[Four cases of idiopathic retroperitoneal fibrosis markedly responsive to steroid therapy].

We report four cases of idiopathic retroperitoneal fibrosis (IRPF) effectively treated with steroid therapy. Computed tomographic (CT) scan showed the density of soft tissue mass enveloping the abdominal aorta in four cases. From radiographic findings we made a diagnosis of IRPF. Management with steroid therapy over three months improved general symptoms and radiographic findings. Prominent calcification in the wall of the abdominal aorta indicated that the arteriosclerosis was related to IRPF. We measured serum antibodies for Chlamydia pneumoniae in four cases.