Update on MR Imaging of cystic retroperitoneal masses
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REVIEW
Update on MR Imaging of cystic retroperitoneal masses Kathleen Nguyen1 · Evan S. Siegelman2 · Wendy Tu1 · Nicola Schieda3
© Springer Science+Business Media, LLC, part of Springer Nature 2019
Abstract Objective This article reviews the MRI appearance of cystic retroperitoneal (RP) masses. Conclusion Lymphangiomas are the most common RP cystic masses and typically appear simple; microscopic fat is a specific but insensitive finding. Location, internal complexity, and enhancement pattern suggest alternative diagnoses which range from normal anatomic variants to congenital abnormalities and importantly include benign, neurogenic, and malignant neoplasms. An approach to the MR imaging of cystic RP masses is presented. Keywords Retroperitoneal · Cyst · Lymphangioma · Neurogenic · Magnetic Resonance Imaging MRI
Introduction Cystic masses of the retroperitoneum (RP) are uncommon; however, are encountered in clinical practice [1]. CT is accurate for detection and preliminary characterization of the cystic nature of RP masses when internal areas measure fluid attenuation (i.e., between − 10 and 20 Hounsfield Units [2]); however, due to its improved soft tissue resolution and ability to differentiate between tissue types, MRI provides more accurate characterization of cystic RP masses [3]. This article reviews the various cystic RP masses which may be encountered in clinical practice and presents an approach to improve characterization and differential diagnoses based upon imaging findings. Cystic RP masses which are typically confined to the pelvis, such as Mullerian cysts and tail * Nicola Schieda [email protected] Kathleen Nguyen [email protected] Evan S. Siegelman [email protected] Wendy Tu [email protected] 1
Department of Medical Imaging, The Ottawa Hospital, The University of Ottawa, Ottawa, Canada
2
Department of Radiology, The Hospital of the University of Pennsylvania, Philadelphia, USA
3
The Ottawa Hospital, The University of Ottawa, 1053 Carling Avenue, Ottawa, ON K1Y 4E9, Canada
gut cysts, have also been described in the literature [1] but are not further discussed in this article which focusses on the upper retroperitoneum.
MRI technique A comprehensive technique for evaluation of the RP should emulate a dedicated renal mass MRI protocol and include: T1- and T2-weighted (W) imaging with and without fat suppression (FS), T1 W dual-echo in- and opposed-phase (IP and OP) imaging, diffusion-weighted imaging (DWI) and dynamic pre- and post-gadolinium enhanced FS T1W images in multiple planes [4]. Our institutional protocol for characterization of renal and RP masses is provided in Table 1. An important aspect of RP mass MRI pertains to adequate coverage of a lesion in the cranio-caudal (CC) plane. When incidentally discovered, it is not uncommon for coverage of a lesion, particularly when more caudally located in the RP, to be incomplete on many sequences. This is especially true if the study was being performed for assessment of an upper abdominal organ such as the liver or sp
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