IMAGES THAT TEACH Lung perfusion imaging in hepatopulmonary syndrome using 99mTc macroaggregated albumin Devaki Shilpa Surasi, MD,a Padma Manapragada, MD,a and Pradeep Bhambhvani, MDa a

Department of Radiology, The University of Alabama at Birmingham, Birmingham, AL

doi:10.1007/s12350-014-9990-5

Hepatopulmonary syndrome is a serious pulmonary vascular complication in patients with chronic liver disease. It constitutes a triad of chronic liver disease, increased alveolar-arterial oxygen gradient, and evidence of intrapulmonary shunt (IPS). The diagnosis of IPS can be made by bubble echocardiography, technetium-99m-labeled macroaggregated albumin (99mTcMAA) scintigraphy or pulmonary arteriography. Though echocardiography is a sensitive screening test, MAA scintigraphy can also quantify the extent of shunting. Key Words: Hepatopulmonary syndrome Æ

INTRODUCTION Hepatopulmonary syndrome (HPS) is a serious pulmonary vascular complication in patients with chronic liver disease. It has a prevalence of 20% in individuals awaiting liver transplantation.1 The characteristic intrapulmonary vascular dilatations seen in HPS lead to impaired oxygen transfer from alveoli to the red blood cells, resulting in a functional intrapulmonary right-to-left shunt (IPS).2 Clinical manifestations include shortness of breath, platypnea (shortness of breath that is relieved when lying down), and orthodeoxia (fall in arterial oxygen saturation when assuming the upright position). The diagnosis of HPS is based on the triad of chronic liver disease, increased alveolar-arterial oxygen gradient ([15, or [20 mm Hg in patients [64 years of age), and evidence of IPS. Medical treatments have proven to be futile and liver transplantation seems to be the only effective therapeutic option.

Reprint requests: Devaki Shilpa Surasi, MD, Department of Radiology, The University of Alabama at Birmingham, Birmingham, AL; [email protected] 1071-3581/$34.00 Copyright Ó 2014 American Society of Nuclear Cardiology.

99m

Tc macroaggregated albumin Æ lung shunt

The diagnosis of IPS can be made by contrastenhanced bubble echocardiography study, technetium99m-labeled macroaggregated albumin (99mTc-MAA) scintigraphy or pulmonary arteriography. Though echocardiography is a sensitive screening test, MAA scintigraphy can also quantify the extent of shunting. The radionuclide study is performed by injecting 1-4 mCi 99mTc-MAA intravenously (90% of the MAA particle sizes are between 10 and 90 lm). Normally, in the absence of free pertechnetate, the MAA particles get trapped in the pulmonary microvasculature and scintigraphy reveals nearly complete uptake in the lungs without visualization of other organs (Case 1). However, when there is intrapulmonary shunting as in HPS, a fraction of these particles passes through the lungs into the systemic circulation into organs like the brain, kidneys and thyroid in addition to the lung (Case 2). There is minimal if any cardiac activity despite the shunt because of the relatively low coronary blood flow as a percent of cardiac output (unlike the brain). Regions of interest are drawn around the brain and lungs and radiotracer counts are recorded. The pulmonary shunt percent is calculated by applying the geometric mean (GM) of brain and lung counts in the formula3: ðGM brainÞ  100 ðnormal\6%Þ: ðGM brain þ GM lungÞ

Surasi et al Lung perfusion imaging in hepatopulmonary syndrome

Figure 1. Normal study: the

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99m

Tc-MAA is localized in the lungs only.

CLINICAL SUMMARY Case 1 (Figure 1) A 48-year-old woman with cryptogenic cirrhosis and shortness of breath. 99mTc-MAA scintigraphy does not demonstrate brain activity. The shunt percent was normal at 0.2% and excluded HPS. The heart-to-lung ratio was 0.001.

Case 2 (Figure 2) A 64-year-old woman with nonalcoholic steatohepatitis (NASH) cirrhosis presented with shortness of breath and suspicion for HPS. 99mTc-MAA scintigraphy reveals brain activity consistent with HPS. The shunt percent was 19.8%. The echocardiogram was also positive for IPS. The heart-to-lung ratio was 0.003.

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Figure 2. Hepatopulmonary syndrome:

Surasi et al Lung perfusion imaging in hepatopulmonary syndrome

99m

Tc-MAA is localized to the lungs, kidneys and brain.

References 1. Rodriguez-Roisin R, Krowka MJ, Herve P, Fallon MB. Pulmonaryhepatic vascular disorders (PHD). Eur Respir J 2004;24:861-80. 2. Abrams GA, Jaffe CC, Hoffer PB, Binder HJ, Fallon MB. Diagnostic utility of contrast echocardiography and lung perfusion

scan in patients with hepatopulmonary syndrome. Gastroenterology 1995;109:1283-8. 3. Abrams GA, Nanda NC, Dubovsky EV, Krowka MJ, Fallon MB. Use of macroaggregated albumin lung perfusion scan to diagnose hepatopulmonary syndrome: a new approach. Gastroenterology 1998;114:305-10.

Lung perfusion imaging in hepatopulmonary syndrome using (99m)Tc macroaggregated albumin.

Hepatopulmonary syndrome is a serious pulmonary vascular complication in patients with chronic liver disease. It constitutes a triad of chronic liver ...
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