Abstract
Background/Objectives: Heart failure (HF) causes systemic and regional haemodynamic alterations that extend beyond the heart, profoundly affecting splanchnic circulation. Venous congestion is a hallmark of heart failure (HF) and a major determinant of clinical deterioration and multiorgan dysfunction. The splanchnic venous system—comprising the portal, hepatic, and renal veins—acts as a key reservoir for intravascular volume redistribution. Conventional ultrasound (US), using grayscale and Doppler imaging, offers a direct, non-invasive approach to visualize these haemodynamic changes. This review, Part 1 of a two-part series, summarizes the current evidence and clinical applications of conventional US for assessing splanchnic, cardiac and pulmonary vascular alterations in patients with HF. Methods: A systematic review was performed in PubMed, Embase, and the Cochrane Library up to current date, following PRISMA 2020 guidelines. Eligible studies included adult human investigations evaluating splanchnic vascular changes in HF using B-mode, color Doppler, or pulsed Doppler ultrasonography. Exclusion criteria were pediatric, animal, or non-English studies and non-standard imaging methods. Data on ultrasonographic parameters, haemodynamic correlations, and prognostic value were extracted and qualitatively synthesized; Results: A total of 148 eligible studies (n ≈ 7000 patients) demonstrated consistent associations between HF severity and alterations in splanchnic, cardiac and pulmonary flow. Findings included increased bowel wall thickness, portal vein dilation with elevated pulsatility, and monophasic or reversed hepatic vein waveforms, all correlating with higher right atrial pressure and adverse clinical outcomes. The integration of these parameters into the Venous Excess Ultrasound (VExUS) framework enhanced detection of systemic venous congestion, in addition to the study of the cardiac and pulmonary circulation. Conclusions: Conventional ultrasound assessment of splanchnic vasculature provides valuable, reproducible insight into systemic congestion in HF. Incorporating hepatic and portal Doppler indices into standard evaluation protocols may improve risk stratification, optimize decongestion therapy, and guide management. Further prospective randomized and outcome-driven studies are required before VExUS-based therapeutic thresholds can be universally recommended and define prognostic thresholds.