This was an observational,
cross-sectional study.
Patients with age of 18 years-old or older,
who underwent native kidney biopsy for evaluation of glomerulopathy or progressive renal failure between July 2017 and March 2018 were recruited.
Pregnant women as well as patients with active infection,
hydronephrosis,
abdominal tumors or lithiasis were excluded.
After informed consent,
demographic,
clinical,
laboratory and biopsy data were obtained,
and the imaging study was performed.
Ultrasound and ARFI assessments were performed by two expert radiologists from the Departament of Radiology of Hospital Clínico Universidad de Chile. All patients were evaluated in a single session with a Philips Epiq 7 Ultrasound system (Koninklijke,
Philips N.V) with the software ElastPQ® for ARFI measurements.
Patients were randomly assigned to one evaluator.
The examination was performed in supine or lateral decubitus position,
according to patient habitus.
Morphologic evaluation with a 5 Mhz probe in B-mode including maximum length,
transverse and antero-posterior diameter in the central kidney (middle third) (Fig. 1) and cortical thickness for each kidney were recorded (Fig. 2).
ROI for ARFI was positioned in the kidney cortex (Fig. 3).
Depth of the acquisition measured as distance from the skin was also recorded (Fig. 2).
For the measurement,
a ROI of 10 mm diameter was used.
3 ROIs for each renal segment,
with a total of 9 measurements for each kidney,
were performed.
Renal elasticity was estimated in kilopascals (kPa) and segmental as well as total media was calculated.
Histological data were obtained from the Department of Pathology of our institution.
All percutaneous biopsy samples were qualified as sufficient for diagnosis and evaluated by an expert renal pathologist.
Fibrosis was staged according to percentage of fibrosis: 0% (no fibrosis),
1-29% (mild fibrosis),
30-49% (moderate fibrosis) and 50% or more (severe fibrosis).
The statistical analysis was performed using GraphPad Prism v.6.0 software.
For numerical variables,
media value and standard deviation were calculated.
Simple linear regression with Pearson was determined and correlation index (R2) calculated.
A p-value less than 0.05 was regarded as significant for each statistical test.