Accurate imaging of primary or metastatic tumor involvement of the liver is crucial for determining appropriate surgical candidates. Careful patient selection avoids unnecessary laparoscopy or laparotorny in most patients with more extensive hepatic and/or extrahepatic tumor involvement. For patients who are deemed appropriate surgical and/or cryotherapy candidates, operative time and decision-making can be minimized by thorough pre-operative assessment. The surgical extent and technical approach can often be well planned before intra-operative ultrasound (IOUS) confirms or alters the pre-operative imaging findings.
IOUS remains the gold standard for lesion detection, revealing 7-35% more tumor than anticipated in prior studies. However, the future of less invasive cryotherapy (e.g., laparoscopic, minilaparotorny , percutaneous) requires continued emphasis on improving the quality of pre-operative imaging. Improved sequences are being developed for computed tomography (CT), magnetic resonance imaging (MRI) and CT arterial portography (CTAP). Many of these techniques also allow improved lesion characterization, thus helping to differentiate concurrent benign findings from the malignant lesion(s) being considered for therapy. The more characteristic appearances of metastatic and primary hepatic neoplasms will be shown in context with the imaging findings encountered with cirrhosis, hemangioma, adenoma, focal nodular hyperplasia, regenerative & adenomatous hyperplastic nodules. Spiral CTAP has the greatest pre-operative sensitivity for hepatic masses over US, CT and MRI. While the specificity of CTAP may be low relative to IOUS (e.g., differentiation of <7 mm cysts), CTAP defines tumor impact upon adjacent vasculature and provides a "road map" for IOUS confirmation of segmental tumor distribution. Posterior aspects of the liver and near the hepatic venous confluence can be difficult to fully image by IOUS and CTAP provides either the reassurance of normal parenchyma, or the imperative for IOUS to better visualize that area in multiple projections. However, the specificity of CTAP is hindered by several diagnostic pitfalls, the simplest of which is to require a preoperative study of no more than 4-6 weeks old. Multiple cases will be shown to offer clarification of normal variants, perfusion defects and enhancement characteristics.
In summary, thorough pre-operative imaging assessment can avoid unnecessary surgery, improve surgical planning, identify concurrent benign findings, improve IOUS assessment and serve as an important baseline for post-cryotherapy follow-up. Continued improvements in pre-operative imaging will narrow the diagnostic gap with IOUS and encourage less invasive approaches of isolated lesions.