Color Doppler Ultrasound in Renal Transplant: Role of Resistive Index versus Renal Cortical Ratio in the Evaluation of Renal Transplant Diseases

Abstract

Background/Aims: Ultrasound (US) and color Doppler are not sensitive enough to detect anomalies in cortical perfusion, which is affected in most graft dysfunctions. The renal cortical ratio (RCR) is a variation in the resistive index (RI) values from the renal artery to cortical vessels, expressed in percent. The aim of this study was to compare the RI and RCR in the differentiation of normal and pathological grafts, to assess the positive predictive value of RCR and show that RCR enables earlier diagnosis than RI. Methods: Based on clinical, biochemical and histological examinations, 494 renal allografts were divided into 3 groups (normal grafts, acute and chronic pathologies). All patients underwent US color Doppler. RI was measured and RCR calculated. Follow-up confirmed the initial division in groups. Statistical significance was calculated using the two-tailed Student’s t test. The positive predictive value was calculated for each group. Results: 24 h after transplant, RCR differentiated normal grafts from acute dysfunctions despite confusing biochemical values and clinical symptoms. In chronic patients, RCR variations occurred later but always before the serum creatinine level increased. Conclusion: RCR presented a higher positive predictive value than RI. RCR curves were already altered in the early stages of transplant pathologies. RCR calculation is easy and makes a significant contribution towards a correct early diagnosis.

Role of color Doppler ultrasound in the evaluation of renal transplantation from living donors

“…Our results show that analysis of RI values obtained before and after transplantation permits distinction between normal and pathological recipients and that a well-functioning kidney can re-establish normal hemodynamic conditions within 24 h. RI is in itself a static parameter. However, correlation between RI values obtained on the renal artery, interlobar artery and arcuate artery of the same kidney provides data for a dynamic analysis (RCR) [17,18].…”

Utilidad del índice de resistencia renal en la valoración y evolución de la uropatía obstructiva: Estudio experimental

“…Una importante limitación esta relacionada con la edad ya que se ha demostrado que el IR es altamente dependiente de la edad en humanos. Ya que el flujo cortical disminuido en las primeras semanas de vida es probablemente debido al gran número de glomérulos inmaduros y esto podría provocar el elevado IR en neonatos 21 .…”

The Serial Duplex Index Improves Differential Diagnosis of Acute Renal Transplant Dysfunction

“…Cellular rejection is characterized by various degrees of tubulitis and interstitial infiltration with lymphocytes and consecutive interstitial edema in the allograft parenchyma . Parenchymal swelling is reflected by an increased CPP on grayscale sonography, whereas cellular infiltration increases the echogenicity of the renal parenchyma . We hypothesize that distinct parenchymal edema in cellular rejection reduces kidney allograft perfusion.…”

“…[3][4][5] In serial scans within the first days after transplantation, a mild reduction of parenchymal width and cortex-pelvis proportions (CPPs) are usually observed because of the resolution of reperfusion injury-associated edema. [6][7][8] Color duplex sonography in well-functioning grafts shows perfusion reaching the subcapsular cortical parenchyma without a deficit. 9,10 Measurement of the vascular resistive index (RI) using Doppler sonography is a noninvasive method to evaluate renal allograft dysfunction, but conflicting reports exist about its clinical utility (Figure 1).…”

“…14 Parenchymal swelling is reflected by an increased CPP on grayscale sonography, whereas cellular infiltration increases the echogenicity of the renal parenchyma. 4,8,15 We hypothesize that distinct parenchymal edema in cellular rejection reduces kidney allograft perfusion. If so, the observed mild-to-moderate increase in the RI on duplex sonography ( Figure 2) might be explained.…”