectious etiologies, and is not diagnostically specific. 4

The combination of fever, ileocecal involvement, and lymphadenopathy creates diagnostic urgency—tissue diagnosis through colonoscopy with biopsy is the definitive next step and should not be delayed. 1, 3