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Vascular Dynamics in Liver Scan “Hot Spot”

Recently, we observed three examples of a focal area of increased activity “hot spot” in the region of the porta hepatis. A review of the literature on this observation has identified it with a variety of causes commonly associated with alteration in superior vena cava (SVC) and hepatic circulatory dynamics. To investigate this alteration in hepatic circulatory dynamics, radionuclide 99 mTc-macroaggregated albumin (MAA)) venacavograms, contrast venacavograms, CT scans, tissue needle biopsy, open surgical biopsy and autopsy were used in these patients. Two additional patients with known mediastinal masses, but with normal or areas of decreased activity on their liver scans, were evaluated by the same methods. The anatomy involved in altered SVC circulation and collateral shunting through the porta hepatis venous circulation producing the “hot spot” was analyzed from radionuclide flow patterns and liver scans. All three patients had SVC or subclavian compression by extrinsic neoplastic masses, creating increased collateral flow through the porta hepatis. Individual variations in collateral shunt patterns were observed. We concluded from our observations that important factors involved in the creation of the liver scan “hot spot” were: 1) site of SVC or subclavian vein compression; 2) degree of SVC or subclavian obstruction; and 3) individual variation in venous collateral patterns.