JMIR Publications

ABSTRACT

Background:

The Renal Resistive Index (RRI) is a non-invasive indicator of renal vascular resistance and systemic hemodynamic status. Elevated RRI values have been consistently associated with subclinical vascular damage and target organ injury, particularly in patients with hypertension, chronic kidney disease, and diabetes. Recent observational studies have suggested that RRI may also serve as a prognostic marker for adverse cardiovascular outcomes and mortality. However, the evidence remains scattered and heterogeneous, and no systematic review has yet synthesized this body of literature.

Objective:

This systematic review aims to evaluate the association between elevated RRI and the risk of cardiovascular events, cardiovascular mortality, and all-cause mortality in adult populations.

Methods:

This protocol has been developed in accordance with the PRISMA-P guidelines and is registered in the PROSPERO database. We will include observational studies (prospective and retrospective cohort studies, and nested case-control studies) involving adults (≥18 years) with RRI measurements obtained through Doppler ultrasound. Studies focused on pediatric populations, pregnant women, and dialysis patients will be excluded. The primary exposure will be elevated RRI, typically defined as RRI ≥ 0.70, compared to lower or normal values. The primary outcomes are cardiovascular events, cardiovascular mortality, and all-cause mortality, with a minimum follow-up of 6 months. A comprehensive search will be conducted in PubMed, Embase, Web of Science, and grey literature sources, using MeSH terms and free-text keywords. Two independent reviewers will screen articles, extract data, and assess risk of bias using Two independent reviewers will screen articles, extract data, and assess the risk of bias using the Rob 1.0 tool for randomized controlled trials and the ROBINS-E tool for observational studies. Meta-analyses will be conducted if at least three studies report comparable data, using RevMan 5.4.1 and R software. Subgroup and meta-regression analyses will be used to explore heterogeneity, while sensitivity analyses will be conducted to assess the robustness of the observed results. The GRADE framework will be applied to evaluate the overall quality of evidence.

Results:

A preliminary exploratory search has been conducted to map the existing literature and to confirm the absence of prior systematic reviews on this topic. The formal study selection and data extraction are expected to begin in September 2025, with completion anticipated by February 2026.

Conclusions:

By systematically synthesizing the available literature, this review will provide a comprehensive overview of the prognostic value of RRI in predicting cardiovascular outcomes and mortality. The findings may inform clinical decision-making, enhance cardiovascular risk stratification, and identify research gaps for future studies focused on standardizing RRI assessment and its clinical applications.