Definition: Retroperitoneal Fibrosis (RPF) is a chronic inflammatory process of the lumbar retroperitoneal region.This fibrosis eventually leads to entrapment and obstruction of retroperitoneal structures, especially the ureters.
Age: usually above 40 years
Frequency: ~1 per 200,000-500,000 population
Male to female ratio is 2 to 1.
Complications: Extrinsic ureteral obstruction leading to renal failure
Aorta and or inferior vena cava obstruction
Prognosis: Good; may require surgery
Clinical symptoms: Most commonly back pain, flank pain, abdominal pain. Renal insufficiency, hypertension, leg edema, anemia.
Causes: Mostly Idiopathic. Other factors include:
•Inflammatory periaortitis (severe atherosclerosis)
•Chronic retroperitoneal inflammation
•Drugs such as beta-blockers, methysergide, methyldopa
Early stage: Inflammatory infiltrate containing macrophages, lymphocytes, plasma cells, and occasional eosinophils.
Chronic stage, the tissue becomes avascular and acellular with scattered calcification and progresses to fibrous scarring.
Malignant retroperitoneal fibrosis demonstrates the presence of scattered nests of malignant cells within the inflammatory tissue.
Soft tissue mass encasing the aorta, inferior vena cava, and the ureters. Location is usually in the lower lumbar region with extension into the pelvis.
In its acute stage retroperitoneal fibrosis can present as a focal unilateral mass in the region of the common iliac vessels. As the disease progresses, fibrosis extends superiorly into the retroperitoneum along the major vessels.
Distinguishing feature between retroperitoneal fibrosis from retroperitoneal lymphadenopathy and lymphoma since that the fibrous tissue envelopes the aorta, IVC, and the ureters but does not displace the aorta anteriorly substantially.
Malignant retroperitoneal fibrosis is most commonly associated with cervical, breast, prostate, bowel, lung, and kidney cancers. The contour of the mass is not lobular distinguishing it from lymphadenopathy. The mass is infiltrative and irregular. The distinction between acute benign retroperitoneal fibrosis and a malignant retroperitoneal fibrosis is difficult. Findings that favor malignancy include a more irregular contour and increased in size and irregularity on follow-up examination. Acute benign RPF has a wispy infiltrative pattern compared to malignant disease which is more solid and the regular. Benign RPF is seen in a population with no pre existing malignant condition. Malignant retroperitoneal fibrosis is more commonly seen in older patients > 40 years of age.
IVP Findings: Hydronephrosis with proximal ureteral dilation above L4-L5. There is medial deviation of the ureters bilaterally. Gradual tapering of the ureters secondary to extrinsic compression.
CT findings: Soft tissue density of variable thickness that may extend from the crus of the diaphragm to the common iliac vessels.
This soft tissue density is most commonly seen extending from the renal hilum to the pelvic brim but may rarely involve the kidneys, pancreas, mediastinum, and the spleen.
The soft tissue mass usually surrounds the aorta, IVC, and the ureters bilaterally. There may be displacement/compression/narrowing of these structures.
Contrast-enhanced CT: Increased enhancement suggests active inflammatory process whereas decreased enhancement suggests organized fibroids tissue.
T1WI: Low homogeneous signal intensity
T2WI: Low to moderate heterogeneous signal intensity
Irregular periaortic soft tissue mass.
Surgical: Ureteral Stenting, Ureterolysis
Good but may require surgery