This case report describes a 14-year-old boy presenting with a barrel-chested appearance and a complaint of shortness of breath on exertion. The patient had a long history of severe constipation with overflow incontinence. Physical examination suggested limited diaphragmatic excursion. Initial pulmonary function studies showed a restrictive pattern. Catharsis resulted in an 11-lb weight loss and normalization of pulmonary function. We speculate that the extrinsic upward pressure imposed on the diaphragm by a full bowel resulted in increased anteroposterior diameter, decreased lung height, and a reversible restrictive pattern on pulmonary function studies.