What is the role of furosemide stress testing in the workup of acute tubular necrosis (ATN)?

Updated: Mar 15, 2021
  • Author: Sangeeta Mutnuri, MBBS; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Answer

In early acute kidney injury (AKI), urine output after a furosemide stress test (FST) can predict the development of stage 3 AKI. Response to the FST may be used to help the clinician determine when or whether to start renal replacement therapy. [23, 24]

Candidates for FST should be euvolemic and stable. For the test, furosemide is infused intravenously, in a dose of 1.0 or 1.5 mg/kg, and urine output is measured for 2 hours afterward. A 2-hour urinary output of 200 ml or less has been shown to have the best sensitivity and specificity to predict development of stage 3 AKI. To minimize the risk of hypovolemia, urine output may be replaced ml for ml each hour with Ringer lactate or normal saline for 6 hours after the FST, unless volume reduction is considered clinically desirable. [24]

In a study by Koyner et al, FST was significantly better than any urinary biomarker tested in predicting progression to stage 3 AKI (P<0.05), and was the only test that significantly predicted receipt of renal replacement therapy. However, these authors found that a higher area under the curve (AUC) for prediction of adverse patient outcomes was achieved when FST was combined with biomarkers using specified cutoffs: urinary neutrophil gelatinase-associated lipocalin (NGAL) >150 ng/mL or urinary tissue inhibitor of metalloproteinases (TIMP-2) × insulinlike growth factor–binding protein-7 (IGFBP-7) >0.3. [23]


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