Paradigm shifts provided by a new means of seeing: the educational value of three-dimensional ultrasonography.

Abstract

s new imaging technology comes on line, it frequently affords us a fresh means of looking at patients’ anatomy, diseases, and treatment. These novel perceptions bring us to new levels of understanding and on occasion cause us to reassess long-held dogma. Three-dimensional ultrasonography (3DUS) is one such new imaging technology. The ability of 3DUS to assess structures in an altogether new fashion has shown that a number of assumptions we have accepted have been incorrect and that evolution of a new way of thinking is appropriate. One commonly held belief by interventionalists is that the main portal vein at the bifurcation and caudally is usually extrahepatic in location.1 During performance of a transjugular intrahepatic portosystemic shunt (TIPS) procedure, access to these portions of the portal vein has been deemed to carry a high risk of intraperitoneal hemorrhage and should be carefully avoided. We have discovered that when portal vein access serendipitously was achieved in one of these locations, 3DUS could be used to simultaneously interrogate in 3 planes the exact point where the catheter entered the portal vein (Fig. 1). In 11 consecutive patients with such portal vein access, we have found the liver to cover these puncture sites in all 3 imaging planes. This 3DUS finding suggested to us that it was safe to place and expand a stent at this location rather than abort the access. The take-home lesson is that although the ventral surface of the portal vein bifurcation and main portal vein are extrahepatic and open to the peritoneal cavity, the dorsal aspect superiorly is applied to the caudate lobe and appears not to have a significant risk of hemorrhage when a TIPS is created at this location. Another cherished belief has been that experienced operators using uniplanar fluoroscopy or two-dimensional ultrasonography (2DUS) truly know the location of their devices. When our attending angiographers believed, on the basis of fluoroscopy or angiography, that they had catheterized the right hepatic vein during performance of TIPS procedures, 3DUS proved that they were wrong nearly half the time.2 The same results were found when they believed that they had catheterized the middle hepatic vein. During the performance of focal ablation of liver tumors, when the interventional radiologist or surgeon had placed ablative needles or probes in seemAbbreviations RFA, radio frequency ablation; 3DUS, three-dimensional ultrasonography; TIPS, transjugular intrahepatic portosystemic shunt; 2DUS, two-dimensional ultrasonography