US confirmation of hepatopetal flow through bladder-umbilical-portal pathway in a patient affected by inferior vena cava obstruction due to retroperitoneal fibrosis and pelvic lipomatosis

Clinical History

A 56-year-old African man with a history of Ulcerative Colitis (endoscopically diagnosed and treated) and haemorroidectomy presented to our emergency department for a swelling of the right lower limb. Physical examination revealed pitting oedema and typical signs of inflammation suspicious for peripheral venous thrombophlebitis.

Imaging Findings

After a negative Colour Doppler investigation of peripheral veins, CT after contrast demonstrated narrowed and obstructed Inferior Vena Cava caused by a solid tissue around vessels extended till the bisiliac-aortic carrefour; ureters were not involved. There was a complete thrombosis of the common iliac veins (Fig. 1).
An uncommon collateral pathway was detected: a vein from ectasic perivescical venous plexus directed to the umbilicus following the way of urachus (Fig. 2) was connected to a patent umbilical vein. The bladder was displaced superiorly and anteriorly and compressed by exuberant pelvic fatty tissue (Fig. 3).
In addition, an area of decreased portal perfusion mimicking a hepatic mass in the medial segment of the left lobe (S4), was observed (Fig. 4).
In order to characterize these findings a Colour Doppler examination of the abdominal vessels was performed and it demonstrated a hepatopetal flow direction (Fig. 4) into the patent umbilical vessel.

Discussion

Obstruction of VC is often an acquired condition. In the event of a chronic occlusion, collateral pathways must develop to maintain venous drainage. Retroperitoneal fibrosis (RFP) can be a rare cause of obstruction of IVC. RFP encompasses a wide range of disease characterized by proliferation of aberrant fibroinflammatory tissue, which usually surrounds the infrarenal portion of the abdominal aorta, IVC and iliac vessels.

The radiologist can confide in several features to differentiate benign and malignant RF forms; this is important because the first ones have a good outcome while malignant secondary forms have a poor prognosis. But to distinguish features lacks sensitivity and specificity and generalization is not always correct [1], (Fig. 1). The major collateral pathways which develop in IVC obstruction are superficial, intermediate, portal and deep ones [2]. Furthermore, uncommon pathways exist: blood may recanalize the paraumbilical veins in the anterior abdominal wall, which drain through the reconstituted patent venosus duct into the hepatic vein. Our patient showed another unusual one:"bladder-umbilical-portal pathway" (Fig. 2). Possible reasons of this condition may consist in the fact that prevesical plexus originates from apical veins that surround urachal and in this case the apex of the patient’s bladder is really close to the umbilical due to "inverted pear” morphology. Paraumbilical venous system leads blood from the navel to the liver. This flow dilutes the portal perfusion causing pseudolesions interpreted as due to “third inflow” [3] as confirmed by US examination (Fig. 4).
Judicious search for reasons of bladder dislocation and of unusual collateral pathways leads to the diagnosis of pelvic lipomatosis (PL). It is a rare non-malignant overgrowth of adipose tissue with minimal fibrotic and inflammatory components compressing soft tissue structures within the pelvis.
The association of RF and PL is a really rare condition [4].
Long et al [5] visualized eosinophil cells and other typical cells of inflammation and for this reasons he did not exclude an allergic component in the aetiology of PL.
PL and RF could be two different manifestations of a systemic condition due to a Th2- cell dominant immune reaction. In fact, our case showed a particular association of these two rare diseases, ulcerative colitis and allergic conditions which are suggestive of a strong Th2 immune polarization [6].

Radiologists should keep in mind specific and diagnostic signs and get curious about strange finding because they could be the key to achieve the correct diagnosis.

Differential Diagnosis List

Final Diagnosis

Inferior vena cava obstructiondue to RF and PL.

URL:	https://www.eurorad.org/case/13587
DOI:	10.1594/EURORAD/CASE.13587
ISSN:	1563-4086