Splenic impedance indices: a useful method to monitor patients after liver transplantation?

Splenic Doppler impedance indices are influenced, in portal hypertensive patients, by the resistance of the portal system. The aim of the study was to verify the usefulness of these indices in evaluating the presence of a pathological increase in portal resistance in patients with complications after liver transplantation. Splenic impedance indices have been evaluated in 46 patients before orthotopic liver transplantation (OLT), and 2 days, 1, 4, 8, and 12 to 18 months after transplantation. The results showed that spleen size slowly decreased after liver transplantation. From a baseline longitudinal diameter value of 18.0+/-3.6 cm (M+/-SD), the decrease was by 0%+/-3%, 8%+/-8%, 13%+/-9%, 15%+/-11%, and 14%+/-11% at 2 days and 1, 4, 8, and 12 to 18 months after liver transplantation. Splenic impedance indices-resistance index = (peak systolic - end diastolic) / peak systolic velocity; pulsatility index = (peak systolic - end diastolic) / mean velocity-which were increased before liver transplantation, showed a rapid decrease to normal values: resistance index: from 0.62+/-0.08 to 0.55+/-0.08 after 2 days, and to 0.49+/-0.09, 0.51+/-0.10, 0.54+/-0.10, 0.55+/-0.11 after 1, 4, 8, 12-18 months; pulsatility index: from 0.96+/-0.21 to 0.82+/-0.17 after 2 days, and to 0.69+/-0.19,0.72+/-0.21, 0.81+/-0.26, 0.84+/-0.26 after 1, 4, 8, and 12 to 18 months. Patients who had a good outcome, without any major complications, showed a clear and steady decrease in splenic impedance indices. On the contrary, patients who had complications affecting portal resistance (e.g., acute rejection, relapse of chronic hepatitis C virus-related hepatitis or cirrhosis, stenosis of portal anasthomosis, portal thrombosis), showed a lack of decrease, or, after an initial decrease, a subsequent re-increase in splenic impedance indices to pathological values. Splenic impedance indices measured in patients with complications were higher than those of patients without complications (P < .0004). Specificity and sensitivity of splenic impedance indices in the evaluation of the presence of complications increasing portal resistance were good. In conclusion, after OLT, splenic impedance indices could be useful aspecific parameters for identifying patients with complications that are able to affect or increase portal resistance.