First attack of inflammatory bowel disease and infectious colitis. A clinical, histological and microbiological study with special reference to early diagnosis.

To investigate the possibilities of differentiating between inflammatory bowel disease (IBD) and infectious colitis on clinical, microbiological, laboratory and histological grounds, a prospective study of 105 patients with a first attack of colitis was undertaken. Rectal biopsy was performed on four occasions during 1 year. In 56% of the patients who proved to have IBD, the mode of onset of diarrhoeal symptoms was insidious and in 44% it was more acute, while 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 any histological features characteristic of IBD. In most IBD patients with a non-insidious onset there were clinical warning signs of IBD, such as slight previous bowel symptoms, a late presentation time (> 1 week) and absence of early fever, or histological features characteristic of IBD. Moreover, 62% of the IBD patients with a non-insidious onset fell ill in connection with travelling abroad, gastrointestinal infection or treatment with antibiotics. Travel abroad seemed to be associated with an increased risk of developing IBD. The strongest histological predictor of IBD was basal plasmocytosis, followed by more than two vertical crypt branches/MPF, crypt distortion, villous mucosa, mucosal atrophy, epithelioid granulomas and Paneth cell metaplasia. These signs were rarely or never found among patients with infectious colitis. Their frequency increased with the interval between the initial symptoms and the first biopsy. The presence of focal basal plasmocytosis seems to be the earliest sign of IBD. The frequency of histological signs indicating IBD was maximal (88%) at the 1-week biopsy. During treatment the basal plasmocytosis and villous mucosa decreased, while crypt distortion and mucosal atrophy remained unchanged. Early treatment did not prevent the appearance of any feature. Nor did it prevent relapse. In 21% of the IBD patients microbial findings were positive. The findings consisted in known colitis-causing agents in 14% and other agents, such as viruses, in another 7%. In 78% of the patients with non-relapsing colitis (NRC), colitis-causing agents were found. Haemolytic strains of E. coli were detected more often in IBD. Among the IBD patients, 65% showed positive immunofluorescence reactivity to neutrophil granulocytes, indicating the presence of antineutrophil antibodies (ANCA). The corresponding figure for NRC patients was 5%. Antibodies against beta-glucuronidase were found in 42% of the patients with granulocyte reactivity.