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Findings: Abnormal uptake of Tc99m macroaggregated albumin in the brain and kidneys.

Diagnosis: Hepatopulmonary syndrome (intrapulmonary arteriovenous shunting secondary to hepatic cirrhosis).

Discussion: Hypoxemia secondary to hepatic cirrhosis is due to abnormally dilated pulmonary vessels, which structurally resemble spider angiomata of the skin and functions as tiny arteriovenous shunts.1,2 Hepatic dysfunction usually predates the presentation of hypoxia. Cutaneous angiomata may or may or may not be present. Angiography may demonstrate the arteriovenous connections, occasionally nodular shadows may be seen in the lower lobes of patients with hepatopulmonary syndrome on conventional chest radiographs.1,2

Whole body radionuclide scans with Tc99m macroaggregated albumin have been diagnostic of right-to-left shunting in patients with hepatopulmonary syndrome.3 In normal lung, 95% of the MAA particles are trapped in the intrapulmonary capillaries. With intrapulmonary shunting MAA particles bypass pulmonary capillaries and become entrapped in the systemic capillary beds, most notably the kidneys and brain. The percentage of MAA which bypasses the lungs 2:5 has been reported to be as high as 60%.3 This corresponds to a significant degree of right to left shunt. Recently there have been reports of reversal of intrapulmonary shunts following liver transplantation.

References:
1. Robin ED, Horn B, Goris ML, et al: Detection, quantitation and pathophysiology of
lung "spiders". Trans. Assoc. Am. Physicians. 1975;88:202-215.

2. Berthelot P, Walker JG, Sherlock S, Reid L: Arterial changes in the lungs in cirrhosis
of the liver - long spider nevi. N. Engl J Med 1966;274:291-298.

3. Bank ER, Thrall JH, Dantzker DR: Radionuclide demonstration of intrapulmonary
shunting in cirrhosis. AJR 140:967-969, May 1993.

4. McCloskey JJ, Schlein C, Schwartz K, Klein A, Colombani P: Severe hypoxemia and
intrapulmonary shunting resulting from cirrhosis reversed by liver transplantation
in pediatric patients. J. Padded 1991;118:902-904.

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