Usefulness of fecal alpha 1-antitrypsin clearance and fecal concentration as early indicator of postoperative asymptomatic recurrence in Crohn's disease. The aim of this study was to evaluate in Crohn's disease the possible usefulness of alpha 1-antitrypsin clearance and fecal concentration in the early detection of postoperative asymptomatic recurrence. Eleven adult patients with small bowel Crohn's disease undergoing elective resection were enrolled in the study and prospectively followed for one year. Three, six, and 12 months after surgery the alpha 1-antitrypsin clearance and fecal concentration were measured, and the disease activity was assessed. All patients were free of active symptoms throughout the study. One year after surgery small bowel radiology was performed in all patients. Radiographic evidence of recurrent macroscopic disease was found in five of the 11 patients. Three months after surgery both alpha 1-antitrypsin clearance and fecal concentration were significantly lower (P less than 0.01) than before surgery. There was no difference at this time between patients with recurrence and those with no recurrence. In patients with recurrence both alpha 1-antitrypsin clearance and fecal concentration significantly increased at six months in comparison with the values at three months (P less than 0.02). Both measurements were significantly higher at six and 12 months in this group of patients than in those with no recurrence and in normal controls (P less than 0.01). At six and 12 months alpha 1-antitrypsin clearance was above the upper normal limit in all patients with recurrence. We conclude that fecal alpha 1-antitrypsin clearance is a noninvasive, inexpensive, sensitive marker of asymptomatic recurrence in CD patients who are under regular supervision after surgery. 