Introduction: ARFI elastography began recently to be used for kidney stiffness (KS) evaluation (especially in transplanted kidneys), but a standardized technique is not available until now.
Aim: To analyze how many measurements are needed for KS evaluation by means of ARFI elastography and which one do we need to use: the mean or median value of ARFI measurements.
Methods: Our study included 263 consecutive subjects, with or without kidney disease in which KS was assessed by ARFI elastography. In each subject we aimed for 5 valid KS measurements in each kidney, the measurements being performed in the
mid-portion of each kidney, in the renal cortex with the patient in lateral decubitus. We compared the values of KS assessed by ARFI elastography in three situations: if the median value of 5 valid ARFI measurements was used; if the mean value of 5 valid ARFI measurements was used; and if the mean value of 3 valid ARFI measurements was used.
Results: We obtained 5 reliable KS measurements in 99.6% of cases in the right kidney and in 98.5% of cases in the left kidney.
The KS values were similar for both kidneys when median value of 5 valid ARFI measurements, mean value of 5 or 3 measurements was used (table).
| Kidney | Median
of 5 ARFI measurements (m/s) (A) | Mean
of 5 ARFI measurements (m/s) (B) | Mean
of 3 ARFI measurements (m/s) (C) | p |
| Right | 2.42±0.83 | 2.40±0.74 | 2.38±0.78 | AB:
p=0.60
AC:
p=0.30
BC: p=0.24 |
| Left | 2.31±0.84 | 2.29±0.76
| 2.32±0.81 | AB:
p=0.72
AC:
p=0.41
BC: p=0.15 |
Conclusions: Our study showed that 3 valid KS measurements by ARFI elastography are enough and that the mean value of these measurements should be used.
