This site is targeted at medical and radiology professionals, contains user contributed content, and material that may be confusing to a lay audience. Use of this site implies acceptance of our Terms of Use.

Chronic periaortitis

Dr Yuranga Weerakkody and Dr Erik Ranschaert et al.

Chronic periaortitis is an inflammatory condition which typically involves the infrarenal portion of the abdominal aorta. It is a rare disease usually occuring in middle-aged men.

It has various clinical presentations:

idiopathic retroperitoneal fibrosis (IRF)
perianeurysmal retroperitoneal fibrosis
inflammatory abdominal aortic aneurysm (IAAA)
isolated periaortitis

Isolated periaortitis corresponds to the non-aneurysmal form of chronic periaortitis and is less frequently encountered.

An exaggerated inflammatory response to advanced atherosclerosis has been thought to be the main pathogenetic process. Autoimmunity has been proposed as a contributing factor.

Epidemiology

The term IRF may be misleading since it is no longer considered idiopathic but secondary to advanced atherosclerosis, and is probably an autoimmune process. The majority is ideopathic (>70%) ; the remainder occur in association with inflammatory disorders, malignancies or medications.

idiopathic retroperioneal fibrosis (IRF)
- estimated annual incidence of 0.2-0.5 per 100.000
- no ethnic difference
- 40-60 years
- men are more commonly affected (2:1 to 3:1)
IAAA (triad of thickened aneurysmal wall, extensive perianeurysmal fibrosis and adhesions) represents
- 3-10% of abdominal aortic aneurysms
- male to female ratio is 6:1 to 30:1
- mean age at presentation ~ 62-68 years

Clinical presentation

Symptoms:

most common: dull diffuse back / abdominal / flank pain (80%)
other: fever, weight loss, anorexia, vomiting, malaise, claudication, testicular pain, ureteral colic

Ureteral obstruction leading to unilateral or bilateral hydronephrosis and consequent renal insufficiency is the most typical presentation of IRF. In IAAA the entrapment of ureters by fibrous periaortic tissue may lead to obstructive uropathy in 10-21% of patients.

In a minority of cases retroperitoneal fibrosis is not idiopathic but secondary to :

metastatic disease
lymphoma
sarcoidosis
carcinoid

Malignant retroperitoneal fibrosis is estimate to occur in up to 8% of cases and has a poor prognosis.

Pathophysiology

The major pathogenetic process leading to chronic periaortitis is inflammation, caused by advanced atherosclerosis. Lymphocyte populations, periaortic inflammation and fibrosis have been demonstrated in histologic specimens of IRF and IAAA.

Autoimmunity to several components (oxidized-low density lipoproteins and ceroid) of atherosclerotic plaque has been proposed as the antigenic stimulus in the initiation of the inflammatory process.

Associations

The association of periaortitis with various autoimmune diseases has been reported, supporting the concept of autoimmunity. Periaortitis can be seen with:

Markers

Elevated ESR is seen in 80-90% of patients.

Radiographic features

Ultrasound

retroperitoneal fibrosis may be defined as hypoechoic or anechoic
the mass surrounding the aorta is usually well-demarcated but irregularly contoured
varying degrees of hydronephrosis and hydroureter may result
comprehensive evaluation of the prevertebral and paravertebral lumbar spine is essential
overall sensitivity of sonography is poor

The definitive diagnostic test is contrast-enhanced CT scanning or MRI. Both CT and MRI typically show a periaortic soft tissue mass as a rind of abnormal tissue around the aorta, with a varying extent of spread

in IAAA the aorta is aneurysmal
in isolated periaortitis the aorta is not aneurysmal and surrounded by a mantle of soft-tissue density
in IRF there is usually entrapment of one or both ureters

CT

fibrosis often manifests as a paraspinal, well-demarcated but irregular retroperitoneal mass, isodense to surrounding muscle
with CE-CT the periaortic mass usually shows varying degree of enhancement; the degree of enhancement correlates with activity of the fibrotic process:
- in acute stages avid enhancement is seen, with increase of 20-60HU
- in chronic disease little or no enhancement may be seen
- in approximately 1/3 of patients with proven retroperitoneal fibrosis no abnormality is seen
in malignancy the fibrosis has a tendency to be larger and bulkier; the sensitivity and specificity of morphologic features is rather poor
CT-guided biopsy is usually adequate to exclude malignancy in IRF, occasionally multiple deep biopsies may be required

MRI

at MRI periaortitis is hypointense on T1 and hyperintense on T2
with gadolinium-enhanced MRI the inflammatory cuff enhances homogeneously

FDG PET

PET scan and PET-CT with 18F-fluorodeoxyglucose (FDG) is a reliable tool in assessing the metabolic activity of the mass: in early inflammatory stages the uptake is avid, in the late fibrotic stage there might be no uptake.

It is also useful to detect other sites of inflammation and disclosing infectious or neoplastic lesions to which periaortitis can be secondary or associated with.

Treatment and prognosis

Treatment

Steroids have been used along with surgery with good results

Medical

steroids are usually effective in chronic periaortitis but their role remains somewhat controversial. There is no accepted standard for dose and duration of steroid treatment
immunosuppressive drugs such as Azathioprine and Methotrexate have been used effectively as steroid-sparing agents and in patients unresponsive to steroids alone.
Cyclophosphamide may be useful in severe cases (if vasculitis is present)

Surgical

ureterolysis with lateral transposition of the ureters and wrapping with omentum is the procedure of choice in patients with hydronephrosis in IRF
ureteral stents are also used
operative repair of the aneurysm is the definitive treatment for IAAA. Surgery is performed when the diameter of the aorta is > 5 cm

Prognosis

The prognosis for patients with benign retroperitoneal fibrosis is considered to be good. In most instances IRF does not lead to long-term morbidity. Malignant retroperitoneal fibrosis has a mean survival of 3 - 6 months.