- Pictorial Review
Non-contrast 3D MR lymphography of retroperitoneal lymphatic aneurysmal dilatation: a continuous spectrum of change from normal variants to cystic lymphangioma
Insights into Imagingvolume 4, pages753–758 (2013)
Our objective was to demonstrate the characteristic features of retroperitoneal lymphatic aneurysmal dilatation with three-dimensional (3D) magnetic resonance (MR) lymphography.
Three-dimensional MR lymphography demonstrates that retroperitoneal lymphatic aneurysmal dilatation exhibits a continuous spectrum of change from normal variants to lymphatic aneurysmal dilatation and so-called cystic lymphangioma.
Non-contrast MR lymphography with very heavily T2-weighted fast spin echo sequences is a useful non-invasive technique without the need of contrast medium injection to obtain a unique evaluation of the lymphatic system
To prove the lymphatic origin of a cystic formation, it is essential to demonstrate the communication with retroperitoneal lymphatic vessels
3D MR lymphography demonstrates that retroperitoneal lymphatic aneurysmal dilatation exhibits a continuous spectrum of change from normal variants to lymphatic aneurysmal dilatation and so-called cystic lymphangioma
The retroperitoneal lymphatic system is markedly complex and characterised by numerous anatomical variants .
For a long time X-ray lymphography performed by injecting a radio-opaque material into a lymphatic vessel, surgically exposed and cannulated, has been the single method to explore the lymphatic system . Presently, X-ray lymphography, which is an invasive procedure, is uncommonly performed in particular selected indications, such as preoperative evaluation before surgery for chylothorax
Non-contrast magnetic resonance (MR) lymphography with very heavily T2-weighted fast spin echo sequences appears to be a useful non-invasive technique without the need of contrast medium injection to obtain a unique evaluation of the lymphatic system [3–5].
In this pictorial review, we analyse the characteristic features of retroperitoneal lymphatic aneurysmal dilatation with three-dimensional (3D) MR lymphography.
Non-contrast MR lymphography protocol
MR lymphography was performed on a 1.5-T unit (Magnetom Symphony; Siemens Medical Solutions/Signa HDXt; GE Medical System) with phased-array body coil. Our protocol has already been described by our group .
Non-contrast MR lymphography techniques exploit the high signal intensity of static fluids in the lymphatic vessels with heavily T2-weighted sequences, which also result in decreased signal from background tissues. A free-breathing 3D high-spatial-resolution fast spin-echo sequence with a very long echo time (TE) and a voxel size of 1 × 1 × 1 mm is used. The main advantage of 3D isotropic MR lymphography is thinner section source images, which allow optimal post-processing of image data to obtain maximum intensity projection (MIP) images and multiplanar reformatted (MPR) images. Use of 3D acquisition allows an improvement of both spatial resolution and contrast-to-noise ratio. Therefore, MR lymphography combines the advantages of projectional imaging with those of cross-sectional imaging. MIP 3D images provide an overview of lymphatic anatomy and abnormalities, while MPR images help visualise small or localised abnormalities such as connexion with normal lymphatic system.
Lymphatic aneurysmal dilatation
The retroperitoneal lymphatic system is characterised by numerous anatomical variants . The lumbar lymphatics, which are the continuation of the iliac lymphatics, ascend on either side of the aorta as two main trunks. They are not single vessels but a plexus of vessels that connect by lymphatics around the aorta. The appearance of retroperitoneal lymph trunks markedly varies from thin to prominent thick channels, parallel or converging channels, or a plexus (Fig. 1). Alternating bands of constriction and dilatation are characteristic of the appearance of lymphatic vessels. Areas of constriction correspond to lymphatic valves .
The cisterna chyli receives the right and left lumbar lymphatic trunks. The cisterna chyli lies in front of the first and second lumbar vertebrae behind the crus of the diaphragm. It is a single sac, usually 1–2 cm wide and up to 5 cm long. Despite this classic description, the cisterna chyli has a highly variable appearance. This wide variation of the cisterna chyli has led some authors to prefer the descriptive term “abdominal confluence of the lymphatic trunks” .
In other cases, aneurysmal dilatation of the retroperitoneal lymphatic system may be more diffuse with dilatation of cisterna chyli and both right and left retroperitoneal lymphatic trunks (Fig. 2). In other cases, aneurysmal dilatation of right or left retroperitoneal lymph trunk may be observed (Fig. 3). This lymphatic aneurysmal dilatation appears as fluid-filled cystic spaces that may be responsible for a mass effect on adjacent organs (Fig. 3). To prove the lymphatic origin of the unilocular or multilocular tortuous cystic formation, it is essential to demonstrate the communication with retroperitoneal lymphatic vessels (Figs. 1, 2, 3, 4, 5 and 6). Demonstration of communication of cystic lesion with the main lymphatic vessels allows a definitive non-invasive diagnosis of lymphatic malformation.
These lymphatic aneurysmal dilatations are unilateral in most cases, but bilateral location may also be observed (Fig. 4).
The content of cystic dilatation is usually homogeneous, but a fluid-fluid level may be observed related to sedimentation caused by haemorrhagic debris or by fatty content of the formation (Fig. 6). Therefore, a signal intensity of lymphatic aneurysmal dilatation may be variable in the same patient at different MR examinations (Fig. 6).
Retroperitoneal cystic lymphangioma
Lymphangiomas are found predominantly in children, usually in the head and neck region, and retroperitoneal location is uncommon .
The aetiology of lymphangioma is poorly understood but is believed to be a developmental abnormality characterised by failure of lymphatic tissue to establish normal communication with regional lymphatic vessels, resulting in dilatation of the abnormal channels .
Histopathologically, lymphangioma is characterised by thin-walled unilocular or multilocular cysts that are lined by a single endothelial layer and contain clear or milky fluid. The wall contains lymphatic tissue, small lymphatic spaces and smooth muscles .
Lymphangiomas are classified as capillary, cavernous or cystic depending on the size of the lymphatic spaces.
Retroperitoneal lymphangioma is mainly the cystic form, composed of large macroscopic lymphatic spaces. It usually appears as a cystic multiseptated mass with thin walls.
Clinical presentation is variable and may be misleading. Although it may be diagnosed incidentally on ultrasonography or computed tomography (CT) scan, chronic non-specific symptoms are relatively common. With MR lymphography, retroperitoneal cystic lymphangioma appears usually as a multilocular mass. These fluid-filled cystic lesions may present as infiltrative lesions with concave margins or bulky round lesions with a mass effect on adjacent organs (Figs. 7, 8). An elongated shape and the involvement of multiple compartments of the retroperitoneum are characteristic features of lymphangioma (Fig. 9). Most lesions are fluid-filled masses with low signal intensity on T1-weighted images and high signal intensity on T2-weighted images (Fig. 10). Sometimes, there are some flow phenomena with signal heterogeneity on T2-weighted images in very large lesions (Figs. 7, 8).
In summary, we believe that 3D MR lymphography demonstrating a communication of the lymphatic aneurysmal dilatation with main lymphatic vessels suggests a continuous spectrum of change from normal variants to lymphatic aneurysmal dilatation. However, in the so-called cystic lymphangioma, lack of communication with lymphatic channels may be observed.
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Conflicts of interest
The authors declare no conflicts of interest. No funding was received for this work.