E2424. Imaging of Retroperitoneal Mass
  1. Bhanupriya Singh; Lohia Institute of Medical Sciences
To review imaging manifestations of primary retroperitoneal masses and outlay an imaging-based diagnostic algorithm. The primary retroperitoneal pathologies are a challenge for the radiologist and clinician. Their unspecific symptoms and low frequency are the principal reason. It is important to recognize the morphology, characteristics like size, shape, wall thickness, calcifications and the role of CT and MRI (ultrasound less frequent) in the correct study of these pathologies.

Educational Goals / Teaching Points
Localization of the lesions- To make a correct localization of the lesions we should know the different spaces and limits, which comprise the retroperitoneum. This anatomic space is delimited Superiorly: diaphragm, Lower limit: the pelvis, Anterior: posterior parietal peritoneum and posterior by transversalis fascia. The retro peritoneum is divided in different areas: 1) posterior pararenal space, 2) anterior pararenal space, 3) perirenal space and space of the great vessels.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Beak Sign : When the border of the affected organ is deformed like a¨beak¨ (acute angle) it should be considered that the lesion or tumor arises from there. If the margins of the organ which is in contact presents a blunt edge, the lesion is shifting the organ. Embedded organ sign (positive or negative): When the border adopts a crescent shape morphology in plastic organs correspond that these lesions don't depend from this organ, because the organ is displaced for these lesions, if the structure is fused with the surface of the lesion (embedded organ sign), indicate invasion or you can conclude that this tumor arise from this structure. Liposarcoma is the most common primary retroperitoneal sarcoma. CT scan features- Predominantly hypoattenuating lesion characterised by fat content. Other components for the tumor are soft tissue and calcification.

Retroperitoneal lesions are a big challenge for both the clinician and the radiologist, many retroperitoneal lesions may be difficult to filial origin, but following a few morphological and radiological signs of invasion or not of adjacent structures, can reach a correct diagnosis using techniques such as CT and MRI.