Renal functional reserve

Praveen Ratanasrimetha MD, Miguel Quirch MD, Sorot Phisitkul MD


Serum creatinine and glomerular filtration rate (GFR) are the current standard tests to measure kidney function. The baseline GFR does not reflect full function of the kidney since human kidneys do not always work at full capacity. Similarly, serum creatinine is not a sensitive measure for kidney function or injury. In healthy individuals the GFR physiologically increases in response to certain stresses or stimuli, such as protein loading.

Renal functional reserve (RFR) is defined as the difference between the maximal glomerular filtration rate (generally determined after oral or intravenous protein loading) and the baseline glomerular filtration rate. The absence of a normal RFR can help identify patients who are more susceptible to kidney injury. The RFR is also important in patients who develop acute kidney injury and chronic kidney disease. Even though the GFR might return to a baseline level, there may be some loss of RFR which can make the patient more susceptible to another episode of kidney injury.

Acute kidney injury and chronic kidney disease are considered interconnected syndromes; each is a risk factor for the other. There are no current recommendations regarding the performance of routine determinations of RFR. Physicians should focus on clinical history and physical examination in patients with a history of prior episodes of acute kidney injury, monitor renal function, and avoid nephrotoxic insults.

Keywords: glomerular filtration rate, renal functional reserve, creatinine, acute kidney injury

Article citation: Ratanasrimetha P, Quirch M, Phisitkul S. Renal functional reserve. The Southwest Respiratory and Critical Care Chronicles 2018;6(25):26–30
From: Department of Internal Medicine, Texas Tech University Health Sciences Center, Lubbock, TX
Submitted: 11/17/2017
Accepted: 6/17/2018
Conflicts of interest: None
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