What are the diagnosis and management options for retroperitoneal fibrosis?

Retroperitoneal Fibrosis: Diagnosis and Management

Diagnosis

CT and MRI are the imaging modalities of choice for diagnosing retroperitoneal fibrosis, with the characteristic finding being a periaortic fibrous mass typically beginning at the L4-L5 level that encases the aorta, inferior vena cava, and often entraps the ureters causing medial deviation and hydronephrosis. 1, 2

Clinical Presentation

• Lumbar or flank pain is the most common presenting symptom, occurring in approximately 53% of patients 3
• Renal failure develops frequently due to ureteral obstruction and hydronephrosis 4, 3
• Clinical symptoms are typically non-specific and insidious, leading to delayed diagnosis 2, 4
• The disease predominantly affects males aged 40-60 years 3, 5

Laboratory Evaluation

• Elevated inflammatory markers (ESR, CRP) are the most common laboratory findings 3
• Immunological studies should be performed to evaluate for autoimmune etiology 4
• Laboratory workup helps distinguish idiopathic from secondary causes 4

Imaging Approach

Multidetector CT and MRI are the preferred imaging modalities for both diagnosis and follow-up 1, 2:

• CT findings: The mass appears isodense with muscle on unenhanced images, typically beginning at L4-L5 level, forming a plaque that encases the aorta and IVC 2
• Contrast enhancement patterns help assess disease activity: greatest enhancement occurs in early inflammatory phase, minimal in late fibrotic phase 2
• MRI characteristics: Hypointense on T1-weighted images; variable T2 signal depending on disease stage (hyperintense in early inflammatory stages, hypointense in late fibrotic stages) 2
• Dynamic gadolinium enhancement is useful for assessing disease activity, monitoring treatment response, and detecting relapse 2

The classic imaging triad includes: medial deviation of ureters, extrinsic ureteral compression, and hydronephrosis 2

Advanced Imaging

• PET-CT with FDG plays an important role in management and follow-up, particularly for assessing metabolic activity 1
• Diffusion-weighted MRI may provide useful information for differentiating retroperitoneal masses 2

Histopathological Confirmation

• Biopsy is necessary when imaging cannot definitively distinguish benign from malignant RPF 1, 4
• Histopathological evaluation confirms diagnosis and differentiates idiopathic from secondary causes 4
• Biopsy was performed in only a minority of cases historically, but should be considered when malignancy cannot be excluded 3

Distinguishing Idiopathic from Secondary RPF

The most critical diagnostic challenge is differentiating benign from malignant RPF, as malignant forms (up to 10% of cases) have poor prognosis 1:

• Idiopathic RPF accounts for approximately two-thirds of cases and is part of chronic periaortitis spectrum 4
• Secondary causes include: drugs (especially ergot derivatives), malignancies, infections, radiation therapy, and trauma 2, 5
• Two subtypes exist: vascular subtype (involving aorta with atherosclerotic risk factors) and renoureteral subtype (predominant obstructive uropathy) 4

Atypical Presentations

• Up to 40% of cases may present in atypical locations including peripancreatic, periduodenal, or pelvic regions 5
• Up to 15% of patients have additional fibrotic processes outside the retroperitoneum 2, 5
• RPF may spread contiguously or involve multiple non-contiguous sites 5

Management

Surgical Intervention

Urological intervention is required when ureteral obstruction causes hydronephrosis and renal failure 4:

• Ureteral stenting or nephrostomy may be necessary for acute management of obstructive uropathy 6
• Surgical evaluation is needed for management of associated aortic aneurysms 4

Medical Therapy

Corticosteroids remain the gold standard pharmacological treatment for idiopathic RPF 4:

• Steroid therapy should be initiated once diagnosis is confirmed and malignancy excluded 4
• Treatment efficacy is monitored using inflammatory markers and serial imaging 4

Multidisciplinary Approach

A multidisciplinary team with expertise in both primary and secondary RPF is essential for optimal outcomes 4:

• Collaboration between urology, internal medicine, rheumatology, and interventional radiology 4
• Referral to centers specialized in rare diseases yields best outcomes 4

Follow-up Strategy

Serial CT or MRI imaging is essential for monitoring treatment response and detecting relapse 1, 2:

• Dynamic contrast-enhanced imaging assesses disease activity 2
• PET-CT can be used to evaluate metabolic response to therapy 1
• Monitoring of renal function and inflammatory markers guides treatment adjustments 4

Prognosis

• Idiopathic and benign forms have good prognosis when promptly diagnosed and treated 1
• Malignant RPF has poor prognosis and requires aggressive management 1
• The disease remains underdiagnosed with delayed recognition contributing to worse outcomes 4

Critical Pitfalls to Avoid

• Do not rely on ultrasound alone for diagnosis, as it can only suggest the diagnosis but lacks specificity 2, 3
• Do not delay biopsy when imaging features are atypical or malignancy cannot be excluded 1
• Do not miss secondary causes, particularly drug-induced (ergot derivatives) or malignancy-related RPF 2, 5
• Do not overlook extra-retroperitoneal fibrotic manifestations which occur in 15% of cases 2, 5