[New kidney function tests: Renal functional reserve and furosemide stress test]

Area of Science:

• Nephrology
• Critical Care Medicine
• Renal Physiology

Background:

• Acute kidney injury (AKI) affects 30-50% of intensive care patients, with high mortality and progression to chronic kidney disease.
• Traditional markers like creatinine and urea are unreliable for assessing kidney function in critically ill patients.
• Accurate assessment of glomerular filtration rate (GFR) is crucial for timely interventions in AKI.

Purpose of the Study:

• To evaluate the utility of novel functional kidney tests, furosemide stress test (FST) and renal functional reserve (RFR), in critically ill patients.
• To determine if these tests can accurately assess kidney function and predict AKI progression and need for renal replacement therapy (RRT).

Main Methods:

• The furosemide stress test (FST) involves administering furosemide (1.0-1.5 mg/kgBW) intravenously to critically ill patients with AKI.
• Renal functional reserve (RFR) is estimated by a short-term high protein load (oral or intravenous).
• Urine output and GFR changes are monitored to assess kidney function and reserve.

Main Results:

• An increased urine output (>100 ml/h) after FST indicates a GFR >20 ml/min and excludes progression to AKI stage III and need for RRT.
• RFR estimation reveals the presence and magnitude of functional reserve, with loss indicating reduced nephron mass and incomplete recovery.
• Both FST and RFR show potential for improving diagnosis and management of high-risk kidney disease patients.

Conclusions:

• The furosemide stress test (FST) and renal functional reserve (RFR) are promising functional tests for critically ill patients with AKI.
• These tests provide more accurate and sensitive assessments of kidney function compared to traditional markers.
• FST and RFR can aid in timely therapeutic decisions, prognosis, and management of acute and chronic kidney disease.