Renal transplantation parenchymal complications: what Doppler ultrasound can and cannot do

Abstract

Kidney transplantation is the treatment of choice in end-stage renal disease, given the better quality of life of transplanted patients when compared with patients on maintenance dialysis. In spite of surgical improvements and new immunosuppressive regimens, parts of transplanted grafts still develop chronic dysfunction. Ultrasonography, both in B-mode and with Doppler ultrasound, is an important diagnostic tool in case of clinical conditions which might impair kidney function. Even though ultrasonography is considered fundamental in the diagnosis of vascular and surgical complications of the transplanted kidney, its role is not fully understood in case of parenchymal complications of the graft. The specificity of Doppler is low both in case of acute complications, such as acute tubular necrosis, drugs toxicity and acute rejection, and in case of chronic conditions, such as chronic allograft nephropathy. Single determinations of resistance indices present low diagnostic accuracy, which is higher in case of successive measurements performed during the follow-up of the graft. Modern techniques such as tissue pulsatility index, maximal fractional area and contrast-enhanced ultrasound increase ultrasonography diagnostic power in case of parenchymal complications of the transplanted kidney.Keywords Ultrasonography Á Doppler ultrasound Á Renal transplantation Á Parenchymal complications Sommario Il trapianto di rene è il trattamento di scelta nella malattia renale allo stadio terminale, data la migliore qualità di vita dei pazienti trapiantati rispetto a quelli che continuano il trattamento dialitico. Nonostante i miglioramenti chirurgici e nuovi regimi immunosoppressivi, parte dei pazienti trapiantati sviluppano ancora disfunzioni croniche. L'ecografia, sia in B-mode che Doppler, è un importante strumento diagnostico in caso di condizioni cliniche che possono alterare la funzione renale. Anche se l'ecografia è considerata fondamentale nella diagnosi di complicanze chirurgiche e vascolari del rene trapiantato, il suo ruolo non è pienamente conosciuto in caso di (2015) 18:109-116 DOI 10.1007/s40477-014-0118-1 complicanze parenchimali. La specificità del Doppler è bassa, sia in caso complicanze acute, quali la necrosi tubulare acuta, la tossicità acuta da farmaci, il rigetto, sia in caso di complicanze croniche, come la nefropatia cronica del trapianto. Singole determinazioni di indici di resistenza presentano bassa accuratezza diagnostica, che è più elevata in caso di misure effettuate successivamente durante il follow-up del trapianto. Tecniche moderne, come l'indice di pulsatilità tissutale, massima frazione di zona ed ecografia con mdc aumentano le potenzialità diagnostiche dell'ecografia in caso di complicanze parenchimali del rene trapiantato.

Retracted: Early Detection of Postoperative Acute Kidney Injury in Acute Stanford Type A Aortic Dissection With Doppler Renal Resistive Index

“…Doppler ultrasonography also offers several advantages: real‐time imaging, rapidity, portability, noninvasivity, high feasibility, simplicity, and ability to easily perform dynamic and repeated assessments of the renal circulation at the bedside . Ultrasonography is an important diagnostic tool in the case of clinical conditions that might impair kidney function . Therefore, DRRI is a very practical marker of detecting postoperative AKI.…”

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

“…Single measurements of the RI have low diagnostic accuracy for acute complications and chronic dysfunction after kidney transplantation, but successive monitoring can improve it . This observation generated the idea for our study to calculate ratios of 2 serial RI and PI measurements, resulting in sensitivity and specificity of greater than 80% in diagnosing acute rejection.…”

“…Major transplant conditions that need to be distinguished from normal graft function are acute tubular necrosis, acute cellular rejection, and acute vascular rejection. Grayscale sonography of the initially normally functioning kidney allograft (normal graft function) usually reveals expanded edematous parenchyma with uniform echogenicity, which is accentuated medullary pyramids . 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 .…”

“…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 ) . Several studies have shown that an elevated RI is considered diagnostic of acute transplant dysfunction, but it may have low specificity in diagnosing kidney allograft rejection . In one report, the sensitivity and specificity of the RI in diagnosing rejection were only 43% and 67%, respectively .…”

“…Grayscale sonography of the initially normally functioning kidney allograft (normal graft function) usually reveals expanded edematous parenchyma with uniform echogenicity, which is accentuated medullary pyramids. [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.…”