Chronic diuretic therapy attenuates renal BOLD magnetic resonance response to an acute furosemide stimulus.
BACKGROUND
Blood Oxygen Level Dependent (BOLD) magnetic resonance (MR) is a novel imaging tool that detects changes in tissue oxygenation. Increases in renal oxygenation in response to a standard 20 mg intravenous furosemide stimulus have been evaluated to assess kidney viability in patients with renal artery stenosis (RAS). The effect of prior exposure to furosemide on the ability of BOLD MR techniques to evaluate renal function is unknown.This study tested the hypothesis that chronic loop diuretic therapy is associated with attenuated responses in renal tissue oxygenation as measured by BOLD MR with an acute 20 mg intravenous furosemide stimulus in participants undergoing evaluation for RAS.


METHODS
Thirty-eight participants referred for evaluation of RAS were recruited for this study. We examined renal cortical and medullary BOLD signal (T2*) intensities before and after a 20 mg intravenous furosemide stimulus. Additionally, we measured changes in renal artery blood flow using phase contrast techniques.


RESULTS
After controlling for covariates age, race, gender, diabetes, glomerular filtration rate, body mass index, and stenosis severity, daily oral furosemide dose was an independent, negative predictor of renal medullary T2* response (p=0.01) to a standard 20 mg intravenous furosemide stimulus. Stenosis severity and ethnicity were also significant independent predictors of changes in T2* signal intensity in response to an acute furosemide challenge. Changes in renal blood flow in response to acute furosemide administration were correlated with changes in T2* in the renal cortex (r=0.29, p=0.03) but not the medulla suggesting changes in renal medullary oxygenation were not due to reduced renal medullary blood flow.


CONCLUSIONS
Chronic furosemide therapy attenuates BOLD MR responses to an acute furosemide stimulus in patients with RAS being evaluated for renal artery revascularization procedures. Thus, patients who are chronically administered loop diuretics may need a different dosing strategy to accurately detect changes in renal oxygenation with BOLD MR in response to a furosemide stimulus.
Michael E
ME
Hall
Michael V
MV
Rocco
Timothy M
TM
Morgan
Craig A
CA
Hamilton
Matthew S
MS
Edwards
Jennifer H
JH
Jordan
Justin B
JB
Hurie
Department of Medicine, Section on Cardiology, Wake Forest University School of Medicine, Winston-Salem, USA. ghundley@wakehealth.edu.
W Gregory
WG
Hundley
D061605:Administration, Intravenous; D000284:Administration, Oral; D000368:Aged; D015415:Biomarkers / Q000097:blood; D004334:Drug Administration Schedule; D005260:Female; D005665:Furosemide / Q000008:administration & dosage; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012077:Renal Artery / Q000187:drug effects* / Q000503:physiopathology; D012078:Renal Artery Obstruction / Q000097:blood / Q000175:diagnosis* / Q000503:physiopathology; D012079:Renal Circulation / Q000187:drug effects*; D049994:Sodium Potassium Chloride Symporter Inhibitors / Q000008:administration & dosage
D015415:Biomarkers; D049994:Sodium Potassium Chloride Symporter Inhibitors; D005665:Furosemide; D010100:Oxygen