Riffat Hussain, Maseehuz Zaman, Sohail Abrar Khan, Nadeem Ahmad.
Extra pulmonary uptake of Tc-99m-MAA Perfusion lung scan as a result of right to left intra cardiac shunt.
J Pak Med Assoc Jan ;56(5):241-2.

Extra pulmonary accumulation of Tc-99m-macroaggregate of albumin (MAA) is rarely seen on perfusion lung scan, and has been reported in less than 4% of a study population of nearly 380 patients. It occurs when the agent bypasses the lungs due to a right to left (R-L) cardiac or pulmonary shunt, when it is shunted to the portal vein before reaching the right atrium and ventricle of the heart, and when the agent is degraded to a submicron particle size. When a pharmaceutical problem is excluded, extra-pulmonary uptake implies unusual hemodynamics with a shunt. A case is reported in which a clinically unsuspected shunt was diagnosed from the lung perfusion scintigraphy.

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