BACKGROUND A lack of change in prevalence of severe ulcer complications requiring emergency operation has been reported, despite the common use of histamine-2 (H2)-receptor antagonists and proton pump inhibitors. This may be attributable to use of ulcerogenic drugs or Helicobacter pylori (HP) infection, or both. In this study, HP infection was evaluated semiquantitatively in patients with peptic ulcer who required surgery, and the severity of histologic change was investigated. METHODS We reviewed a total of 113 consecutive patients (98 men and 15 women) operated on for perforation, hemorrhage, or stenosis of gastroduodenal ulcer between January 1986 and December 1995. Detection of HP was carried out by immunohistochemical staining. We graded the density of HP infection according to the number of individual HP bacteria counted in a highly magnified visual field (x 1,000 of light microscopy). The grade of HP infection was defined as follows: (0) = 0; (1+) = 1-9; (2+) = 10-29; (3+) = 30-99; (4+) > or = 100. The severity of gastritis was evaluated by histologic examination using the criteria of Rauws. RESULTS Although the number of operations for gastroduodenal ulcer declined significantly, the rate of emergency operation for gastroduodenal ulcer increased from 60% to 90%, with the result that the frequency of operations for perforation or bleeding remained virtually constant and that for stenosis significantly decreased. HP infection was more prevalent in perforated ulcer (92%) than hemorrhagic ulcer (55%) or stenotic ulcer (45%). The grades of HP infection were 3.0 +/- 0.14 (mean +/- SEM) in perforated ulcer, 2.3 +/- 0.34 in hemorrhagic ulcer, and 2.5 +/- 0.22 in stenotic ulcer. Perforated ulcer was associated with significantly more severe HP infection and gastritis changes than hemorrhagic ulcer or stenotic ulcer. CONCLUSIONS This study indicates that patients with perforated ulcer were infected with HP more severely than those with hemorrhagic ulcer or stenotic ulcer at the time of surgery. A close relationship was observed between the perforated ulcer and the density of HP infection determined semiquantitatively using immunohistochemical stain.