Functional assessment of transplanted kidneys with magnetic resonance imaging

Abstract

Kidney transplantation has emerged as the treatment of choice for many patients with end-stage renal disease, which is a significant cause of morbidity and mortality. Given the shortage of clinically available donor kidneys and the significant incidence of allograft dysfunction, a noninvasive and accurate assessment of the allograft renal function is critical for postoperative management. Prompt diagnosis of graft dysfunction facilitates clinical intervention of kidneys with salvageable function. New advances in magnetic resonance imaging (MRI) technology have enabled the calculation of various renal parameters that were previously not feasible to measure noninvasively. Diffusion-weighted imaging provides information on renal diffusion and perfusion simultaneously, with quantification by the apparent diffusion coefficient, the decrease of which reflects renal function impairment. Diffusion-tensor imaging accounts for the directionality of molecular motion and measures fractional anisotropy of the kidneys. Blood oxygen level-dependent MR evaluates intrarenal oxygen bioavailability, generating the parameter of R2* (reflecting the concentration of deoxyhemoglobin). A decrease in R2* could happen during acute rejection. MR nephro-urography/renography demonstrates structural data depicting urinary tract obstructions and functional data regarding the glomerular filtration and blood flow. MR angiography details the transplant vasculature and is particularly suitable for detecting vascular complications, with good correlation with digital subtraction angiography. Other functional MRI technologies, such as arterial spin labeling and MR spectroscopy, are showing additional promise. This review highlights MRI as a comprehensive modality to diagnose a variety of etiologies of graft dysfunction, including prerenal (e.g. , renal vasculature), renal (intrinsic causes) and postrenal (e.g. , obstruction of the collecting system) etiologies.

Vascularized composite allotransplantation: a closer look at the banff working classification

“…As an example, Doppler imaging of the mitral annulus can be a sensitive, but not specific technique for detecting severe heart transplant rejection . Newer MRI technologies that allow for diffusion weighted imaging can noninvasively evaluate tissue viability and acute kidney transplant rejection and postpancreatic transplant complications . The utility of these in VCA and cutaneous evaluation, however, may be more tenuous.…”

Untitled

“…Unlike ultrasonography, it is less frequently available because the equipment is not portable, the cost is relatively high, and it requires specialized personnel who may not be available 24 hours/day. 22 Also, there is not a consensus in the literature about MRI technique, b values, and the indications and time of the imaging.…”

Functional magnetic resonance imaging of kidneys

“…Tehnika obilježavanja arterijskih spinova (arterial spin labelling -ASL) može da kvantifikuje perfuziju bubrega, pri čemu voda u krvi predstavlja endogeno kontrastno sredstvo [17,18].…”