Absent pulmonary uptake on 99mTc MAA perfusion lung scan due to severe right-to-left shunt.

c 5 XTRAPULMONARY accumulation of Tc macroaggregated albumin (MAA) is rarely een on perfusion lung scan, and has been reported n less than 4% of a study population of nearly 380 atients.1 It occurs when the agent bypasses the ungs due to a right-to-left (R-L) cardiac or pulonary shunt, when it is shunted to the portal vein efore reaching the right atrium and ventricle of he heart, and when the agent is degraded to a ubmicron-particle size. When a pharmaceutical roblem is excluded, extrapulmonary uptake imlies unusual hemodynamics with a shunt. Absent pulmonary uptake on Tc MAA perusion lung scan with concomitant extrapulmonary ccumulation is indicative of major R-L shunt. A ase is reported in which a major but clinically nsuspected shunt was diagnosed from the scan ndings. Other causes of extrapulmonary uptake re also presented.