From the Guidelines
CT with contrast is the preferred imaging modality over plain CT for assessing retroperitoneal masses. This is because intravenous contrast enhances visualization of these masses by highlighting differences in vascularity between normal tissues and pathological lesions, allowing for better delineation of the mass borders, internal characteristics, and relationship to surrounding structures like blood vessels and organs. The contrast helps distinguish solid from cystic components and can reveal patterns of enhancement that aid in differentiating between various types of masses such as lymphoma, sarcoma, or metastatic disease. According to the UK guidelines for the management of soft tissue sarcomas 1, CT is preferred for diagnosis and managing treatment of retroperitoneal tumors, providing complete staging information on the same scan.
Some key points to consider when using CT with contrast for assessing retroperitoneal masses include:
- Screening patients for contraindications to contrast, including renal impairment and allergies
- Adequate hydration before and after the procedure to reduce the risk of contrast-induced nephropathy
- Using a multiphasic CT protocol, which includes pre-contrast, arterial, venous, and sometimes delayed phases, for optimal imaging
- Considering MRI as an alternative imaging modality in cases where contrast is absolutely contraindicated
While the ACR Appropriateness Criteria for suspected retroperitoneal bleed 1 discusses the use of IV contrast and CT for initial imaging, the most recent and relevant guideline for assessing retroperitoneal masses is the UK guidelines for the management of soft tissue sarcomas 1, which supports the use of CT with contrast as the preferred imaging modality.
From the Research
CT with Contrast vs Plain CT for Assessing Retroperitoneal Mass
- The use of CT with contrast is beneficial in assessing retroperitoneal masses, as it provides better definition of tissue planes and contiguous anatomical structures 2.
- CT is superior to ultrasound in demonstrating the extent of disease, although ultrasound can more easily distinguish cystic from solid masses 2.
- Non-contrast CT scans may be challenging in evaluating vascular structures, but can still provide useful information in certain cases, such as suspected renal calculus or retroperitoneal hematoma 3.
- The use of contrast-enhanced CT is recommended for evaluating retroperitoneal tumors, as it provides clinically useful information regarding the presence, size, extent, and composition of the tumors 4.
- Dynamic contrast-enhanced CT and MRI can be useful in the diagnosis and identification of retroperitoneal localized Castleman's disease, with features such as moderate enhancement in the arterial phase and continuous enhancement in the venous phase 5.
- Contrast-enhanced CT can also be used to assess the activity of idiopathic retroperitoneal fibrosis, with a significant correlation between SUVmax and CE score, as well as with inflammatory markers such as ESR and CRP 6.