What type of CT scan is recommended for a patient diagnosed with tuberculosis (TB) ileitis?

CT Scan Recommendation for TB Ileitis

For a patient with confirmed TB ileitis, order a CT enterography with IV contrast and neutral oral contrast (1300-1800 mL administered over 30-60 minutes). This specialized protocol provides optimal visualization of the terminal ileum and ileocecal region—the most common sites of intestinal TB involvement—while detecting critical complications that impact morbidity and mortality 1, 2.

Why CT Enterography is the Optimal Choice

CT enterography excels at detecting the hallmark features of TB ileitis including:

• Circumferential bowel wall thickening with homogeneous mural enhancement in the terminal ileum and ileocecal junction 2
• Short-segment strictures with symmetrical concentric thickening 2
• Mesenteric lymphadenopathy (present in 46.9% of abdominal TB cases), often with central low attenuation from caseation necrosis 3, 2
• Peritoneal involvement (77.5% of cases) including ascites, peritoneal thickening, or omental masses 3

Critical Complications That Must Be Detected

CT enterography is essential for identifying life-threatening complications:

• Bowel perforation (which can occur even during treatment, as documented in MDR-TB cases) 4
• Small bowel obstruction from ileal strictures 4, 2
• Abscess formation (sensitivity 86-100%) 5
• Fistula formation (sensitivity 68-100%) 5

These complications directly impact mortality and require immediate surgical intervention 4.

Technical Protocol Details

The neutral oral contrast protocol is non-negotiable for TB ileitis evaluation:

• Administer 1300-1800 mL of neutral oral contrast over 30-60 minutes 6
• Image at precisely 60 minutes to ensure complete small bowel distention 6
• Use IV contrast timed to the enteric phase (45-50 seconds post-injection) 6
• Never use positive oral contrast, as it obscures the subtle stratified mural enhancement patterns critical for detecting active inflammation 6, 5

Why Standard CT Abdomen/Pelvis is Inadequate

While standard CT with IV contrast has 75-90% sensitivity for detecting inflammatory bowel disease 5, it lacks the bowel distention necessary to fully evaluate:

• The extent of ileal involvement (TB commonly affects multiple ileal segments) 2
• Subtle early stricture formation 2
• Transmural disease extent 1

Standard CT should only be used if the patient cannot tolerate the large oral contrast volume (e.g., actively vomiting, complete obstruction, severe acute illness) 7, 6.

Distinguishing TB Ileitis from Crohn's Disease

CT enterography helps differentiate TB from Crohn's disease, which is critical because:

• Misdiagnosis leading to steroid administration can worsen TB infection and increase mortality 8
• Features favoring TB ileitis on CT include: transverse ulcers, patulous ileocecal valve, localized involvement, and necrotic lymph nodes with low-density centers 7, 3
• Features favoring Crohn's include: longitudinal ulcers, cobblestone appearance, anorectal lesions, and skip lesions 7

Common Pitfalls to Avoid

• Do not order CT enterography if the patient has complete bowel obstruction or active vomiting—they cannot complete the oral contrast protocol, resulting in a non-diagnostic study 6
• Do not use CT enterography for acute GI bleeding—the large neutral contrast volume can dilute blood and mask active extravasation 6
• Do not accept "CT abdomen/pelvis" as equivalent—the specialized enterography protocol with neutral contrast is essential for optimal small bowel evaluation 1, 6

Alternative if CT Enterography is Unavailable

If CT enterography is not available, order CT abdomen and pelvis with IV contrast alone (without oral contrast):

• This maintains sensitivity of 75-90% for detecting active inflammation 5
• IV contrast alone is superior to IV contrast with positive oral contrast, as positive contrast obscures mural enhancement 5
• This approach is appropriate for detecting complications like abscess (sensitivity 86-100%) and obstruction (sensitivity 85-94%) 5

Complementary Imaging Considerations

Intestinal ultrasound can be considered as an adjunct if available and operator expertise exists:

• Shows 92% sensitivity for small bowel disease presence 7
• Can demonstrate increased vascularity in the bowel wall and mesenteric nodes with power Doppler 9
• However, MRI/CT enterography remains superior for defining disease extent and detecting complications 7