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Findings: There is extensive narrowing and irregularity of the distal ileum, with associated separation of bowel loops in the right lower quadrant (fig. 1). This narrowing and irregularity extends into the cecum, which is markedly narrowed, c/w a "coned cecum." (fig. 2) Note is made of a retrocecal appendix, which appears normal (fig 3.) The esophagus, stomach, and proximal small bowel is normal.
Diagnosis: Crohn's Disease
Discussion: While this patient demonstrates the classic findings of moderately advanced Crohn's disease involving the distal ileum and cecum, there is an extensive differential diagnosis for this appearance in the bowel. The markedly narrowed "coned" cecum can be seen in a variety of diseases, including TB, lymphoma, Crohn's, ulcerative colitis and amebiasis. ( In this case the involvement of the ileum would argue against the diagnosis of Amebiasis, which is limited to the colon). However, the markedly narrowed distal ileum in this case is an example of the "string" sign seen in Crohn's disease, thought by some to be pathognomonic of this entity. The separation of bowel loops in the right lower quadrant can represent surrounding mesenteric inflammatory change, but in chronic cases can be due to the "creeping fat" often seen in long-standing Crohn's disease.
The terminal ileum is the most common site of involvement in Crohn's disease. Pathologically, Crohn's disease is characterized by diffuse, transmural inflammatory involvement of the gut. The pattern of disease is often discontinous, giving rise to the "skip" lesions commonly seen in Crohn's disease. The clinical course is often variable, from benign, infrequent episodes to extensive bowel disease, often requiring resection.
Extraintestinal symptoms are common, and many patients present with polyarthritis/sacroiliitis before manifesting bowel symptoms of the disease.
Radiographically, Crohn's begins with subtle mucosal granularity and edema, with progression to irregular thickening and ulceration of the bowel. Due to the transmural nature of the inflammatory process, fistula formation is common, and fistulization to adjacent bowel, the genitourinary system and skin is often seen. While the terminal ileum is most commonly involved, colonic involvement can be isolated in 25%. Esophageal, duodenal and appendiceal involvement is not unusual.
References:
Eisenberg R.L Gastrointestinal Radiology, Philadelphia, Lippincott-Raven, 1996.
Caroline DF, Evers K. Colitis: Radiographic Features and Differentiation of Idiopathic
Inflammatory Bowel Disease. Radiol Clin North Am 1987; 25:47.
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