Sonographic features of acute colonic diverticulitis: the "dome sign".

PURPOSE: This study was performed to clarify the sonographic features of acute colonic diverticulitis to enable its differentiation from appendicitis.

METHODS: Of 119 patients who were referred to our hospitals for lower abdominal pain between June 1997 and December 1998 and underwent sonography, 12 patients had a definitive diagnosis of acute colonic diverticulitis and 4 patients a tentative diagnosis. Seventy-eight patients were diagnosed as having acute appendicitis, confirmed by appendectomy. In the 16 patients with diagnoses of diverticulitis, the sonographic and clinical features of acute colonic diverticulitis were studied.

RESULTS: Among the 12 patients with definitive diagnoses of acute colonic diverticulitis, sonographic findings included localized thickening of the colonic wall (100%) and a hemispheric mass (the "dome sign") protruding at the thickened colonic wall (100%) and consisting of a hypoechoic wall (100%) and a central echogenic area (66%). The presence of diverticula was confirmed by barium-enema x-ray study in all 12 patients. The 4 patients with tentative diagnoses of acute colonic diverticulitis all had colonic wall thickening but no dome sign. Colonoscopy revealed colitis in 3 of these patients. All 16 patients recovered with conservative treatment, without laparotomy.

CONCLUSIONS: Sonography was useful for differentiating acute colonic diverticulitis from appendicitis. The sonographic finding of the dome sign seems to be specific for acute colonic diverticulitis.