External Validation of IRRIV Test Relationship With Renal Functional Reserve

Normal subjects display a significant capacity to increase in baseline GFR under physiological needs (e.g. pregnancy) or pathological states (e.g. solitary kidney). This capacity is known as renal functional reserve (RFR), and it is calculated as the difference between the measured maximum GFR achieved through a renal stress test and the baseline GFR measured in rest conditions.In clinical practice, the most common renal stress test is performed as a standardized protein loading test. In a pilot study, the investigators demonstrated a significant correlation between RFR and the intra-parenchymal renal resistive index variation (IRRIV) during an echo renal stress test in a cohort of healthy volunteers. IRRIV test has proven to be rapid, safe, bedside and easy to perform and it might represent a preliminary test in screening patients' RFR. For this purpose, externally validation of IRRIV test is performed in a validation cohort of healthy subjects.

Inclusion criteria

were:

• Age more than 18 years old;
• Baseline estimated GFR, calculated using the chronic kidney disease epidemiology collaboration (CKD-EPI) equation, greater than or equal to 60 ml/min/1.73 m2.

Exclusion criteria

were:

• Age less than 18 years old;
• Comorbidities potentially affecting renal function (i.e. arterial hypertension, diabetes, vasculopathy, etc.;
• Chronic administration of drugs able to modify renal blood flow and/or GFR (angiotensin converting enzyme-inhibitors (ACEI), angiotensin receptor blockers (ARB), calcium channel blockers, loop diuretics etc.);
• Pregnancy;
• Ultrasound evidence of morphological kidney abnormalities and/or renal artery stenosis;
• Nonsteroidal anti-inflammatory drugs (NSAIDs) or contrast media in the 2 days before the tests.