The occurrence (incidence) on abdominal or chest X-rays is around 0.1% but it can be up to 1% in series of older adults. It has also been reported in children.
Chilaiditi syndrome
Pneumoperitoneum
Behçet's disease
Neuro-Behçet's disease
Crome syndrome
Rhinitis medicamentosa
Hereditary angioedema
Urticarial syndromes