Sonographic evaluation of venous obstruction in liver transplants.

Objective: The purpose of our study was to identify specific Doppler criteria for portal vein and outflow vein (hepatic veins and inferior vena cava) obstruction in liver transplants.

Materials And Methods: A retrospective review was performed of Doppler sonographic studies and angiograms in 94 liver transplant cases (72 whole liver, 22 lobar) with suspected vascular obstruction. The angiograms were classified as normal, occluded, or stenosed on the basis of appearance and elevated pressure gradient. Sonography was correlated with angiography. The following Doppler parameters were evaluated: for the portal vein, peak anastomotic velocity and anastomotic-to-preanastomotic velocity ratio; and for the outflow veins, venous pulsatility index. Receiver operating characteristic curves were constructed and optimum thresholds for stenosis were defined.

Results: There were 16 cases of portal vein obstruction (11 stenosis, five occlusion) and 35 cases of outflow vein obstruction (34 stenoses, one occlusion). Mean peak anastomotic velocity in normal portal veins was 58 cm/s, whereas mean peak anastomotic velocity in stenosed veins was 155 cm/s (p = 0.0007). Peak anastomotic velocity threshold of > 125 cm/s was 73% sensitive and 95% specific for stenosis. Mean anastomotic-to-preanastomotic velocity ratio in normal portal veins was 1.5, and mean anastomotic-to-preanastomotic velocity ratio in stenosed veins was 4.69 (p = 0.001). A 3:1 ratio was 73% sensitive and 100% specific for stenosis. Mean venous pulsatility index for normal outflow veins was 0.75, and mean venous pulsatility index in stenosed veins was 0.39. A venous pulsatility index of < 0.45 was 95.7% specific for stenosis. The areas under the receiver operating characteristic curve were 0.83 for peak anastomotic velocity, 0.86 for anastomotic-to-preanastomotic velocity ratio, and 0.84 for venous pulsatility index, indicating good correlation.

Conclusion: Peak anastomotic velocity, anastomotic-to-preanastomotic velocity ratio, and venous pulsatility index are useful parameters for diagnosing venous stenosis in liver transplants.