Renal Allograft Rejection: Noninvasive Ultrasound- and MRI-Based Diagnostics

Abstract

To date, allogeneic kidney transplantation remains the best available therapeutic option for patients with end-stage renal disease regarding overall survival and quality of life. Despite the advancements in immunosuppressive drugs and protocols, episodes of acute allograft rejection, a sterile inflammatory process, continue to endanger allograft survival. Since effective treatment for acute rejection episodes is available, instant diagnosis of this potentially reversible graft injury is imperative. Although histological examination by invasive core needle biopsy of the graft remains the gold standard for the diagnosis of ongoing rejection, it is always associated with the risk of causing substantial graft injury as a result of the biopsy procedure itself. At the same time, biopsies are not immediately feasible for a considerable number of patients taking anticoagulants due to the high risk of complications such as bleeding and uneven distribution of pathological changes within the graft. This can result in the wrong diagnosis due to the small size of the tissue sample taken. Therefore, there is a need for a tool that overcomes these problems by being noninvasive and capable of assessing the whole organ at the same time for specific and fast detection of acute allograft rejection. In this article, we review current state-of-the-art approaches for noninvasive diagnostics of acute renal transplant inflammation, i.e., rejection. We especially focus on nonradiation-based methods using magnetic resonance imaging (MRI) and ultrasound.

Difficulties in diagnosing HIV-associated nephropathy in kidney transplanted patients. The role of ultrasound and CEUS.

“…At the same time, acute allograft rejection has a similar US appearance with increased cortical echogenicity and hypoechogenic medulla [6]. Only the use of CD4+ or CD8+ labeled microbubbles was proved in rats to be able to detect cell-mediated acute rejection [6]. In our case, CEUS examination revealed a fast washout of contrast suggesting allograft inflammation, in consensus with the diagnostic of TIN.…”

“…Imaging findings that are suggestive of HIVAN and have been previously reported include normal-sized or enlarged kidneys, increased cortical echogenicity, renal pelvicalyceal thickening, and loss of the renal sinus fat appearance [5]. At the same time, acute allograft rejection has a similar US appearance with increased cortical echogenicity and hypoechogenic medulla [6]. Only the use of CD4+ or CD8+ labeled microbubbles was proved in rats to be able to detect cell-mediated acute rejection [6].…”

A Review of Current and Emerging Trends in Donor Graft-Quality Assessment Techniques

“…Further studies are warranted to analyse the effect of applying early therapeutic approaches to prevent DGF in kidney transplant recipients, thus improving long-term graft success [46]. The use of imaging techniques to diagnose post-renal transplant complications has been discussed extensively in recent reviews [47][48][49]; therefore, the present work will only examine a few of the most recent studies in this field. Promising results have been reported with respect to combining positron emission tomography (PET) with CT or magnetic resonance imaging (MRI) using the glucose analogue radiotracer, 2-deoxy-2-fluoro-Dglucose (FDG), to detect acute kidney allograft rejection, for diagnostic applications, for the functional assessment of grafts, and for therapeutic monitoring [50,51].…”

Diagnosi e trattamento del rigetto acuto cellulo-mediato nel trapianto di rene

“…In caso di rigetto acuto, all'esame ecografico il graft può apparire di dimensioni aumentate a causa dell'edema e ipoecogeno con perdita della differenziazione corticomidollaree prominenza delle piramidi, mentre gli indici di resistenza (IR) intraparenchimali possono essere aumentati (>0.80). Tuttavia, questo patt ern ecografico può essere sovrapponibile a quanto osservato in corso di Necrosi Tubulare Acuta (NTA) e, pertanto, aspecifico di rigetto acuto (6).…”