A prospective study of first attacks of inflammatory bowel disease and infectious colitis. Clinical findings and early diagnosis.

In 105 patients with a first attack of colitis, clinical, microbiologic, laboratory, and histologic features were studied prospectively with the aim of differentiating inflammatory bowel disease (IBD) from infectious colitis as early as possible. Of the patients who proved to have IBD the mode of onset of diarrhoeal symptoms was insidious in 56% and non-insidious in 44%, whereas in 81% of those who proved to have infectious colitis the onset was acute. Most patients with infectious colitis presented within 1 week, had early fever, and did not show histologic features characteristic of IBD. Most IBD patients with a more acute onset had clinical warning signs of IBD such as slight previous bowel symptoms, a late presentation time (> 1 week), and absence of early fever or had histologic features characteristic of IBD. These features were basal plasmacytosis, crypt distortion, more than two vertical crypt branches, villous mucosa, mucosal atrophy, epithelioid granuloma, and Paneth cell metaplasia. Moreover, 61% of the IBD patients with a non-insidious onset fell ill in connection with travelling abroad, gastrointestinal infection, or treatment with antibiotics. Knowledge of the above clinical and histologic factors will facilitate differentiation of IBD from infectious-type colitis.