Imaging in Oncology (answer)

Robert Clark, MD
Professor of Radiology
Chief, Radiology Service
H. Lee Moffitt Cancer Center Research Institute.

Answer:

3. neutropenic colitis (typhlitis)

Typhlitis (from the Greek typhlos for "blind sac" or cecum) is an inflammatory necrotic process involving the ileum, appendix, or cecum. The underlying etiology is neutropenia, usually associated with acute leukemia, lymphoma, aplastic anemia, or acquired immunodeficiency syndrome. The inflammatory process may involve the entire colon but is often limited to the cecum.

In most cases, the pathogenesis is cecal inflammation and ulceration secondary to bacterial overgrowth caused by compromised immunity.[1,2] The cecum may be most susceptible to this necrotizing enteropathy because it is easily distensible, normally has a high bacterial count, has relative stasis of contents, and has a predisposition to mucosal ischemia.[1]

The early diagnosis of typhlitis is essential because, if unrecognized and untreated, it progresses rapidly to transmural gut necrosis, perforation, and abscess. Prompt treatment with high­dose antibiotics and intravenous fluids before onset of transmural necrosis is associated with lower mortality and morbidity than early surgical resection.[2] Surgery usually is reserved for treatment of perforation and abscess.

The radiographic findings depend on the severity and extent of disease.[1,2] Plain films may show bowel wall thickening or "thumbprinting" that is localized to the cecum (as in this case, Fig 1) or distributed more diffusely in the colon. Computed tomography similarly demonstrates colon wall thickening (Fig 2). More severe cases may demonstrate intramural bowel wall gas or pericolonic fluid. With perforation, peritoneal gas and fluid may be present.

Fig 2. ­ Computed tomography shows thickening of the wall of the cecum and right colon.

Appendicitis may mimic typhlitis, but the clinical circumstances of immunosuppression make neutropenic colitis more likely. Ischemic colitis may mimic typhlitis but is unlikely in younger patients who are hemodynamically stable. Intramural hemorrhage may occur with severe marrow suppression, but platelets counts above 50,000/mm-cubed usually are sufficient to prevent gastrointestinal hemorrhage. Leukemia infiltration of the gastrointestinal wall is uncommon and usually does not cause macroscopic bowel wall thickening. In patients who have received bone marrow rescue for immunosuppression, graft­ vs­host disease may produce gastrointestinal mucosal edema and bowel wall thickening.References

1. Stringer, DA. Imaging inflammatory bowel disease in the pediatric patient. Radiol Clin North Am.1987;25:93­113.

2. Jones B, Fishman EK. CT of the gut in the immunocompromised host. Radiol Clin North Am. 1989;27:263­771.Fig 1. ­ Plain abdominal film demonstrates colon gas with "thumbprinting" of cecal wall.

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