Shear Wave Elastography in Native Kidney Disease

In this proposal, the aim is to examine shear wave elastography (SWE) measurements in diseased native kidneys and correlate them with grades of fibrosis using histological samples. The overall goals of the proposed study are addressed by the following specific aim. Specific aim: To determine whether differences exist in elasticity measurements between native kidneys with and without fibrosis. Hypothesis: Kidneys with higher grades of fibrosis will demonstrate higher measures of tissue elasticity and stiffness compared to kidneys with zero fibrosis.

The proposed project is a prospective cross-sectional study correlating native kidney shear wave elastography (SWE) measurements with histology. Briefly, patients referred for a native kidney biopsy will undergo SWE and the shear wave velocity (SWV) will be correlated with degree of fibrosis determined by a pathologist. A list of patients who recently underwent a native kidney biopsy will be obtained from the pathology department on a weekly basis. Patients will then be contacted about participating in the study and consented during a follow up visit with their nephrologist. After their biopsies, patients will be scheduled to come for a renal ultrasound and SWE. SWE examination will be conducted using an ultrasound machine equipped with a Philips Epiq ARFI Shear wave ElastPQ C1-5 mHz transducer. Shear wave velocity will be obtained and an estimate of tissue elasticity (Young's modulus) will be calculated. All measurements will be performed by one of two qualified radiology physicians who will be blinded to the clinical and pathological data. We will allow a period of 90 days to obtain the images after the biopsy; otherwise the patient is no longer eligible to participate. The primary outcome measure of this study is to determine whether tissue elasticity determined by SWE can assess kidney fibrosis. Linear regression analysis will be performed to describe the relation of the extent of fibrosis and parenchymal stiffness.

The shear wave velocity of the kidneys will be determined using the elastography ultrasound machine. This will enable us to calculate the tissue elasticity using a standard formula. Shear wave velocity is measured in meters per second, at a range of 0-5 m/s with the highest number reporting hard consistency (fibrosis - worse outcome).

Inclusion Criteria: All patients over 18 years of age who are referred for a native kidney biopsy. Exclusion Criteria: BMI > 35 Patients with polycystic kidney disease, renal cell carcinoma, hydronephrosis or renal stones. Patients who develop severe post biopsy complications (infection, significant bleeding requiring transfusion or intervention) Pregnant patients.

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