Hello @pbnew, I have no experience with the condition but thought a few references may be helpful while you wait of other members to respond.

"What is retroperitoneal fibrosis associated with?
Approximately 70% of cases are idiopathic and can be immunoglobulin G4 (IgG4)–related. Secondary RPF is most commonly associated with drugs (eg, ergot alkaloids, methysergide, beta-blockers dopamine agonists), malignancies, radiotherapy, and infections (eg. tuberculosis, actinomycosis). Jul 21, 2023"
-- Retroperitoneal Fibrosis: https://emedicine.medscape.com/article/458501-overview
-- Retroperitoneal Fibrosis: https://www.ncbi.nlm.nih.gov/books/NBK482409/

@llcc8800 has mentioned retroperitoneal fibrosis in another discussion and may have some information to share with you.