Early detection of hepatopulmonary syndrome (HPS) may be delayed because of invasiveness of the diagnostic procedures. In this pilot study, we prospectively investigated the usefulness of determining transcutaneous O(2) tension after 100% O(2) (TcPO(2)100) breathing using a transcutaneous hyperoxia test (THT) in 11 children with chronic cholestasis and without primary cardiopulmonary disease. These patients also underwent alveolar-arterial O(2) gradient testing (AaDO(2)) at an inspired oxygen fraction (FiO(2)) of 0.21, lung scintiscan, and contrast transthoracic echocardiography (TTE). Three of them had a liver transplantation because of the downhill course of their liver disease and respiratory status. THT transcutaneous O(2) tension at 21% FiO(2) (TcPO(2)21) was 75 +/- 13 mm Hg, and increased to 488 +/- 106 mmHg after 100% O(2) breathing (TcPO(2)100). Both mean values were not significantly different from those found in 8 age-matched controls (P = 0.9 and P = 0.5, respectively). However, one patient, in spite of her stable liver function, showed an abnormal TcPO(2)21 and TcPO(2)100 (45 mmHg and 210 mmHg, respectively). This same subject was also the only patient with abnormalities of AaDO(2) (54.2 mm Hg; normal value, < 20 mm Hg), lung scintiscan (brain/lung ratio of technetium-99 fixation (B/L SI) = 9, normal value < 1), and TTE, suggesting intrapulmonary vasodilatations and shunts. Given the clinical development of cyanosis and platypnea, all criteria for HPS were fulfilled, and timing of her liver transplantation was therefore accelerated. This resulted in HPS regression. In children with chronic cholestasis, repeated transcutaneous bedside measurements are a rapid and reliable noninvasive test for characterizing the severity of abnormal oxygenation, and may prove useful also in liver posttransplantation monitoring.