What are the radiological differences between neutropenic (a condition characterized by an abnormally low number of neutrophils) colitis and Clostridium (C.) difficile related colitis?

Radiological Differences Between Neutropenic Colitis and Clostridium Difficile Colitis

CT imaging is the preferred modality for differentiating neutropenic colitis from C. difficile colitis, with distinct radiological features that can guide diagnosis and management. 1

Key Radiological Features

Neutropenic Colitis (Neutropenic Enterocolitis/Typhlitis)

• Primarily affects the terminal ileum, cecum, and ascending colon (right-sided colon involvement) 1
• Mean bowel wall thickening is typically moderate (average of 5-8 mm) 2
• Pneumatosis intestinalis (gas within the bowel wall) is a characteristic finding seen in approximately 21% of cases 2
• Can involve any segment of the bowel, not limited to the colon 2
• Diagnostic criteria include: neutropenia (ANC < 500 cells/mL), bowel wall thickening > 4 mm on imaging, and exclusion of other diagnoses 1
• Mortality risk increases significantly with bowel wall thickness >10 mm (60% mortality) compared to ≤10 mm (4.2% mortality) 1

Clostridium Difficile Colitis

• Exclusively limited to the colon (never involves small intestine) 2, 3
• Demonstrates more severe wall thickening (mean of 12 mm) compared to neutropenic colitis 2
• Wall nodularity is significantly more common (36% of cases) 2
• Higher rates of ascites (57%) and mesenteric stranding (71%) compared to neutropenic colitis 2
• Typically presents with pancolitis or segmental colitis with predominant involvement of the rectum and sigmoid colon (82% of cases) 4
• No pneumatosis intestinalis, which helps differentiate from neutropenic colitis 2, 3

Imaging Modality Selection

• CT with IV contrast is the preferred initial imaging modality for evaluating both conditions due to its high spatial resolution and ability to display key features 1
• Ultrasound can be useful for follow-up to assess gradual decrease in bowel wall thickening but is less reliable for initial diagnosis 1
• Plain radiographs have limited value in detecting colitis of either etiology 1
• MRI may be considered in cases where radiation exposure is a concern, with reported 99% accuracy in detecting abdominal abscesses 1

Clinical Context for Radiological Interpretation

• Neutropenic colitis occurs in approximately 5.3% of patients hospitalized for hematologic malignancies receiving chemotherapy 5
• C. difficile colitis should be suspected in patients with recent antibiotic use and healthcare exposures 3
• Both conditions can coexist, particularly in immunocompromised patients receiving chemotherapy 6
• Pseudomembrane formation (characteristic of C. difficile) requires neutrophils and may not be visible in neutropenic patients, making radiological differentiation even more important 1

Management Implications of Radiological Findings

• Bowel wall thickness >4 mm is considered abnormal and consistent with colitis, but is not sufficient alone for specific diagnosis 1, 7
• Abdominal CT is recommended for patients with recrudescent neutropenic fever who have abdominal pain and/or diarrhea 1
• Endoscopy is generally discouraged in neutropenic colitis due to increased risk of bowel wall perforation 1
• Radiological evidence of pneumatosis intestinalis or perforation requires urgent surgical consultation 1

Pitfalls in Radiological Diagnosis

• Considerable overlap exists between the CT findings of C. difficile colitis and other forms of colitis, requiring careful correlation with clinical and laboratory findings 3
• C. difficile colitis in neutropenic patients may present with wall thickening but without the characteristic pseudomembranes visible on endoscopy 1
• Patients with both conditions simultaneously present a diagnostic challenge, requiring stool testing for C. difficile toxin in addition to imaging 6
• The absence of neutrophils may mute the radiological appearance of inflammation in neutropenic patients 1