Age / Sex : 10 / F

Age / Sex : 79 / M

giant cysterna chyli

Discussion

Findings:

CT )

Unenhanced transverse CT scan shows rounded retrocrural structure with the attenuation of fluid to left of aorta.

Contrast-enhanced CT scan shows no definite enhancement of this structure.

MRI)

Axial T2-weighted MR image shows a 2.7x2.1cm sized rounded structure with high signal intensity anterior to the vertebral column at the level of the renal hilum.

Sagittal T2-weighted MR image clearly depicts the saccular structure at a prevertebral location with a homogenously high signal intensity similar to that of cerebrospinal fluid.

Differential Diagnosis : Retrocrural lymphadenopathy

Diagnosis: Giant Cisterna chyli

Discussion:

The cisterna chyli is a dilated lymphatic channel in the retroperitoneal space, usually to the immediate right to the abdominal aorta, and represents the origin of the thoracic duct.

It is joined by two lumbar and intestinal trunks that originate at the level of the L1-L2 vertebral body, after which is continues in the cephalic direction as the thoracic duct.

The cisterna chyli is seen in 15% of patients evaluated with routine abdominal MR imaging that include highly fluid-sensitive T2-weighted imaging sequences. An unusually large cisterna chyli with an anteropostserior or transverse diameter larger than 2cm is rare.

On CT images, an unusually large cisterna chyli may mimic other pathologic conditions of the retroperitoneum and it may mistaken for a retrocrural lymph node. However, the depiction of the fluid content of the cisterna chyli on MR images permits its accurate identification.

The large cisterna chyli does not appear substantially enhanced on dynamic images obtained within 5 minutes after intravenous injection of contrast material. Delayed images at 30 min produces a clear fluid-fluid level. In a CT study of the cisterna chyli in 18 patients following intravenous contrast medium injection, layering within the cisterna chyli occurred. Contrast medium is denser than lymph, and in a dilated segment with a lymphatic flow sufficiently slow to avoid mixing, sedimentation is to be expected.

Radiologists should be familiar with an unusually large size of the cisterna chyli to avoid mistaking it for a pathologic entity.

References:

1. Pinto PS et al. Cisterna chyli at routine abdominal MR imaging: A normal anatomic structure in the retrocrural space. RadioGraphics 2004 ; 24: 809-817

2. Lee KC et al. Unusually large cisterna chyli: US and MRI findings. Abdominal imaging 2006 ; 31 : 719-721

3. Tamsel S et al. Giant cisterna chyli: MRI depiction with gadolinium-DTPA enhancement. Clinical Radiology 2000 ; 55 : 51-55