This 64-years old presented with backache and fever. CT and then subsequently PET/CT showed findings typical of retroperitoneal fibrosis.

The oncologist and rheumatologist wanted a biopsy, to prove the diagnosis and to look for tissue IgG4.

Would you do the biopsy? If so, would it be a supine anterior or prone posterior approach?

To see what I did and to learn more about biopsies of retroperitoneal lesions and retroperitoneal fibrosis in particular, please see the video.