Pulmonary abnormalities in Crohn's disease.

Abnormalities of pulmonary function in Crohn's disease have been described, although the results are conflicting and anecdotal accounts of lung involvement are few. In this study we assessed the prevalence of lung function abnormalities in Crohn's disease, and the relative contributions of age, sex, smoking and past medical history, and Crohn's disease activity to the pulmonary abnormalities found. Twenty-nine patients with Crohn's disease and 29 age-, sex- and smoking-matched volunteer controls underwent detailed respiratory assessment. Airways obstruction due to chronic bronchitis and asthma was present in 13 patients with Crohn's disease, but was not more prevalent than in the control group. FEV1 was similar in both Crohn's disease and control subjects (84.2 +/- 21.2% predicted, mean +/- SD; 93.7 +/- 16.3%, respectively: n.s.). The vital capacity was significantly lower in the Crohn's disease patients than in controls (86.7 +/- 16.6%; 95.9 +/- 12.7%; P less than 0.01), but this may have been influenced by the higher prevalence of past or intercurrent medical illnesses affecting the chest in Crohn's disease patients. No patient had evidence of fibrosing alveolitis or bronchiectasis. The haemoglobin corrected transfer factor was significantly lower in the Crohn's disease patients than in controls (100.4 +/- 17.4%; 113.2 +/- 25.1: P less than 0.05) but the diffusing coefficient was not significantly different. There was a significant correlation (r = 0.44, P less than 0.05) between the residual volume and the Crohn's disease activity index but otherwise no close relationship was observed between Crohn's disease activity, extent or duration and the indices of lung function. These findings suggest that the lungs are relatively unaffected by Crohn's disease.