Teaching Case

A 69-year-old woman was admitted to the hospital with abdominal pain and constitutional syndrome with weight loss in the past 7 weeks. Physical examination revealed diffuse abdominal pain without peritoneal irritation and a hard non-mobile, pulsatile epigastric mass. Laboratory test highlighted impaired renal function not previously present, without other findings. 

Abdominopelvic contrast-enhanced multidetector computed tomography (MDCT) displayed a hypodense periaortic soft-tissue mass extending from the infrarenal aorta down to the aortic bifurcation with minimal left iliac involvement. The mass surrounds the aorta in almost 90% of its circumference without a clear fat plane of separation.  The abdominal aorta maintains a normal calibre with partially calcified atherosclerosis mainly in the infrarenal territory (Fig. 1a, b).

The soft-tissue mass contacts with the left psoas muscle and surrounds the left ureter leading to ureteral and calyceal obstruction (Fig. 1b).

Positron emission tomography scan (PET-TC) was subsequently performed for further evaluation showing pathological metabolic activity in the periaortic soft tissue mass described in the MDCT (Fig. 2a, b). The rest of the study does not provide additional information.

Biopsy confirmation was necessary to obtain the final diagnosis. It showed marked fibrosis and lymphoplasmacytic inflammatory infiltrate which was Immunoglobulin G4 (IgG4) positive.

The steroid-treatment decreased the size of the periaortic mass (Fig. 3a, b).

Immunoglobulin G4-related disease (IgG4-RD) is an immune-mediated fibro-inflammatory condition that includes several entities characterised by lymphoplasmacytic inflammation, fibrosis, increased number of IgG4 cells in the affected tissue and, often but not always, elevation of serum IgG4 levels [1-4].

IgG4-RD was recognised as a systemic disease in 2003 [1, 2, 5]. It can affect any organ and can involve one or multiple organs, the pancreas being the most commonly affected [1-4].

Patients often present with subacute development of a mass or diffuse enlargement of an organ. Multiple organs are affected in 60-90% of the cases. Retroperitoneal involvement of IgG4-RD includes retroperitoneal fibrosis (RPF), aortitis, periaortitis and aortic aneurysm [2-5].

RPF is a rare condition in which a fibroinflammatory tissue appears surrounding the abdominal aorta (mainly the infrarenal aorta), the iliac arteries and the inferior vena cava. The lesion can spread to adjacent organs, frequently with ureteral involvement, which can lead to renal failure [1, 2, 4-7].

The most frequent cause of RPF is idiopathic which typically presents in middle-aged individuals [1, 3, 4-7]. RPF associated with IgG4-RD is believed to be responsible for more than two-thirds of the cases of the idiopathic RPF and is one of the most common subsets of IgG4-RD. RPF can also be secondary to other causes such as infection, radiation therapy, drugs, malignant tumour or trauma [4-6].

As the symptoms are non-specific, the lesion can be detected as an incidental finding. The patient may have abdominal or back pain, constitutional symptoms or symptoms due to hydronephrosis and renal failure [2, 4-6].

MDCT and magnetic resonance imaging (MRI) are essential tools in the non-invasive diagnostic work-up as they can assess the location, morphology and extent of the lesion as well as the involvement of adjacent organs. Besides, they can detect associated diseases or the cause in case of secondary RPF.

MDCT and MRI findings show a soft-tissue mass surrounding the retroperitoneal vascular structures with or without extension to adjacent organs. Contrast uptake depends on the degree of fibrosis and on MRI the signal intensity depends on the degree of active inflammation [1, 2, 4-7].

A biopsy is usually obtained to confirm the diagnosis [2, 3-7].

Corticosteroids are usually the first line of treatment for patients with idiopathic or IgG4-RD RPF. The lesion usually responds to steroid therapy although immunosuppressive therapy can also be used. Imaging techniques can be used to assess response to treatment [1-6].

Written informed patient consent for publication has been obtained.