All measurements were obtained with the same transducer, determining as zero reference level the median axillary line. Pressure measurement was performed in apnea in order to avoid that the patient's respiratory incursions would determine oscillations in the pressure curve. When oscillations persisted in spite of this maneuver, the arithmetic mean of the observed maximum and minimum values was recorded. "hepatic venous block" was considered when a pressure gradient higher than 3 mm Hg was present.(4) Serum creatinine (Cr) was determined in the preoperatory period (immediately before surgery), on postoperative days (PO) 1 to 7 and on 14, 21 and 28. Occurrence of acute renal failure (ARF) was defined as postoperative creatinine peak > or = 2.0. (8) For each case, the area under the curve (AUC) Cr vs. time, calculated by the trapezoidal method (11) and divided by the postoperative observation time (28 days), was used as a postoperative overall creatinine parameter. Each group, conventional and piggyback, are also analyzed according to the RIFLE which classifies ARF in three grades of increasing severity: risk (class R), injury (class I) and failure (class F) - and two outcome classes - loss and end-stage kidney disease. RIFLE classification provides these grades based on changes in either Cr or urine output from the baseline condition. The RIFLE criteria is an important tool to help the international community compare data on ARF and was validated elsewhere (12, 13), being modified in 2005 as RIFLE-AKIN (14). For statistical analysis, in this study, the Class R are unified with the group of patients without renal injuries (considered as nule alterations), and the patients with class I and F were unified. The outcome classes are late consequences of the LTx and were not studied in the present clinical trial.