Retroperitoneal fibrosis
In 1948, Ormond published the histopathologic findings of IRPF. Retroperitoneal fibrosis is idiopathic in 70% of cases and felt to be a subset of idiopathic multifocal fibrosclerosis. It is rare, affects men more than women (3:1) of all ethnicities, and occurs at average age of 40 to 60 years. Patients present (90%) with pain in lower back, abdomen, flank, and/or scrotum. Some patients have systemic symptoms including fever, anorexia, and malaise. Physical exam is usually (75%) unremarkable, although hypertension is common. Lower extremity edema and phlebitis can be seen. Laboratory findings are nonspecific including elevated ESR/CRP (75%–90%) and azotemia (50%). Serologies are typically negative. Radiographic computed tomography (CT) findings show a homogenous mass surrounding the abdominal aorta that occurs most often between the renal arteries and bifurcation of the aorta. Lymphadenopathy is rare. Medial deviation of the mid part of the ureter and hydronephrosis are common (60%–75%). Open, laparoscopic, or CT-guided biopsy shows sclerosis and infiltration of mononuclear cells. SVV is seen in 50% of cases. Biopsy helps rule out secondary causes of RPF (drugs [ergots, methysergide], malignant disease [lymphoma, sarcoma], Erdheim–Chester disease, infections, and IgG4-RD). The etiology of IRPF is unknown but may be an exaggerated local inflammatory reaction to ceroid and oxidized low-density lipoprotein from aortic atherosclerosis. An autoimmune process is also proposed since RPF can occur in patients with other autoimmune diseases. Treatment is high-dose prednisone for a month with taper to 10 mg/day by 3–6 months. Maintenance prednisone continues for 1–3 years. Recurrence of the disease (10%–30%) or treatment resistance is treated with azathioprine, mycophenolate mofetil, tamoxifen, or methotrexate. Patients are monitored with ESR/CRP, creatinine, and CT scans every 3 months while on therapy and every 6 months when off treatment. PET/CT scans have also been used to follow response to therapy. Stenting is needed to relieve ureteral obstruction and surgery or endovascular aneurysm repair is required for large aneurysms.
