Mancianti Nicoletta, Guarnieri Andrea, Iadanza Ernesto, Belluardo Massimo, Lenoci Mariapia, Toraldo Francesca, Rossi Elena, La Porta Edoardo, Calatroni Marta, Salvo Domenica Paola, Ferretti Fabio, Marotta Giuseppe, Garosi Guido
Department of Medicine, Surgery and Neurosciences, Nephrology, Dialysis and Transplantation Unit, University Hospital of Siena, Siena, Italy.
Department of Medical Biotechnologies, University of Siena, Siena, Italy.
J Nephrol. 2025 Jan;38(1):127-133. doi: 10.1007/s40620-024-02163-8. Epub 2025 Jan 4.
Renal functional reserve (RFR) measures the difference between the stimulated glomerular filtration rate (GFR) and the baseline GFR to detect early signs of renal functional decline. The protein load test (RFR-T) is the gold standard for RFR assessment but is a complicated procedure. Renal intraparenchymal resistance index (RRI) variation test (DRRI-T) is a non-invasive method to measure renal function reserve using ultrasound. A saline bag is used to induce renal vasodilation, and the DRRI is found by calculating the difference between baseline (without weight) and stress RRI (with weight). Normal DRRI-T is greater than 0.05.
Our study compared RFR-T and DRRI-T in 50 patients with normal kidney function. We evaluated anthropometric parameters, cardiovascular risk factors, and performed blood and urine tests. Patients were over 18 years old with an estimated GFR (eGFR) CKD-EPI > 60 mL/min/1.73 m. We excluded pregnant patients, those intolerant to milk protein, those with abnormal kidney ultrasound, or taking medication affecting intrarenal hemodynamics. We used Gwet's AC1 statistic to assess concordance between tests.
Our study found moderate concordance (0.545 coefficient value, p-value < 0.001) between preserved RFR-T (≥ 15 mL/min/1.73 m) and DRRI (VN > 0.05). Preserved RFR had a significant association with baseline eGFR. Age and sex have an impact on RFR. RFR deteriorates with age, leading to a significant decrease (p = 0.0220), which is more pronounced in women than men (p = 0.0350).
The Ultrasound test (DRRI-T) can measure RFR in just 10 min. This contrasts the gold standard method for estimating RFR, which involves a protein load test, takes a long time to execute, and requires numerous blood and urine samples, making it challenging for large-scale use. While the DRRI-T demonstrated moderate concordance with the protein load test, it did not meet the criteria to be considered a new gold standard test. We posit that it could serve as a valuable initial screening test, warranting further exploration alongside the more elaborate protein load test. Our study suggests that there may be differences between men and women in RFR changes and with regard to age, warranting further investigation on larger populations through ad hoc studies. Our work is among the first to offer original real-life experience in this field.
肾功储备（RFR）通过测量刺激后肾小球滤过率（GFR）与基线GFR之间的差异来检测肾功能下降的早期迹象。蛋白负荷试验（RFR-T）是评估RFR的金标准，但操作复杂。肾实质内阻力指数（RRI）变化试验（DRRI-T）是一种利用超声测量肾功能储备的非侵入性方法。使用盐水袋诱导肾血管舒张，并通过计算基线（无负荷）和应激RRI（有负荷）之间的差异得出DRRI。正常的DRRI-T大于0.05。
我们的研究比较了50例肾功能正常患者的RFR-T和DRRI-T。我们评估了人体测量参数、心血管危险因素，并进行了血液和尿液检查。患者年龄超过18岁，估计肾小球滤过率（eGFR）根据CKD-EPI公式>60 mL/min/1.73 m²。我们排除了孕妇、不耐受乳蛋白的患者、肾脏超声异常的患者或正在服用影响肾内血流动力学药物的患者。我们使用Gwet's AC1统计量来评估两种检测方法之间的一致性。
我们的研究发现，保留的RFR-T（≥15 mL/min/1.73 m²）与DRRI（VN>0.05）之间存在中度一致性（系数值为0.545，p值<0.001）。保留的RFR与基线eGFR显著相关。年龄和性别对RFR有影响。RFR随年龄增长而恶化，导致显著下降（p=0.0220），女性比男性更明显（p=0.0350）。
超声检查（DRRI-T）只需10分钟就能测量RFR。这与估计RFR的金标准方法形成对比，后者涉及蛋白负荷试验，执行时间长，需要大量血液和尿液样本，难以大规模应用。虽然DRRI-T与蛋白负荷试验显示出中度一致性，但它不符合被视为新金标准试验的标准。我们认为它可以作为一种有价值的初始筛查试验，值得与更精细的蛋白负荷试验一起进一步探索。我们的研究表明，男性和女性在RFR变化以及年龄方面可能存在差异，需要通过专门研究对更大规模人群进行进一步调查。我们的工作是该领域首批提供原始实际经验的研究之一。
