Chronic hypoxia in CCHD results in erythrocytosis causing bloodhyperviscosity. We studied hemodynamic changes in 40 CCHD patients by DopplerUS on renal, femoral & superior mesenteric arteries. We demonstrated progressiveincrease in resistance & pulsatility indices in renal & femoral arteries but it wasstatistically non significant increase. This increase was correlated to the duration ofcyanosis. No changes in superior mesenteric artery hemodynamics. Finally, werecommend doing Doppler examination for assessment of renal condition in CCHD.