The appearance of radiotracer in the systemic circulation to document the visualization of the brain, kidneys, and spleen after intravenous administration of Tc-99m MAA indicates right-to-left shunts because MAA particles (20-60 microns) are supposedly trapped in the pulmonary bed (less than 15 microns). Six hypoxemia patients (1 male, 5 females; age range, 12-52 years) with intrapulmonary right-to-left shunts were evaluated by Tc-99m MAA dynamic perfusion imaging and total-body scans. Tc-99m MAA total-body imaging of the six patients with intrapulmonary right-to-left shunts (3 patients with chronic liver disease/cirrhosis of the liver and 3 patients with pulmonary arteriovenous fistulae) revealed significant radiotracer uptake in extrapulmonary organs such as the brain, kidneys, and spleen; a shunt ratio, estimated by a semiquantitative method, ranged from 17.8% to 52%. All dynamic pulmonary perfusion scans showed a normal sequence of cardiopulmonary flow without intracardiac shunts. Three patients with pulmonary arteriovenous fistulae underwent a second Tc-99m MAA total-body imaging after embolization therapy (2 patients) or lobectomy (1 patient). The result in lobectomized patients were negative for uptake in extrapulmonary organs; the two patients who underwent embolization therapy demonstrated only mild improvement. As a consequence of these findings, the authors conclude that Tc-99m MAA total-body imaging can be used for the diagnosis of intrapulmonary right-to-left shunts, as well as for the evaluation of postshunt therapy.