Renal Scintigraphy Findings in Allograft Recipients With Increased Resistance Index on Doppler Sonography

Abstract

Aim The measurement of intrarenal resistance indices (RIs) by doppler ultrasound plays an important role in the evaluation of renal transplant recipients. Although an elevated RI was initially considered to be specific for rejection, later studies revealed this parameter as a nonspecific marker of transplant dysfunction. In this study, we analysed Tc-99m DTPA renal scintigraphy findings in patients with increased RI during the early posttransplantation period. Methods This study included 22 patients with increased RI on doppler sonography during the first week after transplantation. Twenty-two recipients with uncomplicated early postoperative courses were used as a control group. An RI value >0.7 was considered pathologic. All patients underwent Tc-99m DTPA renal scintigraphy just after doppler sonography. In addition to visual interpretation of images, renogram curves were evaluated for patterns suggestive of acute tubular necrosis and acute rejection. Glomerular filtration rate (GFR) was calculated using computer software. Perfusion time-activity curves were assessed for the presence of peak and plateau patterns to calculate this ratio (P:PL). Results The mean value for P:PL in patients with increased RI and in the control group were 1.37 ± 0.33 and 1.53 ± 0.47, respectively ( P < .05). The mean value for GFR was significantly lower in the patient group compared with control subjects. Six patients had normal perfusion and function (27%). Perfusion pattern and renogram changes were suggestive of acute tubular necrosis in 5 patients and acute rejection in 6 patients. These diagnoses were confirmed later with serial scintigraphic changes or biopsy results. Three patients had an accumulation pattern on the renogram suggesting partial obstruction. Conclusion During the early posttransplantation period an increased RI on doppler sonography was seen in both normal functioning grafts and those with allograft dysfunction. Renal scintigraphy with perfusion and renogram patterns highly suggestive of specific allograft pathologies seemed to provide useful information to distinguish early postoperative renal allograft pathologies.