Assessment of renal allograft fibrosis by transient elastography

Abstract

SummaryTransient elastography (TE, Fibroscan) has been established as a noninvasive assessment tool of liver fibrosis. We evaluated potentials and limitations of TE for identifying renal allograft fibrosis. The technical possibility of kidney examination by TE was assessed in two 10-week-old German landrace pigs and kidney stiffness (KS) was evaluated in 164 renal transplant patients. KS could be determined in all animals at the pole and pars media (29 AE 10 kPa vs. 31 AE 17 kPa). In human renal allografts KS was successfully performed in 94.5% of the test series with reliable results in 72% of the measurements. Mean KS at the pole or pars media were comparable (35.0 AE 19.9 kPa vs. 33.2 AE 18.6 kPa). Significantly higher KS was detected in renal allografts with histologically confirmed advanced fibrosis. Bodymass-index, skin-allograft distance, and peri or intrarenal fluid accumulation were important confounders of successful KS measurements (BMI: r = À0.31; P < 0.001; distance: r = À0.50; P < 0.001). Notably, KS did not correlate with renal function. TE represents a noninvasive approach in selected transplant recipients to identify allografts with severe fibrosis. The heterogeneous kidney morphology and several other confounding factors negatively affect measurability of KS by TE. Further technical modifications are required to improve applicability of TE for kidney assessment.

Renal Allograft Fibrosis: Biology and Therapeutic Targets

“…In renal allografts, the two main modalities to assess fibrosis are ultrasound and magnetic resonance imaging (MRI). Ultrasound-based measurement of tissue elasticity (elastography), an approach relatively well established in the assessment of liver fibrosis, has been suggested to correlate with fibrosis in kidney allografts (420)(421)(422)(423)(424), but others have found no such correlation (425). MRI-based elastography is an alternative approach, but the first findings in kidney allografts with fibrosis were disappointing (426).…”

Value of ultrasound elastography in the diagnosis of native kidney fibrosis.

“…linear increase of renal tissue elasticity associated with elevated urinary pressure [22,26]. Gender [21,34], race [27], weight or body mass index (BMI) [20], and also age [23,34,46] can modify the results in US elastography and several studies have found significant variations of renal parenchymal elasticity in these parameters [20,21,23,27,34,46].…”

“…Therefore, measurements of the stiffness in the same part of the kidney (subcapsular, cortex and medulla) are advisable to obtain valid and uniform results [20,27] and also establish universal technique standards in the future for reliable and comparable results.…”

“…In addition, in renal diseases, 1D transient elastography has an applicability only in the transplanted kidney [19,20], because this is positioned superficially, under the skin. In transient elastography, the sample volume is placed 4 cm long in a window with little variations below the skin surface (25-65 mm) and there is no ultrasound guidance to position the sample on the native kidney which is located at variable depths [18].…”

Kidney Ultrasound Elastography: Review

“…Some of them were about animals [36][37][38][39][40][41][42] , some of them were about MRI or MR elastography [43][44][45][46][47][48][49][50][51][52] , some of them were about other organ systems [53][54][55][56][57][58][59][60][61][62][63][64][65] , some of them were about elastography technic 28,[66][67][68][69] and some of them were about non elastography related kidney studies 70 . We excluded these articles.…”