Sonographic Indices in Patients with Severe Acute Tubular Necrosis during Early Post-Kidney Transplantation Period.

Background: Kidney transplantation is the most effective and optimal treatment for end-stage renal disease.

Objective: To investigate the association between serially measured ultrasound indices during the early post-operative period to determine severe acute tubular necrosis (ATN) in kidney allografts.

Methods: In a prospective study, we assessed sonographic renal indices including interlobar arteries peak systolic velocity (PSV), end-diastolic velocity (EDV), resistance index (RI), pulsatility index (PI), power doppler grading (PDG), acceleration time (AT), and renal volume on the 3^rd and 9^th days after kidney transplantation in 46 adult recipients who had no other significant complications except ATN. Biopsies were performed in patients with prolonged delayed graft function (DGF) to exclude other pathologies, especially acute rejection.

Results: 12 (20%) recipients experienced biopsy-proven severe ATN. The differences in the ultrasound indices and their measured discrepancies on the 1^st and 2^nd examinations between the groups were not statistically significant except for the 1^st examined RI (p=0.029) and PI (p=0.04). No patient had PDG of >2. The first RI, with a cut-off value of 0.66, had a sensitivity of 91.7% and a specificity of 50% for predicting severe ATN (area under the ROC curve = 0.71). To compensate for the low specificity of this index, we suggest using the first PDG scale of equal to 2 with a specificity of 85.3%. Overall sensitivity, specificity, and positive and negative predictive values in established severe ATN throughout early post-operative days for a 3^rd day RI >0.66 and PDG = 2, were 38%, 92.5%, 64.1%, and 80.9%, respectively.

Conclusions: The RI and the PDG measured on the 3^rd day after renal transplantation are useful indices for the diagnosis of established severe ATN in kidney allografts. Furthermore, donor characteristics, post-harvesting organ preservation status, main renal vascular anastomosis, and early post-operative recipient's clinical situations may also influence the incidence of severe ATN. Although the 1^st ultrasound examination on the 3^rd day in early post-transplantation provides important diagnostic and prognostic information, repeated assessment about one week later provides no more valuable information.