Applied Radiology

Prepared by Amy C. Ho, BA; Karen M. Horton, MD; Charlene A. Curry, MD; Kenneth C. Schuberth, MD; and Elliot K. Fishman, MD, Department of Radiology, The Johns Hopkins Medical Institution, Baltimore, MD

CASE SUMMARY

A 14-year-old boy presented to the Emergency Department complaining of 1 week of nonbloody diarrhea and 4 days of right lower-quadrant pain and tenderness. The patient denied any history of fever, vomiting, or anorexia. No previous similar episodes, history of recent travel, or family members with similar symptoms were reported. Physical examination revealed mild diffuse tenderness in the right lower quadrant. There was no rebound tenderness nor were there peritoneal signs. Bowel sounds were normal. Laboratory values were remarkable only for an elevated sedimentation rate of 42 mm/hr. The clinicians suspected appendicitis. Radiologic work-up included a computed tomography (CT) scan of the abdomen and pelvis (figure 1).

DIAGNOSIS

Salmonella infection of the bowel

IMAGING FINDINGS

Contrast-enhanced CT of the abdomen demonstrated thickening of the cecal wall, regional lymphadenopathy, and moderate inflammation involving terminal ileum (figure 1). The CT findings were most compatible with infectious or inflammatory disease. Etiologies such as tuberculosis, Yersinia, and Crohn's disease should be considered based on the CT appearance. There was no evidence of appendicitis. A stool culture was positive for Salmonella . The patient was treated successfully with antibiotics and the symptoms resolved.

DISCUSSION

Salmonella is a major cause of enteric infections and manifests as an acute onset of diarrhea, fever, abdominal pain, and/or vomiting. The disease tends to occur in outbreaks, particularly in warm summer months when unrefrigerated foods spoil rapidly. Although the small intestine is generally the principal site of involvement in human salmonellosis, abnormality of the colon has been recognized since 1969, when Boyd ¹ described necropsy findings of 6 patients with infections caused by Salmonella typhimurium . Several published reports confirm that colonic abnormality is common in nontyphoid salmonellosis. ^2-4

Given the high incidence of salmonellosis in the general population, the scarcity of any radiologic reports describing terminal ileum or colonic involvement is worthy of notice. The explanation lies in the fact that most individuals developing an acute infection do not seek specialized medical assistance, do not undergo radiographic or endoscopic work-up, and, when necessary, are treated empirically but successfully with supportive therapy and broad-spectrum antibiotic therapy. ³

Only three cases of Salmonella involving the colon have been described on CT findings. In a group of 3 patients with Salmonella infection, CT examination by Balthazar et al ² showed slight (5 to 8 mm) symmetrical and homogenous thickening of the wall of the terminal ileum as well as slight (3 to 5 mm) circumferential thickening of the cecum and descending colon. In addition, thickening of the sigmoid colon and the wall of the rectum was seen in 1 case, and small regional mesenteric nodes, <1 cm in size, were visualized in another case.

In the past, barium enema examination has been used to evaluate patients with suspected Salmonella colitis. In those few reports, barium enema usually demonstrated a pancolitis with superficial ulcerations, loss of haustration, ³ and irregular thickening of folds on postevacuation views. ⁴ Segmental colitis in the left colon was described only rarely, and salmonellosis involving only the terminal ileum and, to our knowledge, cecum has not been previously reported.

In our patient, CT demonstrates moderate soft-tissue thickening of the ileum and cecum with pericecal stranding and lymphadenopathy. Although our patient had salmonellosis, this is a nonspecific appearance, and other infectious etiologies should be included in the differential diagnosis. Intestinal tuberculosis most frequently involves the ileocecal region and may be manifested by bowel wall thickening, luminal narrowing, ³ and pericecal lymphadenopathy, with the nodes being either homogeneous or of lower attenuation centrally. ⁵ Likewise, Yersinia enterocolitis usually affects the terminal ileum and right side of the colon, causing fold thickening, nodules, and ulceration. ⁴ However, luminal narrowing is not characteristic of Yersinia infection. ⁵

Other infectious and noninfectious inflammatory processes may also be associated with thickened folds and regional lymphadenopathy, including appendicitis and Crohn's disease. In appendicitis, the wall of the diseased appendix is thickened circumferentially, and periappendiceal inflammation is characteristically present. Secondary inflammatory and edematous changes associated with appendicitis can cause slight mural thickening of the small bowel or cecum. These changes have the potential to be misinterpreted as primary ileocolic inflammatory disease. ² In Crohn's disease, classic barium enema and CT findings include nodular bowel wall thickening, particularly in the terminal ileum. Additionally, segmental disease of the colon is often seen. However, while the imaging findings of Crohn's disease overlap with infectious etiologies, the clinical history tends to have a more chronic course with periodic exacerbations. ⁶

Finally, in some patients, neoplasms involving the ileocecal region, such as lymphoma, may be associated with mesenteric adenopathy and mural involvement of the bowel. These can manifest as circumferential mural thickening or as a focal solid mass, although the mass is usually more extensive. ⁷

CONCLUSION

We report a rare case of ileocecal salmonellosis in a 14-year-old patient, which was characterized by bowel wall thickening, inflammation, and regional lymphadenopathy on CT. The differential diagnosis for such a presentation is broad, encompassing infectious, inflammatory, and neoplastic processes. Although in a pediatric patient Yersinia would be a more common diagnosis, the radiologist must be aware of the range of possible etiologies. A definitive diagnosis requires stool, blood, or tissue-fluid cultures so appropriate antibiotic therapy can be initiated when needed. Early detection will help prevent complications of undiagnosed colitis, in-cluding toxic megacolon, bleeding, over-whelming sepsis, and death. ⁸