[Recurrent Crohn disease--definition and diagnosis].

Recurrence in Crohn's disease is a frequently encountered problem in the history of this chronic incurable disease. A number of studies have shown different recurrence and reoperation rates, which is partly due to different definitions and diagnostic strategies. 'Surgical relapse' as defined as reappearance of disease activity in operated patients, 'clinical relapse' after conservatively induced remission or 'endoscopical recurrence' with new pathological changes in the operated gut may be differentiated. The different definitions of recurrence are discussed and diagnostic procedures like endoscopical, laboratory or radiological methods are explained.